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Multi-Elmac AF-67 Battery Replacement




 
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May 22, 2019, 03:51:29 PM *
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Author Topic: Multi-Elmac AF-67 Battery Replacement  (Read 330 times)
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W1KSZ
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« on: April 27, 2019, 02:48:30 PM »

Just picked up a rather clean AF-67 and Power Supply (caps all replaced in it !!).

As I figured, the 22.5 vdc Bias Battery is kaput (6.6 vdc).

Which would folks prefer, replace the Battery (~$25) or do the Zener in the
Cathode Mod. Is one better than the other ??

Tnx es 73, Dick, W1KSZ
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WA4WAX
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« Reply #1 on: April 27, 2019, 05:58:16 PM »

Have a look.

https://www.qsl.net/w/wb4kdi/Elmac/AF-67/CQFeb57.html
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ka1tdq
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« Reply #2 on: April 28, 2019, 08:17:36 AM »

I had one and as I remember, I did the following:


Removed the battery

Grounded the center tap of that transformer it is connected to

Lifted the cathode lead from ground for the modulator tubes and placed an electrolytic capacitor / paralleled resistor inline.


Jon
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W2PFY
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« Reply #3 on: April 28, 2019, 04:36:32 PM »

Quote
Lifted the cathode lead from ground for the modulator tubes and placed an electrolytic capacitor / paralleled resistor inline

What were their values and watts? I though that you had a rather pristine AF-67 that was a keeper? Did you get rid of it? Did you have the PS or build a new one? Inquiring minds need to know
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ka1tdq
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« Reply #4 on: April 28, 2019, 04:50:54 PM »

I could only guess the values I used, but probably 100uf at 100vdc and a resistor of 500 ohms at 5 watts.  Ballpark.

I got rid of it along with all my other tube stuff (amp included). The last few vestiges of my tube stock are being sold on various platforms as we speak. I'm getting rid of the stuff now while there's still a market. In a few years even the junk guy won't take it.

I'm focusing on making my shack neat looking and solid state. My primary focus now is on my 24 FET transmitter.

Jon
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