Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Multi-Elmac AF-67 Battery Replacement




 
The AM Forum
August 26, 2019, 02:02:31 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Multi-Elmac AF-67 Battery Replacement  (Read 857 times)
0 Members and 1 Guest are viewing this topic.
W1KSZ
Member

Offline Offline

Posts: 220


« 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
Logged
WA4WAX
Member

Offline Offline

Posts: 256


« Reply #1 on: April 27, 2019, 05:58:16 PM »

Have a look.

https://www.qsl.net/w/wb4kdi/Elmac/AF-67/CQFeb57.html
Logged
ka1tdq
Member

Offline Offline

Posts: 1256


Massachusetts Democrat


« 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
Logged

Just follow the instructions, more or less.
http://www.ka1tdq.radio
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13097



« 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
Logged

The secrecy of my job prevents me from knowing what I am doing.
ka1tdq
Member

Offline Offline

Posts: 1256


Massachusetts Democrat


« 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
Logged

Just follow the instructions, more or less.
http://www.ka1tdq.radio
wa1mtz
Member

Offline Offline

Posts: 24


« Reply #5 on: June 17, 2019, 12:42:20 PM »

I've used my af-67 mostly for mobile over the last 30 years,bought some zeners but never put them in, was much easier to put in 2 12v camera batts, abt half the size of an aa batt, in series of course, they will last 10 years. also, the elmac really likes 525v on the plate! load it to 115ma, plenty of mod!!
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1326


« Reply #6 on: June 25, 2019, 02:05:32 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

Here is one possible solution for the bias supply;


Phil - AC0OB

* Multi-Elmac AF67 Bias Supply.pdf (104.84 KB - downloaded 49 times.)
Logged

"What kind of Koolaid do they make you drink in the Physics Department?" Charlie Epps to Dr. Larry Fleinhardt, NUMB3RS   Smiley
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.058 seconds with 19 queries.