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Old 7th April 2007, 04:16 AM   #1
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Default pearl HELP!

So, I've been enjoying (immensely) my pearl for a couple of weeks now. Tonight I went to change the volume, and static jumped from my finger to the volume knob. At first I thought I lost the entire left channel, but now it's playing quietly, and using the volume control (50k noble pot) to "6" brings sound to a semi-listenable level. Normally I'm a "3 or 4" on by control.

I've done enough troubleshooting to know that it's definitely the pearl, and that it's just not playing as loud. Where do I go from here?
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Old 7th April 2007, 10:29 AM   #2
cviller is offline cviller  Denmark
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You might have fried a transistor...

To find the problem, I think you should measure the voltages on your left channel compared to the right channel and waynes numbers. If some of the voltages are way off, you might have the problem in that area or in the circuitry connected.
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Old 7th April 2007, 01:50 PM   #3
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Quote:
Originally posted by cviller
You might have fried a transistor...

To find the problem, I think you should measure the voltages on your left channel compared to the right channel and waynes numbers. If some of the voltages are way off, you might have the problem in that area or in the circuitry connected.
I was hoping that wasn't it. Thanks though.
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Old 7th May 2007, 03:02 PM   #4
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If anyone can help me with this:

Q4 was reading 0.7 V compared to the 13.8 on Wayne's schematic. I replaced this with a new ztx450, and I'm still getting the same reading.

Any ideas what I should go for next before I just start randomly replacing things?
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Old 7th May 2007, 03:12 PM   #5
cviller is offline cviller  Denmark
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What is the voltage between R25 and Q6? And both ends of R14?
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Old 7th May 2007, 03:31 PM   #6
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I'm not exactly sure where on Q6 I should measure. And from which side of R25? From the side of R25 opposite of Q6:

1 2 3 4
.794 .307 .308 .795

5 6 7
.758 .383 .758

If I measure from R25 on the "facing Q6", I would subtract .307 from each measurement.

The voltage across R14 is 28.07 V
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Old 7th May 2007, 03:41 PM   #7
cviller is offline cviller  Denmark
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When I say R25 I mean the voltage on the one leg which is not connected to ground. It is easier if you reference all voltages to gnd.

What is the voltage bias on Q4 - should be 14V?
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Old 7th May 2007, 03:47 PM   #8
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Q4 is reading ~0.78 V from gnd

The leg on R25 "away" from Q6 is the gnd, The voltage drop across R25 is 0.307 V.

Is R26 the additional resistor for cartridge loading? My cart is 47k, so I did not use R26.
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Old 7th May 2007, 03:54 PM   #9
cviller is offline cviller  Denmark
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Quote:
Q4 is reading ~0.78 V from gnd
On the base?

You should have something like:
28V -[R17] - 14V - [R20]- gnd

and the base of Q4 is connected between R17 and R20.

Quote:
The leg on R25 "away" from Q6 is the gnd, The voltage drop across R25 is 0.307 V.
Seems ok...



Quote:
Is R26 the additional resistor for cartridge loading? My cart is 47k, so I did not use R26.
I don't know why I wrote R26, I meant R25.
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Old 7th May 2007, 04:14 PM   #10
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Quote:
Originally posted by cviller


On the base?

You should have something like:
28V -[R17] - 14V - [R20]- gnd

For Q4

Where Wayne has it marked 13.4 V, I'm getting 0.78 V.

Where he has it marked 19.3 V I'm getting 0.75 V

Where it's marked 14 V I'm getting 1.55 V

However, I'm getting a 27 V drop across R17... which definitely doesnt seem right.
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