I've tried all your suggestions. But for this last one ...there is a problem.
That is, there are big blanking pulses on both cathode and grid. This means that the voltages measured on a voltmeter are not necessarily representative of
what they are during the active scan time.

I will retry this evening with the two blanking pulses disabled. And I will
look at the two pulses with a scope and see if they drift.

Add me to the list of working block camera owners!
 

I've had my CRV59 camera working for at least 15 years now and it seems to be about the same today as it was when rebuilt that long ago. I agree about it possibly needing the rear mosaic lamp. I've never had the picture fade out on me as you describe as the bias lamp(s) on this camera do work. (It's been a quite a while since I've opened the camera up so I've forgotten whether or not there's just one or two inside!)

I revamped the scans circuits to standard def sweep rates so I could use a regular broadcast monitor for viewing. No problems there. The camera power supply is solid state.

Ralph, is yours a different camera from the ones I mentioned a couple of posts ago?
How long does yours take to stabilize from turn-on?

My lamp does work.

But old_tv_nut's suggestion did the trick, with my new angle.

Removing the blanking pulses generated a "correct" grid bias of -20 to -22 volts.
The picture faded when I adjusted the control, turned right on, to -26 volts.
When the picture faded with the control all the way up the
picture faded at .... -26 volts! I had not realized how much the blanking pulses
caused a measurement problem.

I will investigate the divider chain drift further, with all pulses sent to it
disabled. If I can't figure out what's the problem and fix it,
replacing a couple of resistors with Zeners should do the trick. That's unless
the blanking pulses cause problems by drifting.

Off to dinner.

Same type of camera as yours
 

I checked on the camera and I can't find the original ID tag that was riveted on, but I did find what I think is RCA Camden's inspection tag; see pix attached. Interesting that they didn't call it a camera, rather a "Conversion Unit!"

The schematic I followed in my work is exactly the same as the excerpt you showed earlier, so we're both talking about the same model of camera.

This camera is definitely not one of those you listed earlier.

Fan added
 

One more thing: I added a square fan to the top via a replacement slide (instead of the tube access slide.) I did this after noticing how much heat there was inside the case when the original slide was in place. Considering how many tubes there are in such a small container, it might be helpful for longevity to do the same with yours even if it doesn't reduce the "blackouts" you've mentioned.

The problem is discovered and apparently fixed. I already had bought the
necessary parts.

The key, and it was absolutely necessary, was to disconnect C134 and C107,
the caps that send the vertical and horizontal blanking pulses to the grid-cathode circuit.
This done, all the voltages measured with my 200MOhm
probe made sense.

C109 and especially C108, the oil HV filter caps, were leaking badly: C108
was at best (cold) 25 MOhm, worse when warm. I replaced them with
0.47 uF 1600V film caps. The voltage on the iconoscope went too high
so I added a 1 MOhm 1 watt resistor in series with R125 (330K). The new
caps are larger than the originals, so I mounted them on a terminal strip
under the chassis. (They are polypropylene high reliability ones, and are very large.)

Its now making better images, the problem being mainly horizontal streaking
after bright or dark areas. Its quite stable.

I will now check C116, C117, and C118, the other oil caps. Only C116
is critical: if leaky it would kill V104. Well, no, I looked at the schematic
and it would just raise the cathode current. But I checked and its OK.

And I'm now the owner of two good iconoscopes.

I tried this gizmo the first time since I moved a year ago and it worked fine the first try.

Does anybody have a military or RCA manual for it? I need it for my collection.

Can we get any updated pictures of it operating?

certainly
The format of this camera is currently 262 @ 60p

Note that it is looking through a window screen.

https://www.videokarma.org/attachmen...1&d=1748712652

https://www.videokarma.org/attachmen...1&d=1748712652

I put the camera outdoors on my patio and get a better picture, attached at higher resolution.

This is the very best it can do. I should add that while its a clear sky and sunny, the sky is white due to
high altitude smoke from soviet canuckistan.


Doug

https://www.videokarma.org/attachmen...1&d=1748716523

thanks

I still need a manual for this gizmo. Web searches are futile.

While running through a test of all my old tubized gear I
tested this thing. It was not working as well as last year
(i.e previous post). I never was able to get it working well with adjustments, even
in the brief periods of sunshine. It did work.

I spent four days trying to diagnose the problem with no success.
It made pictures but the shading was bad, and the horizontal
scan was too wide, i.e. the actual picture area was too narrow on the monitor.

I'm was never able to find what had gone wrong. All voltages and waveforms looked OK per the schematic.
I never got a reply to my query in the post a year ago for a real military manual. So I have no reference for most voltages.

Then the cathode resistor in thge 6L6 horizontal output stage started
smoking. I quickly measured the voltage across it and it was as normal, 17
volts AC ... there is no known correct DC value, but it was rather high.
A NOS 6L6 changed nothing. The resistor and its bypass measured as per the schematic. A new resistor didn't get hot
and nothing changed ... so I have no idea the cause, and must attribute it to a loose flake of
solder shorting something, that fell out while doing the checks.

The HV was only -700 volts, rather low (iconosocpe rating is 1250V), and
the waveform of the horizontal drive at the yoke was wrong at the first part of the scan. I fixed this somewhat by
tweeking the resistor-capacitor series pair across the yoke ( 470 ohm, .02uF) ( it was a small tweek)
and removing the 1 Meg resistor I had installed in series with the
HV rectifier diode. I tried adjusting the width control, but the best setting was at the low inductance end. So I
gave up and added a 2.56 mH "RF choke" across the width coil. This fixed those problems and got 800 volts HV-,
a passable value. It still took a LOT of tweeking to get the values of the two signal
few-pF ceramic trimmer caps set right.

Another problem is that the sync pulses are a larger fraction of the
period than NTSC specifies (its actually 262@60p), because it was designed for 40 Hz, not 60. The overall shape of the
vertical scan was a bit wrong. Adding .22 uF to the horizontal output cathode fixed that and got 900V HV-.

Once done, the picture was a teensy bit better than last year
(not enough better for a new picture here), and it runs on almost all monitors.

I'm still looking for the military repair manual (though, of course, in intended use repairs were, ah, the opposite of what was desired).

One astounding tidbit. Looking at the severe noise (the S/N of a sunlit scene
is like 2:1) I noticed something and measured the frequency response. That's the frequency response looking at the width and shape of a full dark-to-light sharp edge or light-to-dark or stripe test patterns. The 3dB down point.

Its 8 MHz. That's eight megahertz. Eight, 8, e i g h t. And it shows on the high end
Ikegami monitor I'm using. Why would they make such a thing when it was supposed
to feed a transmitter that surely not that wide, nor displays that wide either.

It does demonstrate how sharp iconoscopes can be, such as the talking one in Japan :-)

Given it's a WWII guidance camera and that the military had a lot of leeway on how it used RF during the war it's possible the engineers foresaw the possibility of having a channel wider than 6MHz and higher scan rates for increased resolution for some special application and gave the video circuits enough bandwidth that one could swap the transmitter and tweak the scan to achieve that easily.