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Post by mastertech on Mar 17, 2019 21:45:17 GMT -5
Are you going to try to adjust the other amp then? Maybe it is a balancing act.
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nashou
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Post by nashou on Mar 17, 2019 21:45:47 GMT -5
Also be careful touching these heatsinks when this is on. They may be carrying unprotected voltage. No voltage on transistor heat sinks. Neg probe to chassis posative probe to heat sink. But on that power supply transistor heat sink im getting 26 volts. |
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nashou
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Post by nashou on Mar 17, 2019 21:46:35 GMT -5
Are you going to try to adjust the other amp then? Maybe it is a balancing act. i'll give it a try at balancing. the right amp had 340 mv or so. nashou |
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Post by mastertech on Mar 17, 2019 21:49:10 GMT -5
Question, is the amp that is running hotter the same one with the soldered wires at the thermal location?
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Post by mastertech on Mar 17, 2019 21:59:31 GMT -5
I'm calling it a night. I will check back tomorrow. Good luck.  |
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nashou
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Post by nashou on Mar 17, 2019 22:06:04 GMT -5
I'm calling it a night. I will check back tomorrow. Good luck. ok, got both at 5mv !!!! amps both run cool. but now on left speaker out i have 3.9 vdc and right has 5.4 vdc. Measuring the dc caps on the underside earlier one had an esr of .45 ohm which is good but the other had 2.64 ohm esr |
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nashou
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Post by nashou on Mar 17, 2019 22:08:08 GMT -5
Question, is the amp that is running hotter the same one with the soldered wires at the thermal location? No the one that has the wires loose and broken free of the connector. But now they are a little closer, maybe 10 degrees hotter. Good night mac, thanks nashou |
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Post by mastertech on Mar 17, 2019 22:13:35 GMT -5
I'm calling it a night. I will check back tomorrow. Good luck. ok, got both at 5mv !!!! amps both run cool. but now on left speaker out i have 3.9 vdc and right has 5.4 vdc. Measuring the dc caps on the underside earlier one had an esr of .45 ohm which is good but the other had 2.64 ohm esr The fact that they are different speaker voltages doesn't mean much. I think they are both leaking. I would try changing them even if only one at a time. And I do not see a problem with increasing their value if need be. |
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nashou
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Post by nashou on Mar 17, 2019 22:15:10 GMT -5
ok, got both at 5mv !!!! amps both run cool. but now on left speaker out i have 3.9 vdc and right has 5.4 vdc. Measuring the dc caps on the underside earlier one had an esr of .45 ohm which is good but the other had 2.64 ohm esr The fact that they are different speaker voltages doesn't mean much. I think they are both leaking. I would try changing them even if only one at a time. And I do not see a problem with increasing their value if need be. How high should I go? And I think increased voltage is good as well . nashou |
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Post by stridsvognen on Mar 18, 2019 1:55:01 GMT -5
Ok Some new information. Kurt, Adjusting the trim pots does nothing across the emitters while the output transistors are out of the amp. Now not sure what happened when the output transistors are installed. not ready top test that yet because i have something else going on. Mac, I decided to remove the amps driver boards and power up to test some voltages with out the boards installed. And also went to check for DC on the speaker outputs. DING DING DING DING!!!! I have 17 vdc( fluctuates up and down a volt or two) on the left channel. That is the one that seemed way too loud for the barely above minimum volume control. the right speaker out is ok with a 1 mV reading. So where do I look? My Guess is the relay board . let me probe voltages there Yeah its not really possible to adjust bias without the transistors in place, will be exiting what you find out. nashou Nashou |
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Post by mastertech on Mar 18, 2019 10:10:40 GMT -5
The fact that they are different speaker voltages doesn't mean much. I think they are both leaking. I would try changing them even if only one at a time. And I do not see a problem with increasing their value if need be. How high should I go? And I think increased voltage is good as well . nashou At this point I would just try something you have available to see if it clears it up. |
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nashou
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Post by nashou on Mar 18, 2019 10:27:46 GMT -5
How high should I go? And I think increased voltage is good as well . nashou At this point I would just try something you have available to see if it clears it up. ok, think I have that same value in fact. What has me confused is the voltage on that heat sink in the power supply, why would it be there? seems dangerous to touch that heat sink while also touching the chassis. Not sure if its isolated from anything else etc. Nashou |
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Post by mastertech on Mar 18, 2019 10:40:34 GMT -5
That is normal/common sometimes. These are reasons an isolation transformer should be used when working on older electronics. Sometimes the case of a transistor is a contact of the component and an insulator is not used. If the component had full insulators including the mounting screw then I would not think there would be any voltage on the heatsink. But yeah, that does not surprise me.
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nashou
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Post by nashou on Mar 18, 2019 17:40:52 GMT -5
Ok, I changed out the one cap that showed 2.5 ESR . Fired it up and no change , it actually got worse ( 8 DC ) on right speaker out!! So I checked emitter settings and played around doing that.
Found it easier to do it at the connector on the bottom. And discovered something strange .
After each power cycle I was getting different readings on the speaker out . Sometimes it was the normal 4.5 to 5 volts on that speaker , then other times it go down to the 340 mV then climb up a bit. As would the emitter value.
On the left channel I am testing now It would do the same thing . Started at 20 mV's and now after about 10 minutes its up to .8 volts and rising. Emitter voltage went from 5 mV's to 6.6 mV's .
Might be those transistors on the driver board are bad or maybe the outputs them selves? Now knowledgable to know so you experts would I assume.
Now its up to 1.2vdc and 7.7 mV's ?
Edit: Leaving it powered up while waiting for response .
And adjusting Bias after it goes up a mV or two.
Athanasios
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Post by mastertech on Mar 18, 2019 17:46:17 GMT -5
Do you have another volt meter to try/confirm?
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