Test Equipment Anonymous (TEA) group therapy thread

[Per Hansson]

It looks like it has been converted

My 2005A is running on 230VAC as well:

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3496502/?PHPSESSID=ktt0m6vp6lj8fejvk571234895#msg3496502

Beware potential buyers: the serial number of the unit posted on eBay is the same as the one that BU508A links to above!!! (001120)

[Neomys Sapiens]

Will add that to my cart list for my next order... in the meantime I can maybe just cobble a hand home made termination with a 50ohms discrete resistor, which won't be perfectly 50ohmsd I guess, bvut close enough to see an improvement. Or a little trimmer to make it perfectly 50ohms...  Yeah I will play with that see what that does 

The important part is that you do terminate in a low impedance. I fully expect you to get a long way towards right even with a 75Ω plug. Think of it as relative; the difference between 1MΩ and 50Ω and between 1MΩ and 75Ω is practically the same (it amounts to 0,25% deviation) . So, 49-51Ω or so will do just fine.

A lot of electronicks is "in the ballpark" style stuff, and then sometimes it is not!  But this is a case where you get almost right even with something that's 50% off in value, because the alternative (not terminating) would be 4 orders of magnitude worse.

Excellent explanation! I support the 75 is "good enough". But, beware! If you keep the T on the generator and terminate transmission lines in both directions - now the generator sees 25 on its output! (Or rather, it would if both sides are terminated into 50 , it will be slightly higher in your case...) Not that it will destroy anything, but you will have an unmatched condition still!
Edit: I might add your experiment is a nice demonstration of such effects 

Ohhh..... boy. So... I don't see how can one solve this problem ? You can buy T adapters to send a signal to several devices inputs, but then you don't have 50R anymore so no good. So why do they even sell Tee ?!     

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

Or can you just, silly me I know.... add a 25R resistor in series  with the output of the generator ? This way the two 50R paths of the scope and counter, making up 25R... plus the 25 discrete resistor... the generator would then see 25 + ( 50 // 50 ) = 50R ?  No ? I know, stupid....

The proper way to do this is to use a Wilkinson divider.

[xrunner]

You could go for the self adhesive laminating film that libraries cover the dust jackets of books with. I've books that I covered with the same 30 odd years ago and they are still OK - no yellowing, no delaminating, no getting brittle.

Over here, there is a adhesive plastic film called 'DC-fix'. It is often used to protect heavily used books and also in applications like yours. But I have no idea how widely available it is in the US. Here it is sold at almost every stationery shop. 'Booktac' seems to be a comparable product, else look for 'book protection film'.

Ah good suggestions! Found some on Amazon I'll order a small amount.

If you go down that route and haven't done it before, come back and ask for tips - that stuff is difficult to put on bubble and void free and there's a few non-obvious things you can go to guarantee success.

Yes I would like some tips please, I'm all ears - or eyes in this case ... 

[mnementh]

EDIT2:  There might be a wee bit of snow by GWN standards coming tomorrow, so someone decided to preemptively close all the schools in the region.  There will not even be online classes, since the school board says they can only do that for COVID reasons.  So, now all that cabling is unnecessary 

Hmm, perhaps there's someone with a heart left, who remembers "snow days" from their own childhood and wasn't such a bastard as to say "Well, now we have all this infrastructure and experience of online schooling from Covid, why don't we use it on snow days?" and just made up an excuse "Do we technically have the power to enforce online schooling on a snow day, or does the legislation only give us that power for public health emergencies? [Knowing grin] Just asking?" .

Snow days of my youth were only slightly less awesome.   

mnem
*thinks back on the bonfire incident*   But some were considerably more explosive... 

[mansaxel]

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

The perhaps non-intuitive thing to think of here is that the transmission line must be free from reflections and properly terminated it will, as long as there are no branches.

I'd do it like this:

Code: [Select]

50Ω - T --------- cable --------T--------cable -------T- 50Ω
      |                         |                     |
     OUT                 counter in                  scope in


Yes, there are branches. Even though I wrote there should be none. Now, thing is they'll work fine if they're kept short, and "short" has a relation to the upper frequency limit of the transmission system; the wider the bandwidth the shorter the branches must be to not create havoc.  This is, by the way, not my idea, it's stolen right off 10Base2, the old thin Ethernet. And RS485-based protocols like DMX work the same, like a lot of other bus type systems. There is a termination in each end, the branches are kept short, and things will work.  Another typical application is analog video, where there often was an input BNC, and a loop output adjacent. Sometimes there was a TERM switch, sometimes one was expected to plug a terminator in the output if not used. The T simply was in the box.

