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Old 25th Sep 2009, 9:04 am   #1
davidgsmith
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Default DAC90A Volume problem

Can somebody help?
When I turn the Volume knob to minimum, you can still hear the radio. Is this possible to repair?
Thanks
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Old 25th Sep 2009, 9:14 am   #2
YT2095UK
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Default Re: DAC90A Volume problem

it`s quite possible the carbon track on the "horse shoe" in the pot has work thin at the Earth end, are there any crackles to be heard when you use the volume control?
the Wiper could be dirty, OR... the resistor that takes that end to deck may have gone high value.
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Old 25th Sep 2009, 9:26 am   #3
davidgsmith
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Default Re: DAC90A Volume problem

can't hear any crackles.
As a novice, how do i check out the components you mentioned?
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Old 25th Sep 2009, 9:27 am   #4
peter_sol
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Default Re: DAC90A Volume problem

This can be quite normal.
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Old 25th Sep 2009, 9:50 am   #5
Radio_Dave
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Default Re: DAC90A Volume problem

Yes, leaving on a bit of audio when the volume control is 'turned off' is a good way to let you now that the set's been left on. It's particularly important with battery sets, but also useful with mains operated ones... However, I'm not sure this feature applies to a DAC90a
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Old 25th Sep 2009, 10:49 am   #6
Boom
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Default Re: DAC90A Volume problem

I have eleven DAC90As and they all have a bit of volume at minimum.
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Old 25th Sep 2009, 10:56 am   #7
paulsherwin
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Default Re: DAC90A Volume problem

A very low volume at minimum is normal. A bad UBC41 can cause this symptom too though.

Paul
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Old 25th Sep 2009, 11:55 am   #8
Steve_P
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Default Re: DAC90A Volume problem

I had this over two years ago with a DAC90A on here. Paul's right - UBC41. Might be OK in another radio though.

Cheers,

Steve P.
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Old 25th Sep 2009, 1:14 pm   #9
kalee20
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Default Re: DAC90A Volume problem

Disconnect from the mains. With the volume control at minimum, but the switch definitely 'on', measure the resistance between the control's wiper tag and the outer tag (the one that's connected to the metal braiding on the wires).

Ther resistance should be a few ohms at most. If it's higher, then the control is worn out as post #2. If it is OK, then the problam is almost certainly leakage within the UBC41.

However, it's a fault that is almost certainly liveable with!
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Old 25th Sep 2009, 1:22 pm   #10
paulsherwin
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Default Re: DAC90A Volume problem

Quote:
Originally Posted by kalee20 View Post
it's a fault that is almost certainly liveable with!
If it's a UBC41 problem, it will continue to get worse though.

Paul
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Old 25th Sep 2009, 7:14 pm   #11
davidgsmith
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Default Re: DAC90A Volume problem

Quote:
Originally Posted by kalee20 View Post
Disconnect from the mains. With the volume control at minimum, but the switch definitely 'on', measure the resistance between the control's wiper tag and the outer tag (the one that's connected to the metal braiding on the wires).

Ther resistance should be a few ohms at most. If it's higher, then the control is worn out as post #2. If it is OK, then the problam is almost certainly leakage within the UBC41.

However, it's a fault that is almost certainly liveable with!
Not quite sure which terminals you mean, but like you say, I can live with it i suppose
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Old 25th Sep 2009, 9:28 pm   #12
howard
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Default Re: DAC90A Volume problem

Hello,

This problem can be caused by either a worn volume potentiometer or a slightly leaky UBC41. I have three DAC90As, two late examples and an earlier mid 1950s one and only the latter exhibited this problem and that definitely had a worn pot and I fixed it by fitting a new 500k ohm log potentiometer and DP switch. I gather that one can fit a 330pf capacitor between the grid and cathode tags of the UBC41 to correct the problem if caused by the UBC41.

Howard
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