[Boatanchors] Heathkit GR-78 Receiver - Audio

[Bob Macklin]

The Heathkit GR-78 is a POS! It's not worth the effort.

I bought one and had to build a new NiCd pack for it. Then it did work but 
only good for AM. And the sound was nothing to be proud of.

When I decided to sell it I found the front end had gone south! It was too 
difficult to fix so I sold it for a parts/repair unit.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "Mark Johnson" <mvjohn at sympatico.ca>
To: <boatanchors at mailman.qth.net>
Sent: Thursday, March 10, 2011 11:40 AM
Subject: [Boatanchors] Heathkit GR-78 Receiver - Audio


>
> Team;
>
> Playing with a GR 78 portable SW receiver. I installed a newer style Nicad 
> and Zener Diode to hold voltages around the 9.6VDC mark.....Receiver works 
> fine but the audio output sounds slightly distorated to me. Voltage 
> checking reveals around 7 VDC on the base(s) of each Audio output 
> transistor. According to the doc, it should be around 4.6VDC. I can't get 
> the voltages down to spec; assuming thats the cause of my slight 
> distoration. Audio coming from the detector stage, (before the audio amp) 
> through my Heath Signal Tracer seems to be fine.
>
> I know the audio amp was designed for communications quality audio but 
> it's not quite right to me. I hate to admit I've done a little "shot 
> gunning" with new parts in the audio amp; always a last resort, but no 
> change. The question for the group is, am I trying to fix somehting that 
> is working to spec? The audio is the same out of headphones and speaker. 
> There is just the slightest distoration when listening to AM Broadcast.
>
> Thanks.
>
> Mark V Johnson VE3DJU/VE3LU
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