Hi,
I bought a Hameg 203-5 scope, which had flickering traces whenever the controls are manipulated, it looked like it needed some cleaning so i went ahead and disassembled the unit, gave it a good clean and all worked fine.
The issue is, when i was putting it back together, i couldnt remember which of the TO220 packages devices was screwed down to the chassis without insulation, one of them is the TIP47 npn transistor in the regulation circuit for the 170v rail, i ended up guessing it, i screwed the TIP47 down to the chassis with no insulation shorting its collector to GND, when i powered up the unit it only showed three dots in the center of the CRT, i started measuring the PS voltages, the 170 and 140v rails were showing 25v and 23v respectively, i think i have damaged something in the circuit.
I tried troubleshooting the regulator circuit replacing the TL431 and the BF423 with no success. I still didnt replace the TIP47 yet though.
I decided to inject a 170v from an external source and see what effect it has on the unit, when i did the traces showed up and everything was normal but i noticed a resistor (R707 circled in red) was heating up in an adjacent circuit.
My question is if anyone has run into a similar issue how did u manage to fix it.
And basically where should i start.
Thanks