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Old 25th Nov 2020, 5:58 pm   #1
Scotorvm
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Default 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
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Old 25th Nov 2020, 6:04 pm   #2
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Default Re: Bush AC34 restoration - quiet audio, help, please.

Sorry, forgot to mention, resistors all check out OK.
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Old 25th Nov 2020, 8:05 pm   #3
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Default 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
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Old 25th Nov 2020, 8:12 pm   #4
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Default Re: Bush AC34 restoration - quiet audio, help, please.

Sorry I should have asked do you have the service manual or circuit diagram?
John
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Old 25th Nov 2020, 8:12 pm   #5
Ed_Dinning
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Default 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
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Old 25th Nov 2020, 8:48 pm   #6
Scotorvm
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Default Re: Bush AC34 restoration - quiet audio, help, please.

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Originally Posted by John10b View Post
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
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Old 25th Nov 2020, 8:50 pm   #7
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Default Re: Bush AC34 restoration - quiet audio, help, please.

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Originally Posted by Ed_Dinning View Post
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
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Old 25th Nov 2020, 9:25 pm   #8
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Default Re: Bush AC34 restoration - quiet audio, help, please.

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Originally Posted by Scotorvm View Post
no external aerial plugged in for the test,
You WILL need an aerial to hear anything meaningful. It will be very quiet without one.
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Old 25th Nov 2020, 10:43 pm   #9
McMurdo
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Default 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.
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Old 26th Nov 2020, 1:10 am   #10
electrogram
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Default 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.
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Old 26th Nov 2020, 8:40 am   #11
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Default Re: Bush AC34 restoration - quiet audio, help, please.

What are those blue caps on the tag strip.

Mike
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Old 26th Nov 2020, 8:54 am   #12
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Default Re: Bush AC34 restoration - quiet audio, help, please.

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

Mick.
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Old 26th Nov 2020, 3:28 pm   #13
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Default Re: Bush AC34 restoration - quiet audio, help, please.

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Originally Posted by crackle View Post
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?
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Old 26th Nov 2020, 3:29 pm   #14
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Default Re: Bush AC34 restoration - quiet audio, help, please.

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Originally Posted by vinrads View Post
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
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Old 26th Nov 2020, 4:31 pm   #15
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Default Re: Bush AC34 restoration - quiet audio, help, please.

Yes!
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Old 26th Nov 2020, 5:02 pm   #16
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Default 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
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Old 26th Nov 2020, 8:55 pm   #17
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Default Re: Bush AC34 restoration - quiet audio, help, please.

Quote:
Originally Posted by John10b View Post
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
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Old 26th Nov 2020, 9:16 pm   #18
Simon Gittins
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Default 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.
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Old 27th Nov 2020, 10:42 am   #19
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Default Re: Bush AC34 restoration - quiet audio, help, please.

Cheers Simon
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Old 27th Nov 2020, 1:09 pm   #20
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Default Re: Bush AC34 restoration - quiet audio, help, please.

Did you change any pF caps inside the cans ?
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