Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 1938290 times)

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Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25900 on: February 21, 2019, 05:10:42 pm »
OK. I managed to stop pulling my hair out long enough to accomplish something. The circuitry that, in the manual, is labeled 'calibrator' is completely absent. With that little fact figured out i was able to test the voltages; -9, +76.25, -75 and +183 as opposed to -12.6, +100, -100, and +248. Welp looks like i have a project that may or may not be put as a repair thread.
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25901 on: February 21, 2019, 05:23:41 pm »
OK. I managed to stop pulling my hair out long enough to accomplish something. The circuitry that, in the manual, is labeled 'calibrator' is completely absent. With that little fact figured out i was able to test the voltages; -9, +76.25, -75 and +183 as opposed to -12.6, +100, -100, and +248. Welp looks like i have a project that may or may not be put as a repair thread.

Wow, your power supply is low across the board. I'm surprised the fuse isn't blowing. You sure the fuse is right size? Don't be surprised if it isn't. And I'll bet the power transformer is getting hotter than hell.
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25902 on: February 21, 2019, 05:31:10 pm »
Interesting. Looking at the schematic I reckon there's a wonky cap somewhere. The supplies are all independent and independently fused (unlike tek ones!) so shouldn't be terrible to track down.

I want one now  :-DD
 

Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25903 on: February 21, 2019, 05:41:39 pm »
Interesting. Looking at the schematic I reckon there's a wonky cap somewhere. The supplies are all independent and independently fused (unlike tek ones!) so shouldn't be terrible to track down.

I want one now  :-DD

I'm betting that the caps that i cannot figure out how to get to are duff. Just how the hell ARE you meant to get at those infernal things i wonder... anyone got ideas?
A hopeless addict (and slave) to TEA and a firm believer that high frequency is little more than modern hoodoo.
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25904 on: February 21, 2019, 05:48:30 pm »
Have you seen the film innerspace? :-DD

More seriously it sounds like a strip and rebuild job  :--

If it’s any consolation I’ve seen worse. Telequipment were pretty terrible. I had to split the entire scope in half to get at the power supply.   :palm:

Edit: found post. https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1564258/#msg1564258
« Last Edit: February 21, 2019, 05:51:37 pm by bd139 »
 

Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25905 on: February 21, 2019, 05:53:31 pm »
Interesting. Looking at the schematic I reckon there's a wonky cap somewhere. The supplies are all independent and independently fused (unlike tek ones!) so shouldn't be terrible to track down.

I want one now  :-DD

I'm betting that the caps that i cannot figure out how to get to are duff. Just how the hell ARE you meant to get at those infernal things i wonder... anyone got ideas?

Didn't realize the supplies were independently fused. How difficult would be to pull the CRT? Seems that would at least give you some room to get in there.
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25906 on: February 21, 2019, 05:58:14 pm »
Have you seen the film innerspace? :-DD

More seriously it sounds like a strip and rebuild job  :--

If it’s any consolation I’ve seen worse. Telequipment were pretty terrible. I had to split the entire scope in half to get at the power supply.   :palm:

Edit: found post. https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1564258/#msg1564258

And isn't that the one where you said "fuck it" and gave up on it?  :-// :-DD
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Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25907 on: February 21, 2019, 05:59:59 pm »
Didn't realize the supplies were independently fused. How difficult would be to pull the CRT? Seems that would at least give you some room to get in there.

Not difficult, easy even but it would be finicky and dangerous as hell.
A hopeless addict (and slave) to TEA and a firm believer that high frequency is little more than modern hoodoo.
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25908 on: February 21, 2019, 06:04:29 pm »
Have you seen the film innerspace? :-DD

More seriously it sounds like a strip and rebuild job  :--

If it’s any consolation I’ve seen worse. Telequipment were pretty terrible. I had to split the entire scope in half to get at the power supply.   :palm:

Edit: found post. https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1564258/#msg1564258

And isn't that the one where you said "fuck it" and gave up on it?  :-// :-DD

Yeah I nabbed the CRT out of it to fix someone else’s Tek 7603. That’s working now which is a good win I suppose.
 

