myPinballs
Active member
So this is a bizarre one. And spent an age working out the problem
- HV over volt led on all the time
Changed all sorts of parts on the hv board inc caps, both +24 and -24 regulators, 555 ic, zener and regular diodes in the protection circuit, All transistors, flyback. No different
Changing R6 for 2k instead of 3.9k as per the notes in the amplifone fax/repair doc finally solved it.
According to the notes lowering this resistor lowers the HV output and therefore brings it back into an operating window that the board wont shut down so you can acutally test things. I was expecting to see bad regulators under load but no all fine. So my thought is how the f$%k did this thing work before and what changed that made it suddenly output higher HV??
Also, an extra note, If the voltage regulators (on the hv board) are not able to output correct voltage under load you cannot see this from a bench test with Q3 (BUD406D) removed. This means you have to find a way for the HV circuit to operate to properly check the +24 / -24v reg outputs. Annoying design haha
- HV over volt led on all the time
Changed all sorts of parts on the hv board inc caps, both +24 and -24 regulators, 555 ic, zener and regular diodes in the protection circuit, All transistors, flyback. No different
Changing R6 for 2k instead of 3.9k as per the notes in the amplifone fax/repair doc finally solved it.
According to the notes lowering this resistor lowers the HV output and therefore brings it back into an operating window that the board wont shut down so you can acutally test things. I was expecting to see bad regulators under load but no all fine. So my thought is how the f$%k did this thing work before and what changed that made it suddenly output higher HV??
Also, an extra note, If the voltage regulators (on the hv board) are not able to output correct voltage under load you cannot see this from a bench test with Q3 (BUD406D) removed. This means you have to find a way for the HV circuit to operate to properly check the +24 / -24v reg outputs. Annoying design haha
