Ok. I'll play it more on Aux.
I do hear the relays clicking. But I can't see inside them as they are covered w black covers, not clear ones. Also, when I first played phono and a record, the music cutout on right speaker first (relay tripped?). Then ten seconds later the left speaker cutout (other relay tripped?). This amp has two relays. I assume one for each channel.
But if you are asking why am I seeing 800 mV on the left speaker outs, shouldn't the relay protection shut down the output to protect speaker, that I can't answer you.
I do hear the relays clicking. But I can't see inside them as they are covered w black covers, not clear ones. Also, when I first played phono and a record, the music cutout on right speaker first (relay tripped?). Then ten seconds later the left speaker cutout (other relay tripped?). This amp has two relays. I assume one for each channel.
But if you are asking why am I seeing 800 mV on the left speaker outs, shouldn't the relay protection shut down the output to protect speaker, that I can't answer you.
OK Craig, you got me again ;-) I'm not sure where the Regulators are they you are asking me to check. But I checked some of the voltages on the EQ Assy board according to schematic and they appear good.
Q101C: 32.7V
Q105E: 32.7V
Q103C: -31.8V
Q107E: -31.8V
Q102C: 32.9V
Q106E: 32.9V
Q104C: -31.8V
Q108E: -31.8V
Q101C: 32.7V
Q105E: 32.7V
Q103C: -31.8V
Q107E: -31.8V
Q102C: 32.9V
Q106E: 32.9V
Q104C: -31.8V
Q108E: -31.8V
We're going to learn you yet! OK, those look good. In troubleshooting you have to start with the basics. If the power supply voltages are wrong nothing will work correctly. Now we know the power supply for phono stage appears to be OK. Play the amp on aux/cd whatever if no problems occur we can be sure the phono is to blame. If you compare the phono stage to the power amp stage you'll see they are very similar. The phono stage in this amp is basically a micro power amp. The adjustment is for minimizing the DC offset at the output, C23/24.
Craig
Craig
. Ok. Settling in for some long listening in the basement.So it seems to play fine on CD, Aux1 and Aux2. Though I do notice that left channel sounds a bit lower than right channel. Also notice that when I switch to Line (turn tone on) it's even more noticeable and some static. This may be due to iffy controls that still need another dose of deoxit. Sadly, these amps have poor switches that some have bypassed altogether to eliminate the static.
OK. So suspecting it is the Phono stage, what is best approach?
1. Is there a way to disconnect the output of the Phone stage from the main amplifier to troubleshoot it without effecting main amp components negatively?
2. Should I hook up 2 DMMs to the two Phono stage Test Points (TP1/TP3) and check them again quickly before it heats up the left output board and try setting offset again?
3. How can I check voltage throughout Phono stage without heating up left output board?
1. Is there a way to disconnect the output of the Phone stage from the main amplifier to troubleshoot it without effecting main amp components negatively?
2. Should I hook up 2 DMMs to the two Phono stage Test Points (TP1/TP3) and check them again quickly before it heats up the left output board and try setting offset again?
3. How can I check voltage throughout Phono stage without heating up left output board?
Ugh. Just went to play it again via Aux, and right channel works but no music out of left channel. Checked DC Offset and right channel is 3.8mV and left is back up at 755mV. Apparently enough to trip left relay too since I get no sound.
So, now I'm back to looking at the Voltage and Output assemblies for left channel. Maybe the Phono stage is not a problem after all. And it was just coincidence???
So, now I'm back to looking at the Voltage and Output assemblies for left channel. Maybe the Phono stage is not a problem after all. And it was just coincidence???
That idle current is crazy, man. Your channel there is obviously oscillating. If you're not getting any sound but you still can measure DC offset, then the relay hasn't tripped, unless you're reading that offset before the relay, rather than on the speaker output terminals.
And that cap should be fine. But you have bigger problems than that.
And that cap should be fine. But you have bigger problems than that.
I am reading offset at the speaker terminals. So I noticed the green power light was out and replaced it. Red one was not lighting either. I assume the red one is lit when the protection circuit kicks in. Now when I turn it on, the red light comes on until the relay clicks, and now the green one lights. (I double checked that I have the correct light going to the red condom and the other correct light going to the green condom).
As for the offset, if I continue to measure it, the voltage drops slowly like maybe the IC1 is trying to auto-adjust it, but I have not left it on long enough to see if the voltage drops all the way down to less than 10mV. When it was working, both channels would indicate less than 10 mV at startup (as one might expect).
So, different day, different measurements. Today I'm now seeing this at Q1 and Q2:
Q1 where I should see 6V, I'm seeing 5.85V, and where I should see 0V, I'm seeing 313mV. (DC Offset at speakers is 7.2mV)
Q2 where I should see 6V, I'm seeing 5.8V, and where I should see 0V, I'm seeing 294mV. (DC offset at speakers is -3.4mV)
What changed? Last night I pulled dials and front face off and applied a second dose of contact cleaner to the volume control, balance control, input selector buttons and Straight Line (tone bypass) button.
According to schematic, those areas where I should see 0V connect to the following components:
One leg that should be 0V:
1. C9/C10 which should be 470uF/25V NP (Non-polarized) caps. Mine look original and are polarized (the original component glue is still holding these caps).
2. R21/R22 which are 470 Ohm resistors
3. R23/R24 which are 100k Ohm resistors
4. C11/C12 which are 15p Caps
Other leg that should be 0V
1. R1/R2 which are 220 Ohm resistors which in turn go to Volume Control
I suppose any of these could be suspect as to why I am seeing more voltage than I should at Q1 and Q2. Where should I start, given the fluctuating nature of the voltages I have seen on the left channel and the higher than normal voltages on both channels at Q1/Q2?
