AU-317 running warm?

[h3ll0]

Got some rubber gloves and the bias was at 30mV on the right channel and 20mV on the left so i adjusted it to the correct 10mV. Also upon further inspection the cap was not leaky it was just glue that burnt. No more extra warmth yay! Turns out it was a bias issue......

 

[petehall347]

its a good thing to get rid of the glue as it goes conductive ...try setting your meter on a high ohms setting and pressing the meter probes into the glue ... be sure the unit is unplugged first though ...
i have seen some very conductive glue in the past .

 

[roger2]

Got some rubber gloves and the bias was at 30mV on the right channel and 20mV on the left so i adjusted it to the correct 10mV. Also upon further inspection the cap was not leaky it was just glue that burnt. No more extra warmth yay! Turns out it was a bias issue......

Very cool !!!

So while you are right there...

Checking/adjusting DC offset is very similar. Same page in the Service Manual, same tools, same kind of process except for this the goal is 0mv or as close as you can get it. The trim pots for DC offset are right there in the same part of the amp. The only difference is there are two trimpots for each channel: one for the "rough" adjustment and the second for the "fine" (final) adjustment.

DC offset is measured across the speaker terminals.

 

[h3ll0]

its a good thing to get rid of the glue as it goes conductive ...try setting your meter on a high ohms setting and pressing the meter probes into the glue ... be sure the unit is unplugged first though ...
i have seen some very conductive glue in the past .

I did what you said any got no reading on any mode.
I don't really know what the black crusty crap is, but the cap isn't leaking.

 

[Karl vd Berg]

Got some rubber gloves and the bias was at 30mV on the right channel and 20mV on the left so i adjusted it to the correct 10mV. Also upon further inspection the cap was not leaky it was just glue that burnt. No more extra warmth yay! Turns out it was a bias issue......

Very good.

After DC offset, next step. (don't worry, just a reading...)

http://audiokarma.org/forums/showthread.php?t=430439 (post #4, too)

 

[h3ll0]

Very good.

After DC offset, next step. (don't worry, just a reading...)

http://audiokarma.org/forums/showthread.php?t=430439 (post #4, too)

How do I take these readings? Just put the probes on the contacts on either side of the resistor? With the amp on or off?

 

[vigman]

See that didn't hurt now did it...LOL
GREAT JOB!!!

 

[h3ll0]

See that didn't hurt now did it...LOL
GREAT JOB!!!

What decimal place should I shoot for on my DMM for the bias?
Because I think I did it right but I'm just double checking

Just checked the fuse resistors with the same settings as skippy and got 152 ohms on each resistor and they are 150 ohm resistor so it is within spec.

 

[roger2]

Push the slider to the "V" with the solid and dashed lines above it. This is DC voltage. Turn the rotating selector knob to "2". Use this meter setting for both bias and DC offset readings.

For bias you want 10mV which, on the meter, should look like 0.010 or similar (not sure how many digits will show on your meter, might read .01 or 0.01)

For DC offset the goal is as close to 0.00 as possible. You may or may not be able to get exactly 0mV. If you are able to get DC offset at 10mV or less that would be excellent. 20mV or less would be very good. Let us know what you are able to do with the DC offset.


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As far as those fuse resistors you definitely want the amp OFF, and UNPLUGGED when reading those. In that case you are not measuring circuit voltages as in bias of DC offset. With the fuse resistors you are measuring the actual value of the resistors in ohms. Those fuse resistors tend to drift very high so you may need to try different settings on your meter to find one that will give you a reading.

For measuring the fuse resistors push the slider on the meter to the upside down horse shoe symbol. That is the symbol for "ohms", the unit of measurement for resistance.

 

[h3ll0]

Push the slider to the "V" with the solid and dashed lines above it. This is DC voltage. Turn the rotating selector knob to "2". Use this meter setting for both bias and DC offset readings.

