dr*audio
Fish fingers and custard!
That cap is for stability. It rolls the opamp off at some frequency so it doesn't oscillate. It is configured for unity gain. The feedback comes from R536 and R562.
Denon POA 6600 Thread
- Thread starter Bratwurst7s
- Start date
dr*audio
Fish fingers and custard!
The diode below it is D527. Sorry, I was looking at it on my phone and had no way to open the schematic. Please test D527, TR551 and D509. On the schematic D509 looks like a LED..
dr*audio
Fish fingers and custard!
We are babysitting our grand daughter tomorrow and I don't know if I will have time to check this, so I wanted to tell you you can use a 5532 as a temporary replacement for either opamp, but if you find that that is the problem, order a couple LM4562 opamps in 8 pin dip package. They are excellent audio opamps.
I will temp try a 5532 in those positions, one at a time starting with IC502.
I may have a couple of LM4560 but for sure have over 90 LME49720's. Afaik they are nearly the same part?
James
I may have a couple of LM4560 but for sure have over 90 LME49720's. Afaik they are nearly the same part?
James
OK, I have not pulled the board yet, I got off in another direction that might still be useful.
I realized that when I tested for stated schematic voltages earlier I neglected to check fir 1.78v/-1.82v at R553/R554, and for 1.07/-1.17v at the base of the drivers TR511/TR512.
I also wanted to try testing TR551 under power.
Here is a front side photo of the area where TR551 is. By cutting a piece of 0.8mm wire and trimming a small bit of insulation from each end I can grab it with a mini-grabber and insert it into the holes in the front side of where 551 is.
I probably should note that up till now I have been testing with the input volume fully off (counterclockwise) and the idle current trim pot also fully counterclockwise.
With those in mind and still with the original opamps installed I got the following measurements.
TR551:
E) = 9mV
C) = 0.81v
B) = 0.51v
D509:
C) = 0.51v
A) = 0.818v
D527:
C) = -0.82v
A) = -0.158v
IC502:
1) = 8mV
2) = 1mV
3) = 1mV
4) = -15.2v
5) = 1mV
6) = 2mV
7) = 9mV
8) = 15.16v
I realized that when I tested for stated schematic voltages earlier I neglected to check fir 1.78v/-1.82v at R553/R554, and for 1.07/-1.17v at the base of the drivers TR511/TR512.
I also wanted to try testing TR551 under power.
Here is a front side photo of the area where TR551 is. By cutting a piece of 0.8mm wire and trimming a small bit of insulation from each end I can grab it with a mini-grabber and insert it into the holes in the front side of where 551 is.
I probably should note that up till now I have been testing with the input volume fully off (counterclockwise) and the idle current trim pot also fully counterclockwise.
With those in mind and still with the original opamps installed I got the following measurements.
TR551:
E) = 9mV
C) = 0.81v
B) = 0.51v
D509:
C) = 0.51v
A) = 0.818v
D527:
C) = -0.82v
A) = -0.158v
IC502:
1) = 8mV
2) = 1mV
3) = 1mV
4) = -15.2v
5) = 1mV
6) = 2mV
7) = 9mV
8) = 15.16v
After that I replaced IC502 with a 5532 and remeasured.
1) = 2mV
2) = -0.87v
3) = -8mV
4) = -14.85v
5) = -1.1mV
6) = -1.2mV
7) = 1.1mV
8) = 14.8v
Then measured the input side of R553 = 0.996v and R554 = -0.97v
James
1) = 2mV
2) = -0.87v
3) = -8mV
4) = -14.85v
5) = -1.1mV
6) = -1.2mV
7) = 1.1mV
8) = 14.8v
Then measured the input side of R553 = 0.996v and R554 = -0.97v
James
Then I started thinking about what would happen if I measured the voltages at R553/554 and tried adjusting the idle current trim pot.
The voltage at those points tracks with increasing the trim pot.
I adjusted until I got +1.79v / -1.763v at those points.
