Recently purchased a Tek 2235 (does not have military option). It displays
both traces ok as well as a square wave on both channels. Both traces
respond to the 'A' intensity control, while the 'B' intensity control has no
effect. Has anyone else experienced this problem? Both the 'A' & 'B'
intensity control pots check out ok. Voltage at the base of Q814 varies when
the 'B' pot is turned as well as the output voltage on the emitter of Q814.
Voltages here are correct too. There is no voltage change at the node of
anodes CR818 and CR820 while turning the 'B' pot, but it does change here
when the 'A' intensity pot is turned. I've checked all related
diodes --CR818, CR820, CR805, CR817, CR816, CR680, etc., and related
resistors. Q586 is biased and stays on in "Ch1", "CH2", and "Both"
positions, at least as far as I can tell with the voltmeter. I don't see
any components with visible damage, but there is a place on the board that
is brown from heat around Q254, Q255, Q256 which is the Vertical output to
CRT section. I'm guessing that this is unrelated to the intensity problem.
any help or ideas would be greatly appreciated.

Thanks,
John

KB9WTK

John:

Are you triggering the B sweep before checking out the B intensity control?
The B intensity controls only the delayed B sweep, not the main (A) sweep.
You may know this already and have other hardware problems, but set the B
trigger
to the 'runs after delay' position, then decouple the A and B sweep knobs.
The
delayed sweep will be offset from the main sweep (you can see 4 traces),
and the B intensity should control just the delayed sweep. Usually the
delayed
sweep is a lot fainter than the main sweep because it's effective trigger
rate is low
compared to the sweep rate.

-- Tom, N5EG




"John B .att.net" robotwizard@removethis wrote in message
...
Recently purchased a Tek 2235 (does not have military option). It displays
both traces ok as well as a square wave on both channels. Both traces
respond to the 'A' intensity control, while the 'B' intensity control has
no
effect. Has anyone else experienced this problem? Both the 'A' & 'B'
intensity control pots check out ok. Voltage at the base of Q814 varies
when
the 'B' pot is turned as well as the output voltage on the emitter of
Q814.
Voltages here are correct too. There is no voltage change at the node of
anodes CR818 and CR820 while turning the 'B' pot, but it does change here
when the 'A' intensity pot is turned. I've checked all related
diodes --CR818, CR820, CR805, CR817, CR816, CR680, etc., and related
resistors. Q586 is biased and stays on in "Ch1", "CH2", and "Both"
positions, at least as far as I can tell with the voltmeter. I don't see
any components with visible damage, but there is a place on the board that
is brown from heat around Q254, Q255, Q256 which is the Vertical output to
CRT section. I'm guessing that this is unrelated to the intensity problem.
any help or ideas would be greatly appreciated.

Thanks,
John

KB9WTK

John:

Are you triggering the B sweep before checking out the B intensity control?
The B intensity controls only the delayed B sweep, not the main (A) sweep.
You may know this already and have other hardware problems, but set the B
trigger
to the 'runs after delay' position, then decouple the A and B sweep knobs.
The
delayed sweep will be offset from the main sweep (you can see 4 traces),
and the B intensity should control just the delayed sweep. Usually the
delayed
sweep is a lot fainter than the main sweep because it's effective trigger
rate is low
compared to the sweep rate.

-- Tom, N5EG




"John B .att.net" robotwizard@removethis wrote in message
...
Recently purchased a Tek 2235 (does not have military option). It displays
both traces ok as well as a square wave on both channels. Both traces
respond to the 'A' intensity control, while the 'B' intensity control has
no
effect. Has anyone else experienced this problem? Both the 'A' & 'B'
intensity control pots check out ok. Voltage at the base of Q814 varies
when
the 'B' pot is turned as well as the output voltage on the emitter of
Q814.
Voltages here are correct too. There is no voltage change at the node of
anodes CR818 and CR820 while turning the 'B' pot, but it does change here
when the 'A' intensity pot is turned. I've checked all related
diodes --CR818, CR820, CR805, CR817, CR816, CR680, etc., and related
resistors. Q586 is biased and stays on in "Ch1", "CH2", and "Both"
positions, at least as far as I can tell with the voltmeter. I don't see
any components with visible damage, but there is a place on the board that
is brown from heat around Q254, Q255, Q256 which is the Vertical output to
CRT section. I'm guessing that this is unrelated to the intensity problem.
any help or ideas would be greatly appreciated.

