DECCA Type 88 Monitor / Chassis HELP!! please - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

gavinmorgan · 15th Apr 2013, 6:35 pm

I am rather confused now ....

which chassis is this then ?

and does anybody have a schematic and an idea of where I might
source a replacement part.

All of your help is greatly appreciated.

Gavin

Welsh Anorak · 16th Apr 2013, 1:11 pm

Hi there
Right - what you have there is a Decca 92 series chassis. I've got a rather poor service manual in front of me. I assume the fault is in the power supply. It uses, rather unusually, a TDA2581 control IC and a Darlington switcher (TR605, BUW81A) with a BSR59 driver (TR604). These latter two transistors can cause trouble and should be replaced together, along with C631 (2n2, 2kV) and any other silicon that's been killed. It's a fairly complex circuit by more recent standards, but I don't recall any problems with the transformer which, by the way, does have the part number you quote.
I think you'll have your work cut out finding a transformer for this set so it's important you are sure it has failed. The 70/72 chassis used a similar circuit but, as it was for a portable, had a different transformer.
I could try scanning the diagram but I suspect it won't come out well as it's already a photocopy.
Glyn

Welsh Anorak · 16th Apr 2013, 1:32 pm

Hi
Here's a scan of the PSU which should be just about readable. If not PM me your email and I can send you a higher-res copy.
Glyn

gavinmorgan · 17th Apr 2013, 10:25 am

Thanks Glyn,

Your help is greatly appreciated.

I will see if I can read the diagram.

Diolch yn fawr.

Gavin

15th Apr 2013, 6:35 pm	#21
gavinmorgan Retired Dormant Member Join Date: Jan 2013 Location: Abergele, North Wales, UK Posts: 13	Re: DECCA Type 88 Monitor / Chassis HELP!! please I am rather confused now .... which chassis is this then ? and does anybody have a schematic and an idea of where I might source a replacement part. All of your help is greatly appreciated. Gavin

16th Apr 2013, 1:11 pm	#22
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,928	Re: DECCA Type 88 Monitor / Chassis HELP!! please Hi there Right - what you have there is a Decca 92 series chassis. I've got a rather poor service manual in front of me. I assume the fault is in the power supply. It uses, rather unusually, a TDA2581 control IC and a Darlington switcher (TR605, BUW81A) with a BSR59 driver (TR604). These latter two transistors can cause trouble and should be replaced together, along with C631 (2n2, 2kV) and any other silicon that's been killed. It's a fairly complex circuit by more recent standards, but I don't recall any problems with the transformer which, by the way, does have the part number you quote. I think you'll have your work cut out finding a transformer for this set so it's important you are sure it has failed. The 70/72 chassis used a similar circuit but, as it was for a portable, had a different transformer. I could try scanning the diagram but I suspect it won't come out well as it's already a photocopy. Glyn

16th Apr 2013, 1:32 pm	#23
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,928	Re: DECCA Type 88 Monitor / Chassis HELP!! please Hi Here's a scan of the PSU which should be just about readable. If not PM me your email and I can send you a higher-res copy. Glyn Attached Thumbnails

17th Apr 2013, 10:25 am	#24
gavinmorgan Retired Dormant Member Join Date: Jan 2013 Location: Abergele, North Wales, UK Posts: 13	Re: DECCA Type 88 Monitor / Chassis HELP!! please Thanks Glyn, Your help is greatly appreciated. I will see if I can read the diagram. Diolch yn fawr. Gavin