Repairing 2109

Discussion of the P4228 / P4428 cameras and derivatives.

Get advice and repair hints from fellow owners to get or keep yours going.
Post Reply
forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Repairing 2109

Post by forum_admin » Fri Dec 30, 2016 1:28 pm

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....

forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Re: Repairing 2109

Post by forum_admin » Fri Dec 30, 2016 1:40 pm

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

forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Re: Repairing 2109

Post by forum_admin » Fri Dec 30, 2016 2:09 pm

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

forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Re: Repairing 2109

Post by forum_admin » Mon Jan 02, 2017 2:05 pm

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

forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Re: Repairing 2109

Post by forum_admin » Sun Jan 15, 2017 8:08 pm

Attachments
P4428.png

forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Re: Repairing 2109

Post by forum_admin » Sun Jan 15, 2017 8:53 pm

Annotated view of Scan PCB side
scan.jpg

More details in the service manuals on the site

forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Re: Repairing 2109

Post by forum_admin » Sun Jan 15, 2017 8:53 pm

and the video PCB side

video.jpg

forum_admin
Site Admin
Posts: 55
Joined: Sun Mar 06, 2016 2:03 am

Re: Repairing 2109

Post by forum_admin » Sun Jan 15, 2017 8:54 pm

and the underside tube / chopper arrangement

under.jpg

Post Reply