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Old 31st March 2010, 11:58 PM   #11
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Check out the values on the other channel which operates
at 49 deg.

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Old 1st April 2010, 07:41 PM   #12
Mywing is offline Mywing  Italy
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Then, I can only identify the resistor to take that measurement.
Could you help to do that? Where is it?
Thanks again
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Old 1st April 2010, 08:53 PM   #13
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There's a big fat power resistor, usually 1 ohm, next to each
of the output devices. Pick one near the middle and measure
the DC voltage across it. It will be less than 1 volt.

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Old 1st April 2010, 10:28 PM   #14
Mywing is offline Mywing  Italy
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I don't see resistors near output devices... Maybe it need demount heatsinks?
[IMG]Click the image to open in full size.[/IMG]
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Old 4th April 2010, 03:08 PM   #15
mgm31 is offline mgm31  France
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I don't know about the SA4e but I have a SA3 optical bias upgraded to e version with the two blue pots.

I measure 190mV between the 1 ohms resistors. You can see pictures here : www.thresholdlovers.com • View topic - Threshold SA3e.
Your picture is too small to see anything.

I don't know exactly but the 4e is the mono version of the 3.9e, so I suppose 160mV / 190mV to be the good bias.
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Old 4th April 2010, 06:50 PM   #16
Mywing is offline Mywing  Italy
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Thanks for answer mgm.
After patients lenghty attempts through the blue pots, I obtained a temperature at 51 degrees for both heatsink. Now I would to check dc voltage on emitter resistor (I found that it would be 165-170 mV) but I can not see them close to the output devices. Maybe they are on the rear and I must remove the heatsink to see them?
Here is a picture more visible


Click the image to open in full size.

Where are the emitter resistors?


Happy Easter
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Old 5th April 2010, 03:10 AM   #17
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Forget about the emitter resistors. Use an AC ammeter (maybe
a Kill-a-watt (tm)) to watch the current draw of the whole amp
while you trim the bias slightly downward. Readjust after you
note the temperature after warm-up.

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Old 5th April 2010, 06:09 PM   #18
Mywing is offline Mywing  Italy
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Which value I would see on the meter?

Anyway, adjusting bias only through the heatsinks temperature I obtained 51-52 degr. on both channels... Can I be satisfied or does it is so important to check the current draw?

Thanks again
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Old 5th April 2010, 08:08 PM   #19
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I would be satisfied.

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Old 10th June 2010, 04:35 AM   #20
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Quote:
Originally Posted by Nelson Pass View Post
I would be satisfied.

And if it's good enough for the one and only, it should be good enough for Mying.
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