Plus AB Voltage Issues, Resoldering Failure.

[Ike]

Yeah, I broke something again... Feel like an idiot; Everything I put my hands on breaks lately, so here goes:

One of my pluses suffered from your average no-video problem, hit the side, would flash back into video, just to lose it again sometime later.

So on to resoldering then, discharged the CRT, resoldered all the connections with the plugs left mated so the whole thing wouldn't melt down.

Resoldered the Flyback.

Turned it on... now the screen was filled with horizontal retrace lines, the screen was WAYYYYY too bright, even on the lowest setting on the (consumer accessible-) brightness knob. So after some fiddling with the internal pots. It boots up quite ok. Then when it hits the questionmark screen the screen begins to flash into 'superbright' mode and I quickly kill the power.

So before my logicboard would emit the magic smoke I removed it and tried to measure voltages at the internal connector to the logic board. Turned the plus on and 'whup-whup-whup'!!! that sounded to me like the overvoltage-overcurrent protection so again, quickly killed the power after two or tree 'whups'.

Now WHAT did I kill with simply resoldering the connections? It was working fine before so I'm at a loss. After checking everything for any bridged traces I found none.

 

[CC_333]

Turned the plus on and 'whup-whup-whup'!!! that sounded to me like the overvoltage-overcurrent protection so again, quickly killed the power after two or tree 'whups'.

Without the logic board connected, it will do that I've found.
I had an analog board that I tried rebuilding, and it just wouldn't work (kept making that sound). So, on a whim, I decided to try hooking it up to a logic board ("what did I have to lose?" I thought to myself). To my amazement, it worked perfectly!

As for the brightness problem, try resoldering the connections at the brightness pot. It sounds like there might be a loose connection there.

If that doesn't work, there might be a flaky resistor in that circuit (I forget what Larry Pina's book says past that).

c

 

[Ike]

Thank you! That's already a relief! :O

I will probably de-solder some of the resistors near the connector to the neck and see if something is flaky there.