FallenAngel
Headphoneus Supremus
Hey guys,
I just got a SinglePower MPX3 to play with and the insides look like a rats nest of messy wiring and crappy looking electrolytics! Luckily, nothing looks unsafe to my untrained eye. After reading just about every article on HV safety and jigging up a 33R 35W resistor to a plastic extender to drain all caps, I looked around, then measured that the transformer output only about 250VAC, 370VDC over the big caps and I think they're rated at 450V. There is barely 250V across the interstage caps (Jensen PIO in this case) and 120V across the HORRIBLE looking little electrolytic output caps - found they these are Panasonic TS-UQ.
Here is the "before" photo, as I will surely be changing things.
Anybody with experience with these or other tube amps is very much welcome to chime in and point out things to change/improve.
Surprises
1) WHOAH! Big discovery - transformer is actually putting out 650VAC! That's 325VAC with center tap to the ground - as in chassis and earth ground on IEC! He uses half-wave rectification to get about 405VDC pre-filtering, drops about 25V through a big ass resistor, then a pair of filter caps.
2) I'm really confused - why parallel a HUGE 220uF film Sonicap with 100uF electrolytic? Doesn't make sense to me at all. If you're putting on a film cap that big, why bother with the electrolytic?
3) Mikhail forgot to solder something
Input resistor was attached to wire but not soldered.
Planned upgrades
1) Looks like the 6.3V supply uses 4 1N5408 General Purpose Rectifiers rated for 3A @ 1000V. I've got some nicer considerably nicer MBR360 Schottky rectifiers that are 3A @ 60V. I think this will be the first upgrade.
2) Replacing the 2 Jamicon 4700uF/25V with something decent
3) Getting some decent output caps.
Thanks
I just got a SinglePower MPX3 to play with and the insides look like a rats nest of messy wiring and crappy looking electrolytics! Luckily, nothing looks unsafe to my untrained eye. After reading just about every article on HV safety and jigging up a 33R 35W resistor to a plastic extender to drain all caps, I looked around, then measured that the transformer output only about 250VAC, 370VDC over the big caps and I think they're rated at 450V. There is barely 250V across the interstage caps (Jensen PIO in this case) and 120V across the HORRIBLE looking little electrolytic output caps - found they these are Panasonic TS-UQ.
Here is the "before" photo, as I will surely be changing things.
Anybody with experience with these or other tube amps is very much welcome to chime in and point out things to change/improve.
Surprises
1) WHOAH! Big discovery - transformer is actually putting out 650VAC! That's 325VAC with center tap to the ground - as in chassis and earth ground on IEC! He uses half-wave rectification to get about 405VDC pre-filtering, drops about 25V through a big ass resistor, then a pair of filter caps.
2) I'm really confused - why parallel a HUGE 220uF film Sonicap with 100uF electrolytic? Doesn't make sense to me at all. If you're putting on a film cap that big, why bother with the electrolytic?
3) Mikhail forgot to solder something
Planned upgrades
1) Looks like the 6.3V supply uses 4 1N5408 General Purpose Rectifiers rated for 3A @ 1000V. I've got some nicer considerably nicer MBR360 Schottky rectifiers that are 3A @ 60V. I think this will be the first upgrade.
2) Replacing the 2 Jamicon 4700uF/25V with something decent
3) Getting some decent output caps.
Thanks