Retired Texas TI99/4A engineer needs help please.

[Refugee]

Now that we have a photo of the board it looks like the 723 may be running as a switching regulator judging by the size of the choke.
It looks like the circuit in the link a post or two back with a PNP driver and an NPN output.
On the board there is a mangy looking capacitor right next to the heat sink for the TIP31. It looks like it has been hot so that the plastic jacket has shrunk back. That will play hell with a switching regulator.
To the right of it is another component I can't identify that also looks mangy. What is it?
Lets see what happens once that duff capacitor has been changed?

[Nick]

The standard replacement seems to be the Meanwell GP25A13A-R1B.

https://www.mouser.co.uk/ProductDetail/M...Tvoxh7QCoA==

[boater sam]

Now that we have a photo of the board it looks like the 723 may be running as a switching regulator judging by the size of the choke.
It looks like the circuit in the link a post or two back with a PNP driver and an NPN output.
On the board there is a mangy looking capacitor right next to the heat sink for the TIP31. It looks like it has been hot so that the plastic jacket has shrunk back. That will play hell with a switching regulator.
To the right of it is another component I can't identify that also looks mangy. What is it?
Lets see what happens once that duff capacitor has been changed?

That electrolytic is in the 12v reg circuit output, its fine.
The component to the right is the TIP31 in its clip on heatsink.

Q1 and Q2 , the 723 reg chip and the obsolete and unobtainable  LT331 voltage comparator are now all blown after the catastrophic domino  fail.

So I am giving up, stripping all the right side components off and fitting a buck.

Thanks for all the help guys, there does come a time when its just too much to bother with if there is an easier way out.

Sam.

[Terry]

You seem to have developed a stammer!

That's the second time in 24 hours that you have involuntarily repeated yourself ...