Mullard HSVT problem - UK Vintage Radio Repair and Restoration Discussion Forum

Alf Fisher · 7th May 2019, 8:53 pm

Hi folks,

My HSVT has a problem most noticeable when trying to test FW rectifiers such as 5Z4. One side works fine but on trying to test the other side, it immediately blows the cutout.

I've traced the fault to one of the fixed matrix contacts where the insulating bush has tracked across to the chassis.

Is it feasible to replace one of these bushes given that a spare one can be found or could the burnt bit be dremeled away or would it be simpler to swap the whole matrix panel if a donor part was available.

Alf

Electronpusher0 · 8th May 2019, 8:22 am

I would hesitate to try and change the whole matrix panel, all those wires, to say nothing of alignment.
It would also mean finding a doner set and I would hate to see one scrapped.

Why not try demeling the burnt part and then using epoxy, you've nothing to lose.

Peter

Alf Fisher · 13th May 2019, 7:05 pm

Hi Peter,

Yes I'm not keen on removing all those wires and links and then get them all back in the correct places.

I think I might give it the dremelling treatment.

I did it some years ago with the W plug on a Gee Indicator Type 95. The EHT tracked across from the pin to the shell. I dremeled away the carbonised Bakelite and then filled the crater with araldite and it's still working fine.

Cheers, Alf

7th May 2019, 8:53 pm	#1
Alf Fisher Hexode Join Date: Sep 2005 Location: Potton, Bedfordshire, UK. Posts: 293	Mullard HSVT problem Hi folks, My HSVT has a problem most noticeable when trying to test FW rectifiers such as 5Z4. One side works fine but on trying to test the other side, it immediately blows the cutout. I've traced the fault to one of the fixed matrix contacts where the insulating bush has tracked across to the chassis. Is it feasible to replace one of these bushes given that a spare one can be found or could the burnt bit be dremeled away or would it be simpler to swap the whole matrix panel if a donor part was available. Alf

8th May 2019, 8:22 am	#2
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,296	Re: Mullard HSVT problem I would hesitate to try and change the whole matrix panel, all those wires, to say nothing of alignment. It would also mean finding a doner set and I would hate to see one scrapped. Why not try demeling the burnt part and then using epoxy, you've nothing to lose. Peter

13th May 2019, 7:05 pm	#3
Alf Fisher Hexode Join Date: Sep 2005 Location: Potton, Bedfordshire, UK. Posts: 293	Re: Mullard HSVT problem Hi Peter, Yes I'm not keen on removing all those wires and links and then get them all back in the correct places. I think I might give it the dremelling treatment. I did it some years ago with the W plug on a Gee Indicator Type 95. The EHT tracked across from the pin to the shell. I dremeled away the carbonised Bakelite and then filled the crater with araldite and it's still working fine. Cheers, Alf