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/#msg3496502
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 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'.
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.
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?" .
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 ?
50Ω - T --------- cable --------T--------cable -------T- 50Ω
| | |
OUT counter in scope in
(...)
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
(...)
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
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.
(...)
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.
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.
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.
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/#msg3496502Beware potential buyers: the serial number of the unit posted on eBay is the same as the one that BU508A links to above!!! (001120)
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.
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!
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.
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.
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 !
<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.
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 ...
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...
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.
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")
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.