Deux fois esprit d'escalier:

1. The top frequency relation is probably why it worked differently depending on rise time.
2. I don't remember the second until I press "Save"
2bis. Perhaps it is better to put the counter in the end and the scope in the middle.

[tggzzz]

(...)
Ohhh..... boy. So... I don't see how can one solve this problem ? You can buy T adapters to send a signal to several devices inputs, but then you don't have 50R anymore so no good. So why do they even sell Tee ?!     

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

Or can you just, silly me I know.... add a 25R resistor in series  with the output of the generator ? This way the two 50R paths of the scope and counter, making up 25R... plus the 25 discrete resistor... the generator would then see 25 + ( 50 // 50 ) = 50R ?  No ? I know, stupid....

Put the generator on one end and the scope on the other. The Tee on the counter LF (1 Meg) input. Now both ends are terminated, both see 50 . Technically there is still a "bump on the road" where the counter is, but it is usually "close enough". In this world "usually" and "close enough" heavily depend on the frequencys involved 

The problem with that won't be the 1Mohm, but the ~20pF in parallel with it. The reactance of 20pF at 100MHz is lower than most people realise - and a pothole (since it it capacitative) will probably be visble.

[Vince]

(...)
Ohhh..... boy. So... I don't see how can one solve this problem ? You can buy T adapters to send a signal to several devices inputs, but then you don't have 50R anymore so no good. So why do they even sell Tee ?!     

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

Or can you just, silly me I know.... add a 25R resistor in series  with the output of the generator ? This way the two 50R paths of the scope and counter, making up 25R... plus the 25 discrete resistor... the generator would then see 25 + ( 50 // 50 ) = 50R ?  No ? I know, stupid....

Put the generator on one end and the scope on the other. The Tee on the counter LF (1 Meg) input. Now both ends are terminated, both see 50 . Technically there is still a "bump on the road" where the counter is, but it is usually "close enough". In this world "usually" and "close enough" heavily depend on the frequencys involved 

OK will do shortly ! 

For now here are a couple pictures... I cobbled together a 50R termination. I sticked a couple resistors into a banana adapter, quite practical !
Wanted to put two 100R in  // of course, but alas I don't seem to have any ! So I ended up putting 56R in // with 470R. Got me close enough, about 50.5R measured right at the adapter BNC contacts. That's 1% off, good enough 

Well the change is spectacular as you can see !!

First pic is with a 50ns pulse, it's worlds apart with the garbage I got before ! 

Then I decreased the width of the pulse until the counter would stop counting....
Previously as stated earlier, below 27ns it would fail to count. Now, see pic #2, I can go all the way down to 10ns (the minimum the generator can do), and the counter still counts just fine !
So instead I increased the frequency of the signal. So still that 10ns pulse of course, but I progressively decreased the "off" time, to lower the period of the signal. Down to about 65/70ns or so, still works. About 15MHz then. Above that it quits... unless I start increasing the pulse width a little bit again, then it catches up !   

So both the frequency and the pulse width come into play for the counter "sensitivity". The smaller the pulse and/or the higher the frequency, the harder it gets.
So if you want to get max frequency response, upping pulse width / duty cycle can help a bit...

I am having a lot of fun playing with my TE and shiny cables and adapters !

So it shows as you said that even two 50R paths in // is not the end of the world... at least with single digit rise times like I have here. You can still see relevant / helpful waveforms.

[tggzzz]

Will add that to my cart list for my next order... in the meantime I can maybe just cobble a hand home made termination with a 50ohms discrete resistor, which won't be perfectly 50ohmsd I guess, bvut close enough to see an improvement. Or a little trimmer to make it perfectly 50ohms...  Yeah I will play with that see what that does 

The important part is that you do terminate in a low impedance. I fully expect you to get a long way towards right even with a 75Ω plug. Think of it as relative; the difference between 1MΩ and 50Ω and between 1MΩ and 75Ω is practically the same (it amounts to 0,25% deviation) . So, 49-51Ω or so will do just fine.

A lot of electronicks is "in the ballpark" style stuff, and then sometimes it is not!  But this is a case where you get almost right even with something that's 50% off in value, because the alternative (not terminating) would be 4 orders of magnitude worse.

