Hi,
I bought this scope in need of repair, and can't find a source of schematics or manuals for it. The trace doesn't sweep, and fades out to nothing shortly after turning the scope on, even with the intensity control all the way up. The screen has some burns in it. I checked the tubes, V130(12AT7) was 47% on emissions, V160(6AN8) was 41%, V704(6AQ5) failed a short test, V701(12AU7) had a 32% gas reading, V602(6BH6) over 100% emission reading, V501(12AU7) gas 34%. I don't know where the different circuit functions are located.

Can anybody help me with this? It appears to be a really neat scope and a work of art inside. I would like to restore it to service.

Thanks,
Bart

For starters, it would be useful to know what tube tester you're using. Some test more stringently than others. Chances are, the scope will work somewhat, with the old tubes in place.

I restored a 310A and wrote a page on my experiences in my book "Tube Testers and Classic Electronic Test Gear." You're right, it's a beautiful little instrument. Unfortunately the manual is quite lengthy and even the schematics alone would be a job to copy. You might try a post to the Tek forum:

http://www.reprise.com/host/tektronix/forum/default.asp

Hi, Alan

Thanks for replying. I'm using a Knight Kit KG600B tester. It tests for emission, shorts, and gas. I tested all the tubes that I had a chart for. There are probably a couple tubes that I don't have a chart for, but I think the odds favor those tubes being good. I'm guessing that I have one or more bad capacitors. I didn't see anything obvious in a visual check.

It has some weird values on some capacitors, unless I read them wrong. One comes to mind with a 6.25 mf value. If that really is the value, would a 4.7 mf work instead?

If I knew what tubes perform the sweep generator function and what could be causing the electron beam to fade away, that might give me some place to start. I did find the Tek Forum and asked for help in finding a schematic or a manual there, but I haven't returned there to see if anyone posted a reply. This is such an active forum and visited by so many knowlegeable people, I had to try here too! Don Black made some mention of working for Tectronix, so that seemed to help the odds here.

Thanks again.
Bart

: For starters, it would be useful to know what tube tester you're using. Some test more stringently than others. Chances are, the scope will work somewhat, with the old tubes in place.

: I restored a 310A and wrote a page on my experiences in my book "Tube Testers and Classic Electronic Test Gear." You're right, it's a beautiful little instrument. Unfortunately the manual is quite lengthy and even the schematics alone would be a job to copy. You might try a post to the Tek forum:

: http://www.reprise.com/host/tektronix/forum/default.asp

:Hi, Alan
:
:Thanks for replying. I'm using a Knight Kit KG600B tester. It tests for emission, shorts, and gas. I tested all the tubes that I had a chart for. There are probably a couple tubes that I don't have a chart for, but I think the odds favor those tubes being good. I'm guessing that I have one or more bad capacitors. I didn't see anything obvious in a visual check.
:
:It has some weird values on some capacitors, unless I read them wrong. One comes to mind with a 6.25 mf value. If that really is the value, would a 4.7 mf work instead?
:
:If I knew what tubes perform the sweep generator function and what could be causing the electron beam to fade away, that might give me some place to start. I did find the Tek Forum and asked for help in finding a schematic or a manual there, but I haven't returned there to see if anyone posted a reply. This is such an active forum and visited by so many knowlegeable people, I had to try here too! Don Black made some mention of working for Tectronix, so that seemed to help the odds here.
:
:Thanks again.
:Bart
:
:: For starters, it would be useful to know what tube tester you're using. Some test more stringently than others. Chances are, the scope will work somewhat, with the old tubes in place.
:
:: I restored a 310A and wrote a page on my experiences in my book "Tube Testers and Classic Electronic Test Gear." You're right, it's a beautiful little instrument. Unfortunately the manual is quite lengthy and even the schematics alone would be a job to copy. You might try a post to the Tek forum:
:
:: http://www.reprise.com/host/tektronix/forum/default.asp
:
:

