If you used the same signal source material (mp3 file), maybe the MP3 file is distorted. For testing, you need to leave the files in wav or another lossless format.
Not unless the short is in the 2 we left connected, which I was gambling against so I am going to presume the outputs are fine until further notice. The components you got the results from disconnecting were the feedback link so that is operating as well. Bear in mind this is incredibly unorthodox troubleshooting but it at least tells me a few things without having it in front of me. Once you get everything resoldered you'll want to power it up once more with a measurement just to verify that nothing was made worse. I'll assume it wasn't, but just be sure.
Next, clamp your negative meter probe down in the speaker ground terminal and leave it there. You will use no input source for any of this, no speakers hooked up.
1) turn the bias pot fully counter clockwise.
2) note the measurement at the + speaker terminal (post it as well, including the polarity the meter is reading +/-)
3) measure and post the voltage at the gate of q42 & the gate of q10 (be as exact as possible.)
Hi,
We actually left four connected; there are two that do not have an emitter resistor on them, one on the positive and on on the negative rail.
Things have went from bad to much worse. Last night when I was working on the amp, my desoldering braid managed to get under the board and it shorted against a capacitor and now I have +38VDC on speaker out.
I've pulled all the of the 2SC3263's from the positive rail. The voltage only dropped to +29VDC.
We actually left four connected; there are two that do not have an emitter resistor on them, one on the positive and on on the negative rail.
Things have went from bad to much worse. Last night when I was working on the amp, my desoldering braid managed to get under the board and it shorted against a capacitor and now I have +38VDC on speaker out.
I've pulled all the of the 2SC3263's from the positive rail. The voltage only dropped to +29VDC.
Awesome.. What cap was it and what was it shorted to? itself? across the pcb? You never gave me my measurements at the other two points, you need to keep your work area open and clean and if you have things missing from the PCB it helps to tell me that.
I do not know which cap it shorted to, or what it hit as it did not arc it self together. I have an idea which cap it is, but I have had a hard time removing it from the board.
Also I have not moved forward with the extra tests due to the new problem of +38VDC.
I pulled all the outputs on the positive rail, and the voltage only dropped down to +29VDC.
When we originally started testing, the board was complete and no parts were missing.
Also I have not moved forward with the extra tests due to the new problem of +38VDC.
I pulled all the outputs on the positive rail, and the voltage only dropped down to +29VDC.
When we originally started testing, the board was complete and no parts were missing.
Ok, I'll do so in a bit when I get back from supper. I reinstalled everything as it was originally. I have +40VDC on the output again.
Also, will I be turning V1 or VR2?
Also, will I be turning V1 or VR2?
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+38VDC before any adjustments.
+38VDC with the pot turned fully counter clockwise.
Q42 is a 2SC3263 and it does not have a gate, it has base collector and emitter. I tested on the emitter and got around +25.8VDC. I know you want precision, however it does not settle on one number, it constantly fluctuates down.
Q10 is a 2SA1294 and it does not have a gate, it has base collector and emitter. I test on the emitter and got around +25.8VDC.
+38VDC with the pot turned fully counter clockwise.
Q42 is a 2SC3263 and it does not have a gate, it has base collector and emitter. I tested on the emitter and got around +25.8VDC. I know you want precision, however it does not settle on one number, it constantly fluctuates down.
Q10 is a 2SA1294 and it does not have a gate, it has base collector and emitter. I test on the emitter and got around +25.8VDC.
gate = base. I know, semantics.. I figured you might have guessed. I need the measurements at the bases.
Of course out of three possibilities, I guess wrong.
On the base I get +38.5 on Q42
On the base I get 19.3 on Q10
I will have to confirm the polarity on Q10, I tested quickly this morning before coming in to work.
Again, this is as accurate as I can get, since these numebers constantly drop by a little bit the longer that I I hold the test prob in position.
On the base I get +38.5 on Q42
On the base I get 19.3 on Q10
I will have to confirm the polarity on Q10, I tested quickly this morning before coming in to work.
Again, this is as accurate as I can get, since these numebers constantly drop by a little bit the longer that I I hold the test prob in position.
