Well, the power supply rectifier diodes are nothing special. Forwards voltage can vary from .450 to .770 on the DVM without meaning anything. Modern ones tend to be lower voltage, that is more efficient and not possible in 1970. Just be sure if one is defective, don't buy schottky, fast recovery or ultra-fast recovery diodes. These make more RF from the sharp cutoff edge to interfere with the amp circuit. Sharp edges can cause 100 hz (Europe) buzz. Designers bypass the rectifier bridge with a .01 or .1 us ceramic 500v cap to reduce the buzz. There are more sophisticated tricks involving a cap series a 10 to 100 ohm resistor across the bridge.
To buy diodes, I use the selector table on farnell, select semiconductors, select diodes, check stock only, then select standard recovery diodes, then minimum 400 PIV and current 3 to 6 A. Select leaded parts. That got me 1n5404 in August; you may come up with different stock in the UK.
Factories tend to save money by buying different rectifier diodes each run. I paid $.11 each for the 1n5404, whereas generic diodes from a "no free catalogs no salesmen" supplier like GI or hang seng are probably $68 for 10000.
To buy diodes, I use the selector table on farnell, select semiconductors, select diodes, check stock only, then select standard recovery diodes, then minimum 400 PIV and current 3 to 6 A. Select leaded parts. That got me 1n5404 in August; you may come up with different stock in the UK.
Factories tend to save money by buying different rectifier diodes each run. I paid $.11 each for the 1n5404, whereas generic diodes from a "no free catalogs no salesmen" supplier like GI or hang seng are probably $68 for 10000.
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Just wanted to post a big thank you to both of you for your help. I finally fired up the MA50's and they are utterly fabulous. If you get the chance to hear a pair that have been rejuvenated with love and determination you will not regret it. Massively pleased. I put on a record andsat there with a smile "like a Cheshire cat" as we say over here.
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