Great video !

thank you...many people are getting back in to vintage audio...most all these amps...are very old and have problems....this sounds like a 1st step...to ensure you don't have....excessive voltage going to your speakers....again thank you.....

Love the knowledge you share here.

@vintageaudioaddict

Жыл бұрын

Thank you for watching.

Very helpful.

@vintageaudioaddict

3 жыл бұрын

Glad to hear!

Thanks!

@vintageaudioaddict

4 жыл бұрын

Your welcome and thank you for watching!

Hi great videos you put out. I got a question. I have a Pioneer SX-727. One ch is solid with stable DC offset. The other ch is flakey DC offset all over the place. Got any ideas were I should start looking? Caps on amp board? Protection circuit?

Second hand store used to let me plug the units in. But they do allow returns.

Good video! If the dc offset is good, does that mean the output transistors and/or electrolytic caps on the drive board are okay? Thanks.

Hello. Thank you very much. I have an old amplifier that, if I measure bias with speakers installed, show less than 1mv DC, but if I measure without load the bias is 3.2 volts DC. I don't understand if this is a problem or not? If with speakers the bias is almost absent shouldn't be risks for the speakers, or not? Can you explain why the test is done without speakers/load? Thank you very much.

Some good information here. I'm no expert but I disagree with your advice, on starting the measurements with less than 1mV scale. I'd put it on to the highest setting to begin with, and drop down from there. After all, you're looking to see if there's a problem with the amp. When you have 38V at the outputs, like I did recently, you know you have a problem!

@vintageaudioaddict

Жыл бұрын

Thanks a lot for sharing and for watching. Yes, 38 volts is an issue!

If I have an amplifier with 200 millivolts of offset on both of its channels what’s the best course of action to get that below 30 millivolts ? Thanks for any assistance.

Thanks, question, when i run the procedure my voltimeter goes to -98 mv ... If i turn off that channel... Then it starts going to +50 and keep going up. Then if i turn on the channel again, it goes to -90 again. Both left and right channel. And i. a, B or C set of speakers, i have to say, last week it burned my left speaker. Thanks for the advise.

Volume set to zero ?

can this test be applied to a amp for a subwoofer .

what is volume contol set at during the test? I also noticed that the right channel had a - DC mV reading and the left channel had a +DC mV reading, is that considered normal?

@kevinhollenbeck7503

Жыл бұрын

I wish he would answer this question.

After measuring my 2270- Main L & Remote L both read ~13mv when selected and 0mv when not selected. On the right side; Main R reads 52mv when selected and unselected, while Remote R reads 52mv when selected and 0 mv when not selected. From what you said, I'm less concerned about the number, but more concerned that the Main R is giving a reading when not selected. Where would you start to troubleshoot? Thanks!

Cool video! Can you elaborate? What is the DC offset telling you?

@rl7487

2 жыл бұрын

They never replied to you. There is not supposed to be any DC current in the output since the output is AC current. DC current will burn the speaker. But In tiny millivolts it’s not harmful, yet .

Thanks for the video, can I use this method on a SET tube amp?

@vintageaudioaddict

2 жыл бұрын

In tube amplifiers there is no DC on the speakers as they are transformer isolated from any DC by the output transformers. There is no DC offset to adjust unless it is output-transformerless, but there are not many of those.

@audiorick841

2 жыл бұрын

@@vintageaudioaddict Thank you for the clarification, I can confirm the amp I have has output transformers but I was lacking the knowledge to know what it meant for DC offset. Thanks for the new knowledge!

Nice info but remember this only works for direct coupled outputs. Capacitor coupled outputs will block DC. If there is an issue with the amplifier you'll have to do other tests.

@vintageaudioaddict

4 жыл бұрын

Good comment. Thanks!

@chwk2003

9 ай бұрын

@@vintageaudioaddictHow can one know if he's testing a direct coupled output or a capacitor coupled output? Is there an easy "rule of thumb"?

Hi, I have a question, is it normal for dc voltage to raise over time? a month ago I adjusted dc voltage about 5 mV on both channels, now Im having -70mV on L and -60mV on R. Sugested voltage is +-10 mV for my reciever, it is sansui 8080. Thanks

@jhjove

4 жыл бұрын

Could weak differential pair, thermal issues, leaky capacitor... Have any upgrades been completed on this chassis?

@jovanj.9400

4 жыл бұрын

@@jhjove No, everything is original, I just cleaned the pots and switches. It sounds fine but that dc voltage bothers me.

@jhjove

4 жыл бұрын

@@jovanj.9400 yes, anything over 50mV and increasing is of concern, more distortion+more problematic for the speaker VC. This chassis is at least 45 years old, I have to believe there are over stressed and now weak components. At the very least the power supply caps should be changed. That said when you do your adjustments for Bias and DC offset were these after the unit was on for 10-30 minutes (controls flat, no source, volume minimum)?

@jovanj.9400

4 жыл бұрын

@@jhjoveYes, folowed instructions by service manual, volume on lowest, no sorce, didn't adjusted bias and offset on same time when powered on, I waited at least 5 minutes for curent to be stable. Only thing that i did adjustments with speakers hooked because i dont have a dummy load for testing...that dc voltage on output didnt raise same day to 70mV, it is was raisin gradually day after day...do you suggest that I try to adjust bias and offset again?

@jhjove

4 жыл бұрын

@@jovanj.9400 I think the circuit, with the age of the components, is going be wide ranging for current and voltage measurements/adjustments. And it could be a simple solder connection gone bad in the 45 years. If you're gonna use it you'd best do a maintenance job on it.

I have a Sony TA-F60 with the right channel issue : the voltage at the C of Q213 and Q214 is always -8,0V, so the protection relay do not work. I turn the RT201 to maximum but it can not reach 0V. All orther voltages are ok. Could you please advice me some solutions? Sorry for my bad English Thank you in advance. TuTrong from Viet Nam. I have the service manual of TA-F60. If you need I will send you via email.

v olume and balance control presets before turning on? I would imagine volume down and balance to one side to test, thanks great info as usual!