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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 29th May 2021, 11:24 am   #1
Vintage Engr
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Default Panasonic AG 7350

I have just acquired one of these, which is (was!) in very good condition. After a basic service the machine performed excellently on playback.
However there was no E-E video or S-video.

I soon discovered the problem. When the machine had been removed from it's previous owners, someone had obviously forgotten to disconnect the BNC connector from the 'video in' socket.
The unfortunate result is that the rear jack board PCB has been severely damaged with large cracks & pieces of print missing. It should have been a simple repair, but tracing the tracks proved difficult. This was due to the fact that the only service manual I could find was online, and the particular scan for the foil side of the PCB was missing.

I thought it should be a simple matter to just trace it out from the cct. diagram, not so; as the diagram did not match up to the board in my possession!
It's only an input/output board, but it seems I have a different version, with extra passive components around the Y/C input.

Does anyone have a service manual for this model? All I require is the rear jack circuit, and also the foil side layout. It's listed as VJB04344 / VEP0344 (not /A)

If only this were 20 years ago, when I had a hard copy manual...!

Thanks,

David.

Last edited by Vintage Engr; 29th May 2021 at 11:31 am. Reason: missing part number.
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Old 6th Jun 2021, 11:51 am   #2
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Default Re: Panasonic AG 7350

Thanks to all those who viewed this post, obviously very few service manuals still out there! I don't remember whether any supplements were ever issued that might show the rear input/output board differences.
I think I will have to therefore modify the PCB to fit the only diagrams available.

It s the Y/C and composite video inputs that are different on the board I have. For some reason, on the S-Video input socket, there's some extra passive component circuitry, that takes off the chroma & luma, to another connector (not shown on either the PCB layout, or the circuit) which then goes off to who-knows-where. As a result of this, if I hard-wire the main edge-connector to the mother-board, as per the cct diagram, I end up with a double-termination of both Y & C, all rather odd. I shall just have to trace out where the video goes to, & hard-wire it accordingly. By then someone will have come up with an amendment diagram...

Dave.
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Old 7th Jun 2021, 10:07 am   #3
steve c
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Default Re: Panasonic AG 7350

Sorry Dave just seen this
Hope this attached helps

Steve
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Old 8th Jun 2021, 5:33 pm   #4
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Default Re: Panasonic AG 7350

Thanks Steve,
Unfortunately, that's the same circuit that is in the manual that I have an online copy of.
However, the rear jack pcb that I have is quite different. I'm not sure whether it is an earlier or later one.

Strange things happen with both the composite video & Y/C on the board I have. For instance, three's a 10k resistor connected to pin 4 (Y) of the S-video input connector, that disappears off to another socket P6905, that's not on the cct that we both have. Also extra capacitors and fine tracks connected to this point.

The board had been quite badly damaged by the Video in BNC socket being ripped off the print, and all the very fine tracks broken in the area round the socket, with small pieces of SRBP missing, making it difficult to trace.

I tried connecting the BNC video in, and also the Y/C video in, direct to the relevant pins on P6902, the one that mates with the mother board. The produced a very odd result, in that both the composite video in, and the Luma in of the Y/C connector, then become double-terminated!

It was then that I realised that the board was different, and also that I didn't have a foil side layout of the circuit that I do have, so due to the track damage, it's nearly impossible to trace what's going on. In the absence of a revised version of both the cct & PCB layout, I may resort to disconnecting the extra passive components not shown, & also cut all the original tracks from P6902, leaving only my miniature co-ax cables connecting back up to the relevant input sockets.

Should have been a simple, albeit fiddly job, but has turned out a little more difficult.
What is so annoying, is that some 20 years ago, I took all my 'old' video manuals over to Chas Miller, RIP, he sorted out what he might use, & the rest went, somewhere westwards...

Moral; don't dispose of anything!

Thanks anyhay,

David.
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Old 23rd Jun 2021, 2:34 pm   #5
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Default Re: Panasonic AG 7350

I have now managed to re-wire the PCB, removing the extra components that seem to have been fitted on this later version. This sorted out the double-termination of the video input.
Pleased to say that the VTR now works as well as when it was made.
Fortunately the Video heads have very little wear, with excellent RF being recovered off an alignment tape.
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