Bush AC34 restoration - quiet audio, help, please. - UK Vintage Radio Repair and Restoration Discussion Forum

Scotorvm · 25th Nov 2020, 6:58 pm

Bush AC34 restoration - quiet audio, help, please.

Guy's
Have attempted a restore of what is quite a large set, to me anyway.
I acquired this for £20, which seemed like a good deal when you look at all the workmanship on this.

The case was in poor condition, the laminate peeling, scratched and missing in sections.

Spent a few days on the case and replacing all the wax caps, before attempting to power up.

Audio is there, but very quiet, a couple of stations on MW, no external aerial plugged in for the test, hum from the speaker, but all quiet when the external speaker knob un-screwed on the rear, so somethings working.

Any pointers on where to start appreciated, no voltages checked so far.

Thanks again

Scotorvm · 25th Nov 2020, 7:04 pm

Sorry, forgot to mention, resistors all check out OK.

John10b · 25th Nov 2020, 9:05 pm

Just as a starter switch to Gram and touch the PU sockets with metal probe , or your finger, with volume control turns right up you should get a Healthy buzz.
John

John10b · 25th Nov 2020, 9:12 pm

Sorry I should have asked do you have the service manual or circuit diagram?
John

Ed_Dinning · 25th Nov 2020, 9:12 pm

Hi Scot, voltage checks I'm afraid it has to be.
If you have the service data from the forum note that if your figures are within 10% of the values given there is no problem.

Also observe if anything is getting hot and resist the temptation to twiddle the coil cores and trimmer caps

Ed

Scotorvm · 25th Nov 2020, 9:48 pm

Quote:

Originally Posted by John10b

Sorry I should have asked do you have the service manual or circuit diagram?
John

Hi John, thanks for the tip re the probe, will try that, I do have the circuit diagram.
Cheers.
Lee

Scotorvm · 25th Nov 2020, 9:50 pm

Quote:

Originally Posted by Ed_Dinning

Hi Scot, voltage checks I'm afraid it has to be.
If you have the service data from the forum note that if your figures are within 10% of the values given there is no problem.

Also observe if anything is getting hot and resist the temptation to twiddle the coil cores and trimmer caps

Ed

Thanks Ed, yes I have the DVD from the forum, back to work tomorrow, but will check next week

Sideband · 25th Nov 2020, 10:25 pm

Quote:

Originally Posted by Scotorvm

no external aerial plugged in for the test,

You WILL need an aerial to hear anything meaningful. It will be very quiet without one.

McMurdo · 25th Nov 2020, 11:43 pm

Most of my radios here would be pretty dead without an external aerial...at least ones without their own internal aerial like yours.

electrogram · 26th Nov 2020, 2:10 am

Looking at the second pic it looks like some of the pF caps in the RF stages have been replaced... Built in frame aerial for MW/LW.

crackle · 26th Nov 2020, 9:40 am

What are those blue caps on the tag strip.

Mike

vinrads · 26th Nov 2020, 9:54 am

Looks like the mica capacitors have been replaced! That needs checking out.

Mick.

Scotorvm · 26th Nov 2020, 4:28 pm

Quote:

Originally Posted by crackle

What are those blue caps on the tag strip.

Mike

Mike

The blue caps are in on the strip paralleled to double the value to what it should be.

I replaced the small waxy pF caps too, should I have left them?

Scotorvm · 26th Nov 2020, 4:29 pm

Quote:

Originally Posted by vinrads

Looks like the mica capacitors have been replaced! That needs checking out.

Mick.

Mick, yes I replaced those, a mistake? the old ones were waxy and replaced with the correct pF rating.

Lee

HamishBoxer · 26th Nov 2020, 5:31 pm

Yes!

John10b · 26th Nov 2020, 6:02 pm

Do I understand correctly that the Radio works, after you changed the components, as you say in post #1, but with low volume?
John

Scotorvm · 26th Nov 2020, 9:55 pm

Quote:

Originally Posted by John10b

Do I understand correctly that the Radio works, after you changed the components, as you say in post #1, but with low volume?
John

Yes John, on MW can hear at least 2 stations, very quiet at almost full volume, without an external aerial. I think I saved the pF wax caps from another Bush set which I can put in this set, if it would help.

Cheers
Lee

Simon Gittins · 26th Nov 2020, 10:16 pm

The reason the advice is given not to change the pF values is that they are rarely faulty and to change them may affect the alignment. However, now that you have changed them, there is no point putting old wax types back in.
The best thing is to follow the advice in post 5 and carry out voltage checks. Changing the capacitors may not have affected alignment too badly and it's best not adjusted without a signal generator.