Excellent explanation! I support the 75 is "good enough". But, beware! If you keep the T on the generator and terminate transmission lines in both directions - now the generator sees 25 on its output! (Or rather, it would if both sides are terminated into 50 , it will be slightly higher in your case...) Not that it will destroy anything, but you will have an unmatched condition still!
Edit: I might add your experiment is a nice demonstration of such effects 

Ohhh..... boy. So... I don't see how can one solve this problem ? You can buy T adapters to send a signal to several devices inputs, but then you don't have 50R anymore so no good. So why do they even sell Tee ?!     

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

Or can you just, silly me I know.... add a 25R resistor in series  with the output of the generator ? This way the two 50R paths of the scope and counter, making up 25R... plus the 25 discrete resistor... the generator would then see 25 + ( 50 // 50 ) = 50R ?  No ? I know, stupid....

The proper way to do this is to use a Wilkinson divider.

They only work over a limited frequency range. If you can tolerate the power loss, use resistive splitters.

[Vince]

(...)
Ohhh..... boy. So... I don't see how can one solve this problem ? You can buy T adapters to send a signal to several devices inputs, but then you don't have 50R anymore so no good. So why do they even sell Tee ?!     

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

Or can you just, silly me I know.... add a 25R resistor in series  with the output of the generator ? This way the two 50R paths of the scope and counter, making up 25R... plus the 25 discrete resistor... the generator would then see 25 + ( 50 // 50 ) = 50R ?  No ? I know, stupid....

Put the generator on one end and the scope on the other. The Tee on the counter LF (1 Meg) input. Now both ends are terminated, both see 50 . Technically there is still a "bump on the road" where the counter is, but it is usually "close enough". In this world "usually" and "close enough" heavily depend on the frequencys involved 

The problem with that won't be the 1Mohm, but the ~20pF in parallel with it. The reactance of 20pF at 100MHz is lower than most people realise - and a pothole (since it it capacitative) will probably be visble.

See my results above (our posts collided.... ). I added a 50R termination at the counter, hence still having the "high" input capacitance, yet it significantly improved the waveform 

[mnementh]

Agreed, Marantz gear was very good quality, but these days everyone only wants DAB sets, and while FM is still a perfectly good platform, people just do not want it , partly because of their sheer size, more modern units are far smaller, but the audio quality could be debatable.

Buddy still has the matching Marantz amp hence the wish to get the tuner working again too.

Haven't seen it yet as it hasn't yet arrived as everyone is still getting back into gear after the Xmas break.
Probably will give to Defpom for a repair video as there seems to be bugger all info about these online. 

IIRC, there isn't much to them. Pretty sure "Servo Control" is just audiophoolery for AFC. The point of interest mostly is it has the weighted horizontal tuning knob that was a Marantz "thing", while trying to somehow bring that iconic device into the digital age. 

I'd lay a dollar on some simple power supply issue; as there is nothing high power in the box at all, these separate tuners tended not to cook themselves to death like the amplifiers did.

mnem
Discworld was inspired by this thing.

[Neomys Sapiens]

Will add that to my cart list for my next order... in the meantime I can maybe just cobble a hand home made termination with a 50ohms discrete resistor, which won't be perfectly 50ohmsd I guess, bvut close enough to see an improvement. Or a little trimmer to make it perfectly 50ohms...  Yeah I will play with that see what that does 

The important part is that you do terminate in a low impedance. I fully expect you to get a long way towards right even with a 75Ω plug. Think of it as relative; the difference between 1MΩ and 50Ω and between 1MΩ and 75Ω is practically the same (it amounts to 0,25% deviation) . So, 49-51Ω or so will do just fine.

A lot of electronicks is "in the ballpark" style stuff, and then sometimes it is not!  But this is a case where you get almost right even with something that's 50% off in value, because the alternative (not terminating) would be 4 orders of magnitude worse.

Excellent explanation! I support the 75 is "good enough". But, beware! If you keep the T on the generator and terminate transmission lines in both directions - now the generator sees 25 on its output! (Or rather, it would if both sides are terminated into 50 , it will be slightly higher in your case...) Not that it will destroy anything, but you will have an unmatched condition still!
Edit: I might add your experiment is a nice demonstration of such effects 

Ohhh..... boy. So... I don't see how can one solve this problem ? You can buy T adapters to send a signal to several devices inputs, but then you don't have 50R anymore so no good. So why do they even sell Tee ?!     

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

Or can you just, silly me I know.... add a 25R resistor in series  with the output of the generator ? This way the two 50R paths of the scope and counter, making up 25R... plus the 25 discrete resistor... the generator would then see 25 + ( 50 // 50 ) = 50R ?  No ? I know, stupid....

The proper way to do this is to use a Wilkinson divider.