Then remeasured the following:
TR551:
E) = 1.12v
C) = 1.773v
B) = -0.54v
D509:
C) = -0.451v
A) = -0.2v
D527:
C) = -1.736v
A) = -1.104v
TR509:
E) = 1.108v
C) = 79.1v
B) = 1.71v
TR510:
E) = -1.102v
C) = -78.8v
B) = -1.703v
TR511:
E) = 0.529v
C) = 16mV
B) = 1.103v
TR512:
E) = -0.524v
C) = Could not get a probe in there, will have to find an upstream spot to measure.
B) = -1.703v
IC501: (still original)
1) = 81mV
2) = 2.7mV
3) = -0.4mV
4) = -14.92v
5) = 3mv
6) = 0.6v
7) = -0.6v
8) = 14.93v
IC502: (5532)
1) = 1mv
2) = 12mV
3) = -2mV
4) = -14.93v
5) = -2mV
6) = 25mV
7) = -0.1mV
8) = 14.91v
I don't think that I will get any more done today. But some of the above measurements now look a lot more like they are supposed to.
Cheers,
James
The voltage at those points tracks with increasing the trim pot.
I adjusted until I got +1.79v / -1.763v at those points.
Then remeasured the following:
TR551:
E) = 1.12v
C) = 1.773v
B) = -0.54v
D509:
C) = -0.451v
A) = -0.2v
D527:
C) = -1.736v
A) = -1.104v
TR509:
E) = 1.108v
C) = 79.1v
B) = 1.71v
TR510:
E) = -1.102v
C) = -78.8v
B) = -1.703v
TR511:
E) = 0.529v
C) = 16mV
B) = 1.103v
TR512:
E) = -0.524v
C) = Could not get a probe in there, will have to find an upstream spot to measure.
B) = -1.703v
IC501: (still original)
1) = 81mV
2) = 2.7mV
3) = -0.4mV
4) = -14.92v
5) = 3mv
6) = 0.6v
7) = -0.6v
8) = 14.93v
IC502: (5532)
1) = 1mv
2) = 12mV
3) = -2mV
4) = -14.93v
5) = -2mV
6) = 25mV
7) = -0.1mV
8) = 14.91v
I don't think that I will get any more done today. But some of the above measurements now look a lot more like they are supposed to.
Cheers,
James
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One other thing that I did, just to eliminate the thought that one of the test point posts might have a bad connection.
Left a lead on TP1 and put the other lead on R587 = no improvement,
Left a lead on TP2 and moved the other lead to R 586 = no improvement.
If one of the test points was bad I should have seen some idle current on the meter by going backwards in the circuit with the other probe was my thinking.
Left a lead on TP1 and put the other lead on R587 = no improvement,
Left a lead on TP2 and moved the other lead to R 586 = no improvement.
If one of the test points was bad I should have seen some idle current on the meter by going backwards in the circuit with the other probe was my thinking.
There is a typo in the schematic.
R529 & R532 are shown as 2.2 ohm 1W. They are actually 2.2k ohms
James
R529 & R532 are shown as 2.2 ohm 1W. They are actually 2.2k ohms
James
Ohah. By the time that I was finished with the above measurements my brain was fried and I needed a break.
But I was just sitting and listening to Every Picture Tells A Story with a beer and some sipping rum and looked over my notes.
And it hit me, where is my ~+/(-)80v on the driver collector(s)?!
The pre-drivers look good but I don't have +80v collector voltage on driver TR511. I couldn't get a probe in there to measure the collector of TR512 but will have to find an upstream spot on a jumper or such to measure that.
But it doesn't seem like the drivers can do much if they don't get rail voltage.
Tomorrow I need to find out what is going on there.
Cheers,
James
But I was just sitting and listening to Every Picture Tells A Story with a beer and some sipping rum and looked over my notes.
And it hit me, where is my ~+/(-)80v on the driver collector(s)?!
The pre-drivers look good but I don't have +80v collector voltage on driver TR511. I couldn't get a probe in there to measure the collector of TR512 but will have to find an upstream spot on a jumper or such to measure that.
But it doesn't seem like the drivers can do much if they don't get rail voltage.
Tomorrow I need to find out what is going on there.
