Repairing 2366

Discussion of the P4228 / P4428 cameras and derivatives.

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Repairing 2366

Post by forum_admin » Mon Jul 04, 2016 1:10 am

This is one of 3 cameras to be sorted out for museum / archive purposes. While I suppose no-one would mind that much if they did not work, there is a point here and they WILL be working.

This will be a kind of blog going through getting it (and its' friends) going

So it is all present in the standard metal box, but has been taken out of the yellow 'muff' and there has been some investigation into the battery box. The screen can / heatsink is missing and the wires are a bit of a mess.
2366a.JPG
Tidy up the wiring, clear out the silicone sealant from everywhere. Green is 0V, red is battery V, blue should be the regulated 8.7V.
The wires go slightly odd routes to allow the box to be sealed.
The black wire is just for screening.
2366b.jpg
As it seems complete, might as well try turning it on, as always from a current limited supply not batteries. Should go with 600mA.
Doesn't go and no LED on the battery box, so no regulator output. Just taking a few mA.
Unplug camera, now we get an LED and 8.75V. So the camera is not OK.

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Re: Repairing 2366

Post by forum_admin » Mon Jul 04, 2016 1:18 am

Turn the white plastic ring to unlock the front and back of the case, and remove the back. The camera chassis is fixed to the front part.

Further signs that a repair has been tried, the screen is unsoldered.
2366c.jpg


to be continued...

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Re: Repairing 2366

Post by forum_admin » Tue Jul 05, 2016 12:10 am

Once inside the metal cover over the video amplifier is also missing.
On the scan side, CRT is loose and none of the plugs have their retainers on. Definitely been 'got at'.
2366d.jpg
So I connected in the junction box seen above that replaces the battery box, regulator and the front panel wiring. It goes straight into the 8 way header.

Turn on - current limit - pop - smell :shock:
One smoked tantalum on the video side, a big 100u 6V3 on 5V supply.

Remove the casualty.

Turn on - and away it goes, we are in business :D .
What is obvious is that the internal picture does not have the usual circular blanking, it shows a full screen. However in the middle is a pretty respectable picture of the Pevicon target. It can even see hot things until the iris shuts.

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Re: Repairing 2366

Post by forum_admin » Tue Jul 05, 2016 12:18 am

Now to hunt for the missing circular blanking.
All logic outputs from the sync generator are Ok, so onto the analogue stuff.

This is one of the more bizarre bits of circuit in these cameras. The line and field drives go into R-C-opamp integrators (making saw tooth waveforms) and then these again integrated to give parabolas at line and field rate respectively.
Pop those into a comparator and you get a circle on the video.
Well you would if the DC levels at the field signals integrator were OK, but not. 2/3 of an 8.7V rail is not 1V !
Remove IC (fortunately socketed), better but still wrong
Remove tant C and all is well. Another dud tant (10u/16V on 4V this time) as well as the IC.

Replace the two tants and the IC, plus borrow a head amplifier cover from elsewhere and we have a working camera chassis.

A run through the camera setup to follow

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Re: Repairing 2366

Post by forum_admin » Tue Jul 12, 2016 11:46 pm

Thought I had broken it, but just shorted out the head amp input lead with the new screening can :oops:

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Re: Repairing 2366

Post by forum_admin » Sat Nov 12, 2016 4:41 pm

The camera setup is in the Technical manual which was supplied with all cameras. This was because most of the cameras were sold to Navies who wer expected to be able to fix them at sea or at least on base. How many did or not is a different question !

The manual is on the P4428 page but here are extracts with the setup process:
http://www.fire-tics.co.uk/datasheets/P4428_setup.pdf
and adjustment locations:
http://www.fire-tics.co.uk/datasheets/P4428_adjust.pdf

To complete the setup we need:
20MHz+ scope with video triggering. Analogue scopes are fine, and actually better than a poor digital one. Teks are pretty useless at video triggering, Philips are good.
AVO to measure 50uA. A DVM might struggle as we are trying to set 6uA.
A video monitor is helpful, but not vital as long as the camera has a picture on the internal screen.
Be aware that there's exposed voltages around that will nip a bit, including the tabs of the two TO220 FET. Nothing dangerous to those in good health but avoid if you have a pacemaker.

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Re: Repairing 2366

Post by forum_admin » Sun Nov 20, 2016 7:30 pm

Setup detailed along with some scope pictures

http://www.fire-tics.co.uk/4428_setup.htm

Now going back together

Bill

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