Online Mr. Scram

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25909 on: February 21, 2019, 06:05:15 pm »
I also find that WD40 (not the switch cleaner) is pretty good and is gentle on other serfaces surfaces, at least it has been for me. Spray it on and leave it for a few minutes and it will normally lift with ease.
I've looked into this and apparently WD40 is helpful when you want to remove silk screening from plastic. That's exactly what I'm trying to prevent, so in this case it isn't the best option.
 

Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25910 on: February 21, 2019, 06:06:23 pm »
Didn't realize the supplies were independently fused. How difficult would be to pull the CRT? Seems that would at least give you some room to get in there.

Not difficult, easy even but it would be finicky and dangerous as hell.

Don't be afraid of CRT's. Just make sure the HV is totally discharged and work slowly and carefully and don't knock it. I've done it and I'm sometimes clumsy as hell.  :-DD

https://www.eevblog.com/forum/testgear/teardown-bk-2120-scope/msg822920/#msg822920
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Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25911 on: February 21, 2019, 06:09:30 pm »
Didn't realize the supplies were independently fused. How difficult would be to pull the CRT? Seems that would at least give you some room to get in there.

Not difficult, easy even but it would be finicky and dangerous as hell.

Don't be afraid of CRT's. Just make sure the HV is totally discharged and work slowly and carefully and don't knock it. I've done it and I'm sometimes clumsy as hell.  :-DD

https://www.eevblog.com/forum/testgear/teardown-bk-2120-scope/msg822920/#msg822920

Its the same mounting system as is in my heathkit O-12, i'm just more scared of HP in this area than i am heathkit.  :-DD
A hopeless addict (and slave) to TEA and a firm believer that high frequency is little more than modern hoodoo.
 

Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25912 on: February 21, 2019, 06:12:35 pm »
Didn't realize the supplies were independently fused. How difficult would be to pull the CRT? Seems that would at least give you some room to get in there.

Not difficult, easy even but it would be finicky and dangerous as hell.

Don't be afraid of CRT's. Just make sure the HV is totally discharged and work slowly and carefully and don't knock it. I've done it and I'm sometimes clumsy as hell.  :-DD

https://www.eevblog.com/forum/testgear/teardown-bk-2120-scope/msg822920/#msg822920

Its the same mounting system as is in my heathkit O-12, i'm just more scared of HP in this area than i am heathkit.  :-DD

I'm familiar with Heath O-12. It's the same as my Father's O-10. Getting THAT CRT out is dirt simple. If the HP is the same what the hell are you waiting for??  :-// :-DD :-DD :-DD 
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Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25913 on: February 21, 2019, 06:16:03 pm »
I'm familiar with Heath O-12. It's the same as my Father's O-10. Getting THAT CRT out is dirt simple. If the HP is the same what the hell are you waiting for??  :-// :-DD :-DD :-DD
Good question. Giving it an hour to let the voltage drop would make a good excuse.
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25914 on: February 21, 2019, 06:24:38 pm »
I'm familiar with Heath O-12. It's the same as my Father's O-10. Getting THAT CRT out is dirt simple. If the HP is the same what the hell are you waiting for??  :-// :-DD :-DD :-DD
Good question. Giving it an hour to let the voltage drop would make a good excuse.

Carefully pull the CRT base socket and use an insulated shorting stick from all the CRT pins to ground. Then do the same to those connections which appear to be to the deflection plates. I assume this CRT does NOT have an anode cap to the bell of the CRT, correct? If it does you have to discharge that puppy too. Then you are good to go.  :-+
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Offline GregDunn

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25915 on: February 21, 2019, 06:40:28 pm »
I also find that WD40 (not the switch cleaner) is pretty good and is gentle on other serfaces surfaces, at least it has been for me. Spray it on and leave it for a few minutes and it will normally lift with ease.
I've looked into this and apparently WD40 is helpful when you want to remove silk screening from plastic. That's exactly what I'm trying to prevent, so in this case it isn't the best option.

When I went to clean up my L&N resistor decade, I pulled the top and knobs and let them sit in lukewarm water with some mild dish soap for about 5 minutes.  The dirt and grime completely dissolved - along with the century-old paint.   :P  So even the mildest cleaner may have unintended consequences.

On a happier note, I finally got round to modding my DE-5000 to accept a decent pair of Kelvin clips.  Fully guarded, and they cal out just fine; the high impedance measurements are probably better than with the original alligator clips, just because I sluiced a gram of leftover flux off the board when making the changes.   :o

 

Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25916 on: February 21, 2019, 06:44:56 pm »
Carefully pull the CRT base socket and use an insulated shorting stick from all the CRT pins to ground. Then do the same to those connections which appear to be to the deflection plates. I assume this CRT does NOT have an anode cap to the bell of the CRT, correct? If it does you have to discharge that puppy too. Then you are good to go.  :-+
I'm going to sound like a suicidal idiot who doesn't normally work with crts, i assure you its only an idiot with a death wish that doesn't normally work with CRTs.

There was one connection to the side of the tube, cafeully removed that, then 6 pins on it's side, carefully removed each one of those then popped the socket cap off. The CRT then, once lined up, gently popped out. Nothing broken and i aint dead, i was more worried i was going to break something if i'm being honest. Now i got the shield to get out of my way and i'm in.


Like the heathkit, except this one actually has shield and a few more wires.

EDIT; oh, well that wasn't strictly necessary. I figured out how to get at the damn capacitors with the shield still in place.
« Last Edit: February 21, 2019, 06:49:33 pm by neo »
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25917 on: February 21, 2019, 06:56:29 pm »
Carefully pull the CRT base socket and use an insulated shorting stick from all the CRT pins to ground. Then do the same to those connections which appear to be to the deflection plates. I assume this CRT does NOT have an anode cap to the bell of the CRT, correct? If it does you have to discharge that puppy too. Then you are good to go.  :-+
I'm going to sound like a suicidal idiot who doesn't normally work with crts, i assure you its only an idiot with a death wish that doesn't normally work with CRTs.

There was one connection to the side of the tube, cafeully removed that, then 6 pins on it's side, carefully removed each one of those then popped the socket cap off. The CRT then, once lined up, gently popped out. Nothing broken and i aint dead, i was more worried i was going to break something if i'm being honest. Now i got the shield to get out of my way and i'm in.


Like the heathkit, except this one actually has shield and a few more wires.

EDIT; oh, well that wasn't strictly necessary. I figured out how to get at the damn capacitors with the shield still in place.

Good boy!  :-+ :-+ :-DD
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Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25918 on: February 21, 2019, 07:04:19 pm »
Good boy!

The way i see it, i took the crt out and got my head around how they think then the capacitors were easy. That gives me a valid reason for removing the crt i think.  :-DD
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Online Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25919 on: February 21, 2019, 07:07:45 pm »
That’s quite a nice bit of reuse that  :-+

Added to project list.
Made mine from an old PC PSU case as well. Another good source of incandescent light bulbs is eBay, got mine there.
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25920 on: February 21, 2019, 07:28:56 pm »
Good boy!

The way i see it, i took the crt out and got my head around how they think then the capacitors were easy. That gives me a valid reason for removing the crt i think.  :-DD

ya' pulled the crt?  ok....but remember to be very very careful when handling that hv ribbon.  after you mess with them they are liable to start arcing.  some say they have had luck with cleaning them with ipa.  in my experience that just made them worse.  bending them too much can cause them to delaminate (they are getting pretty brittle),  and then you are screwed.

and remember "the +100 volt supply is independent and provides a reference voltage for the -100 volt supply.  the +248 and -12.6 volt supplies are dependent on the -100v supply for reference voltages".  start with the +100 then work on the -100 then the others.

good luck and keep one hand in your pocket when probing.   better yet.....connect the probes when powered down and stand back to observe when powering up.
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Offline nixiefreqq

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25921 on: February 21, 2019, 07:33:39 pm »
Good boy!