They only work over a limited frequency range. If you can tolerate the power loss, use resistive splitters.

That was indeed a lapse on my side - I thought that these are the resistive type.

[BU508A]

It looks like it has been converted

My 2005A is running on 230VAC as well:

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3496502/?PHPSESSID=ktt0m6vp6lj8fejvk571234895#msg3496502

Beware potential buyers: the serial number of the unit posted on eBay is the same as the one that BU508A links to above!!! (001120)

Yes, you are right.
I've bought mine from this seller and it seems, he has recycled the pictures from my PD 2005A.

Just checked: mine is still here. 

[cyclin_al]

EDIT2:  There might be a wee bit of snow by GWN standards coming tomorrow, so someone decided to preemptively close all the schools in the region.  There will not even be online classes, since the school board says they can only do that for COVID reasons.  So, now all that cabling is unnecessary 

Hmm, perhaps there's someone with a heart left, who remembers "snow days" from their own childhood and wasn't such a bastard as to say "Well, now we have all this infrastructure and experience of online schooling from Covid, why don't we use it on snow days?" and just made up an excuse "Do we technically have the power to enforce online schooling on a snow day, or does the legislation only give us that power for public health emergencies? [Knowing grin] Just asking?" .

You make a good point.  I know I would have appreciated a snow day off back in the day.  However, back then all the neighbourhood kids would be out together.

At the moment, the kid has no social life.  He also needs a prolonged break from Minecraft, rather than opportunity for more of it 
He would be very happy if he could see his friends, even if distanced at school.

EDIT3:  SWMBO is changing decorating ideas again!  I am going to delay running more Cat6 until there is more certainty (which may never happen).  After all, I have to leave enough room on the patch panel for TE.  I think I have to go shovel snow now... 

[Robert763]

The "snow days" of my childhood were far and few. Back then they put chains on the school buses and come hell or high water we went to school. It took a significant snow or a blizzard to cancel school. Today the threat of snow is enough to cancel.

Yes, I am older than dirt. 

We don't have "snow days" as such in the UK even though it sometimes snows enough to bring the whole world to a standstill (Moreso than places where they expect snow, it comes as a shock to the average urban, southern, Brit, causing chaos). When I were a lad if it snowed enough to bring the roads (and commercial buses, we don't have school buses) to a standstill you were expected to walk to school, no excuses. I did, more than once.

Back in the mid-eighties London got hit by unexpected heavy snow overnight. At the time a colleague who passed by my place every morning used to give me a lift into work. He didn't turn up, and after waiting 30 minutes past his expected arrival time I put my proper boots on and set off to walk to work, three odd miles away. I got there and was greeted by a head-office building that normally housed about a 100 people with only perhaps 5 people in it. Big girl's blouses the lot of them!

When I worked for a small airline in Jersey (CI) we had an unexpected snowfall. Snow is rare there. I got into work OK in my little FWD car but there was virtually noboby there. This included pilots. Apparently they didn't know how to drive in the snow or had frozen coolant. I got a telephone and address list of operations and the old crew bus. The bus was a rear engined air cooled VW. I managed to get everyone who was neeed to work. A bit of weight over skinny rear wheels works well in snow.

[Specmaster]

NYC Schools are similar. They rarely shut down since the vast majority of the students walk to school or take mass transit.

My elementary school was damn near 8 miles away on secondary roads. I'd like to say that we were tough enough to walk it, uphill both ways in the snow, but alas didn't happen.

My infant/junior school (ages 5-11) 0.5 miles, my secondary school (ages 12-18) 1.6 miles, both uphill all the way as that's the nature of Brighton or everything would get very wet (slopes from the South Downs to the sea and I lived 100-150yds from the sea).

When you're 8 years old half a mile seems a long way and I was expected to walk it on my own most days. Tell that to most parents nowadays and they'd be horrified "Little Johnny on the streets, on his own?" but the truth is that over time the streets have got safer. The scariest thing I ever encountered on my walks to school was a harmless local man who was an albino (with red eyes) whose daily routine and mine frequently crossed in a railway underpass. The first time I saw him I was genuinely frightened and even years later after finding out what he was and getting used to seeing him regularly some primitive part of my hindbrain still flashed "Danger, different!" at me.

Yep, back then, we could leave your doors unlocked as well, shocking to see just low society has been dragged down in just a handful of decades. I used to cycle for miles and in the summer holidays, I'd cycle to Maldon, Colchester, Clacton, Harlow, Romford and even Southend on Sea with a couple of school pals and think nothing of it.

