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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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29th Nov 2018, 2:25 pm | #1 |
Tetrode
Join Date: Sep 2017
Location: Dorchester, Dorset, UK.
Posts: 81
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Bush DAC90A blocking capacitor location?
Got a crackly volume switch issue and the volume is loud I have been told to check the blocking capacitor, could someone point me into where this is please?
I have changed all the caps and resistors and a new audio transformer and have brought a dead set back to life just need to sort out this issue and I am done. Thanks Mike |
29th Nov 2018, 2:44 pm | #2 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,059
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Re: Bush DAC90A blocking capacitor location?
A noisy volume control can be caused by excessive DC on the volume control, caused by a leaky coupling capacitor. But not in the DAC90a, where the design does inherently put DC on the control, albeit just a few volts, and nothing to do with a bad capacitor.
It's a new control you'll need. |
29th Nov 2018, 2:54 pm | #3 |
Rest in Peace
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
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Re: Bush DAC90A blocking capacitor location?
Or take the control apart and carefully clean the track and metal centre contact. Dont rub the carbon track hard or you may wipe away the carbon.
Then put a thin smear of grease on the track and the centre metal contact where the centre wiper makes contact. Mike |
29th Nov 2018, 5:08 pm | #4 |
Tetrode
Join Date: Sep 2017
Location: Dorchester, Dorset, UK.
Posts: 81
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Re: Bush DAC90A blocking capacitor location?
Found a replacement from Bowood electronics so will give that a go
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29th Nov 2018, 6:37 pm | #5 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,675
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Re: Bush DAC90A blocking capacitor location?
Changing all the capacitors and resistors seems unnecessarily heroic. Perhaps you meant a limited number of components recommended for replacement.
Any such list should have included the output grid coupling capacitor 0.01uf circled below.
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29th Nov 2018, 7:14 pm | #6 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
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Re: Bush DAC90A blocking capacitor location?
Generally a waste of time changing all the resistors. Even if the originals are slightly off tolerance, changing them will make little or no difference. Valve radios are very forgiving (with a few exceptions) with resistor values.
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