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previous: Morris I've got a Hammond 270FX (275-0-275... -- 4/23/2000 3:31 PM View Thread

Re: Need EL84 PS Advice

4/23/2000 4:06 PM
Lee M.
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Re: Need EL84 PS Advice
I used this tranny for Randy Aiken's November design (Marshall Plexi preamp with EL84 power amp). Used a Hammond 157J choke in between two 33uf filters. My line voltage is 122 or so. I get about 305vac out of the tranny under load.  
 
With a Sovtek 5Y3 I got about 362v. B+. I switched to an old (Silvertone branded) 5Y3 and B+ dropped to 327v. A GE 5Y3 gave me 334v. Yesterday I added 100 ohm resistors between the tranny and the rectifier input (per the November schematic). This brought my B+ down to 300v. with the Silvertone 5Y3 and finally got the tube dissipation under 12 watts (cathode resistor measures 128 ohms.)  
 
Try Duncan Munro's power supply designer to see the effects of varying circuit topologies. Based on my experience, a s.s. rectifier is going to give you very high B+. The Traynor Guitar Mate that I rebuilt used a s.s. rectifier with a CRC input and gave 438v. B+ with a tranny that put out about 330vac.  
 
I didn't notice any difference in tone (or volume) in the range of B+ voltages.  
 
Lee

 
Replies:
Morris Could you tell me what voltage you ... -- 4/23/2000 8:48 PM