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  #1  
Old 06-10-2016, 03:56 PM
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dtvmcdonald dtvmcdonald is offline
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CRV59-AAE Military Iconoscope Camera restoration

I am beginning the restoration process on the CRV59-AAE Military Iconoscope Camera (and spare Iconoscope) that I bought at the May RTF meeting.

Some time ago I ordered uo from Mouser the needed list of parts.
The only odd ones are for the power supply. First is the power transformer
for the +405 and -50 volt supplies, which is a Hammond 290EX Guitar Amp transformer. It has the requisite 50 volt (RMS) tap for the -50v. The +27 volt
filament and bias supply is a Meanwell LRF-150F-24 switching supply to which I intend to add a bit of switching crap filtration.

Last night I had again inspected the chassis, tried to remove the bad-looking iconoscope, and tried following wires and testing pots.
I could not get the iconosocpe out. It looked like the yoke was set to make that impossible without removing pots. Today I bought new batteries
for my flashlight and inspected better: yes, there is an adjustment and if moved a bit the tube comes out safely.

All the stuff I tested looks OK especially the low-ohm pots I was able to test in-circuit. Except that the bias lamp appears
missing entirely, no lamp, no wire, no socket. Huh??? The shutter was removed previously.

With the old iconoscope out I was able to test it in a tube tester for
emission and gas (transconductance too, but that's expected to be very very low). I had previously tested the new one, and it looked OK. The old one
is clearly very very gassy, and a retest of the new one under identical settings shows no gas.

There is hope!

Next up is lots and lots of photos and more circuit tracing.

Has anyone else around here other than McVoy had any experience with one
of these?

Doug McDonald
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Old 06-12-2016, 05:54 PM
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I have now replaced all the 450 volt (B+) electrolytics, C127, C142, C101, C126.
The first two are cans in the main part and were restuffed. C101 was not resutuffed
because the tabs were too stiff to twist into removal position. C126 was not resutffed out of "symmetry" with C101, and there's a nice spot for it.

The two 0.05 uF caps in the preamp area were replaced with modern ones (C113 and C114).

I have not decided whether to replace the LV (15 volt) electrolytics, C147 and C115.
C115 would be easy, C147 even more impossible than C101, to restuff, so if
they are bad they will just have their wires cut and the replacements
tacked in. These caps are usually OK.
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Old 06-13-2016, 10:38 PM
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All the tubular paper caps are now replaced.

Next up is disconnecting the 6X5 plate and catghode and replacing with
1600PIV silicon diodes.

Then I will test the +28 and -50 volt resistor chains using the 28 volt supply,
and the +400 (no filament power) using a lab supply.
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Old 06-14-2016, 12:22 PM
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dtvmcdonald dtvmcdonald is offline
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It turns out that the modifications mentioned in the ham radio article,
to use AC on the filaments, were done at some point, and will have to be
undone (very easy, but its good we have a local source for ordinary resistors
and a few caps.).
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Old 06-14-2016, 09:39 PM
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dtvmcdonald dtvmcdonald is offline
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The circuit changes in the +28 volt area were undone, not physically easy, as big
wires were twisted on tightly. The 6x5s (except heaters) were removed from the circuit
and replaced with 1800V PIV silicon diodes, these being specifically specified
for damper and CRT supply use.

The +28 and minus 50 circuits were checked out using the 28v supply and
appear to work OK.

Next is build the power supply.
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Old 06-16-2016, 09:32 PM
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The 405 volt supply is built and tested. It was applied to the set
and immediately showed that R210, the 1000 resistor that feeds the
gas regulator tubes, was open, These are still available.

I was able to temporarily replace it with 200 ohm resistors in series.
This showed that at least most of the B+ chain is working OK.

Next up is the -50 volt supply, the noise filter for the 28 volt supply,
and the power cable.
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Old 06-17-2016, 09:23 PM
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dtvmcdonald dtvmcdonald is offline
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The power supply is complete and connected.

The electronics, without the iconoscope, was turn completely on.

All the various sections work. The vertical frequency adjust is out of range,
it wont reach as high as 40Hz.
This would not matter if I were forcing it to 60Hz, but I've not done that yet.

