Test Equipment Anonymous (TEA) group therapy thread

[mansaxel]

...more that the street value of a working ST450 means you can't afford to spend a lot of time trying to resurrect one that's got major problems. Better to shotgun recap a working one and cut your losses. 

Oh, if I were a person making a living from repairing stuff, yes, why, absolutely!

Now, this is a labour of love, because our receiver has History and therefore needs more care.  With that in mind, I've seen working ones  on the Bay for about 750USD, so there's some difference there too.

[Vince]

Yeah but the scope is 50R terminated so I didn't think that putting 1Meg in  // with the counter, would make that much of a difference.. 1Meg // with 50R is still pretty much 50R 

Played with rise times. That did it, was interesting.

Since the beginning the pusle generator was set to its fastest rise time, 5ns.

So what I did was increase the puls width until the 1Meg input would regsiter. It happened with a pulse width of 27ns.

Then I backed off a little, 26ns, so the counter would not register anymore.

Then I started increasing the rise time (and fall time equally)  to see how / if it would have an impact on the shape of the waveform, and it the counter would behave any differently.

That was success.

I increased rise time very progressively, in 0.1ns increments. At 7.2ns the counter started flickering, was picking up some pulse.. and at 7.4ns, it was able to read reliably, was stable.

The shape of the signal however is barely changed to thje naked eye.. but clearly the counter does see the difference !
It was like clock work : redude pulse width by one ns : doesn't count anymore. Increase by 1ns.. hey presto works again. Same with rise time. 7.4ns works solidly, 7.2 it's unstable, 7.0ns no counting at all.

It's fun being to control pulse width and rise times, accurately, and see how the counter reacts while looking at the waveform on the scope 

Yes, but every cable is a transmission line. The question is: where is the T-piece? If you have the T-piece on generator or scope, the cable between generator and scope is terminated (by scope) but the other end is "flapping in the breeze". If that is the case, put the T-Piece on the counter: Now the whole line from generator with the counter in the middle is terminated by the scope on the other end.

Ah thanks yes I was starting to wonder about that... beginner here... I am in a new territory here... now that I have fancy cables and adapters, I am leaving the "cobble any piece of wire and banana together until you can display "some" signal... to " you have got all the proper cables and adapters now, so it's about to get the PROPER signal, rather than just "some" signal " ! 

As can bee seen in my pics, I put a ' Y ' splitter at the generator output. One coax cable going to the scope, 50R termination because it offers that possibility, and another cable from the generator to the counter 1Meg input. OK so I need to add a 50R termination at the counter to see if that improves things, which it probably will ! 

I have a bucket load of 75R termination but not a single 50R one ! Oh boy how come I didn't think of adding that to my Farnell order the other day when I ordered all the cables and adapters ! 

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 

[mansaxel]

...DAB...

but the audio quality could be debatable.

Indeed. DAB, being a channel-multiplex (designed to fit into an E1 PDH channel, by the way) rather than a dedicated transmitter per channel, has a fixed cost per multiplex, and some leeway in bit rate available for programs inside that multiplex. Therefore, the logic is that one wants as many programs as possible inside one multiplex, to recuperate costs. This will then happen at the expense of bitrate, which means that programs like BBC Radio 4 (IIRC) are mono 96Kbit. Somewhere around 256Kbits the sound quality for the ancient codec system used in DAB will be bearable.

Debatable indeed.

[capt bullshot]

On the Bench In The Kitchen Tonight: Drying 3-Year-Old Filament


Before I go spending money I don't have to spare, I decided to take a try at drying this old filament out and seeing if it can be made serviceable again. Much to my delight, the convection oven I fixed last month actually has a setting for 100°F/40°C, so I've been running them for ~5 hours now stacked with soda caps as spacers while I go over the Tornado and reassemble it.

Let's see what happens...

mnem
 

So I read your post despite of the coioring - to confirm you didn't put the filament into a microwave oven (that was my impression by the photo) 

[mansaxel]

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.

[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?" .

[ch_scr]

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 

[capt bullshot]

So... maybe that means it's normal and my unit works just fine ?!  Being a pulse generator, it's not meant / expected to have any kind of stability in frequency when used in continuous mode ?
Must be that... OK cool, so if it's normal, that's one less TE that needs fixing, great ! 

My guess is: The Metrix pulse gen is of a similar kind as the HP 8116 (mentioned somewhere later) - analog electronics controlled by a fancy digital frontend instead of analog knobs and buttons. So it kind of cheats on you: Showing digital "precision" while the accuracy and resolution of the signal generation is similar to some older analog equipment. And after reading a later post from you: To me it looks just like you found one of these borderline cases, when the digital settings try to do something the analog part can't do really good.

[med6753]

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?" .

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. 

[Cubdriver]

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?" .

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. 

Hell, here they now cancel school if it gets too COLD!  Can't have the poor little ones getting chilly!   

-Pat

[med6753]

Hell, here they now cancel school if it gets too COLD!  Can't have the poor little ones getting chilly!   

-Pat

Haven't seen that level of stupidity here.......yet. 

[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!

[med6753]

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. 

[tautech]

Flip side of that is analog tuner feature-set, so not a lot of demand...

The Marantz FM tuners of old aren't bad. If the sound and the ability to dig signals out of noise (while dealing with deafening commercial stations a bit too close) counts for something, they clearly are worth the job.  Here, we've just revived the Model 4230 Quad-receiver my father bought back in 1976, but now in Middle Boy's room, together with the AR-6 loudspeakers that were part of the same original deal, and the Thorens TD166 Mk V I bought in the 90s.  Very Classy.

There are a few scale illumination lamps out, and the scale is some 350-500KHz off, pots are a bit scratchy, all as can be expected from a 45yo consumer device, albeit a very high quality one.

I have calculated and made a simple dipole which gives full signal level on all relevant stations, so I'm guessing the FM tuner is basically OK. (but we've got excellent RF reception here, on a hill, practically line-of-sight to the main Nacka transmitter. OTOH, I can get the regional FM stations from all around lake Mälaren with my circular dipole that's feeding the rest of the FM reception units at home)

Service manual has been downloaded, and schematic of course was supplied with the unit so I now have a few reasons to learn to use all the measurement things I have.

Well, no... my point was not that they were a bad tuner; more that the street value of a working ST450 means one can't afford to spend a LOT of time trying to resurrect one that's got major problems. Better to shotgun recap a working one and cut your losses. 

mnem
 

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. 

[xrunner]

Advice request

The original set-up procedures sticker on the top of the Boonton 4220 is and has been tearing over the years. What kind of protective "sticker" or covering can I put over it to prevent further damage (not clear package tape please   )?

[Cerebus]

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.

[McBryce]

https://youtu.be/31kgOCo2WhA   Hmmm... it sure does like to sing while it works, doesn't it...? 

mnem
 

I recently updated the controller board on my 3D printer. It now uses a Creality 4.2.7 board which has TMC2225 motor drivers: https://creality3d.shop/products/creality3d-upgrade-silent-4-2-7-1-1-5-mainboard-for-ender-3-ender-3-pro-ender-5-3d-printer
The printer went from being a "singer" to being incredibly quiet.

McBryce.

Yeah, I've had this printer for 4 years; a lot has changed in 3DP since I last had hands on it. Both my newer printers have Trinamic drivers; the difference in noise and finished surface quality is pretty amazing. OTOH, as this is now a 3rd printer, and will likely be only used where I need its large build volume, not a lot of motivation to fuck with it as it is working quite nicely for a CR-10 clone of its generation. 

Most likely once I get a really rigid bench/table/crate to set it up on, I'll put a 24" x 24" flagstone under it and ladder bars for the top frame and call it good.

Maybe upgrade to a kit of these for it (tho not likely for a while at $20 per each) :



https://www.cnckitchen.com/blog/bondtech-cht-high-flow-nozzle-reviewed

Thanks for enabling my addiction, ch_scr...

mnem

I can confirm that putting the printer on a rigid table (which I did last year) made a visible difference to the print quality and moving the printer away from the door (which caused a rush of cold air over the printer every time I came in to check it) also had a noticable positive effect. The other thing that I under-estimated at the start was how often and exact I re-leveled the bed. I now do it before each print.

McBryce.

McBryce.

[Robert763]

What are ΩF?

Insilation reesistance per Farad. Foe  given construction the insultion resitnce is inversely proportional to the capacitance.
So for 1000 ΩF 1uF would be 1 GΩ. 10uF would be 100 MΩ.

[Vince]

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....

[Cerebus]

Advice request

The original set-up procedures sticker on the top of the Boonton 4220 is and has been tearing over the years. What kind of protective "sticker" or covering can I put over it to prevent further damage (not clear package tape please   )?

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. 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.

[tautech]

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 same 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 ! 

[ch_scr]

(...)
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 

[Neomys Sapiens]

Advice request

The original set-up procedures sticker on the top of the Boonton 4220 is and has been tearing over the years. What kind of protective "sticker" or covering can I put over it to prevent further damage (not clear package tape please   )?

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'.

[Cerebus]

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....

You need the terminating impedances to match the impedance of the cable for the magic to happen in each case. You can't fix the fact that the termination impedance is what it is, you can ameliorate things by driving from as low an impedance as possible, calculating what's happening, and adjusting your understanding of what readings mean in light of that. You can't achieve a perfect match throughout the system with 'T's with one impedance of cable unless you add passive splitters/impedance matchers.

[Robert763]

<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.