Page 1 of 1

Repairing 2109

Posted: Fri Dec 30, 2016 1:28 pm
by forum_admin
Time for the next patient !

This has a much clearer history in coming direct from the original user and 'working'. No problem acknowledging the original owner was London Underground, and this camera was swapped for a more modern model to get this one for the museum. It smells slightly of tunnels but has not been into fires or had the inevitable naval / brigade knockabout.

Initial checks are good, correct current draw at 430 mA, some iris motor noises as usual during startup and the external video is OK with a thermal image. All that seems to be missing is internal video.
capture.jpg
So open it up....

Re: Repairing 2109

Posted: Fri Dec 30, 2016 1:40 pm
by forum_admin
A lot of time and effort can be saved by not 'undressing' the camera.

Just slacken the harness to release the power cable and then the camera can be removed complete by releasing the outer ring
L1000046.jpg
L1000047.jpg
There is enough slack to power the camera from the battery unit with the cables in situ. Final setup needs this arrangement as it is very sensitive to the input voltage (8.7V).

Diagnostics are OK on another supply wired into the PCB directly or making up a lead for either the Cannon plug or the 8 way input connector

Re: Repairing 2109

Posted: Fri Dec 30, 2016 2:09 pm
by forum_admin
Get straight to the CRT inputs:

See manual for circuits, http://www.fire-tics.co.uk/datasheets/P4428_TM_B.pdf

Scans on yoke connector (PL105) - all OK

G1 (the video signal) on D108 / R123 - -ve but DC. This is wrong but consistent with the observed fault.

So off to RV106 / D117 - video present. So the fault is somewhere between.

25V on D109 / C127 - OK

R117 0V both ends, R119 25V both ends, R116 has video.
Q102 not working as it should

Re: Repairing 2109

Posted: Mon Jan 02, 2017 2:05 pm
by forum_admin
New transistor and it is working :D

The bare PCB on these are pretty fragile though, clearing solder from the holes lost a pad.
Quick setup check and it is good to go.

I'll take a few photos while it is open and post an illustrated guide to the insides of these cameras.

Bill

Re: Repairing 2109

Posted: Sun Jan 15, 2017 8:08 pm
by forum_admin

Re: Repairing 2109

Posted: Sun Jan 15, 2017 8:53 pm
by forum_admin
Annotated view of Scan PCB side
scan.jpg

More details in the service manuals on the site

Re: Repairing 2109

Posted: Sun Jan 15, 2017 8:53 pm
by forum_admin
and the video PCB side

video.jpg

Re: Repairing 2109

Posted: Sun Jan 15, 2017 8:54 pm
by forum_admin
and the underside tube / chopper arrangement

under.jpg