Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 14549277 times)

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Offline med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37325 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 #37326 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 »
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Offline med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37327 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 AVGresponding

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37328 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
nuqDaq yuch Dapol?
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Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37329 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 bitseekerTopic starter

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37330 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.
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37331 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 »
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Online tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37332 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 #37333 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 #37334 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 #37336 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 #37337 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.  ;)
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Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37338 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

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Offline bitseekerTopic starter

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37339 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)
TEA is the way. | TEA Time channel
 

Offline bitseekerTopic starter

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37340 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.
TEA is the way. | TEA Time channel
 
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Online factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37341 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 #37342 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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Online factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37343 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 bitseekerTopic starter

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37344 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
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Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37345 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 #37346 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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Online factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37347 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 »
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37348 on: August 23, 2019, 10:14:26 pm »
Huh...

https://hackaday.com/2019/08/22/electric-dump-truck-produces-more-energy-than-it-uses/

mnem
*back to house-packing hell*
Very interesting truck but it does operate under very limited set of circumstances, where else do you regularly come across a situation where something climbs to the top of a hill empty but always descends heavily laden where gravity alone provides more enough force to propel the vehicle all the way to its destination, so the power generated is then stored and as a result of the huge payload and the resultant recovered energy as a product of the speed and gravity effect has the unique ability to produce more energy then it uses?
Who let Murphy in?

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Online factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #37349 on: August 23, 2019, 10:26:30 pm »
Just got the 1740A. Appears to have some problems with it. Comes up but not HT. Debug time!  :-+

Hopefully it won't be a circle jerk like my 485 issue has been.  :scared:

Nope was easy-ish.

Bar the hour I just spent on the blower to a provider on a finger pointing misssion (work), we have a victory at least.

Power supply shot. Took the thing to bits (I bloody love 1740A construction) and yanked off the interface board thus disconnecting both vertical and horizontal boards. Discovered 5V was at 8V (fuck!) and -15V was at 1.02V (double fuck). Powered it down. Reading the service manual it looks like the two supplies are related so I had a feel around. Checked pass transistors. Both fine. Checked ESR on all the power supply caps. All good. Checked the LM723 on the -15V rail. Burning hot! Pulled the pass transistor off and jumped the -15V rail with a power supply and bingo it came up and everything works apart from the flood gun illumination (should be easy to debug). Looks like the high 5V rail has done no damage fortunately  :phew:

Patient on the bench (need bigger bench!):



Bingo:



Now to work out what is dead. Hopefully not the LM723 as they are TO-100 canned ones and are a good tenner a go  :--

That's a nice 1740A, but I could have sworn you said you wanted a HP 180 Series scope, there is a 181A north of me but the price is too far north as well.
Anyone buy the faulty 200MHz 1715A that was on a one day auction?

Just found a strip merchant. eBay user goodmeasures is buying old HealthKit stuff up and selling the guts  :--

What happened to the rest of the Heathkit scopes?  :'(

David
 


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