My soldering iron died and the old 250 watt gun is too clumsy,
so I'm out of doing changes until I can borrow one from a colleague's lab.
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Old 06-18-2016, 08:49 PM
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I got a new iron.

I got the vertical in range.

As designed it is NOT random interlace! It in fact is roughly (now)
260 x 60p. But at these extended frequencies (originally it was about 300 x 40p)
the stability is marginal.

I will continue testing before installing the iconoscope.
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Old 06-19-2016, 04:16 PM
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Doug, would you by chance have any pictires of this restoration? That would really be interesting!
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Old 06-19-2016, 06:03 PM
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I have a very complete set of "before" pictures. I'm rather tired out this evening, so its
unsafe to do more work. I'll try to take the "after" pictures and ones of the power supply,
which still lacks the sync modifier suggested bu McVoy.

Today was devoted to troubleshooting (electronic tests only ... the first
iconoscope test will be tomorrow).

The power to the iconoscope filament was inadequate. It took quite a while to
prove this, as I have no AC voltmeter that works at 16 kHz. I had to
use an analog scope or compare filament brightness between two identical tubes,
one on the camera and one on 6.3vac. Tomorrow I'll bring a digital scope that can
do true RMS AC. The problem was that the screen resistor, supposed to be 82K,
was 106K. This caused the screen voltage to drop to zero at high power, thus
limiting. Even 82K did not work, I eventually used 60K.

Then I worked more on the video amplifier chain. It was horrendously microphonic,
as if there were a broken lead connection. There was., onC154, a 1000pF mica in series
with a 0.05 uF film cap (??? WHY ... its not a high voltage area.?) It had a lead
that was broken off about 1/2 millimeter inside its case. This was not easy to find,
though tapping and poking eventually found it.

Another source of problem was found in a noisy gain pot. This is wirewound 10K.
At least for the moment is was fixed with DeOxit ... you have to take the
case off and flood it, as the noise seems to come not from the wiper on the
resistor element but on the connection of the wiper to the outside.

The shading pots are similar, but are not so bad.
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Old 06-20-2016, 01:26 PM
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dtvmcdonald dtvmcdonald is offline
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The iconoscope I bought at the ETF convention is good.

The horrible white spot at the low left is present exatly the same
without the iconoscope. It is caused by the scanning rulses being to long
and ringing. Working on this is the next step.

Picture attached. It is of a window looking out
on a sunlit scene. All you see is the wooden things holding the panes of glass
and the Venetian Blind slats. At lower left is the head of a wooden turtle
(bought in Papua New Guinea!) and the corne of an RCA 9T249.
Attached Images
File Type: jpg _MG_6205.jpg (68.8 KB, 38 views)

Last edited by dtvmcdonald; 06-20-2016 at 01:29 PM.
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Old 06-20-2016, 02:42 PM
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After about an hour and a half running the image faded out.

Had the iconoscope gone bad?

After leaving it off for 45 minutes and turning it back on,
changing no adjustments, I got the very best picture I have seen,
even though the sun had gone behind a cloud so it was a dimmer scene.
Maybe something charged up? Is that why a bias light from the back?
Time will tell.
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  #13  
Old 06-20-2016, 05:21 PM
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Here's a better picture, made just after turning on. I have seen better.

I have to turn up the iconoscope bias as it (or something?)
warms up.

It seems to work best with the iconoscope filament runnig at
5 to 5.7 volts RMS.
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  #14  
Old 06-20-2016, 05:48 PM
WISCOJIM WISCOJIM is offline
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Missing pictures?
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  #15  
Old 06-21-2016, 11:03 AM
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dtvmcdonald dtvmcdonald is offline
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Yes, missing picture. Its only somewhat better. I'll try
again tonight.

I measured the iconoscope grid current. It is OK
at turn on, then climbs to a couple of microamps when
the picture fades, in tirection that gas makes.

Thus, only a marginally good tube. Nevertheless, its a working demo.

Ad placed for better 1846 iconoscope in the "usual suspect" classifieds.
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