Q1 where I should see 6V, I'm seeing 5.85V, and where I should see 0V, I'm seeing 313mV. (DC Offset at speakers is 7.2mV)
Q2 where I should see 6V, I'm seeing 5.8V, and where I should see 0V, I'm seeing 294mV. (DC offset at speakers is -3.4mV)
What changed? Last night I pulled dials and front face off and applied a second dose of contact cleaner to the volume control, balance control, input selector buttons and Straight Line (tone bypass) button.
According to schematic, those areas where I should see 0V connect to the following components:
One leg that should be 0V:
1. C9/C10 which should be 470uF/25V NP (Non-polarized) caps. Mine look original and are polarized (the original component glue is still holding these caps).
2. R21/R22 which are 470 Ohm resistors
3. R23/R24 which are 100k Ohm resistors
4. C11/C12 which are 15p Caps
Other leg that should be 0V
1. R1/R2 which are 220 Ohm resistors which in turn go to Volume Control
I suppose any of these could be suspect as to why I am seeing more voltage than I should at Q1 and Q2. Where should I start, given the fluctuating nature of the voltages I have seen on the left channel and the higher than normal voltages on both channels at Q1/Q2?
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I don't where you are up to on this but a couple of thoughts.
1/ DC offset as measured at the speaker terminals. If there were any DC present that was emanating from in front of the power amp input, and you suspected that was then getting passed to the power amp and causing a problem, then turning the volume control to minimum would reduce it to zero.
2/ You should have 0.000 volts on R1 and R2 in the power amp at all times and with all settings of the volume control.
3/ The voltage across D1 and D2 should be constant at around 30 volts at all times. The exact value is not important but the stability is.
Have you tried seeing if you can pick up any 'voltage' on the board itself around the FET's. I'm not talking about on the components but on the board material... both sides. If you can get a reading then you might have contamination that is conductive and causing odd problems.
1/ DC offset as measured at the speaker terminals. If there were any DC present that was emanating from in front of the power amp input, and you suspected that was then getting passed to the power amp and causing a problem, then turning the volume control to minimum would reduce it to zero.
2/ You should have 0.000 volts on R1 and R2 in the power amp at all times and with all settings of the volume control.
3/ The voltage across D1 and D2 should be constant at around 30 volts at all times. The exact value is not important but the stability is.
Have you tried seeing if you can pick up any 'voltage' on the board itself around the FET's. I'm not talking about on the components but on the board material... both sides. If you can get a reading then you might have contamination that is conductive and causing odd problems.
Hi Mooly, so here's what I got.
1. I always measure DC Offset at speakers at minimum volume.
2. OK, dang, I think I made this mistake earlier. Here are current measurements on all points of Q1 and Q2:
Q1:
R1: 0V
Q3E: 5.79V
Q5E 5.78V
R21: 7.3V
R17: (this is connected to 2 of the 6 FET pins). This one started at 313mV, and rises as the amp warms up? Last measurement was 330mV and still rising.
Q2:
R2: 0V
Q4E: 5.88V
Q6E: 5.88V
R22: 3.5V (half of R21's reading above)
R18: (this too is connected to 2 of the 6 FET pins). This one started at 294mV, and it too rises as the amp warms up? Last measurement was 305mV and still rising.
Both R17/R18 rise about .1mV per second. Should I let amp warm up 5 minutes and recheck those values to see if they level off?
3. Voltage across D1 and across D2 are both about 29.7V.
How would I go about trying to measure stray voltage on the board itself? Ground the black lead and put red lead directly on the board any various places around Q1/Q2?
1. I always measure DC Offset at speakers at minimum volume.
2. OK, dang, I think I made this mistake earlier. Here are current measurements on all points of Q1 and Q2:
Q1:
R1: 0V
Q3E: 5.79V
Q5E 5.78V
R21: 7.3V
R17: (this is connected to 2 of the 6 FET pins). This one started at 313mV, and rises as the amp warms up? Last measurement was 330mV and still rising.
Q2:
R2: 0V
Q4E: 5.88V
Q6E: 5.88V
R22: 3.5V (half of R21's reading above)
R18: (this too is connected to 2 of the 6 FET pins). This one started at 294mV, and it too rises as the amp warms up? Last measurement was 305mV and still rising.
Both R17/R18 rise about .1mV per second. Should I let amp warm up 5 minutes and recheck those values to see if they level off?
3. Voltage across D1 and across D2 are both about 29.7V.
How would I go about trying to measure stray voltage on the board itself? Ground the black lead and put red lead directly on the board any various places around Q1/Q2?
Another observation with R17/R18. These resistors connect to the 2 pins on each FET (and also to R113/R114) and on the other side connect to D39/D40.
I'm reading the 313mV and rising (now it seems about 1mV per second) on the 2 pins/R17/R113, but on the other side of R17 where it connects to D39, I'm currently reading -14.45V (and it is dropping by about 10mV every second).
How can I read positive voltage on one side of a resistor, and negative voltage on the other side?
I'm reading the 313mV and rising (now it seems about 1mV per second) on the 2 pins/R17/R113, but on the other side of R17 where it connects to D39, I'm currently reading -14.45V (and it is dropping by about 10mV every second).
How can I read positive voltage on one side of a resistor, and negative voltage on the other side?
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