Diodes for a Twin

[trem]

I replaced the boards and components in a 1969 Twin. I used the AB763 schematic. About the only stuff that did not get replaced was the 3 transformers, the choke, and the diodes in the bias and rectifier circuit. I really have no knowledge of diode specs, and I am not sure what to use for replacements. I will order anything that is necessary. But this is what I have in my drawers:
(10) 1N4007
(5) 1N5408G
(3) UF5408
(10) 1N5408
What would you guys recommend?
Thank You

[Albert Kreuzer]

Any of these will work fine. 1N4007 (1A/1000V) are good enough, the 5408 types are 3A/1000V parts (overkill).
But why replace them? The old ones are usually good, they do not "age" like electrolytics.

Cheers,
Albert

[trem]

Any of these will work fine. 1N4007 (1A/1000V) are good enough, the 5408 types are 3A/1000V parts (overkill).
But why replace them? The old ones are usually good, they do not "age" like electrolytics.

Cheers,
Albert

Thanks -
Why indeed? That is a question I did not ask. It just seemed that sense I am in here replacing everything else that I would somehow be "negligent" if I did not change the diodes. But again, honestly, I have no knowledge of diodes or how they age. If the diodes that are in there now are likely to go anther 40 years, I will leave them be. I just did not want to make a stupid mistake over a few dollars worth of parts.
Thanks Again.

[jrfrond]

I usually "bomb-proof" those diodes in old Fender's by replacing the triple-string with a single 6A10 (6A/1kV) diode. Fits perfectly across the outer eyelets. Yes, it's overkill, but tell THAT to the guy whose amp takes a sh*t on the gig.

The bias diode is just a simple 1N4007.

Since these diodes may have been subjected to any number of current draw and transient spike situations over the years, I always replace them whenever possible. It's cheap insurance. Semiconductor junctions can and do get "holes" blown in them by transient spike, but might still work perfectly until the right conditions cause the hole to blow wide open. I found this out when working in military electronics.

[Rick Erickson]

I've used standard 1N4007 diodes as replacements in Fender amps for over 30 years and never had one fail on me. 6A is overkill and 1000V is not enough. The original diodes were 600V PIV in seires of three per side, or 1800V PIV. I would not recommend going lower than this or you probably will see a meltdown.

RE

[trem]

I've used standard 1N4007 diodes as replacements in Fender amps for over 30 years and never had one fail on me. 6A is overkill and 1000V is not enough. The original diodes were 600V PIV in seires of three per side, or 1800V PIV. I would not recommend going lower than this or you probably will see a meltdown.

RE

OK -
So 2 x 1N4007 per side should be fine in the rectifier I assume. I appreciate the info.
Thanks Again

[jrfrond]

I've used standard 1N4007 diodes as replacements in Fender amps for over 30 years and never had one fail on me. 6A is overkill and 1000V is not enough. The original diodes were 600V PIV in seires of three per side, or 1800V PIV. I would not recommend going lower than this or you probably will see a meltdown.

RE

1kV is WELL within the safe operating area for the amp. I am more concerned with current draw. Like you, I haven't had a failure yet. Besides, if the amp sees a line transient of anywhere near 1kV, the last thing you'd need to worry about would be diodes!