Test Equipment Anonymous (TEA) group therapy thread

[PA0PBZ]

Well that 2445 sure looks good, are they new BNC's or has it just had a sheltered life. I do like a 4 channel scope with cursors and shit but that one has a fan as well and you hate fans? Did you see it working or did they say it was working?

It's a fake 4 channels, notice that there are only 2 Volts/Div knobs.

[SilverSolder]

Unfortunately I really can't get along with linux, and some of the software I use doesn't like it either.

EDIT: The bizarre thing is, I didn't forget or mistype the pw. Further, if I restart the pc, the pw works. Also I have some resolution issues, some apps recognise the 1920x1080, some don't, which causes some odd results...

I had this issue before, and decided to use a fresh SSD and a clean install to try and get rid of it, but it's back right away. I really want to throw the whole fkking lot out the window at this point...

Right now I really don't know what to try next; this issue has followed me across motherboards, HDD/SSDs, video cards. Am I cursed?
 

I gave up on Windows 8.2 after being locked out of a tablet permanently...   it is just bad news.

[Specmaster]

Well that 2445 sure looks good, are they new BNC's or has it just had a sheltered life. I do like a 4 channel scope with cursors and shit but that one has a fan as well and you hate fans? Did you see it working or did they say it was working?

It's a fake 4 channels, notice that there are only 2 Volts/Div knobs.

Yeah, its like my old scope, Iwatzu that 4 channels but the the 3rd and 4th only had 2 settings 500mV and 1V on the input, selected via push buttons, still better than just 2 channels though.

[Cerebus]

I guess I could join in, but not sure if anyone (even the other Brits) will understand my Yorkshire accent   

Ay up! 'Appen we will, 'appen we won't. Thee divna knaa until thee try. 

[bd139]

Ok so stuff review. We'll start with the 3400A. It needs some work before it'll work as expected but no show stoppers. None of the legend on the meter is lost so I reckon I can actually carefully dismantle it and stick the stuff back down again (somehow, TBD) and save it. Oldest date code 1974. I have removed some shielding to take these photos - don't worry it wasn't missing

Paid £10.

Picture time!

Top showing encapsulated transformer and the thermistor bits:



Power supply board. Just slides out for maintenance. Phew.



Meter face. Need to find out how to stop this progression and fix it all back down again.



Side showing filter cans and adjustment pots.



Close up of the thermistor



Front end. Notice the cheeky little nuvistor tube hiding in there. TC401/402 is the chopper amplifer.



Underneath (yes it has feet!)



So plan of attack for this one is:

1. Test all the electrolytic caps ESR and values for potential hand grenades.
2. Swap the mains socket out for something modern and lose the ceramics across the line (will use modern ones instead!)
3. Fire up and see what happens.
4. Fix the meter face somehow.

[bd139]

On to the 2445.

Ok this is a good one. I took it to bits and (a) it doesn't have a schaffner filter (it's a TDK) and (b) there's only one RIFA in it and it's a Y class one with no potential across it and it's not even slightly fizzled. Full inspection took place. The power switch DOES work. The issue is there is a big hole in the base of the case which is where someone shipped it with a 13A plug. I have fixed this (hammered it back out) and the power switch works fine now! The switch bar was jammed on it  . The fan does work absolutely fine in the end. It just had a large dust bunny in it. U800 is good. The whole scope is good actually and I can't find anything wrong with it!!

Paid £70

So the lid wouldn't come off to start with because of the plug dent and another dent. I managed to work it lose then hammered them back out and it's fine now. Slides on and off properly. Obvious guilt here:



Main board. U800 probably needs a heatsink 



Top and power supply



Computah innit. No nasty batteries or Dallas bastards here!



High voltage stuff I'm going to leave alone:



No RIFAs! Entire front end is free of them. The TDK filter will be replaced just to makes sure it doesn't have any hiding in it.



Quick power up and test. All inputs good. No 50 ohm terminations toasted



Quick trigger test on AM signal. Yep all good



Very happy with this scope!



Ok so plan now is to clean it and replace the mains filter. The rest seems healthy so I'm going to leave it until something goes wrong etc. 

Edit: you can't get a scope and not measure some rise time. So here's the HP 3312A's square output into the internal 50 ohm termination of the scope.



Manual quotes 20ns for this so it's looking pretty good.

[AVGresponding]

It looks a bit like it's a layer of lacquer that's peeling up.

I wonder if it can be fixed by using some artists fixative spray and gently pushing it back down with a small soft brush.

After that you'd want a coat of matte or satin lacquer on top

[bd139]

It looks a bit like it's a layer of lacquer that's peeling up.

I wonder if it can be fixed by using some artists fixative spray and gently pushing it back down with a small soft brush.

After that you'd want a coat of matte or satin lacquer on top

Thanks - that's the sort of ideas I'm after. Straight to top of list

[Kosmic]

I have to wonder what was going through the minds of the Solartron engineers when they designed the 7061. While using the same specially selected 1N829A diode as the other meters that they made, they seem to have made no effort to keep air currents and temperature gradients away from the reference.

Here's the poor thing, flapping in the breeze at the rear right of the analogue PCB (D301A).





Unlike the 7075 (which also has the reference diode in an oven), which has air slots in the upper and lower covers, the 7061 is a sealed unit. In operation, there are large temperature differences within the case, mainly from the transformer, which heats up the left rear of the unit considerably. Here's what it looks like to my thermal camera.





All that heat is going to add up to some significant thermally induced air currents inside that case. With the unit tilted upwards on its stand, the air currents are probably even larger.

I have had the 7061 powered on since Friday evening, so it's now had more than a 48 hour warm up. Putting my Weston cell on the meter again showed good short term accuracy (+13μV compared to the calculated voltage), but I saw some +/- 3μV variations over time, which is something that my 7075 with its ovenised reference doesn't exhibit.

The solution is a simple as can be. I took a piece of cotton pad, split it down the middle and enclosed the reference diode inside it.





After letting the meter warm up again, I'm now seeing +/- 300nV variation on the Weston cell's voltage over a 30 minute period.

The 1N829 Zener diode is temp compensated and do not need an oven. TC has been measured when the unit was produced and is compensated on the board (can be changed by soldering / unsoldering some solder bridges). The Solartron 7081 (8.5 digits) also has the ref placed on the board like that with no protection. But in the case of the 7081, there's a temperature sensor on the board used to correct the voltage reference dynamically.

Nevertheless, it’s true that the transformer is getting really hot. I always wonder if it was always like that or this is something that appeared over time ?

In term of noise, on my 7061, I had a lot more success when I readjusted the internal clock. The procedure is described briefly at the end of the maintenance manual.

[tggzzz]

Harwell good stuff: meeting a couple of TEAers and a couple of ex-HPers.

Bad stuff: the punters. Not many of them, unsurprisingly considering the weather.Too many only interested in "oooh I had one of those at work", takings 90% down on last year. I heard that the bloke selling sweets was doing OK.

[bd139]

Harwell good stuff: meeting a couple of TEAers and a couple of ex-HPers.

Bad stuff: the punters. Not many of them, unsurprisingly considering the weather.Too many only interested in "oooh I had one of those at work", takings 90% down on last year. I heard that the bloke selling sweets was doing OK.

I think that's because it was full of cheap bastards like myself  . Also the weather was not good.

[BU508A]

I have to wonder what was going through the minds of the Solartron engineers when they designed the 7061. While using the same specially selected 1N829A diode as the other meters that they made, they seem to have made no effort to keep air currents and temperature gradients away from the reference.

Here's the poor thing, flapping in the breeze at the rear right of the analogue PCB (D301A).



[...]