Remove q35 and test it out of circuit. If it's good, put it back. if in doubt, post measurements. Give me the base measurment at q33 if the prior test yields a good device. if not, replace it and retest the amplifier.
Based on the test here http://www.bcae1.com/ampfail.htm Q35 tests ok.
Q33 is an MJE340 and on the base I get +37.4VDC.
Q33 is an MJE340 and on the base I get +37.4VDC.
lift a leg of d28 and diode check the part. Is it leaking? if not, pull q33 out and check it out of circuit next. Hell, test them both.
Hmmm.. are you SURE all 2sc3263's are still OK? The output rail ties BACK into the drive via the feedfback system but your voltages are getting WEAKER as you go back towards that point.
I'm really not use to helping someone at this experience level, with these tools, over the internet. I'm sorry if i'm failing you on this, but if something doesn't give soon i'll have to suggest we move on. Verify your outputs are OK.
I'm really not use to helping someone at this experience level, with these tools, over the internet. I'm sorry if i'm failing you on this, but if something doesn't give soon i'll have to suggest we move on. Verify your outputs are OK.
Good Morning,
Thank you for your help. My apologies if this is frustrating. I understand my skill level and lack of better tools is not helping you to help me. However, I do thank you for the help this far.
I am not sure if all the outputs are good (3263s). However, if read back a few posts, even with all the outputs removed I still had +29VDC on speaker out; which is significantly higher than the original problem of +1.2VDC.
Thank you for your help. My apologies if this is frustrating. I understand my skill level and lack of better tools is not helping you to help me. However, I do thank you for the help this far.
I am not sure if all the outputs are good (3263s). However, if read back a few posts, even with all the outputs removed I still had +29VDC on speaker out; which is significantly higher than the original problem of +1.2VDC.
Yeah, I just caught that. You see jp1 / jp2 jumper note in the schematic? It will disconnect the raw output from the feedback circuit. Pull that and leave everything else in. test the voltage on the output again.
Ok,
After much fighting, i managed to get part of JP1/JP2 disconnected from the board.
I have retested the amplifier and now get +.5mVDC on speaker out.
After much fighting, i managed to get part of JP1/JP2 disconnected from the board.
I have retested the amplifier and now get +.5mVDC on speaker out.
You had to fight to remove a jumper? nevermind.. I don't wanna know.
I feel like I failed ya some how on this. It's just not how I chase after things when I have them here. I'm spoiled with a signal injector, scope, all the toys. it's fairly cut and dry for 99% of the cases using those tools and a personally established troubleshooting routine.
Can I safely assume you've taken the initiative to test all the sub 100 ohm value resistors in the pre-drive, differential, and drive sections? There are things you can proactively check between posts. It'll save time if you can catch it in something simple. Resistors fail UP, not down. So if you're directly across one, it should read within 5% of it's value or LESS depending on what might be parallel with it in circuit, If in doubt you can lift a leg to check. There are 11 transistors in the block I'd like you to focus on, any resistor from 1 - 100 ohms. You're just gonna have to start beasting it out on this one, There is a bad part in there somewhere.
I feel like I failed ya some how on this. It's just not how I chase after things when I have them here. I'm spoiled with a signal injector, scope, all the toys. it's fairly cut and dry for 99% of the cases using those tools and a personally established troubleshooting routine.
Can I safely assume you've taken the initiative to test all the sub 100 ohm value resistors in the pre-drive, differential, and drive sections? There are things you can proactively check between posts. It'll save time if you can catch it in something simple. Resistors fail UP, not down. So if you're directly across one, it should read within 5% of it's value or LESS depending on what might be parallel with it in circuit, If in doubt you can lift a leg to check. There are 11 transistors in the block I'd like you to focus on, any resistor from 1 - 100 ohms. You're just gonna have to start beasting it out on this one, There is a bad part in there somewhere.
What's the DC voltage on the base of Q16 and either leg of R37?
What is the DC voltage on the emitter leg of any of the output transistors?
What is the DC voltage on the emitter leg of any of the output transistors?
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