Re: {Collins} 75A3 So Close yet So Far Away



Bill,

There is a mod for the A4 which addressed the mute/standby problem also in the A3(same ckt). The fix is to cut off or bend back one of the tube pins...  

I'm at work and don't remember which pin on which tube. I will look it up tomorrow and get back to you.

As for the AVC, check the tube and also male sure the wafer switch contacts are good.

Dave

---------- Original Message ----------
From: "Bill & Becky Marvin" <wmarvin@xxxxxxxxxxxxxxx>
To: <collins@xxxxxxxxxxxxx>
Subject: {Collins} 75A3  So Close yet So Far Away
Date: Fri, 12 Feb 2010 16:55:19 -0600

Hello Group  I have completely recapped my 75A3 including Electrolytic and on a preliminary Check-out  It's a No-Go.

I have lost AVC control thus the receiver now overloads on AM unless I use the RF Gain and reduce the radio's overall gain...........But the
strangest symptom is switching to Standby the radio still receives albeit at 1/2 overall gain.

My early measurement on the Can Electrolytic ( C95) are:

R70 mount tab             240 VDC

3 Wire junction           215 VDC

R 71, R72 Junction   - 60VDC

I  am apprehensive to power on measurements per manual but would prefer a Resistance Table which the manual lacks.  Does anyone have
a Resistance Table for tube measurements for the 75A3.  It seems like a Bias problem??

Thanks for possible help.

73

KBIT
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