[Vince]

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

The perhaps non-intuitive thing to think of here is that the transmission line must be free from reflections and properly terminated it will, as long as there are no branches.

I'd do it like this:

Code: [Select]

50Ω - T --------- cable --------T--------cable -------T- 50Ω
      |                         |                     |
     OUT                 counter in                  scope in




Yes, there are branches. Even though I wrote there should be none. Now, thing is they'll work fine if they're kept short, and "short" has a relation to the upper frequency limit of the transmission system; the wider the bandwidth the shorter the branches must be to not create havoc.  This is, by the way, not my idea, it's stolen right off 10Base2, the old thin Ethernet. And RS485-based protocols like DMX work the same, like a lot of other bus type systems. There is a termination in each end, the branches are kept short, and things will work.  Another typical application is analog video, where there often was an input BNC, and a loop output adjacent. Sometimes there was a TERM switch, sometimes one was expected to plug a terminator in the output if not used. The T simply was in the box.

Deux fois esprit d'escalier:

1. The top frequency relation is probably why it worked differently depending on rise time.
2. I don't remember the second until I press "Save"
2bis. Perhaps it is better to put the counter in the end and the scope in the middle.

Thanks for the nice ASCII Art ! 

Looks like a graphical representation of the setup ch_scr suggested.... so I did that.  See pics below.

It's a success. The 10ns pulse looks just as good as it did with my previous setup but now no need for my home made termination any more + the counter now can go up to 25MHz instead of 15MHz ! So better indeed !

Can't really expect it to go higher than 25MHz.. it's the LF input not the RF one ! I don't even remember the spec for the LF input on that counter, but 25MHz seems pretty good to me, happy with that.

[mnementh]

An old school buddy asked me about getting his 80's Marantz ST450 AM/FM tuner fixed. Anyone here know about these old tuners ?

The usual issues with old VFDs, dried out caps, and buttons going flaky.

IIRC, these are analog/VCO tuning with digital display derived from the VCO. Refurb should be a pretty humdrum affair, as long as the tuner string is intact and not gone stiff/flaky.

Flip side of that is analog tuner feature-set, so not a lot of demand; I see a working one on eBay Klumphzinger for 59€ :

   
https://www.ebay-kleinanzeigen.de/s-anzeige/marantz-st-450-hifi-tuner/1993128648-172-16495

hifiengine has UM & SM, but you have to register for a free account to download:

https://www.hifiengine.com/manual_library/marantz/st450.shtml

Cheers,

mnem
 

Thanks mnem. 
I did find the L model SM easily which seems pretty similar and shows these are old school multiple gang variable cap tuners. 
https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Marantz-ST-450-L-Service-Manual.pdf
Apparently it's stuck on one station and buddy that used to fiddle in electronics reckoned the tuner string was still intact so maybe the mechanism is dried out and stuck without enough torque to shift it. 

Alan and I were good buddies as 14yr olds until he moved away and we lost contact until some 20 yrs later when one evening at that same high school at a parent teacher meeting both our older son's were in the came form class as we had been all those years earlier ! 
Alan's done decades of freight forwarding and is a NZ Customs agent so naturally he got all our import business a few years after we'd made contact again when Tautech got going.
Even our Larry Minor has a good relationship with Alan whom arranged to get a 78 LTD coupe back to NZ that he picked up in Texas when he did a 6 mth stint on harvest there. Since Alan has given Larry a pile of earthmoving work on a property he developed a few years back.
Pretty cool to think we've known one another nearly 50 yrs ! 

Oh, if it's stuck on a station then a simple restring is probably all that's required.

The string gets stiff and stretched out and can't keep the correct tension on the wraps at the knob end. Other end is attached fast and kept tension by the usual spring. If you see flaky bits on the string, that's what's happened; the string has reached EOL. 

Correct fix is new string, as once it stretches it'll usually continue to do so at an accelerated rate or break as soon as any tension is put on it... but you can try just adding a loop at the knob. Since this one doesn't have a tuning dial, no worries about it offsetting the pointer.

Otherwise, just check the tuning cap and idler pullies to make sure none of them are froze up/dragging excessively; a little Teflon or graphite dry lube on the bushing pin is usually all that's needed to make them happy again, unless they're gummed up with 50-year-old lithium grease and need to be cleaned.

And good on ya for trying to help a buddy out.