:Hi, Alan
:
:Thanks for replying. I'm using a Knight Kit KG600B tester. It tests for emission, shorts, and gas. I tested all the tubes that I had a chart for. There are probably a couple tubes that I don't have a chart for, but I think the odds favor those tubes being good. I'm guessing that I have one or more bad capacitors. I didn't see anything obvious in a visual check.
:
:It has some weird values on some capacitors, unless I read them wrong. One comes to mind with a 6.25 mf value. If that really is the value, would a 4.7 mf work instead?
:
:If I knew what tubes perform the sweep generator function and what could be causing the electron beam to fade away, that might give me some place to start. I did find the Tek Forum and asked for help in finding a schematic or a manual there, but I haven't returned there to see if anyone posted a reply. This is such an active forum and visited by so many knowlegeable people, I had to try here too! Don Black made some mention of working for Tectronix, so that seemed to help the odds here.
:
:Thanks again.
:Bart
:
:: For starters, it would be useful to know what tube tester you're using. Some test more stringently than others. Chances are, the scope will work somewhat, with the old tubes in place.
:
:: I restored a 310A and wrote a page on my experiences in my book "Tube Testers and Classic Electronic Test Gear." You're right, it's a beautiful little instrument. Unfortunately the manual is quite lengthy and even the schematics alone would be a job to copy. You might try a post to the Tek forum:
:
:: http://www.reprise.com/host/tektronix/forum/default.asp
:
:

Hi Bart

Check the Horizontal Sweep circuit. The oscillator may be stopping. Low B+ voltage could cause this problem?

Even though this is an older Tektronix scope I wouldn't go changing parts. Most are high quality and some odd values are needed for calibration.

Electrolytic filter caps used in the power supply will dry out and go bad over time.

Norm

: Hi,
: I bought this scope in need of repair, and can't find a source of schematics or manuals for it. The trace doesn't sweep, and fades out to nothing shortly after turning the scope on, even with the intensity control all the way up. The screen has some burns in it. I checked the tubes, V130(12AT7) was 47% on emissions, V160(6AN8) was 41%, V704(6AQ5) failed a short test, V701(12AU7) had a 32% gas reading, V602(6BH6) over 100% emission reading, V501(12AU7) gas 34%. I don't know where the different circuit functions are located.

: Can anybody help me with this? It appears to be a really neat scope and a work of art inside. I would like to restore it to service.

: Thanks,
: Bart

Thank you, Norm. I didn't consider the B+ supply, but I'm not sure what it should be. I was concerned about the odd capacitor values and what would happen if I changed the parts. Since the simplest solution is usually the best, changing the filter capacitors may be all that is needed.

I did finally find a source for a manual, but I don't yet know if it includes a schematic. W7FG Vintage Manuals lists the operating manual. They may let me know pretty soon about the schematic part.

Thanks again, Norm.
Bart

: Hi Bart

: Check the Horizontal Sweep circuit. The oscillator may be stopping. Low B+ voltage could cause this problem?

: Even though this is an older Tektronix scope I wouldn't go changing parts. Most are high quality and some odd values are needed for calibration.

: Electrolytic filter caps used in the power supply will dry out and go bad over time.

: Norm

:

: : Hi,
: : I bought this scope in need of repair, and can't find a source of schematics or manuals for it. The trace doesn't sweep, and fades out to nothing shortly after turning the scope on, even with the intensity control all the way up. The screen has some burns in it. I checked the tubes, V130(12AT7) was 47% on emissions, V160(6AN8) was 41%, V704(6AQ5) failed a short test, V701(12AU7) had a 32% gas reading, V602(6BH6) over 100% emission reading, V501(12AU7) gas 34%. I don't know where the different circuit functions are located.

: : Can anybody help me with this? It appears to be a really neat scope and a work of art inside. I would like to restore it to service.

: : Thanks,
: : Bart