The AM Forum
December 03, 2024, 12:27:41 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: Replacing A 5AR4 With Diodes?  (Read 2835 times)
0 Members and 1 Guest are viewing this topic.
KN4SMF
Member

Offline Offline

Posts: 19


« on: June 20, 2024, 02:07:56 PM »

I have a BC-348 here that  somebody had built a pretty nice 5AR4 power supply for. Problem is, voltage is a bit low for my taste, and the tube is too tall for the radio to slide into its cabinet without scraping the top of the tube. I don't want to buy one of those ebay plug-in rectifier modules, and I have some 1N4007 diodes right there. How do I solder them up to the bottom of the tube socket? Which pins to which, and proper way to turn the bands on the diodes? I'm not interested in breaking up an old tube for its base and wiring the diodes inside it. Surely it can be easily done by wicking enough solder out of the tube socket lugs to slip the pigtails of the diodes through, without changing any of the existing socket wiring. Thank you.
Logged
WD8BIL
Contributing
Member
*
Offline Offline

Posts: 4413


« Reply #1 on: June 20, 2024, 02:37:42 PM »

The band on the diode indicates the CATHODE end.
For the 5AR4 cathode is pin 8. Anodes are pins 4 and 6.

So, the banded end of each diode goes to pin 8. The other ends go to 4 and 6. Doesn't matter which ones.

Now here's the rub; the peak inverse voltage rating on the 5AR4 is 1700V. 1N4007s have 1000V PIV. You'll need to string 2 in series on each leg.
Logged
KN4SMF
Member

Offline Offline

Posts: 19


« Reply #2 on: June 20, 2024, 03:17:53 PM »

Thank you very much. As for the diode ratings, the BC 348 is a pretty low voltage rig. 220-230V of B+, at most. I would think 2 diodes would work. The 5AR4 was overkill big time for what this radio needs. Right now I'm sitting at 195V of B+. The specs call for abut 220 or so. Although I doubt the diodes will get me that high, even if they get me to 210 or so, I guess I can call it good and button it up.
Logged
KN4SMF
Member

Offline Offline

Posts: 19


« Reply #3 on: June 20, 2024, 05:52:08 PM »

Well I got the job done. It raided my B* from 195 to 203.4V. Anemic and disappointing. It should be AT LEAST 220. But I just recapped and re-resistored and aligned the radio just as it came to me, with the home made power supply that was in it. And it does indeed play quite well, for what it is. It's not a Hammarlund or a Hallicrafters. I guess I should be happy enough. Because to re-engineer and build a new power supply will likely give me pretty much the same thing.
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1806


« Reply #4 on: June 20, 2024, 09:18:24 PM »

Here is a PS I use, depending on the rig.


* 5AR4 GZ34 SS MV Choke or CAP Power Supply.pdf (76.78 KB - downloaded 95 times.)
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
WD8BIL
Contributing
Member
*
Offline Offline

Posts: 4413


« Reply #5 on: June 21, 2024, 08:25:41 AM »

Good to hear, Henry! Enjoy.

Buddly
Logged
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 0.071 seconds with 19 queries.