Cheers!

mnem
 

[Vince]

<SNIP>

I'm suprised no one has said this: YOU NEED TO CHECK THE EARTH CONNECTIONS  . Even if the capactors are leaky you would not have got a shock if the units mains earth was intact (all the way back to the supply, it could be a faulty extension lead or badly wired socket).
Even if the capacitors are OK if there is no earth the chassis will be at around 120V AC. This is because the two capacitors act as a AC voltage divider. Not much current due to the low values but enough to feel if you touch it or read on a DMM to ground.
Note that replacement capacitors should be Y type rated for mains use.

Rob I don't understand what you mean ? These old Metrix as you can see on the pictures, have a two pronged power cord.  There is no earth connection to speak of 

The " earth " looking symbol on the schematic refers to chassis ground only. The front/face plate of the instrument is used as a ground plane. So these two caps connect the two mains wire to the enclosure of the instrument...

That's why earlier I was mentioning that I might want to retro-fit a 3 pronged cable with an IEC socket hidden at the back of these units, for extra safety.

Are you sure you have the correct plug and it s complete? Many old appliance connectors had side contacts. See No.8 on this page:
https://www.plugsocketmuseum.nl/PowerCord2.html
The unit is potentally lethal without an earth. You need to change the connetor to an earthed type.

Yep 100% sure ! No earth on that socket, and cable is perfectly period, original cable.

I have 3 different TE pieces from Metrix of that vintage (the RF generator, the Wobuloscope, and a little type 620 LCR bridge). They are all designed the same way, all have the same socket and cable.
Every piece of Metrix of that vintage I have ever seen is the same.

My universal Nixie counter of similar vintage though, is made by Rochar not Metrix, and this one does have a socket with an earth connection. Metrix just didn't use them 

[Ice-Tea]

Solartron 7055 on the bench. Restarts continuously. Also smells something fierce when warming up. So, naturally I dug up my bag of replacement Schaeffners and opened her up. Much to my surprise, the filter is in one piece. But...

[Vince]

Lab V2.0 making : one more step in the right direction today !

Just received.... a lovely rolling chair !

I know, I know... doenst sound like much but trust me... it is a game changer.

Previous chair did not roll, so had to get up even just to get to the soldering iron on the far left, or to get to the big drawer blocks on either side. A pain.
The bench is almost 3.5m long, shelves 2m long, so I had to get up the chair to get to ANY thing, all the time. 

Also, there is no cushion, butt hurt quick.

Also, the bench sits 50mm / 2" higher than standard, because 3.5m is quite long, so had to support the OSB panels that make up the bench, with a couple long wooden beams, 50X150mm cross section, themselves supported at either end by the drawer blocks.
So I was sitting way too low, really not comfortable at all.

So I put a folded blanket on the chair to both provide some cushion and at the same time rise my butt closer to the bench surface a little bit... helps, but still a pain.

ENTERS... this beauuuuutiful rolling chair ! It solves all 3 problems at once ! All for 90 euros delivered to my door, this morning. There were cheaper ones at local stores but they were really shitty, so I ordered that one on-line from a website that sells office stuff. Was discounted, looked good enough, gave it a try.. not disappointed, does the job.

Has seen only maybe an hour of use so far today, but I am already sold, I am in heaven, in love with this thing... doing anything at the bench is now an order of magnitude more pleasurable, it is an invitation to work at the bench and do stuff ! 
Also, the springy action of the pneumatic cylinder helps getting my big butt airborne, so even more comfort  ! 

[Cerebus]

You could go for the self adhesive laminating film that libraries cover the dust jackets of books with. I've books that I covered with the same 30 odd years ago and they are still OK - no yellowing, no delaminating, no getting brittle.

Over here, there is a adhesive plastic film called 'DC-fix'. It is often used to protect heavily used books and also in applications like yours. But I have no idea how widely available it is in the US. Here it is sold at almost every stationery shop. 'Booktac' seems to be a comparable product, else look for 'book protection film'.

Ah good suggestions! Found some on Amazon I'll order a small amount.

If you go down that route and haven't done it before, come back and ask for tips - that stuff is difficult to put on bubble and void free and there's a few non-obvious things you can go to guarantee success.

Yes I would like some tips please, I'm all ears - or eyes in this case ... 

