[R-390] R-725 AGC quits working after 1 hr.

[David Wise]

Correction: Gary Gitzen, not Gary Biasini.  (Gary B laid out a circuit board for my 3DW7 design.)

Dave Wise

________________________________
From: David Wise <d44617665 at hotmail.com>
Sent: Saturday, November 9, 2024 2:47 PM
To: Les Locklear <leslocklear at hotmail.com>; Larry Haney <larry41gm2 at gmail.com>; Geoff Brozny <geoff at glorb.net>
Cc: r-390 at mailman.qth.net <r-390 at mailman.qth.net>
Subject: Re: [R-390] R-725 AGC quits working after 1 hr.

Thanks, Jordan, multiple radios with one cap each didn't occur to me.

The op-amp circuit and the V506A AGC Time Constant tube will work fine regardless of meter resistance.  If you add 18 ohms, you'll need more meter gain, that's all.  Gary Biasini and I worked that all out when developing our own meter retrofit mod.

Dave Wise

________________________________
From: Les Locklear <leslocklear at hotmail.com>
Sent: Saturday, November 9, 2024 2:22 PM
To: David Wise <d44617665 at hotmail.com>; Larry Haney <larry41gm2 at gmail.com>; Geoff Brozny <geoff at glorb.net>
Cc: r-390 at mailman.qth.net <r-390 at mailman.qth.net>
Subject: Re: [R-390] R-725 AGC quits working after 1 hr.

LED’s + 1 why not?

Les Locklear

Get Outlook for iOS<https://aka.ms/o0ukef>
________________________________
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of David Wise <d44617665 at hotmail.com>
Sent: Saturday, November 9, 2024 2:49:14 PM
To: Larry Haney <larry41gm2 at gmail.com>; Geoff Brozny <geoff at glorb.net>
Cc: r-390 at mailman.qth.net <r-390 at mailman.qth.net>
Subject: Re: [R-390] R-725 AGC quits working after 1 hr.

Jordan,

"film caps" plural?  Do you mean that you did the partial-mitigation for moment of silence mod that uses one cap for LONG and another cap for MED?

If I were to do it again, I would do Charles Steinmetz's moment of silence mod, placing the caps behind the front panel, and abandon the original C551 in place.  Once you've committed to removing the panel, you can also illuminate the frequency readout with LEDs, and install Jan Skirrow's universal carrier meter circuit if you don't feel like doing mine and Gary Biasini's.

Dave Wise

________________________________
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Geoff Brozny via R-390 <r-390 at mailman.qth.net>
Sent: Saturday, November 9, 2024 10:22 AM
To: Larry Haney <larry41gm2 at gmail.com>
Cc: r-390 at mailman.qth.net <r-390 at mailman.qth.net>
Subject: Re: [R-390] R-725 AGC quits working after 1 hr.

On 11/9/2024 1:09 PM, Larry Haney wrote:
> Geoff,  the minimum voltage for that cap is a good quality 250 vdc or
> more (200 vdc on the plate of the 'time constant' tube).  You might find
> one 2mfd cap that will work.
>
> Regards, Larry
>

Thanks Larry, I appreciate it. Hopefully I can get it back up and
running this next week.

Thanks,
Geoff
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