I have had the 7061 powered on since Friday evening, so it's now had more than a 48 hour warm up. Putting my Weston cell on the meter again showed good short term accuracy (+13μV compared to the calculated voltage), but I saw some +/- 3μV variations over time, which is something that my 7075 with its ovenised reference doesn't exhibit.

The solution is a simple as can be. I took a piece of cotton pad, split it down the middle and enclosed the reference diode inside it.



After letting the meter warm up again, I'm now seeing +/- 300nV variation on the Weston cell's voltage over a 30 minute period.

Have you seen this suspicious-looking solder joint of the 1N829A?

Click on the attached picture.

[med6753]

Bd.....2445 looks good!  If the fan is working and U800 is happy....as it apparently is....LEAVE IT ALONE. Don't heat sink it. Not necessary as long as you don't run it too long outside the case.

[BravoV]

On to the 2445.

...

Main board. U800 probably needs a heatsink 

...

Congrats on the 2445, looks really nice. 

On U800, my personal opinion only ... leave it as is, but unscrew the two nuts as they serve no purpose at all, and may do more harm than good. (subject to debate/argument)

-> My reasoning ...

-> Older alternative one ...

Btw, do not let the scope run without the case on, as the vent holes below will blow air specifically to the U800, without it, it will heat up. Or use big fan blowing the whole A1 board if without the case.

[Mortymore]

@bd139

I think there's a blue filter screen missing.

Congrats for your "new" scope 

EDIT: just now saw the previous page were the filter in on.

[med6753]

Progress....it's proceeding as I planned. No issues so far. Cap in foreground single 120uf/450V. Far right was two 125uf/250V cans in parallel. So single strip with two 125uf/250V in parallel as shown.

The 2 center cans are more complex. They are isolated from the chassis. In other words, the caps are connected between 2 B+ voltages. For example: between +500V and +325V. So I have to be REAL careful to make sure replacements are connected correct polarity or there will be enormous amounts of magic smoke.

[bd139]

@bd139

I think there's a blue filter screen missing.

Congrats for your "new" scope 

It’s there. My phone seems to make it disappear in photos though.

On to the 2445.

...

Main board. U800 probably needs a heatsink 

...

Congrats on the 2445, looks really nice. 

On U800, my personal opinion only ... leave it as is, but unscrew the two nuts as they serve no purpose at all, and may do more harm than good. (subject to debate/argument)

-> My reasoning ...

-> Older alternative one ...

Btw, do not let the scope run without the case on, as the vent holes below will blow air specifically to the U800, without it, it will heat up. Or use big fan blowing the whole A1 board if without the case.

Thanks for the tips. I will make sure I don’t do that 

[BravoV]

Well that 2445 sure looks good, are they new BNC's or has it just had a sheltered life. I do like a 4 channel scope with cursors and shit but that one has a fan as well and you hate fans? Did you see it working or did they say it was working?

It's a fake 4 channels, notice that there are only 2 Volts/Div knobs.

Yep, 1st & 2nd channels are connected to a dedicated and encased metal box that has Tek hybrid chip in it.

While 3rd and 4th channels, are connected to the board with hand soldered dirt cheap carbon type resistors. 


Photo of the input channels, back of the BNC of the 4th at the front, and the 3rd in the background.

[bd139]

Good enough for digital inputs and triggering though 

[mnementh]

I have to wonder what was going through the minds of the Solartron engineers when they designed the 7061. While using the same specially selected 1N829A diode as the other meters that they made, they seem to have made no effort to keep air currents and temperature gradients away from the reference.

Here's the poor thing, flapping in the breeze at the rear right of the analogue PCB (D301A)...      ...The solution is a simple as can be. I took a piece of cotton pad, split it down the middle and enclosed the reference diode inside it.   

After letting the meter warm up again, I'm now seeing +/- 300nV variation on the Weston cell's voltage over a 30 minute period.