Cheers,
James
dr*audio
Fish fingers and custard!
Bingo!
Unfortunately, false alarm.
I got up this morning and went straight to the amp and checked TR511,512 again, before even having coffee.
I have voltage on the collectors, roughly +/-79v. I must have not gotten the probe properly on the lead of 511 yesterday, and R557 is on the same trace as 512 and I have voltage there.
Back to the search. Coffee first.
James
The amp definitely does not like 5532 opamps in IC501.
I put one in and immediately measured it's pins and it had pulled my +/-15v down to ~8.5v, also in IC502. Making the guess that it is oscillating.
I turned it off right away and re-installed the original NJM082BD.
Back when I first started this I tried to find a sub for that opamp and the best answer that I came up with was a Ti TL082CP, also a dual JFET. I can't upload the data sheet for the it here, too large. But I am attaching the data sheet for the 082BD.
I put one in and immediately measured it's pins and it had pulled my +/-15v down to ~8.5v, also in IC502. Making the guess that it is oscillating.
I turned it off right away and re-installed the original NJM082BD.
Back when I first started this I tried to find a sub for that opamp and the best answer that I came up with was a Ti TL082CP, also a dual JFET. I can't upload the data sheet for the it here, too large. But I am attaching the data sheet for the 082BD.
Actually, after putting a 5532 in IC502 I noticed that the 15v supply dropped to about 14.8v.
I have now re-installed the M5218P there.
The input voltages on IC502 are symmetrical. But IC501 is missing anything on pin3, 0v.
So I started checking to the left.
The -41v that is supposed to show D506 & D507 is missing, 0v.
TR507 emitter, schematic shows -21mv, I think that is a typo and it is supposed to be +? I have +21mv there.
TR508 emitter is supposed to show -61mv, I have -20mv there.
TR505 and 506 are nearly correct, 0.63v and -0.61v.
Simply placing the probe on the base of TR503 or the drain of TR501 caused the meter on the idle current test points to jump and show voltage and the power supply starts to lightly hum. I don't think that I want to do that again.
Note: I have a second DMM left on TP1 and TP2 at all times. The DMM that I am testing with has the Neg lead hooked to the Ground test point with a mini-grabber and the Pos probe has shrink wrap covering the probe tip with only about 1mm showing to limit the chance of causing a short.
James
I have now re-installed the M5218P there.
The input voltages on IC502 are symmetrical. But IC501 is missing anything on pin3, 0v.
So I started checking to the left.
The -41v that is supposed to show D506 & D507 is missing, 0v.
TR507 emitter, schematic shows -21mv, I think that is a typo and it is supposed to be +? I have +21mv there.
TR508 emitter is supposed to show -61mv, I have -20mv there.
TR505 and 506 are nearly correct, 0.63v and -0.61v.
Simply placing the probe on the base of TR503 or the drain of TR501 caused the meter on the idle current test points to jump and show voltage and the power supply starts to lightly hum. I don't think that I want to do that again.
Note: I have a second DMM left on TP1 and TP2 at all times. The DMM that I am testing with has the Neg lead hooked to the Ground test point with a mini-grabber and the Pos probe has shrink wrap covering the probe tip with only about 1mm showing to limit the chance of causing a short.
James
2SK184 N-channel JFet's are NLA like most transistors in this amp.
But the 2SK209 is functionally identical with the exceptions of being a SMD part and being only 150mW compared to the original parts 200mW dissipation. I hope that they will hold up.
I only have to solder legs to these things and then I can test them to find a matched pair.
Cheers,
James
But the 2SK209 is functionally identical with the exceptions of being a SMD part and being only 150mW compared to the original parts 200mW dissipation. I hope that they will hold up.
I only have to solder legs to these things and then I can test them to find a matched pair.
Cheers,
James
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dr*audio
Fish fingers and custard!
You are going in a million directions at once, you need to be more methodical and look at one thing at a time. If you see a voltage that is grossly off, that is an area to concentrate on. voltages that are off by mV aren't likely to be a problem. D506 and D507 should have +/- 15V on them as shown below. Please re-check, as it is the power supply for the opamps.
