2325 bias question

bobinaz

Active Member
Checking the bias on my 2325 that I've had out of rotation for a long time and I get about 5 to 6 mv as measured on the main speaker outputs. On the REMOTE outputs I get the same 5 or 6mv on the right outputs, but get around 35mv on the left remote output. I know trim pot r713 is to adjust the bias. I didn't want to mess with those because they were already good on the main channels. Is the other trim pot on that board for adjusting the bias at the REMOTE speaker outputs? thanks. 35 mv is still relatively low, but I would like them all to match as close as I can with the adjustment.
 
First, on your power supply board connect a DC digital multimeter between pins J804 (-) and J805 (+) and adjust the trimming resistor R809 for 35 v DC.

THEN, On the speaker terminals you are measuring DC offset, which should be '0' on your DMM, and is adjusted with R713. When your mains are adjusted the remotes will automatically be the same setting. Your Idle-Current is measured between pins J702 (-) and J708 (+) and is adjusted with R740. Rotate it fully counter-clockwise, then rotate it clockwise until the DMM reads 15mV DC. When it's correct then re-check your DC offset.
 
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I thought that the remote speaker outputs WOULD be the same as the main speaker outputs. That's why I was puzzled when the remote left was different than the main left. When I get home I will check the pins j804 805 for the 35v, then the other adjustments and see how things are after that. thanks.
 
Got it, Yes they are the same as the mains, so if you have 6mv on 3 outputs and 35mv on the fourth, you do have something odd going on, but 35mv is nothing to worry about.
A few questions,
Did you check the remote left output with both the main& remote in the off position?
Did you check both left outputs with both switches on?
Its hard to believe that you have two different voltages on two different ends of the same wire.
Did you use the same volt meter for these voltages?
Was the speaker connected when you did the check?
The Capacitors in your crossover can feed back and screw up your results....

Make sure the volume is off.
Make sure your on DC volts.

Read Mr wurlyman's Post again.
Do exactly as he has it written.
Warm unit up first.
Note: Your adjustment is only going to be as accurate as your voltmeter.;)
 
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Umm, I think turning the bias pots full CCW will turn up the bias not down like it would on a 2270 say. You'd really not want that! I'd say leave them where they are at and adjust from that point. Remember that you have to let it run at least ten minutes before doing the final tweaking.
 
Umm, I think turning the bias pots full CCW will turn up the bias not down like it would on a 2270 say. You'd really not want that! I'd say leave them where they are at and adjust from that point. Remember that you have to let it run at least ten minutes before doing the final tweaking.

That's the directions right out of the 2325 service manual.
 
That may teach me to go from memory! Thanks for posting that Wurly. I have one on the bench, I'll confirm and report back. Then take some "memory" pills! :biggrin:
 
OK...Silly me... I had only the remote speaker selector switch enabled when I was doing my checking. So, after having both switches enabled, checked the voltages as indicated above, adjusting as directed, both channels now are down to just about 0 volts dc. Thank you for your replies and help. Finally gonna get it back in rotation, powering either KEF 104.2 or a pair of DCM TF-700's. On to my next project....
 
Okay it took me all day but I checked the 2325 I had. The bias indeed rises when the pot is turned CCW. The manual indeed say to turn it fully CCW first. I never pre turn the bias pot and just see what it does when it is adjusted. Keeps one from having it run away and blow up outputs.

OP - Glad you got it all sorted out!
 
Okay it took me all day but I checked the 2325 I had. The bias indeed rises when the pot is turned CCW. The manual indeed say to turn it fully CCW first. I never pre turn the bias pot and just see what it does when it is adjusted. Keeps one from having it run away and blow up outputs.

OP - Glad you got it all sorted out!

So is that an error and should we scratch that line in our service manuals? If so, that should be posted in the error thread.
 
Brings up the question of what to do if you replace the trimmer. Should you start in the middle of the trimmer setting or go fully CCW?
 
Whenever I replace a trimmer I measure the resistance of the setting on the old one first and then preset the new to that for a baseline.
I also watch the bias and dc offset on both channels simultaneously (4 meters) so I can immediately see if there maybe an issue and act accordingly.

Bob
 
Whenever I replace a trimmer I measure the resistance of the setting on the old one first and then preset the new to that for a baseline.
I also watch the bias and dc offset on both channels simultaneously (4 meters) so I can immediately see if there maybe an issue and act accordingly.

Bob

What if the old one is bad and not giving a good reading?
 
I think I’ve been very lucky. I have replaced trimmers on several units, including my 2325, and I’ve always done the CCW thing to start. I’m lucky I haven’t blown something up. Looks like I need a trip to harbor freight for a couple more cheap meters. Thanks for sharing this.:thumbsup:
Steve​
 
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