Hi all. It's been awhile. Had a few health problems, so was out of it for almost a year...
Not sure I'm in the right forum - got this nice SP6B preamp, found a dead diode, burnt resistor and a shorted cap in power supply, replaced. Brought it up on variac - all is nice: current draw is about 350 mA, HV and LV all check out. But when I plug it in directly, and turn it on - boom! - fuses blow one after another. From what I was able to catch on my digital ampermeter, it draws a lot on turn-on, like 5 or 6 amps. there must be a problem somewhere in power supply. Any suggestions appreciated. Thank you.
Not sure I'm in the right forum - got this nice SP6B preamp, found a dead diode, burnt resistor and a shorted cap in power supply, replaced. Brought it up on variac - all is nice: current draw is about 350 mA, HV and LV all check out. But when I plug it in directly, and turn it on - boom! - fuses blow one after another. From what I was able to catch on my digital ampermeter, it draws a lot on turn-on, like 5 or 6 amps. there must be a problem somewhere in power supply. Any suggestions appreciated. Thank you.
Hi. Thx.
Turn-on timer only works by muting outputs, not the in-rush current, and yes, it's working. These preamps never had a slow-start circuit. Fuses I have are the specified T500mA slow-blow.
If it works with the Variac, and all the DC voltages you checked are nominal
(and you should check ALL of them), probably some part of the start-up circuit is bad.
Have you checked all of the parts for good/bad?
(and you should check ALL of them), probably some part of the start-up circuit is bad.
Have you checked all of the parts for good/bad?
No, not yet. There are three windings and three power supplies, so it could be any one. I think I should replace the first electrolytics just to be sure
