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Old 11th July 2008, 01:56 AM   #1
rtate is offline rtate  Canada
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Default another BOZ problem....

I got my boz all set up and the bias set to 30ma.(3v at R108)
My problem is when i play music it is very loud even with the volume controls(2 separate ladder attenuators)set at the minimum.
If I turn the volume up the sound goes up accordingly but it is way to loud at the minimum setting.
When I measure the volume pot it reads 14.7k ohms at min and
0 ohms at max.

What could be the problem??
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Old 11th July 2008, 10:20 AM   #2
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Default Re: another BOZ problem....

Quote:
Originally posted by rtate
When I measure the volume pot it reads 14.7k ohms at min and
0 ohms at max.

What could be the problem??
What are the shunt value(s) at these readings?
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Old 11th July 2008, 12:25 PM   #3
Tolu is offline Tolu  Germany
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Are you sure that you have connected the pot correctly?

in, wiper to preamp in, ground!

At lowest pot position you will hear nothing, cause the signal runs to ground!
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Old 11th July 2008, 12:38 PM   #4
AndrewT is offline AndrewT  Scotland
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did you buy the ladder attenuators ready assembled or did you make them up yourself?

I suspect you have a variable series resistor in the line feed, instead of an attenuator.
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Old 11th July 2008, 01:15 PM   #5
Magura is offline Magura  Denmark
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Quote:
Originally posted by AndrewT
did you buy the ladder attenuators ready assembled or did you make them up yourself?

I suspect you have a variable series resistor in the line feed, instead of an attenuator.

I think you're right Andrew....but the terms you just used, means little to a newbe

Rtate:

Take a look at your volume control. It's got 3 legs, 2 that measures the same no matter what setting you choose, and a third that varies according to the other two.
Now make sure you connect the leg the varies to ground, as well as one of the other two legs.
Depending which way the Log. is according to the legs, you may have to swap the two legs that didn't change resistance when you turned the knob, in order to make it work proper.

Hmm, easy to do yourself.....somewhat more complicated to explain on print

Magura
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Old 11th July 2008, 01:20 PM   #6
AndrewT is offline AndrewT  Scotland
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Rtate is from Canada, hopefully he is not solely French speaking.
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Old 11th July 2008, 04:58 PM   #7
rtate is offline rtate  Canada
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Thanks for the replys!!
I got the BOZ from a friend who built the ladder on his own.
He said that the preamp worked before he put it into storage.
I do believe that the connections are correct and I think that you are correct about the variable series resistor.
When I measured the resistance it was between C1 and the output connection.
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Old 11th July 2008, 06:21 PM   #8
rtate is offline rtate  Canada
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Further measuring...
The 2 legs that do not vary are measured from C1 to Gnd.
They are a constant 15k.

From C1 to the output measure
15K at minimum setting and
0 ohms at max setting

From the output to ground measure
90 ohm at minimum setting and
15K at maximun setting.

Could this just be an input overload issue from my CD player??
I read that using resistors at the input will limit the bandwidth of the preamp by rolling off the high frequencies
I have the bias set at 30ma(3v at R108)but something is still not right!

IF so, sorry about the double post as I am trying to cover all my bases...
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Old 11th July 2008, 06:51 PM   #9
AndrewT is offline AndrewT  Scotland
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This is going to take a while.
I'm away dancing.
Who's going to volunteer?
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