OK. This is for non-porous surfaces which won't be damaged by a little temporary contact with water. You will need:

• Non-porous surface to be covered.
• A reel/sheets of film. I'm assuming that you'll have the type with silicone backing paper. Some types come just on a reel without backing paper, this is much harder to use. Get it with backing paper if you can.
• A squeegee of some sort. The idea type is one like this:
  
  made by 3M. Obviously it's quite easy to make something similar by glueing a bit of felt or velvet around the rounded edge of a piece of plastic or metal. Note the round corners, sharp corners will quickly bring you trouble.
• A spray bottle filled with demineralised water with a very small quantity of detergent in it. Just enough to make it wet surfaces, not enough to make it foam. Ideally use a pure detergent like SDS (Sodium dodecyl sulphate aka sodium lauryl sulphate) but ordinary washing up detergent will do if necessary. It's just that ordinary washing up detergents contain a lot of other crap including a surprising amount of salt.

There are two techniques that you need to make use of:

• A very thin mist of water on the surface to be covered will stop the adhesive on the film sticking to the surface but you can make it stick by pushing the water out with a squeegee. Use this technique for large flat areas, where it would be difficult to get the whole surface to stick both 'at once' and 'without air bubbles'.
  
  Mist the area to be covered.
  
  Lay the film on as carefully and as flat as you can. (One way to do this is to cut a piece to size, peel back the backing paper off one edge for only perhaps an inch, lay it on the surface to be covered, fix the exposed edge with the squeegee working outward from its centre, and then gently lower the film to the surface by evenly pulling the backing paper out.)
  
  Then, with the film laying on top of the thin misting of water, fix the film in place by working outward from the centre (or the fixed edge if you've done it that way) with the squeegee pushing the water towards the edge and eventually out from underneath the film completely. Go slowly, go gently, be careful not to stretch the film as you go (this is one reason for a felt/velvet covered squeegee, it will slide rather than grip and pull the film).
  
  
• The film is slightly elastic. This means that you can hold it in tension very slightly off the surface to be covered and stretch it into place with a squeegee where it will then adhere. You can combine this with a misting of water, but it's not necessary. The trick is to stretch the film as little as possible, so as not to deform it unevenly, but with just enough space to give you "not sticking". Sticking one, or both, edges of the film to a batten can make this easier and more controlled, but you can only do that where it's possible to trim the film in situ when you're finished and can strip off the margins complete with the areas that will have been marred by the batten(s).

Plan, and practice. Think about how the film is going to bend and stretch as it goes on, account for it both in the shape of the piece of film and on how you're going to approach attaching it. If you have any chance to do a throw away practice piece first, do it. In any case, if this is the first time you've used the film, do some practice pieces first, even if they are unlike your first intended 'finished' piece, this stuff needs you to develop a feel for how it will stretch, stick and move.

Work on as small an area as possible at once. If you can use the backing paper to keep a section of film "out of play" while you do one area, do so. The film is very thin, creases easily, and the adhesive is tenacious. If you accidentally touch it down somewhere you don't yet want it to stick it probably will stick, and probably won't be where you wanted it at the end - resulting in creases or air bubbles. Using the backing paper creatively minimises this risk. Also the film loves to stick to itself if you touch two adhesive faces to each other - keep a little tension on the film at all times when it's not protected by the backing paper.

If you do get air bubbles in the finished item, cut a small vent at the centre of the air bubble and, working from the edges to the centre, push the air out of this vent. Use a scalpel or similar very sharp knife to cut the vent, don't use a pin, they raise a little 'pip' of stretched film that is very difficult to press down into invisibility.

This stuff can produce great results, but can also make a real mess if you're less than careful or rush. It's worth the time and care to get a result that doesn't annoy you in the future with a crease or trapped air bubble.

[Cerebus]

EDIT2:  There might be a wee bit of snow by GWN standards coming tomorrow, so someone decided to preemptively close all the schools in the region.  There will not even be online classes, since the school board says they can only do that for COVID reasons.  So, now all that cabling is unnecessary 

Hmm, perhaps there's someone with a heart left, who remembers "snow days" from their own childhood and wasn't such a bastard as to say "Well, now we have all this infrastructure and experience of online schooling from Covid, why don't we use it on snow days?" and just made up an excuse "Do we technically have the power to enforce online schooling on a snow day, or does the legislation only give us that power for public health emergencies? [Knowing grin] Just asking?" .

You make a good point.  I know I would have appreciated a snow day off back in the day.  However, back then all the neighbourhood kids would be out together.

At the moment, the kid has no social life.  He also needs a prolonged break from Minecraft, rather than opportunity for more of it 
He would be very happy if he could see his friends, even if distanced at school.

EDIT3:  SWMBO is changing decorating ideas again!  I am going to delay running more Cat6 until there is more certainty (which may never happen).  After all, I have to leave enough room on the patch panel for TE.  I think I have to go shovel snow now... 

A Norwegian friend of mine from the past told me that when he was a child if his parents had had enough of him around the house in winter they would just slap a pair of skis on him, shove him out of he door and say "Don't come back until tea time". The first time they did this he had never even worn skis before, let alone knew how to ski. (He told me this on a ski holiday in Italy where he was skiing rings around the rest of us.)

[Cerebus]

The "snow days" of my childhood were far and few. Back then they put chains on the school buses and come hell or high water we went to school. It took a significant snow or a blizzard to cancel school. Today the threat of snow is enough to cancel.

Yes, I am older than dirt. 

We don't have "snow days" as such in the UK even though it sometimes snows enough to bring the whole world to a standstill (Moreso than places where they expect snow, it comes as a shock to the average urban, southern, Brit, causing chaos). When I were a lad if it snowed enough to bring the roads (and commercial buses, we don't have school buses) to a standstill you were expected to walk to school, no excuses. I did, more than once.

Back in the mid-eighties London got hit by unexpected heavy snow overnight. At the time a colleague who passed by my place every morning used to give me a lift into work. He didn't turn up, and after waiting 30 minutes past his expected arrival time I put my proper boots on and set off to walk to work, three odd miles away. I got there and was greeted by a head-office building that normally housed about a 100 people with only perhaps 5 people in it. Big girl's blouses the lot of them!

When I worked for a small airline in Jersey (CI) we had an unexpected snowfall. Snow is rare there. I got into work OK in my little FWD car but there was virtually noboby there. This included pilots. Apparently they didn't know how to drive in the snow or had frozen coolant. I got a telephone and address list of operations and the old crew bus. The bus was a rear engined air cooled VW. I managed to get everyone who was neeed to work. A bit of weight over skinny rear wheels works well in snow.

Having been driven around Guernsey I can only say that if the roads on Jersey are similar (single track, winding, with high walls and/or hedges on both sides) then that must have been 'interesting'.

[Bud]

A Norwegian friend of mine from the past told me that when he was a child if his parents had had enough of him around the house in winter they would just slap a pair of skis on him, shove him out of he door and say "Don't come back until tea time")

That made me curious what "tea time" in Norway is ? 

[Neomys Sapiens]

Will add that to my cart list for my next order... in the meantime I can maybe just cobble a hand home made termination with a 50ohms discrete resistor, which won't be perfectly 50ohmsd I guess, bvut close enough to see an improvement. Or a little trimmer to make it perfectly 50ohms...  Yeah I will play with that see what that does 

The important part is that you do terminate in a low impedance. I fully expect you to get a long way towards right even with a 75Ω plug. Think of it as relative; the difference between 1MΩ and 50Ω and between 1MΩ and 75Ω is practically the same (it amounts to 0,25% deviation) . So, 49-51Ω or so will do just fine.

A lot of electronicks is "in the ballpark" style stuff, and then sometimes it is not!  But this is a case where you get almost right even with something that's 50% off in value, because the alternative (not terminating) would be 4 orders of magnitude worse.

Excellent explanation! I support the 75 is "good enough". But, beware! If you keep the T on the generator and terminate transmission lines in both directions - now the generator sees 25 on its output! (Or rather, it would if both sides are terminated into 50 , it will be slightly higher in your case...) Not that it will destroy anything, but you will have an unmatched condition still!
Edit: I might add your experiment is a nice demonstration of such effects 

Ohhh..... boy. So... I don't see how can one solve this problem ? You can buy T adapters to send a signal to several devices inputs, but then you don't have 50R anymore so no good. So why do they even sell Tee ?!     

So how does one do then ? Maybe put a little buffer that takes the generator output, then provides several 50R outputs on which you can hook your various TE inputs ? I guess same principal as a 10MHz amplifier / distributor for 10MHz frequency standard that you want to distribute to all your TE ?

Or can you just, silly me I know.... add a 25R resistor in series  with the output of the generator ? This way the two 50R paths of the scope and counter, making up 25R... plus the 25 discrete resistor... the generator would then see 25 + ( 50 // 50 ) = 50R ?  No ? I know, stupid....

The proper way to do this is to use a Wilkinson divider.

They only work over a limited frequency range. If you can tolerate the power loss, use resistive splitters.

Wilkinson is (a), while I was thinking about (c). Apparently some people refer to such a resistive divider/combiner as 'modified Wilkinson', but that is probably not correct. You can find them easily, most often by MiniCircuits (ZX or ZFRSC types), but also many others. Insertion loss is 6 dB. But here you go: