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Hoffman Amps Forum image Author Topic: Diodes for 1970 Twin Reverb  (Read 1869 times)

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Offline bbmade

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Diodes for 1970 Twin Reverb
« on: June 17, 2022, 12:00:50 pm »
Hello - I've searched the forum for an answer here but...

I'm working on a 1970 Fender Twin Reverb and have replaced the bias cap and resistor.  It has the original diodes. 

My question is:

Do I want 1N4007 rated at 1000V 1A or would I be better off with the 1N5408 rated at 1000V 3A?

The 4007 diode is so much smaller than the originals but, I'm guessing it's because the technology is better now.

Any insights are welcome.  Thank you

Here's the board:


Offline sluckey

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Re: Diodes for 1970 Twin Reverb
« Reply #1 on: June 17, 2022, 12:05:52 pm »
I'm working on a 1970 Fender Twin Reverb and have replaced the bias cap and resistor.  It has the original diodes. 

Do I want 1N4007 rated at 1000V 1A or would I be better off with the 1N5408 rated at 1000V 3A?
Your choice. Either is a fine replacement. However, there's no reason to replace the originals unless you know one or more has failed. If your B+ is good then the original diodes are good too.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline bbmade

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Re: Diodes for 1970 Twin Reverb
« Reply #2 on: June 17, 2022, 12:23:06 pm »
Thank you.  Voltages are good amp sounds good but there's an oscillation when I crank the volume on the vibrato channel.  I think I'll start another thread for that because the amp had mods done in 1972 and I thought they were the culprit but I'll explain what I can in a new thread.

 


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