Test Equipment Anonymous (TEA) group therapy thread

[factory]

Mystery TE time, just pulled this board after noticing an expired tant  , my web search has drawn a blank on the BBC Metrawatt V-Modul block and the Datel AM 490-2C IC.
Some electrolytic capacitors on another board are past it too.

Edit: why does search work better after I post?  The Datel is apparently a chopper stabilized op-amp.

David

Whether it helps or not idk, but in this case BBC will not be British Broadcasting Corporation, and instead will be Brown, Boveri & Cie, now ASEA Brown Boveri (ABB)...

After working on train electrics/electronics for many years, I'm  very familiar with both BBC & ABB, some of the units were made in the years after the merger are a mix of both brands.
But in this case the web is suggesting the
BBC/ABB Metrawatt brand ended up with Gossen.

David

[m k]

Somewhere should be a collection of merger treeviews.

[factory]

Think I've got it fixed, multiple shorted tantalums across power rails again. 

The board seems to be for a 0 to 3000.00mV function, of the mystery device, I'm wondering if it's used in something else, as there are parts that were removed for use in this device.





I didn't have a 1.5uF tant beads in stock, a 0.47 & 1uF went in, the yellow STC 1uF promptly went tits up. 
It got cut out of circuit, +/- 15V rails were now working, but not for long, another blue tant expired quickly (without smoke), I'm thinking 35V tants across the unregulated 25V rails are maybe too low.



At this point I got fed up with the tants and fitted some 4.7uF 50V electrolytics in place of the lot, much better. 



While I was in there I checked the rest of the capacitors and replaced a few tired ones on the other board, this board is part of the remote control for the 300V output.





David

[tautech]

Think I've got it fixed, multiple shorted tantalums across power rails again. 



I didn't have a 1.5uF tant beads in stock, a 0.47 & 1uF went in, the yellow STC 1uF promptly went tits up. 
It got cut out of circuit, +/- 15V rails were now working, but not for long, another blue tant expired quickly (without smoke), I'm thinking 35V tants across the unregulated 25V rails are maybe too low.

Hell yeah !
50V ratings for those and really all the old ones should be replaced with modern tants that are more reliable.

[factory]

Voltage de-rating is more important, modern tants are just as unreliable if you don't de-rate, YMMV.

In this case 50V tants were not available from my stock and I didn't know the expected voltages before replacing the first dead 1.5uF at 35V, which someone else smoked before I acquired it. The brown 0.47uF at 35V is still fine. The 4.7uF Nichicon caps were left over from the Tek 24xx series scope repairs. There are no more tants in this device.



David

[Robert763]

TE incoming!
Bought a bench thermometer on ebay last night. Only £28 including shipping. Doesn't seem a great bargain until you know it's an ASL F25. Dual channel Platinum tesistance, 0.001 degree resolution and 0.025 degree accuracy. And it has two probes. Update when it arrives....

[tggzzz]

... 0.001 degree resolution and 0.025 degree accuracy ...

Now you'll have to test that claim 

[factory]

I've had a delivery from France yesterday, the HP 10525A logic probe from Vince. 

Today I've had a closer look at it and opened it up, first thing I notice is the over-voltage protection Zeners are a bit cooked, thankfully they went short circuit and have prevented further damage.









For some unknown reason the two diodes fitted are different, one is a 1902-0049 (6.19V), but the other is a 1902-0025 (10V), the slightly older one in the pdf from a week ago has a pair of 1902-0056, the 1973/74 parts price list states this part is 23.7V  , must be a mistake somewhere. 

I've put a pair of 1902-0049 in, next problem is the lamp being blown, it's smaller than the one I had to hand, but I was able to connect it in parallel and confirm the probe is functioning fine. 





David

[abeyer]

So I talked myself out of buying a Fluke 760A this afternoon, despite it being a good deal... Told myself it's just too big and heavy to keep around for something I don't really have any real need for. Now I'm having second thoughts. Convince me I did right! 

[TERRA Operative]

You should buy it.

[Peter_O]

+1. Space consumption does not qualify as an argument.   

[Robert763]

What about structural collapse of the building? 

[wkb]

Bah humbug! Properly designed T&M equipment is a structurally sound substitute for a building!

[K0ELB]

Heartbreak:




This is from my “new to me” Tektronix 585. Worst part is, it’s P2 phosphor, one of my favorites.  :'(

[m k]

Dang.

Luckily it's almost the summer and you have the roadtrip to come.

[Robert763]

... 0.001 degree resolution and 0.025 degree accuracy ...

Now you'll have to test that claim 

I'll compare it to my Comark 3001 which is 0.010 degree accuracy and a couple of standard resistors ....

[Robert763]

The F25 Thermometer arrived and all looks good. Need to do some detailed testing though.
It uses an AC (400Hz) bridge circuit with a Vishay 100 Ohm 0.01% hermetic (HC45/U crystal can) resistor as a 0 degree C reference. 

[factory]

Did you take any pictures of the insides? Can't imagine there are any others on the forum.

Mouser delivered a few parts yesterday, some capacitors for some Astec computer PSUs and the lamps for the HP 10525A logic probe.
Last week I didn't have the manual and was working from the circuit diagram in the patent, but I found out the power consumption was listed in the catalog at 75mA, without a working lamp it was drawing 12mA from 5V, nearest available lamp was a 5V 60mA, a bit more digging through the later probe manuals and there was a note of a type 2140-0016, this crossed to a CM683, a 5V 60mA lamp.

And here are the new lamps, first one out of the pack was a disappointment, as it was too big to fit down the tip assembly, but the next one was fine. 



Tonight I see the notice that KO4BB is back online after an outage, the 10525A manual can be found there and it confirmed I got the correct Zener diodes at 6.19V and the correct lamp. 

Here it is back together, the missing tip was a standard part, I've borrowed one from the 3406A probe kit, will need to make a clear plastic sleeve to cover the lamp at some point in the future.



David

[Vince]

Wow thanks for all the hard work you put into little guy, he must love you so much by now ! 

Incredible for the probe tip ! I thought it missing would be a show stopper and condemn little guy to the trash... and in the end it was a standard part, who would have thought !! 

The tolerance on anything with a glass envelope is rather..wild. Like that Nik-c tube on my Rochar DVM that just won't fit at all inside the tube bracket...... or like you here, light bulbs that won't !
Luckily small light bulbs you can buy lots of, for cheap... so you can just pick one that fits.

Thanks for your work !

[CalibrationGuy]

Could not help myself. Gotta stop doing this...

OK, drumroll please!

See pic.

TomG.

[shakalnokturn]

Could not help myself. Gotta stop doing this...

OK, drumroll please!

See pic.

TomG.

Volt nut alert!

I have frequency counters with less digits 
If only I had the budget for that level of nuttery... Nothing has made it past the 6.5 digit limit here, the price curve is kinda exponential.
I'd have to flip 500 to 1k basic handhled DMM's to be able to afford even a used model of that dark matter meter, then they hardly show-up used anyway.

[CalibrationGuy]

Could not help myself. Gotta stop doing this...

OK, drumroll please!

See pic.

TomG.

Volt nut alert!

I have frequency counters with less digits 
If only I had the budget for that level of nuttery... Nothing has made it past the 6.5 digit limit here, the price curve is kinda exponential.
I'd have to flip 500 to 1k basic handhled DMM's to be able to afford even a used model of that dark matter meter, then they hardly show-up used anyway.

Yes, 10k used is a bit much, but I own a calibration lab, so I tell myself that we need another one!

TomG.

[McBryce]

Could not help myself. Gotta stop doing this...

OK, drumroll please!

See pic.

TomG.

For a moment I thought I was having a heart attack, but it was actually just my wallet cramping up and hurting when I looked at that picture.

McBryce.

[Wolfgang]

Same sad story here:

https://electronicprojectsforfun.wordpress.com/finally-i-was-caught-in-a-tea-rabbit-hole/

But still, its the one and only Forget the Flukes ...

[factory]

Same sad story here:

https://electronicprojectsforfun.wordpress.com/finally-i-was-caught-in-a-tea-rabbit-hole/

But still, its the one and only Forget the Flukes ...

I'm guessing a time machine was involved, to find those 20 year old Keysight DMMs. 

Keysight DMMs are really top class, in my opínion. I have never seen one fail, either, in about 20 years.

David