Thread: Marconi TF2370
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Old 3rd Aug 2022, 7:38 pm   #1
peter_scott's Avatar
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,176
Default Marconi TF2370

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.

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