Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 1823799 times)

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Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37325 on: August 23, 2019, 02:53:36 pm »
Wasn't rectifier. They all just tested good. Also it powers up through them fine. I've desoldered them for rework but this appears to have burned up due to a bad solder joint or connector pin or two. Looking at replacement Molex KK 394 headers now and some horrid looking rework
Yep, I had that same problem with mine, fortunately the donor had a good transformer and connector. The header I was able to clean up with some fine emery paper and then a thin  coating of solder to build up the lost material and all was good then.

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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37326 on: August 23, 2019, 03:19:43 pm »
Done. Everything agrees with your readings including the distorted sine wave at the output of U740. On to that tunnel diode.

Good.

With the 2.5 division 1kHz sinewave and trigger level roughly centered, u740.9 looks like this... Ignore the intensity variation, but note the 1 division gaps in the vertical dimension; they are due to the tunnel diode nonlinearity. If you don't see those, then the triggering won't be working correctly - could be the TD biassing (follow the manual procedure) or u780 outputs or another fault in that region.

BTW, if you do chuck it out the window please make sure it is in a box with my name on it, and there's a waiting UPS van :)

I'm getting a solid distorted waveform with no gaps. I did try changing the tunnel diode with one from a 465 but it's a different P/N and there was no change so for now I'm assuming CR751 is OK. (I reinstalled the original). So more troubleshooting.
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37327 on: August 23, 2019, 04:11:15 pm »
Done. Everything agrees with your readings including the distorted sine wave at the output of U740. On to that tunnel diode.

Good.

With the 2.5 division 1kHz sinewave and trigger level roughly centered, u740.9 looks like this... Ignore the intensity variation, but note the 1 division gaps in the vertical dimension; they are due to the tunnel diode nonlinearity. If you don't see those, then the triggering won't be working correctly - could be the TD biassing (follow the manual procedure) or u780 outputs or another fault in that region.

BTW, if you do chuck it out the window please make sure it is in a box with my name on it, and there's a waiting UPS van :)

I'm getting a solid distorted waveform with no gaps. I did try changing the tunnel diode with one from a 465 but it's a different P/N and there was no change so for now I'm assuming CR751 is OK. (I reinstalled the original). So more troubleshooting.

I didn't have the gain turned up high enough. Here's the waveform at tunnel diode CR751. it appears to be working properly but still no trigger lock.

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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37328 on: August 23, 2019, 04:20:35 pm »
I just pulled together my Taxes for last year. I spent almost $200 just on probes/test leads and stuff to make test leads/patch cables. Another $300 on meters. And $900 on wrenches and power tools. 
mnem
Amatuer !
I spent much more on just one scope !  :P

True, true... but I was SUPPOSED TO BE hoeing out/reducing/liberating my crap for the move, not gathering more. That 12ga silicone wire is EFFING BIG & EFFING HEAVY!!!  :-DD


      
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2314755/#msg2314755

Not ONLY did I commit THAT indiscretion, but ALL OF THIS     AND THIS     and these         were back then too.    :scared:

I'm beginning to suspect that maybe... JUST MAYBE... I was subconsciously self-sabotaging. A little.   :-DD

mnem
And we wont speak of THIS little 40 Kilo transgression:  "  818193-0   *Scene of the Crime Linky* "  But ONLY because it happened THIS year...  :palm:



« Last Edit: August 23, 2019, 04:58:35 pm by mnementh »
 

Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37329 on: August 23, 2019, 04:39:28 pm »
Now that I've determined with a certain level of confidence that the "front end" of the A Trigger circuit is OK up thru CR751 I now find myself pushing up against U780 again. I've been over that ground for the past 2 weeks and can't determine why the damn trigger light is stuck on. So before I totally lose it and do something brash and stupid I'm putting this 485 aside. I'm on vacation all next week (painting Lady Copper's deck) and when I return I'll determine what I'm going to do. Strong thought process right now is a total "cop out" and buy a 485 junker and just swap out the Trigger board and be done with it. This 485 didn't cost me a lot of cash so it may be worth in the end and I'll have a parts mule. But for now I'm just plain pissed off and want nothing else to do with it.  |O
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Offline ThickPhilM