For bias you want 10mV which, on the meter, should look like 0.010 or similar (not sure how many digits will show on your meter, might read .01 or 0.01)

For DC offset the goal is as close to 0.00 as possible. You may or may not be able to get exactly 0mV. If you are able to get DC offset at 10mV or less that would be excellent. 20mV or less would be very good. Let us know what you are able to do with the DC offset.


---------------------------------------------------------

As far as those fuse resistors you definitely want the amp OFF, and UNPLUGGED when reading those. In that case you are not measuring circuit voltages as in bias of DC offset. With the fuse resistors you are measuring the actual value of the resistors in ohms. Those fuse resistors tend to drift very high so you may need to try different settings on your meter to find one that will give you a reading.

Thanks roger I got 152 ohms on the DMM with the setting on the ohm sign and tried every setting and got .152 or .15 or .1 depending on the setting.

 

[roger2]

......Just checked the fuse resistors with the same settings as skippy and got 152 ohms on each resistor and they are 150 ohm resistor so it is within spec.

That's awesome because those things can go waayyyyy off spec. You dodged a bullet there, lol

 

[h3ll0]

That's awesome because those things can go waayyyyy off spec. You dodged a bullet there, lol

I know I was expecting them to be wayyy off. lol

For the bias I got .1 on the setting you gave me and with one knotch up I got .10 so should it be .10 or .01?

 

[roger2]

should be .01 that is 10mV

.1 is 100mv and way too high

try again and see if you can get to a .01 reading

 

[h3ll0]

should be .01 that is 10mV

.1 is 100mv and way too high

try again and see if you can get to a .01 reading

alright ajusting it accordingly and wow the bias was at 300mV then.

 

[roger2]

yeah, I don't know about that. that would be extremely high. are you sure you might not have misinterpreted the reading somehow or had the meter on the wrong setting?

no matter though. sometimes these things take a couple tries to nail down, no big deal. just make certain that when you are done that the meter was set correctly and you have .01 (10mV) or as close as possible for the bias on both channel

FYI
.001 = 1mV (one milivolt or one thousandth of a Volt)
.01 = 10mV
.1 = 100mV
1.0 = 1000mV

 

[h3ll0]

yeah, I don't know about that. that would be extremely high. are you sure you might not have misinterpreted the reading somehow or had the meter on the wrong setting?

no matter though. sometimes these things take a couple tries to nail down, no big deal. just make certain that when you are done that the meter was set correctly and you have .01 (10mV) or as close as possible for the bias on both channel

FYI
.001 = 1mV (one milivolt or one thousandth of a Volt)
.01 = 10mV
.1 = 100mV
1.0 = 1000mV

Ok I got the .01 on the setting you said for me to use and thanks for the conversions. Got the bias set on both channels at .01

So to set the DC offset it says I have put the probes on the speaker terminals. Is that where the speaker wire comes out?

 

[roger2]

Yes. You can just stick the probes into the speaker terminals and let the springs hold them. That way you can watch the readings change as you turn the trimpots. Make sure to have no speakers connected and the speaker selector switch set to whichever terminals you are measuring. Volume all the way down and other settings neutral just like when doing the bias.

Congrats on sticking with it and dialing in the bias :thmbsp:

 

[h3ll0]

Yes. You can just stick the probes into the speaker terminals and let the springs hold them. That way you can watch the readings change as you turn the trimpots. Make sure to have no speakers connected and the speaker selector switch set to whichever terminals you are measuring. Volume all the way down and other settings neutral just like when doing the bias.

Congrats on sticking with it and dialing in the bias :thmbsp:

Ok thanks.

I ended up not buying the caps as they are working just fine, but when they start venting I'll give it to a repair guy to recap it for $60 as buying a soldering iron,solder,and desoldering bulb and wick would almost be the same cost.

 

[roger2]

You have a local tech who will do a full recap for $60?

Including the big main filter caps? That doesn't seem likely...it is a lot of work.

 

[h3ll0]

You have a local tech who will do a full recap for $60?

Including the big main filter caps? That doesn't seem likely...it is a lot of work.

I guess I should of said $60/hour so I guess it would be $120-$180.

Anyways I got the DC offset to zero it was at .005/