On Sunday I wasn't making good progress and added my tuppence worth to this
"I'm an Idiot" thread after killing a regulator chip.
Well my replacement linear regulator arrived today which is a 10 pin circular can and not too easy to replace a second time with tracks falling off the board but after that I was still struggling to identify why one of the 5 volt rails was shorted.
The TF2370 is in two halves and fortunately it can be powered up with the RF section unplugged. Even with all the plug-in cards removed from the digital chassis I still had a short circuit and it wasn't obvious to me where else this rail supplied. There is a thyristor over volt protection on the rail but disconnecting that I still had a 0.3 ohm short.
Some of the wiring harness has rather tightly packed connections in places and with shaky hands and poor close vision I was a bit reluctant to unsolder parts of it but desperation forced my hand and I eventually tracked it down to the front panel and to one of the push button switches. I thought this was a bit odd but on turning it upside down I discovered that there was a ground wire with the insulation cracking off. In an instrument that is entirely wired in plastic coated wires this was a big surprise.
Anyway, I glad to report that the old TF2370 back in operation again.
Peter