The way i see it, i took the crt out and got my head around how they think then the capacitors were easy. That gives me a valid reason for removing the crt i think.  :-DD

ya' pulled the crt?  ok....but remember to be very very careful when handling that hv ribbon.  after you mess with them they are liable to start arcing.  some say they have had luck with cleaning them with ipa.  in my experience that just made them worse.  bending them too much can cause them to delaminate (they are getting pretty brittle),  and then you are screwed.

and remember "the +100 volt supply is independent and provides a reference voltage for the -100 volt supply.  the +248 and -12.6 volt supplies are dependent on the -100v supply for reference voltages".  start with the +100 then work on the -100 then the others.

good luck and keep one hand in your pocket when probing.   better yet.....connect the probes when powered down and stand back to observe when powering up.


the good news is none of the resistors in the ps had the really toasty scorched looked that a lot of them develop.  typically they get pretty warm even when all the ps voltages are normal.
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Offline neo

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25922 on: February 21, 2019, 07:37:00 pm »
ya' pulled the crt?  ok....but remember to be very very careful when handling that hv ribbon.  after you mess with them they are liable to start arcing.  some say they have had luck with cleaning them with ipa.  in my experience that just made them worse.  bending them too much can cause them to delaminate (they are getting pretty brittle),  and then you are screwed.

and remember "the +100 volt supply is independent and provides a reference voltage for the -100 volt supply.  the +248 and -12.6 volt supplies are dependent on the -100v supply for reference voltages".  start with the +100 then work on the -100 then the others.

good luck and keep one hand in your pocket when probing.   better yet.....connect the probes when powered down and stand back to observe when powering up.

A summary of what i've done and intend to do, with reasons.
Opened it, checked the voltages and decided i'd start with the capacitors.
Couldn't figure out what magic they used to make that cap board stay in place.
Can't think of anything else to do so in desperation i pull the CRT, their idea not mine.
With the knowledge gained into how they think i suddenly figured out the capacitor boards mount.
What i'm going to do;
Replace that 3 wire ribbon because it needs to go. If it didn't before it does now.
Replace all the main capacitors just to be safe.
Reinstall CRT.
Carefully power up, pray i didn't screw too much up and check the voltages again if needed.
Go from there dependent upon results.
A hopeless addict (and slave) to TEA and a firm believer that high frequency is little more than modern hoodoo.
 

Offline nixiefreqq

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25923 on: February 21, 2019, 07:42:32 pm »
ya' pulled the crt?  ok....but remember to be very very careful when handling that hv ribbon.  after you mess with them they are liable to start arcing.  some say they have had luck with cleaning them with ipa.  in my experience that just made them worse.  bending them too much can cause them to delaminate (they are getting pretty brittle),  and then you are screwed.

and remember "the +100 volt supply is independent and provides a reference voltage for the -100 volt supply.  the +248 and -12.6 volt supplies are dependent on the -100v supply for reference voltages".  start with the +100 then work on the -100 then the others.

good luck and keep one hand in your pocket when probing.   better yet.....connect the probes when powered down and stand back to observe when powering up.

A summary of what i've done and intend to do, with reasons.
Opened it, checked the voltages and decided i'd start with the capacitors.
Couldn't figure out what magic they used to make that cap board stay in place.
Can't think of anything else to do so in desperation i pull the CRT, their idea not mine.
With the knowledge gained into how they think i suddenly figured out the capacitor boards mount.
What i'm going to do;
Replace that 3 wire ribbon because it needs to go. If it didn't before it does now.
Replace all the main capacitors just to be safe.
Reinstall CRT.
Carefully power up, pray i didn't screw too much up and check the voltages again if needed.
Go from there dependent upon results.


that sounds like a pretty good plan.


if you get all 4 lv ps voltages fixed and it still does not play.......check cr26 and then those transistors in the horizontal driver board. 
"free range primate"
 

Online Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #25924 on: February 21, 2019, 07:52:28 pm »
To get at the one under the relay, just pull the relay from its socket, hook on to the cap legs with grabber probes and measure away, the relay could be plugged back in while the grabs are on the cap if required?

Edit, you could also if needed cut one leg , measure the cap and ESR  while there and then resolder the leg again.
« Last Edit: February 21, 2019, 07:55:03 pm by Specmaster »
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