Hi,
I have a battered old IBM 5150 PC (64-256k revision) that I am trying to resurrect. I cleaned up the mainboard and power supply, but when I came to test powering on the board, the C7 Capacitor at the top right of the mainboard (near J7 / COMP text) popped and smoked after about 10 seconds.
After reading up I learned that I should be able to snip the Capacitor and the board would function without.
After removing the failed cap, I re-tested the PSU voltages ( 11.67V, 4.93V, -12.14, -4.88 ) and retested the board, but after 8 seconds it emits a continuous tone, sometimes the tone sounds distorted. Or multi tone.
I have checked the DIP switches for the memory config, and reduced the RAM to banks 0,1 (DIPs set to 128k). I have even tested with the CGA GFX card removed and the CPU removed. In all cases after ~8 seconds the continuous tone starts.
I guess the first question I have for any 5150 experts is are the voltages for the PSU in spec?
Should I replace the removed C7 Capacitor before testing further?
Is there any other area I should investigate?
Any help much appreciated.
Tricky
I have a battered old IBM 5150 PC (64-256k revision) that I am trying to resurrect. I cleaned up the mainboard and power supply, but when I came to test powering on the board, the C7 Capacitor at the top right of the mainboard (near J7 / COMP text) popped and smoked after about 10 seconds.
After reading up I learned that I should be able to snip the Capacitor and the board would function without.
After removing the failed cap, I re-tested the PSU voltages ( 11.67V, 4.93V, -12.14, -4.88 ) and retested the board, but after 8 seconds it emits a continuous tone, sometimes the tone sounds distorted. Or multi tone.
I have checked the DIP switches for the memory config, and reduced the RAM to banks 0,1 (DIPs set to 128k). I have even tested with the CGA GFX card removed and the CPU removed. In all cases after ~8 seconds the continuous tone starts.
I guess the first question I have for any 5150 experts is are the voltages for the PSU in spec?
Should I replace the removed C7 Capacitor before testing further?
Is there any other area I should investigate?
Any help much appreciated.
Tricky