Attachments
I have +15.2 and -15.2 at D506/507 as long as the OEM opamps are installed.
Those zeners, as well as D501/502 all tested at 14.4v to 14.6v when removed 2 weeks ago. At that time I was only getting ~+/-14.8v. They were replaced with MTZJ15SC R0G, sorted and tested at 14.8v. (The HZ datasheet shows the HZ-15-2 as a nominal value of 14.8v).
After installing a 5532 in IC502 my 15v dropped to about 14.8v, at both opamps and anywhere along that area. I tested those voltages right after installing it.
Installing a 5532 in both positions made the 15v drop to about 8.5v, as well as anywhere else in the area!
Re-installing the OEM opamps restored the supply rails to +/-15.2v. That is when I took a long walk in the sun.
I made the guess that the most likely reason that those opamps were pulling the voltage down is that they were oscillating, especially in the IC501 position.
Yeah, I understand your statement about me going in too many directions at once, you are correct, I gotta slow down sometimes.
James
Those zeners, as well as D501/502 all tested at 14.4v to 14.6v when removed 2 weeks ago. At that time I was only getting ~+/-14.8v. They were replaced with MTZJ15SC R0G, sorted and tested at 14.8v. (The HZ datasheet shows the HZ-15-2 as a nominal value of 14.8v).
After installing a 5532 in IC502 my 15v dropped to about 14.8v, at both opamps and anywhere along that area. I tested those voltages right after installing it.
Installing a 5532 in both positions made the 15v drop to about 8.5v, as well as anywhere else in the area!
Re-installing the OEM opamps restored the supply rails to +/-15.2v. That is when I took a long walk in the sun.
I made the guess that the most likely reason that those opamps were pulling the voltage down is that they were oscillating, especially in the IC501 position.
Yeah, I understand your statement about me going in too many directions at once, you are correct, I gotta slow down sometimes.
James
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After re-installing the OEM opamps the only thing that I have done is spend several hours re-checking all of the shown schematic voltages and recording what I measured on my notepad.
No other parts have been changed, nothing has been disturbed.
The OEM opamps are installed.
Testing voltages in the direction of the pre-drivers, drivers and outputs I got values very close to the schematic, with the exception of the 585mV and -611mV shown at R601/602 feeding the bases of TR519/520. There I read 538mv and -533mv respectively. Still doesn't seem that low.
TR511 base: 1.09v (should be 1.07v)
TR512 base: -1.12v (should be -1.17v) (so these look pretty nominal)
R553/C530 junction: 1.63v (should be 1.78v)
R554/C531 junction: -1.74v (should be -1.82v)
Going back to the opamps and checking their pins:
IC502:
1: 8mv (plus v, should be -37mv)
2: -1mv
3: 1mv
4: -15.23v
5: 1mv
6: 1mv
7: 9mv (plus, should be -38mv)
8: 15.2v
IC501:
1: 87mv (should be half that at 43mv)
2: -2mv
3: 0 (setting my meter on the 300mv scale I see a fluctuating zero to 0.1mv)
4: -15.23v
5: 1mv (this pin goes nowhere, unused)
6: -2.2mv
7: -2.2mv (pins 6 and 7 are bridged)
8: 15.2v
In the section of schematic that you show above the -41mv shown at the junction of D506/507 is missing. I read zero volts here and zero volts on pin 3 of IC501.
This is what caused me to follow through into the voltage amp section.
I wanted to see if I could find an indication of where that voltage goes missing.
Also shown in that same section of the schematic, the junctions of R529/531 and R530/532 are supposed to show 47.6v and -47.8v respectively.
I am only getting 43.4v and -43.7 volts there respectively.
TR507 emitter is shown as -21mv. I have +20mv there.
TR508 emitter is shown as -60mv. I have -20mv there.
TR505 collector is shown as 0.59v. I have 0.63v there.
TR506 collector is shown as -0.64v. I have -0.61v there.
I missed the collector of TR504.