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37330 on: August 23, 2019, 05:04:15 pm »
I just pulled together my Taxes for last year. I spent almost $200 just on probes/test leads and stuff to make test leads/patch cables. Another $300 on meters. And $900 on wrenches and power tools. 
mnem
Amatuer !
I spent much more on just one scope !  :P

I believe a truer measure would be TEA expenditure as a proportion of income  ;D
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Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37331 on: August 23, 2019, 05:22:31 pm »
Just for med: I've found this guy with a Tek 485 and he has built a wooden front cover for it. Very nice!





His website:

https://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/485.html

Edit:

Main paige:  https://www.amplifier.cd/index.html
« Last Edit: August 23, 2019, 05:29:09 pm by BU508A »
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Offline bitseeker

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37332 on: August 23, 2019, 05:46:48 pm »
Wow! Now, that's a nice cover. 8) Looks like it belongs on med's bench. Would fit in nicely.
I TEA.
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37333 on: August 23, 2019, 06:00:36 pm »
I know, right? Totes giving me a complex after all my work on that 454 cover... :palm:   

I just pulled together my Taxes for last year. I spent almost $200 just on probes/test leads and stuff to make test leads/patch cables. Another $300 on meters. And $900 on wrenches and power tools. 
mnem
Amatuer !
I spent much more on just one scope !  :P

I believe a truer measure would be TEA expenditure as a proportion of income  ;D



mnem
 |O


« Last Edit: August 23, 2019, 06:42:13 pm by mnementh »
 

Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37334 on: August 23, 2019, 06:14:15 pm »
Now that I've determined with a certain level of confidence that the "front end" of the A Trigger circuit is OK up thru CR751 I now find myself pushing up against U780 again.

The front end does look fine, but there are TDs and other stuff between cr751 and u780. Have you set or changed the bias trimpots for those TDs?

One problem at this stage is that there are feedback loops from u780 to the TDs, e.g. via q768 q778 and similar.

Here's a couple more images. Timebase 2ms/div, 100Hz (N.B.!) sinewave input. Note DC coupled, with 0V at the bottom of the screen. The picture at 1V/div is the "out TD" TP, the one with 2V/div is the "arm TD" TP. The amplitudes are constant, but the relative timings of the various steps depend on the input frequency, the timebase, and the holdoff (set in the normal fully ccw position).

Note that the various voltage levels are a function of whether q768 and q778 are conducting or not. I'd look closely at all the voltages around there (inc q802 etc).
« Last Edit: August 23, 2019, 06:20:01 pm by tggzzz »
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37335 on: August 23, 2019, 06:16:25 pm »
Just found a strip merchant. eBay user goodmeasures is buying old HealthKit stuff up and selling the guts  :--
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37336 on: August 23, 2019, 06:47:08 pm »
Taking the HP 1740A off to its own thread here: https://www.eevblog.com/forum/testgear/hp-1740a-power-supply-burn-up/

A certain D. Jones did a video about a 1740 where the rectifier was faulty.
Nope, that was 2 videos that Dave did, I did a link to them a while ago because he also used about 5 meters with the min/max feature on them because he was power rails go down at odd times. Can never have too many meters  >:D >:D
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Offline mnementh

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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37338 on: August 23, 2019, 07:09:06 pm »
Taking the HP 1740A off to its own thread here: https://www.eevblog.com/forum/testgear/hp-1740a-power-supply-burn-up/

A certain D. Jones did a video about a 1740 where the rectifier was faulty.
Nope, that was 2 videos that Dave did, I did a link to them a while ago because he also used about 5 meters with the min/max feature on them because he was power rails go down at odd times. Can never have too many meters  >:D >:D

Indeed and he's right there.

