• The swap meet forum is for private non-commercial transactions. Only unmoderated members can post here.

    diyAudio provides this forum for the convenience of our members, but makes no warranty nor assumes any responsibility. We do not vet any members. Use of this facility is at your own risk. Customers can post any issues in those threads as long as it is done in a civil manner. All diyAudio rules about conduct apply and will be enforced.

WTB Power transformer for 300B

Wanted to buy
I've got options, depending on what B+ you are shooting for and how. And assuming 120V line.

Hammond 290CX. This is a horizontal mount/guitar amp style transformer. With a 5AR4 CLC, depending a bit on bias, you can get around 370-380V on my line. That's with a choke at like 75 or 80 ohms, so quite a bit of room to get lower or higher with different PS configurations. Near new. Only run for testing. Stayed cool and quiet. Maybe $80 shipped (US)?

I've got an VERY ugly horizontal mount guitar amp transformer. Banged up; ugly bolts; no moisture/lams not rusty. Similar to the Hammond, but higher voltage secondaries. Single primaries. More like 390V run similarly. It runs warm but quiet. I'm running it right now in the test version of the amp. Maybe $40 shipped (US)?

I've also got an Edcor 179. Also like new. It makes a little noise. Like an Edcor. I'm probably going to use this one in the final build with some damping in the bells. It is giving me like 385V and I was thinking 400V, so at the right price, it might be available for rehoming. ($150 shipped?)

Paul
 
  • Like
Reactions: jamesswarren
I always use a separate heater trafo with the Rod Coleman 300b heaters. I use the 6.3 only for the driver heater, also regulated with a low drop reg. I find the HV doesn't sag as much as with a regular EI core trafo.
 
Last edited:
I have used Antek at least 12 times but they don't think they have enough windings for all the heaters?

I've used Antek trafos in several of my amps (300b included). I think I currently used this in my TSE-II build AS-3T325. I think plenty windings for heater options. Two 6.3VAC@4A each: one for 300B heaters (2.4A total), one for input tubes. Send each through DC converter + regulator (nothing fancy, just based on LM317 or something similar). The only negative thing on Antek is no center-tap secondary, but a rectifier bridge can solve that

Can't beat on Antek price and availability (immediate shipping)
 
Last edited: