vanderk
Experienced Member
I have been working on two Astec Kaypro power supplies (AA12450 and AA12350) on and off for the better part of a year or so. I simply cannot get them working! Both units have been totally recapped, resistors checked, and I even replaced all the transistors to include the power transistor. Also replaced were all the diodes and bridge rectifier. I have replaced almost everything except for chokes. All resistors were good and I see no shorts on the common mode, control and power transformer (T1, T2, and T3).
Here is the issue with both units (they both exhibit the same problem):
- While slowly increasing voltage on a variac, the crowbar engages at around 40-50VAC. I do have B+. There is a high pitch chirp coming from the capacitors, and I can also hear the crowbar clicking.
- I see -12vdc when the crow bar engages and, as intended, no output on the 5VDC and 12VDC points.
- Lowering the variac voltage to just before the crowbar kicks in, I see approximately -12VDC, 6VDC, and 14VDC.
I am completely stumped and refuse to give up on this! I was careful when replacing components and used only exact replacements and close values.
Any assistance would be greatly appreciated!
Thank you,
Chris
Here is the issue with both units (they both exhibit the same problem):
- While slowly increasing voltage on a variac, the crowbar engages at around 40-50VAC. I do have B+. There is a high pitch chirp coming from the capacitors, and I can also hear the crowbar clicking.
- I see -12vdc when the crow bar engages and, as intended, no output on the 5VDC and 12VDC points.
- Lowering the variac voltage to just before the crowbar kicks in, I see approximately -12VDC, 6VDC, and 14VDC.
I am completely stumped and refuse to give up on this! I was careful when replacing components and used only exact replacements and close values.
Any assistance would be greatly appreciated!
Thank you,
Chris