Bush SRG88 losing volume - UK Vintage Radio Repair and Restoration Discussion Forum

Audio1950 · 11th Nov 2008, 9:42 pm

Firstly, please be patient with a raw recruit! I have recently acquired a Bush SRG88 stereogram, which is all working beautifully, except for one problem.
When the treble control is turned about three quarters of it's travel towards minimum, (anti-clockwise), although the treble continues to decrease, the volume suddenly drops by about half!
The valve line-up, if it helps is 1x ECC85, 1xECH81, 2xEF89, 2xEABC80, 2EL84 1xEZ81, and1xEM81. I have had limited experience with the electronics side of repair, but can replace components with confidence. Any help would be much appreciated.

Ed_Dinning · 11th Nov 2008, 10:03 pm

Hi Audio, I think the first thing to check could be the cap in series with the treble pot. This combination is usually connected across the output transformer primary.
Then check the pot is not damaged as well.
Then change the audio coupling cap (if not already done) as it will be leaky.

Ed

Darren-UK · 11th Nov 2008, 10:10 pm

I note Paul Stenning doesn't do the data for this model. Therefore if Ed's suggestions don't solve the problem, perhaps someone who happens to have the cct could post a scan of the relevant section of the circuit.

Steve_P · 11th Nov 2008, 11:13 pm

I have the SRG86 up - it's nearest!

Anyway : C59 and C60 (Anodes of the Triodes EABC80) first. These are known as 'That Capacitor' round here and should be changed.

Also check C62 and C65 - Across the Bass Controls, and C67 and C68. These go to earth.

Then please come back if these don't cure it!

Cheers,

Steve P.

Audio1950 · 12th Nov 2008, 11:20 pm

Thanks for the suggestions. I'll get the relevant caps, and work on it this weekend. I think I'll replace the lot while I'm in there. Will let you know how I get on.

Audio1950 · 16th Nov 2008, 12:54 am

I got as far as taking the chassis out, with a view to making a list of caps required, and getting them replaced, and then chickened out! To be honest, after all the references I've seen on here regarding polarity, values, sizes etc, I don't feel confident enough to tackle the job. I really don't want to end up with more problems than I started with, and would rather give the job to one of the experts!
Is there anyone who would be willing to replace the suspect caps, and any thing else that needs replacing? I would obviously be willing to deliver the chassis to them, (presumably this is all that's needed) and collect when ready. I really would like to get this instrument back to A1 condition, so if anyone could help, I would be grateful. I am based in Whittlesey, Peterborough.
Thanks.

Audio1950 · 17th Nov 2008, 7:02 pm

One of the forum members has now offered to do this for me, for which I am grateful. Many thanks to the others who offered their advice.
Audio1950

Audio1950 · 30th Nov 2008, 9:05 pm

Sorted! No, more than sorted, restored completely.
Thanks, Neil.

Audio1950

11th Nov 2008, 9:42 pm	#1
Audio1950 Dekatron Join Date: Nov 2008 Location: Whittlesey, near Peterborough, Cambridgeshire, UK. Posts: 3,761	Bush SRG88 losing volume Firstly, please be patient with a raw recruit! I have recently acquired a Bush SRG88 stereogram, which is all working beautifully, except for one problem. When the treble control is turned about three quarters of it's travel towards minimum, (anti-clockwise), although the treble continues to decrease, the volume suddenly drops by about half! The valve line-up, if it helps is 1x ECC85, 1xECH81, 2xEF89, 2xEABC80, 2EL84 1xEZ81, and1xEM81. I have had limited experience with the electronics side of repair, but can replace components with confidence. Any help would be much appreciated.

11th Nov 2008, 10:03 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Bush SRG88 losing volume Hi Audio, I think the first thing to check could be the cap in series with the treble pot. This combination is usually connected across the output transformer primary. Then check the pot is not damaged as well. Then change the audio coupling cap (if not already done) as it will be leaky. Ed

11th Nov 2008, 10:10 pm	#3
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	Re: Bush SRG88 losing volume I note Paul Stenning doesn't do the data for this model. Therefore if Ed's suggestions don't solve the problem, perhaps someone who happens to have the cct could post a scan of the relevant section of the circuit.

11th Nov 2008, 11:13 pm	#4
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Bush SRG88 losing volume I have the SRG86 up - it's nearest! Anyway : C59 and C60 (Anodes of the Triodes EABC80) first. These are known as 'That Capacitor' round here and should be changed. Also check C62 and C65 - Across the Bass Controls, and C67 and C68. These go to earth. Then please come back if these don't cure it! Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

12th Nov 2008, 11:20 pm	#5
Audio1950 Dekatron Join Date: Nov 2008 Location: Whittlesey, near Peterborough, Cambridgeshire, UK. Posts: 3,761	Re: Bush SRG88 losing volume Thanks for the suggestions. I'll get the relevant caps, and work on it this weekend. I think I'll replace the lot while I'm in there. Will let you know how I get on.

16th Nov 2008, 12:54 am	#6
Audio1950 Dekatron Join Date: Nov 2008 Location: Whittlesey, near Peterborough, Cambridgeshire, UK. Posts: 3,761	Re: Bush SRG88 losing volume I got as far as taking the chassis out, with a view to making a list of caps required, and getting them replaced, and then chickened out! To be honest, after all the references I've seen on here regarding polarity, values, sizes etc, I don't feel confident enough to tackle the job. I really don't want to end up with more problems than I started with, and would rather give the job to one of the experts! Is there anyone who would be willing to replace the suspect caps, and any thing else that needs replacing? I would obviously be willing to deliver the chassis to them, (presumably this is all that's needed) and collect when ready. I really would like to get this instrument back to A1 condition, so if anyone could help, I would be grateful. I am based in Whittlesey, Peterborough. Thanks.

17th Nov 2008, 7:02 pm	#7
Audio1950 Dekatron Join Date: Nov 2008 Location: Whittlesey, near Peterborough, Cambridgeshire, UK. Posts: 3,761	Re: Bush SRG88 losing volume One of the forum members has now offered to do this for me, for which I am grateful. Many thanks to the others who offered their advice. Audio1950

30th Nov 2008, 9:05 pm	#8
Audio1950 Dekatron Join Date: Nov 2008 Location: Whittlesey, near Peterborough, Cambridgeshire, UK. Posts: 3,761	Re: Bush SRG88 losing volume Sorted! No, more than sorted, restored completely. Thanks, Neil. Audio1950