I have an st-35 that was blowing the fuse. I found that one of the rectifier diodes was shorted. I replace both diodes with 1N5404, as well as installing a new quad capacitor. A few weeks later, the fuse blows and one diode is again shorted. Bias is set to 35ma/tube. Any idea what can be the cause?
3 posters
Dynaco ST-35 Power Supply Diodes
rudes- Posts : 63
Join date : 2012-03-07
rudes- Posts : 63
Join date : 2012-03-07
I'm going to try two 1N4007 in series on each high voltage transformer wire.
peterh
peterh- Posts : 1869
Join date : 2012-12-25
Location : gothenburg, sweden
rudes wrote:I have an st-35 that was blowing the fuse. I found that one of the rectifier diodes was shorted. I replace both diodes with 1N5404, as well as installing a new quad capacitor. A few weeks later, the fuse blows and one diode is again shorted. Bias is set to 35ma/tube. Any idea what can be the cause?
You really should use 1N5408 that has 1000V reverse voltage capacity.
Rec and Seamus like this post
Rec- Posts : 77
Join date : 2020-03-11
PIV is too low on 5404. You can use a single 5408, the 4007 will also work. Series diodes are also used to increase PIV, but come with their own issues. Just get diode with large PIV. 1000v or more. 5404 is only 400v, it would regularly see more on startup and… eventually fail.
Seamus likes this post