[Johnson] Johnson Digest, Vol 60, Issue 7

[Chuck Hurley]

Mike,

I have been restoring several pacemakers recently.  They were all factory 
built I believe, however it looks like the OA2 was added after the fact. 
The socket hole is not punched cleanly and the wiring looks like it was 
scabbed on.  Could have been done at the factory or the factory may have 
supplied a mod kit that owners installed.  Read page 28 of the manual and it 
explains the function of R76 as it relates to the OA2.  Principally I think 
it is to regulate the idling current.

Chuck  K1TLI




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Sent: Wednesday, January 07, 2009 12:00 PM
Subject: Johnson Digest, Vol 60, Issue 7


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> Date: Tue, 6 Jan 2009 15:45:37 -0600
> From: "Langston, Mike" <MLangston at pricegregory.com>
> Subject: [Johnson] Pacemaker
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> Date: Wed, 7 Jan 2009 08:53:49 -0600
> From: "Langston, Mike" <MLangston at pricegregory.com>
> Subject: [Johnson] Pacemaker
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> I am working on a nice Pacemaker and started the alignment last night. I
> have a good copy of the manual w/schematic. The schematic indicates
> there is a VR tube in the bias circuit (OA2 as I recall). My unit does
> not have regulation in the bias circuit. Does anyone know if there were
> 2 different variants; one with regulation and one without? Was bias
> regulation added on later units to cure some kind of problem? It would
> be simple enough to add a zener if there is any advantage to be gained.
>
>
>
> Thanks in advance for any help.
>
> Mike KL7CD
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