Scotorvm · 27th Nov 2020, 11:42 am

Cheers Simon

Freya · 27th Nov 2020, 2:09 pm

Did you change any pF caps inside the cans ?

25th Nov 2020, 7:04 pm	#2
Scotorvm Pentode Join Date: Jul 2020 Location: Falkirk, Stirlingshire, UK. Posts: 200	Re: Bush AC34 restoration - quiet audio, help, please. Sorry, forgot to mention, resistors all check out OK.

25th Nov 2020, 9:05 pm	#3
John10b Nonode Join Date: Nov 2016 Location: Aberaeron, Ceredigion, Wales, UK. Posts: 2,882	Re: Bush AC34 restoration - quiet audio, help, please. Just as a starter switch to Gram and touch the PU sockets with metal probe , or your finger, with volume control turns right up you should get a Healthy buzz. John

25th Nov 2020, 9:12 pm	#4
John10b Nonode Join Date: Nov 2016 Location: Aberaeron, Ceredigion, Wales, UK. Posts: 2,882	Re: Bush AC34 restoration - quiet audio, help, please. Sorry I should have asked do you have the service manual or circuit diagram? John

25th Nov 2020, 9:12 pm	#5
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Bush AC34 restoration - quiet audio, help, please. Hi Scot, voltage checks I'm afraid it has to be. If you have the service data from the forum note that if your figures are within 10% of the values given there is no problem. Also observe if anything is getting hot and resist the temptation to twiddle the coil cores and trimmer caps Ed

25th Nov 2020, 11:43 pm	#9
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,269	Re: Bush AC34 restoration - quiet audio, help, please. Most of my radios here would be pretty dead without an external aerial...at least ones without their own internal aerial like yours. __________________ Kevin

25th Nov 2020, 6:58 pm	#1
Scotorvm Pentode Join Date: Jul 2020 Location: Falkirk, Stirlingshire, UK. Posts: 200	Bush AC34 restoration - quiet audio, help, please. Bush AC34 restoration - quiet audio, help, please. Guy's Have attempted a restore of what is quite a large set, to me anyway. I acquired this for £20, which seemed like a good deal when you look at all the workmanship on this. The case was in poor condition, the laminate peeling, scratched and missing in sections. Spent a few days on the case and replacing all the wax caps, before attempting to power up. Audio is there, but very quiet, a couple of stations on MW, no external aerial plugged in for the test, hum from the speaker, but all quiet when the external speaker knob un-screwed on the rear, so somethings working. Any pointers on where to start appreciated, no voltages checked so far. Thanks again Attached Thumbnails

26th Nov 2020, 2:10 am	#10
electrogram Heptode Join Date: Jul 2008 Location: Hereford, UK. Posts: 719	Re: Bush AC34 restoration - quiet audio, help, please. Looking at the second pic it looks like some of the pF caps in the RF stages have been replaced... Built in frame aerial for MW/LW.

26th Nov 2020, 9:40 am	#11
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Bush AC34 restoration - quiet audio, help, please. What are those blue caps on the tag strip. Mike

26th Nov 2020, 9:54 am	#12
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,754	Re: Bush AC34 restoration - quiet audio, help, please. Looks like the mica capacitors have been replaced! That needs checking out. Mick.

26th Nov 2020, 5:31 pm	#15
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,931	Re: Bush AC34 restoration - quiet audio, help, please. Yes! __________________ G8JET BVWS Archivist and Member V.M.A.R.S

26th Nov 2020, 6:02 pm	#16
John10b Nonode Join Date: Nov 2016 Location: Aberaeron, Ceredigion, Wales, UK. Posts: 2,882	Re: Bush AC34 restoration - quiet audio, help, please. Do I understand correctly that the Radio works, after you changed the components, as you say in post #1, but with low volume? John

26th Nov 2020, 10:16 pm	#18
Simon Gittins Heptode Join Date: Jan 2006 Location: Cornwall, UK. Posts: 505	Re: Bush AC34 restoration - quiet audio, help, please. The reason the advice is given not to change the pF values is that they are rarely faulty and to change them may affect the alignment. However, now that you have changed them, there is no point putting old wax types back in. The best thing is to follow the advice in post 5 and carry out voltage checks. Changing the capacitors may not have affected alignment too badly and it's best not adjusted without a signal generator.

27th Nov 2020, 11:42 am	#19
Scotorvm Pentode Join Date: Jul 2020 Location: Falkirk, Stirlingshire, UK. Posts: 200	Re: Bush AC34 restoration - quiet audio, help, please. Cheers Simon

27th Nov 2020, 2:09 pm	#20
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,989	Re: Bush AC34 restoration - quiet audio, help, please. Did you change any pF caps inside the cans ? __________________ Stephen _________"It`s only an old telly" ___