J
Joerg Hau
Guest
Hi,
Yet another scope in trouble ...
HP 1222A. Has always been working fine, but recently (after a longer
pause) it suddenly has developed a "sawtooth" baseline.
- periodicity ~9 ms, int'y ~1 graticule
- both channels are equally concerned
- A/B gain setting or grounding does not change amplitude
- both channels can be moved up/down w/o problems
- input signal overlays the "sawtooth"
- sawtooth reacts on trigger (or vice versa ;-)
- sawtooth becomes "steeper" if moved beam is moved to the
lower part of the CRT
Power supplies:
+95 V adjusted, OK
+210 V reads +219.5 V
+12 V reads +14.20 V, -12 V reads -14.25 V (at least symmetrical ;-)
I suspect that the input channels are OK and that the problem is
probably related to the vertical deflection (or sweep?).
Before diving into the circuit ... does that ring a bell ... anybody?
Please feel free to contact me either via the newsgroup, or per direct
mail.
Thanks in advance for any help,
and greetings from Lausanne!
- Joerg
[ xpost to s.e.equipment & s.e.repair, f'up to s.e.e. ]
--
joerg dot hau at swissonline dot ch * Lausanne, Switzerland
http://www.mysunrise.ch/users/joerg.hau/
"All standard disclaimers apply".
remove "nospam." from my address to reply
(this became necessary due to increasing SPAM)
Yet another scope in trouble ...
HP 1222A. Has always been working fine, but recently (after a longer
pause) it suddenly has developed a "sawtooth" baseline.
- periodicity ~9 ms, int'y ~1 graticule
- both channels are equally concerned
- A/B gain setting or grounding does not change amplitude
- both channels can be moved up/down w/o problems
- input signal overlays the "sawtooth"
- sawtooth reacts on trigger (or vice versa ;-)
- sawtooth becomes "steeper" if moved beam is moved to the
lower part of the CRT
Power supplies:
+95 V adjusted, OK
+210 V reads +219.5 V
+12 V reads +14.20 V, -12 V reads -14.25 V (at least symmetrical ;-)
I suspect that the input channels are OK and that the problem is
probably related to the vertical deflection (or sweep?).
Before diving into the circuit ... does that ring a bell ... anybody?
Please feel free to contact me either via the newsgroup, or per direct
mail.
Thanks in advance for any help,
and greetings from Lausanne!
- Joerg
[ xpost to s.e.equipment & s.e.repair, f'up to s.e.e. ]
--
joerg dot hau at swissonline dot ch * Lausanne, Switzerland
http://www.mysunrise.ch/users/joerg.hau/
"All standard disclaimers apply".
remove "nospam." from my address to reply
(this became necessary due to increasing SPAM)