Help a Newb? Upgrade/Modify a Tube Amp Power Supply
I recently procured a Jolida SJ-502a integrated tube amplifier for next to nothing and I want to use it to regain my soldering skills and to learn some things about tube amplifiers. I'm thinking about turning it into a straight power amplifier and building a separate pre-amp for it.
As most of the components in this amp are original and at least 15 years old I figured I would replace them all and modify with any reasonable suggestions I can find. I am going to start with the Power Supply section and then move to the pre-amp and amplifier sections.
Jolida SJ-502a Schematic
For VD1-4: I'm thinking about using UF4007 diodes. I've read a decent amount about using F.R.E.D. diodes instead but many people seem to think that the UF4007 diodes are fine. Any suggestions or feedback here?
For C0 and C9, is there any benefit to increase the capacitance here? Same question for C10/11.
For R23/24 I'm looking at using Vishay/Dale Wirewound 1% resistors, specifically these: Datasheet Is 1% tolerance over-kill? There is a similar VD WW resistor with a 5% tolerance for about half the price.
I don't want to overload so I'll follow-up on some of the other components in a separate post. I hope that I've come to the right place to beg for this level of help...thanks in advance for any you can provide.
I recently procured a Jolida SJ-502a integrated tube amplifier for next to nothing and I want to use it to regain my soldering skills and to learn some things about tube amplifiers. I'm thinking about turning it into a straight power amplifier and building a separate pre-amp for it.
As most of the components in this amp are original and at least 15 years old I figured I would replace them all and modify with any reasonable suggestions I can find. I am going to start with the Power Supply section and then move to the pre-amp and amplifier sections.
Jolida SJ-502a Schematic
For VD1-4: I'm thinking about using UF4007 diodes. I've read a decent amount about using F.R.E.D. diodes instead but many people seem to think that the UF4007 diodes are fine. Any suggestions or feedback here?
For C0 and C9, is there any benefit to increase the capacitance here? Same question for C10/11.
For R23/24 I'm looking at using Vishay/Dale Wirewound 1% resistors, specifically these: Datasheet Is 1% tolerance over-kill? There is a similar VD WW resistor with a 5% tolerance for about half the price.
I don't want to overload so I'll follow-up on some of the other components in a separate post. I hope that I've come to the right place to beg for this level of help...thanks in advance for any you can provide.
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I would start by replace the electrolytics with similar values, and get it working properly first.
Then you can decide about doing any further work/upgrades. Larger supply capacitors
may cause surge issues, though.
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Thanks for the quick reply. Are there any "preferred" electrolytics for power supplies?
The largest are 470uF/400V. From Digikey or Mouser, you can get many types of Panasonic
or Nichicon types. I'd also get the next higher voltage, 450V. You may have to adapt a different case style.
Other than the folks who replaced the 1N4007 diodes with HEXFRED or other Fast Recovery diodes I haven't been able to find any other info regarding possible power supply upgrades. I'm trying to decide if it's worth it to use something like a Fairchild Stealth/Stealth II or just use UF4007's in the rectifier bridge.
Fairchild UF4007 Data Sheet - https://www.fairchildsemi.com/datasheets/UF/UF4007.pdf
Fairchild Stealth II 8A/600V Data Sheet - https://www.fairchildsemi.com/datasheets/FF/FFP15S60S.pdf
I'm not sure if those are the right FRED's or not, the original UF4007's are only rated at 1 amp but people seem to be using 15/16 amp FREDs in some old forum threads I've found.
I'm going to build one of the Quasimodo jig's that Mark Johnson designed to help me figure out the right snubber network to put in place for whichever diode bridge I go with.
Fairchild UF4007 Data Sheet - https://www.fairchildsemi.com/datasheets/UF/UF4007.pdf
Fairchild Stealth II 8A/600V Data Sheet - https://www.fairchildsemi.com/datasheets/FF/FFP15S60S.pdf
I'm not sure if those are the right FRED's or not, the original UF4007's are only rated at 1 amp but people seem to be using 15/16 amp FREDs in some old forum threads I've found.
I'm going to build one of the Quasimodo jig's that Mark Johnson designed to help me figure out the right snubber network to put in place for whichever diode bridge I go with.
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