Thanks,
John

KB9WTK

Thanks Tom. you were right, the B sweep wasn't triggered. I'm not used to
this model, and (as you can probably tell) it's been a number of years since
I have even used a scope. Nothing is more frustrating than to chase a
problem that doesn't even exist. :-)

73's,

John


"TOM" wrote in message
...
John:

Are you triggering the B sweep before checking out the B intensity
control?
The B intensity controls only the delayed B sweep, not the main (A) sweep.
You may know this already and have other hardware problems, but set the B
trigger
to the 'runs after delay' position, then decouple the A and B sweep knobs.
The
delayed sweep will be offset from the main sweep (you can see 4 traces),
and the B intensity should control just the delayed sweep. Usually the
delayed
sweep is a lot fainter than the main sweep because it's effective trigger
rate is low
compared to the sweep rate.

-- Tom, N5EG




"John B .att.net" robotwizard@removethis wrote in message
...
Recently purchased a Tek 2235 (does not have military option). It
displays
both traces ok as well as a square wave on both channels. Both traces
respond to the 'A' intensity control, while the 'B' intensity control
has
no
effect. Has anyone else experienced this problem? Both the 'A' & 'B'
intensity control pots check out ok. Voltage at the base of Q814 varies
when
the 'B' pot is turned as well as the output voltage on the emitter of
Q814.
Voltages here are correct too. There is no voltage change at the node of
anodes CR818 and CR820 while turning the 'B' pot, but it does change
here
when the 'A' intensity pot is turned. I've checked all related
diodes --CR818, CR820, CR805, CR817, CR816, CR680, etc., and related
resistors. Q586 is biased and stays on in "Ch1", "CH2", and "Both"
positions, at least as far as I can tell with the voltmeter. I don't
see
any components with visible damage, but there is a place on the board
that
is brown from heat around Q254, Q255, Q256 which is the Vertical output
to
CRT section. I'm guessing that this is unrelated to the intensity
problem.
any help or ideas would be greatly appreciated.

Thanks,
John

KB9WTK

Thanks Tom. you were right, the B sweep wasn't triggered. I'm not used to
this model, and (as you can probably tell) it's been a number of years since
I have even used a scope. Nothing is more frustrating than to chase a
problem that doesn't even exist. :-)

73's,

John


"TOM" wrote in message
...
John:

Are you triggering the B sweep before checking out the B intensity
control?
The B intensity controls only the delayed B sweep, not the main (A) sweep.
You may know this already and have other hardware problems, but set the B
trigger
to the 'runs after delay' position, then decouple the A and B sweep knobs.
The
delayed sweep will be offset from the main sweep (you can see 4 traces),
and the B intensity should control just the delayed sweep. Usually the
delayed
sweep is a lot fainter than the main sweep because it's effective trigger
rate is low
compared to the sweep rate.

-- Tom, N5EG




"John B .att.net" robotwizard@removethis wrote in message
...
Recently purchased a Tek 2235 (does not have military option). It
displays
both traces ok as well as a square wave on both channels. Both traces
respond to the 'A' intensity control, while the 'B' intensity control
has
no
effect. Has anyone else experienced this problem? Both the 'A' & 'B'
intensity control pots check out ok. Voltage at the base of Q814 varies
when
the 'B' pot is turned as well as the output voltage on the emitter of
Q814.
Voltages here are correct too. There is no voltage change at the node of
anodes CR818 and CR820 while turning the 'B' pot, but it does change
here
when the 'A' intensity pot is turned. I've checked all related
diodes --CR818, CR820, CR805, CR817, CR816, CR680, etc., and related
resistors. Q586 is biased and stays on in "Ch1", "CH2", and "Both"
positions, at least as far as I can tell with the voltmeter. I don't
see
any components with visible damage, but there is a place on the board
that
is brown from heat around Q254, Q255, Q256 which is the Vertical output
to
CRT section. I'm guessing that this is unrelated to the intensity
problem.
any help or ideas would be greatly appreciated.

Thanks,
John

KB9WTK