No voltnuttery going on here... nope, none at all. Nothing to see here folks; move along, move along...

mnem

[Specmaster]

@bd139, you struck gold there for sure, so it was well worth the trip even in the crappy weather and slow pace because of it. Wishing I'd gone now, but as SWMBO's birthday, I'd have been sleeping in the dog kennel (which we don't have) in the garden tonight for sure 

[bd139]

Bad weather for sleeping in the garden too 

[factory]

Ok so stuff review. We'll start with the 3400A. It needs some work before it'll work as expected but no show stoppers. None of the legend on the meter is lost so I reckon I can actually carefully dismantle it and stick the stuff back down again (somehow, TBD) and save it. Oldest date code 1974. I have removed some shielding to take these photos - don't worry it wasn't missing

Paid £10.

Power supply board. Just slides out for maintenance. Phew.



Close up of the thermistor chopper



So plan of attack for this one is:

2. Swap the mains socket out for something modern and lose the ceramics across the line (will use modern ones instead!)

That's a 1960's 3400A with a newer replacement chopper PCB, you also have the TC (thermocouple) & chopper pics mixed up. I may have a IEC rear panel if you want to swap with that earlier one, assuming it's not already been cut up.

David

P.S. If anyone noticed, I've been absent for quite a while due to a bereavement, over 200 pages behind, not going to able to catch up.

[factory]

On to the 2445.

Ok this is a good one. I took it to bits and (a) it doesn't have a schaffner filter (it's a TDK) and (b) there's only one RIFA in it and it's a Y class one with no potential across it and it's not even slightly fizzled. Full inspection took place. The power switch DOES work. The issue is there is a big hole in the base of the case which is where someone shipped it with a 13A plug. I have fixed this (hammered it back out) and the power switch works fine now! The switch bar was jammed on it  . The fan does work absolutely fine in the end. It just had a large dust bunny in it. U800 is good. The whole scope is good actually and I can't find anything wrong with it!!

Paid £70

Top and power supply



No RIFAs! Entire front end is free of them. The TDK filter will be replaced just to makes sure it doesn't have any hiding in it.

Ok so plan now is to clean it and replace the mains filter. The rest seems healthy so I'm going to leave it until something goes wrong etc. 

I kept the TDK filter in mine, check those silver capacitors in the PSU, most of mine were leaking from the bottom and it wasn't obvious till they were pulled.



David

[grizewald]

The 1N829 Zener diode is temp compensated and do not need an oven. TC has been measured when the unit was produced and is compensated on the board (can be changed by soldering / unsoldering some solder bridges). The Solartron 7081 (8.5 digits) also has the ref placed on the board like that with no protection. But in the case of the 7081, there's a temperature sensor on the board used to correct the voltage reference dynamically.

Nevertheless, it’s true that the transformer is getting really hot. I always wonder if it was always like that or this is something that appeared over time ?

In term of noise, on my 7061, I had a lot more success when I readjusted the internal clock. The procedure is described briefly at the end of the maintenance manual.

I get 2.91V -  2.97V at TP402, so I should be good there.

I know that the Zener current is hand adjusted to match each specific diode to set it to the 0 tempco point, and that's all well and good. What that adjustment can't help is when a temperature differential is created over the diode body or the diode's leads.

The transformer really does get quite warm. With the lid off, I'm measuring over 42°C. Then again, my 7150 gets just as hot, so it's probably quite normal.



I think I'll see if I can get my thermocouple probe in through the earth screw on the back and see what the temperature looks like around the reference area once the meter is closed again and warmed up.

Have you seen this suspicious-looking solder joint of the 1N829A?

It does look a little suspicious - you have eagle eyes! Looking closer, the leads appear not to have been soldered on the top of the board. My assumption is that they hand soldered the reference after the rest of the PCB had been flow soldered and probably used a heat sink on the top of the PCB while they soldered the legs on the bottom side.



Certainly, given the current reasonable accuracy that the meter exhibits, I don't have any reason to believe that there is any problem with the connections to the reference diode.