Quick HP porn. HP power supplies testing HP power supply. This is the TEA life...  :-+

 
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Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37339 on: August 23, 2019, 07:52:36 pm »
I just pulled together my Taxes for last year. I spent almost $200 just on probes/test leads and stuff to make test leads/patch cables. Another $300 on meters. And $900 on wrenches and power tools. 
mnem
Amatuer !
I spent much more on just one scope !  :P

I believe a truer measure would be TEA expenditure as a proportion of income  ;D
Declared income.  ;)
Avid Rabid Hobbyist
 

Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37340 on: August 23, 2019, 07:57:53 pm »
Thanks for your answer.  :)
Yes, the knob is made of Bakelite and I found one in the US. Shipping costs are really a PITA.

https://www.ebay.com/itm/123832283457


Is that the one you ordered for your 3460A? As it's nearly double the size of the original and is usually found as the main range selector on the VTVM's.

David

P.S. Here are the modifications for the H04-3460A version, they added 11 pages to the inside cover of the 3460A manual.

Argh! those damned Inch units!  |O

My knob arrived today. Damned imperial units.  |O    When will you guys use proper SI units?  :box:   :-DD

“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 

Offline bitseeker

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37341 on: August 23, 2019, 09:35:04 pm »
I know, right? Totes giving me a complex after all my work on that 454 cover... :palm:   

Whacha mean? That 454 cover is mine, mine, all mine. 'Ain't no one gettin' that off my bench. 8)
I TEA.
 

Offline bitseeker

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37342 on: August 23, 2019, 09:38:21 pm »
My knob arrived today. Damned imperial units.  |O    When will you guys use proper SI units?  :box:   :-DD



Where's the fun in that? :-DD

Nice knobs.
I TEA.
 
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Offline factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37343 on: August 23, 2019, 09:41:30 pm »
Thanks for your answer.  :)
Yes, the knob is made of Bakelite and I found one in the US. Shipping costs are really a PITA.

https://www.ebay.com/itm/123832283457


Is that the one you ordered for your 3460A? As it's nearly double the size of the original and is usually found as the main range selector on the VTVM's.

David

P.S. Here are the modifications for the H04-3460A version, they added 11 pages to the inside cover of the 3460A manual.

Argh! those damned Inch units!  |O

My knob arrived today. Damned imperial units.  |O    When will you guys use proper SI units?  :box:   :-DD



You just need to find a nice VTVM or similar that needs one of those.  ;D

David
 
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37344 on: August 23, 2019, 09:42:47 pm »
My knob arrived today. Damned imperial units.  |O    When will you guys use proper SI units?  :box:   :-DD



Hahaha that went full Mars Climate Orbiter  :-DD
 
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Offline factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37345 on: August 23, 2019, 09:51:01 pm »
Anyone interested in the older brother to the K20-5280A?  :)
818385-0

There is one on the favourite wallet draining site at the moment in the US.
5280A eBay auction: #254336971401

David
 

Offline bitseeker

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37346 on: August 23, 2019, 09:51:19 pm »
My knob arrived today. Damned imperial units.  |O    When will you guys use proper SI units?  :box:   :-DD



You just need to find a nice VTVM or similar that needs one of those.  ;D

Perfect TEA response, David. +1
I TEA.
 

Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37347 on: August 23, 2019, 09:54:03 pm »
What did med say? Bunch of comedians here ....  :-DD
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 

Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37348 on: August 23, 2019, 10:01:09 pm »
You just need to find a nice VTVM or similar that needs one of those.  ;D

Something like this?



Naa, I'm a VTVM-snob.  8)
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 
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Offline factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37349 on: August 23, 2019, 10:07:38 pm »
You just need to find a nice VTVM or similar that needs one of those.  ;D

Something like this?



Naa, I'm a VTVM-snob.  8)

That would do nicely apart from not needing a knob, it's a HP 400 series, I have a 400H and a pair of 400D's one of which was given to me when I bought a 410B locally (only bidder).  ;)

David
« Last Edit: August 23, 2019, 10:11:00 pm by factory »
 


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