Yes, it was the hybrid 155-0242-01.
Fastened to its place and everything OK.
A special thanks to Joe Mc Elvenney, G3LLV, who gave me one of those rare specimens!
I just had to re-adjust the bias grid, and will check it again according to the service manual.
I'm just wondering what can be the meaning of "A1 -0.8V ?" displayed on top left of the screen... Have to check in the manual, unless someone knows it...
Many thanks to this community
Regards,
Jose Viana CT1DGN.
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--- In TekScopes@..., "viagioz" <viagioz@...> wrote:
Yesterday envening I've been re-checking VZ OUT and VQ OUT arround DC RESTORER.
The signals in the photos I published are reversed but I updated them.
Signal VQ OUT(waveform 66) is the one which is OK. By setting INTENSITY and
READOUT to mid point and HOLDOFF as well, I can get the same waveform (66) as in
the service manual.
In DC RESTORER, signal 72 is very similar to the manual, except the clamping
levels which depend from VZ OUT.
Signal 65, issued from U950 seems to be really dead:
- Isolating U950 output by dessoldering R1913 and R1920 (in DC RESTORER), VZ OUT
is about 5V not changing with INTENSITY.
- I did not load VZ OUT comming from U950, but I think it is not a current
source (it should vary between +8 and 73V according to Figure 3-9).
- Connecting VZ OUT and VQ OUT with 4K7 resistor, the trace appears and varies
with INTENSITY.
- My last check before removing U950 will be CR987, that supplies U950 thru pins
27 and 28. Anyway, VQ OUT works and supply is the same therefore it may be ok...
Now... is it worth to X-RAY it? Can be the ceramic pad removed from the heatsink
or is it fixed with resin?
I never saw one... yet, but in some manufacturer hybrids the circuitry,
including silicon chips and bounding is visible (Hi-Fi STK power out hybrids). I
gess it is not the case...
It is still a mistery how did it fail during a measurement... and the scope was
in function for few minutes, not really hot...
Regards,
Jose
CT1DGN
--- In TekScopes@..., "Tom Miller" <tmiller@> wrote:
The readout should be set to off, the midpoint, for those two displays. Not sure what effect that will have.
Tom
----- Original Message -----
From: viagioz
To: TekScopes@...
Sent: Wednesday, December 14, 2011 5:26 AM
Subject: [TekScopes] Re: 2465B no trace (cont.¡ì4)
Hi Tom,
Yes, I uploaded 2 photos. They are visible in:
Album: 2465B no trace
Description: Z channel waveforms 65 and 66
(Readout knob is fully counterclockwise, Intensity fully clockwise)
Thanks!
--- In TekScopes@..., "Tom Miller" <tmiller@> wrote:
