Restoring Sony DXC-1820P cameras, suggestions

[platux]

Dear all,

I've been collecting professional video cameras from the 70s to 90s for quite some time now. I love their design, construction, build quality and the organic image look and quality they provide. You cannot believe how people born in the digital era I deal with like them, from all points of view, and ask those camera to me for video productions. Analog video reinassance at the corner? Hope so!
I like to restore all the equipment I have, aesthetically and functionally, but my experience with tube cameras and electronics in general is limited. I hope you guys who have a lot, from what I've read in the forum, can give me some advice.

So I have these two Sony DXC-1820P cameras (single 2/3" SMF Saticon tube, early 80's, ABO) coming from different sources, which exhibit the same issue:

After the camera is turned on and still "cold" everything is fine, the image is stable, but after 1 minute or so the image start to slightly shaking vertically AND flickering
If the camera is shut down and re-started the issue persist. it gets worse as the camera is left on. then if shut down and left off for some hours the issue disappears.

See the video output from the camera here (file can be downloaded at its full quality). notice the vertical and signal intensity jitter:

https://drive.google.com/file/d/1IP6-cUHt_Kuis4S1JLV9w96Hi6EIG18j/view?usp=drive_link


So I´ve spent quite some nights investigating and probing, I have the schematics (here), and checked the following:

- signal coming out from the saticon tube: it already jitters in intensity and time as the image, so I discarded issues in the processing board. must be something in earlier stages

- camera power is stable, tried with different power supplies, and also added a low pass filter to the power input
- vertical and horizontal deflection signals: OK
- vertical and horizontal deflection sawtooths: OK, perfectly synched with HD and VD signals, no jitter etc.
- beam focus circuit: seems OK, stable voltage at the coil entrance, also substituted the high-power transistors who drive coil current, issue persist.
- 5V and -5V for the focus coil seem stable (pending substituting last high power transistor)

so my suspects start to focus on the high-voltage circuits for the tube that drive the various grids:
- K discharge circuit (although its input signal is stable)
- G1, G2 voltage etc.
but I did not check all of that yet, as I'm quite hesitant
Also I'm not imaging an unstable voltage in the grids might cause a vertical jittering (?)

In your opinion and experience, any clue on which area the issue might be in? is this a common type of fault?

Any suggestion appreciated, thanks in advance

[Alex KL-1]

Welcome to the VK!
Possibly someone here had experience with these cameras.

[jhalphen]

Hi to all,
Hi Platux,

watched your video several times.
downloaded (heavy!) SM, 26Mb.
not a Sony Trinicon expert, but a few suggestions.

H/V sizes do not seem to vary.

When you say video level varies straight at the Trinicon pickup tube,
did you measure at the preamp output (schematic of preamp photo #2)
or directly at the Trinicon's Target electrodes? (photo #1)

Video level at the target is in hundreds of microvolt/millivolt range.
Any bad ground at the faceplate or noisy preamp (look at the FET amp) can induce signal fluctuations.

just suggestions until a Sony camera expert comes along....

You have a PAL camera, correct? could try asking on UK-VRR forum, lots of ex-Broadcast experts there.
Appropriate sub-forum (TV & video) :
https://www.vintage-radio.net/forum/...splay.php?f=37

Best Regards
jhalphen
Paris/France

[old_tv_nut]

I'm not convinced there is really vertical jitter in the .mov playback, but perhaps video coding artifacts as the signal level changes abruptly. Do you see vertical jitter when viewing directly on an analog monitor?

Beyond that, I do not know enough to point to a specific cause, but since the problem occurs after the camera warms up, I would suggest using freeze spray to try to find a sensitive component.

[platux]

Welcome to the VK!

Thanks Alex!

When you say video level varies straight at the Trinicon pickup tube,
did you measure at the preamp output (schematic of preamp photo #2)
or directly at the Trinicon's Target electrodes? (photo #1)

Good spot, jhalphen.. I measured it at the preamp output (photo 2), not at the target. I'll definitely check out the pre-amplifier stage. thanks for the suggestion and for pinpointing that forum, and yes it´s a PAL camera

Beyond that, I do not know enough to point to a specific cause, but since the problem occurs after the camera warms up, I would suggest using freeze spray to try to find a sensitive component.

what a trick! never thought of that, thanks old_tv_nut. the file preview from google is heavily compressed but in the almost lossless downloadable .mov they are clearer, and yes I observed them in the non compressed video capture and in the viewfinder too, and heavier than those in that video

[ARC Tech-109]

While I couldn't download and watch the posted video I'd say the jitter might be mains leaking past the power supply from bad capacitors. Do keep in mind this camera was 1970s vintage so bad electrolytic capacitors are a strong possibility and this is where I'd start. As the old_TV_nut suggested some freeze spray or keyboard duster in a can sprayed lightly might help narrow down the problems.

[platux]

Hi Arc, I'm aware of the electrolytic caps issue, they are the elephant in the room :\ I saw caps in the main camera power supply module (9V, 9.5V) and also some high capacity, high voltage ones around the high-voltage transformer for the grid, and were of my concern
not that you mentioned them, I see 9 and 9.5v also feed the PA, the K discharge circuit and the high-voltage transformer so might be the single root cause for the two issues..
thanks for the suggestion, do you think there a way to test them without desoldering?

for the video download, once you click on the google drive link and the video preview opens, there is an icon on the top right part of the page , an arrow down, you should be able to get it from there

[platux]

btw related with internal power supply modules, have some you got any idea of what POWER OSC CONT IN line and attached circuit might be for? (in the attached picture)