Tektronix 2335, no trace, no beam

[Bob Kelly]

Hi all,

I just bought a Tektronix 2335 oscilloscope, one minute working, the
next minute the trace is gone. The beam finder does not work. nothing
works. However I do see a flash of a blurry beam when I first turn it
on, but that's it. When opened I see small resistor is burned open
just to the left of q114 off the emitter on the vert out/HV power pcb.
I can't tell what the value is and I don't have any schematics. The
big question is this: What else is gone and why? I don't suppose
anybody has the schematic for this board?? (same as 2336 scope)

Please help if you have ANY ideas!!

Bob
email: [email protected]
To email remove NOSPAM

 

[Len]

Hi all,

I just bought a Tektronix 2335 oscilloscope, one minute working, the
next minute the trace is gone. The beam finder does not work. nothing
works. However I do see a flash of a blurry beam when I first turn it
on, but that's it. When opened I see small resistor is burned open
just to the left of q114 off the emitter on the vert out/HV power pcb.
I can't tell what the value is and I don't have any schematics. The
big question is this: What else is gone and why? I don't suppose
anybody has the schematic for this board?? (same as 2336 scope)

Please help if you have ANY ideas!!

Bob
email: [email protected]
To email remove NOSPAM

Bob,
I believe the resistor you are referring to is R113, 1.6k. If you still
need the print, reply to the group and I will email you a scan.

Len Johnson

 

[Bob Kelly]

Yes that is the correct resistor, however replacing it doesn't seem to
help. It just burns up again. I pulled Q114 and Q115 and they check
out ok. Even during the burn-up I get no trace. Everything else seems
to look good. I do have the schematic thanks to a good samaritan,
although I don't have the part list, so I can't tell what the
transistors are exactly. (can tell pnp npn no trouble) Does anybody
have any ideas?? see attached pdf. (I hope attachments are ok)
Thanks Len!!
I'll take a scan of the part list if you have it.

Bob

 

[Bob Kelly]

Yes that is the correct resistor, however replacing it doesn't seem to
help. It just burns up again. I pulled Q114 and Q115 and they check
out ok. Even during the burn-up I get no trace. Everything else seems
to look good. I do have the schematic thanks to a good samaritan,
although I don't have the part list, so I can't tell what the
transistors are exactly. (can tell pnp npn no trouble) Does anybody
have any ideas?? see attached pdf. (I hope attachments are ok)
Thanks Len!!
I'll take a scan of the part list if you have it.

Bob