UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Retired Texas TI99/4A engineer needs help please.

Boater Sam · 21st Oct 2018, 9:02 pm

I have TIP31B in now. It should make no difference.
Pushed for time so it will have to wait till later, I'm on a deadline for going away for winter, lots of boat maintenance to do in the next month.
In view of the distorted picture when this psu is running the computer I may have a ripple on one or other of the supplies.
If I scope them just how clean can I expect them to be?
I'm trying to understand what instigated the failure, was it the leaky cap or the O/C diode?
I would have thought that even with the power transistor O/C the 100 ohm resistor would not have passed enough current to burn out, they look to be 1/4 watt.
Sam.

21st Oct 2018, 9:02 pm	#6
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Retired Texas TI99/4A engineer needs help please. I have TIP31B in now. It should make no difference. Pushed for time so it will have to wait till later, I'm on a deadline for going away for winter, lots of boat maintenance to do in the next month. In view of the distorted picture when this psu is running the computer I may have a ripple on one or other of the supplies. If I scope them just how clean can I expect them to be? I'm trying to understand what instigated the failure, was it the leaky cap or the O/C diode? I would have thought that even with the power transistor O/C the 100 ohm resistor would not have passed enough current to burn out, they look to be 1/4 watt. Sam.