This is when I wanted to check the base of TR503. Should be 12.8v and that is about what I saw but when I put my probe on the base that is when it started to do odd things.
I am using 2 meters.
The entire time that I have power on the amp a Fluke 79 III is on the idle current test points.
I am using a Fluke 77 for general testing. Still my favorite meter.
If I need it I have a 3rd DMM, an OTC 100 automotive meter.
When I put a probe on the base of TR503 or the drain of TR501 the idle current immediately starts to show fluctuating voltage and a light hum comes from the power supply area. This scared the crap out of me and I have not done anything further from that point. All that I did was touch the darn things.
I am very paranoid about causing a short with the test probe. So the probe tip is covered with shrink wrap tubing except for the very last mm of the tip, there is very little exposed that could short 2 legs of anything.
Anyway, way early on when I bought the amps I started looking into potential subs for all of the transistors just in case that I needed them and ordered large quantities from Mouser.
So at this point I have backups on hand but have not changed any of the above mentioned parts.
But in case that they are needed I am getting some N-channel JFETs ready.
James
edit: Concerning R529 &532. The schematic shows them as 2.2 ohms /1w. This has to be a typo, there are 2.2k ohm 1w parts there.
From my notes R529, 532 both measured at 2224 ohms.
R530, 531, 1.8k ohms measured at 1811 and 1806 ohms respectively.
So all 4 resistors are very nominal.
Posting this because of my low +/-47.8v.
No other parts have been changed, nothing has been disturbed.
The OEM opamps are installed.
Testing voltages in the direction of the pre-drivers, drivers and outputs I got values very close to the schematic, with the exception of the 585mV and -611mV shown at R601/602 feeding the bases of TR519/520. There I read 538mv and -533mv respectively. Still doesn't seem that low.
TR511 base: 1.09v (should be 1.07v)
TR512 base: -1.12v (should be -1.17v) (so these look pretty nominal)
R553/C530 junction: 1.63v (should be 1.78v)
R554/C531 junction: -1.74v (should be -1.82v)
Going back to the opamps and checking their pins:
IC502:
1: 8mv (plus v, should be -37mv)
2: -1mv
3: 1mv
4: -15.23v
5: 1mv
6: 1mv
7: 9mv (plus, should be -38mv)
8: 15.2v
IC501:
1: 87mv (should be half that at 43mv)
2: -2mv
3: 0 (setting my meter on the 300mv scale I see a fluctuating zero to 0.1mv)
4: -15.23v
5: 1mv (this pin goes nowhere, unused)
6: -2.2mv
7: -2.2mv (pins 6 and 7 are bridged)
8: 15.2v
In the section of schematic that you show above the -41mv shown at the junction of D506/507 is missing. I read zero volts here and zero volts on pin 3 of IC501.
This is what caused me to follow through into the voltage amp section.
I wanted to see if I could find an indication of where that voltage goes missing.
Also shown in that same section of the schematic, the junctions of R529/531 and R530/532 are supposed to show 47.6v and -47.8v respectively.
I am only getting 43.4v and -43.7 volts there respectively.
TR507 emitter is shown as -21mv. I have +20mv there.
TR508 emitter is shown as -60mv. I have -20mv there.
TR505 collector is shown as 0.59v. I have 0.63v there.
TR506 collector is shown as -0.64v. I have -0.61v there.
I missed the collector of TR504.
This is when I wanted to check the base of TR503. Should be 12.8v and that is about what I saw but when I put my probe on the base that is when it started to do odd things.
I am using 2 meters.
The entire time that I have power on the amp a Fluke 79 III is on the idle current test points.
I am using a Fluke 77 for general testing. Still my favorite meter.
If I need it I have a 3rd DMM, an OTC 100 automotive meter.
When I put a probe on the base of TR503 or the drain of TR501 the idle current immediately starts to show fluctuating voltage and a light hum comes from the power supply area. This scared the crap out of me and I have not done anything further from that point. All that I did was touch the darn things.
I am very paranoid about causing a short with the test probe. So the probe tip is covered with shrink wrap tubing except for the very last mm of the tip, there is very little exposed that could short 2 legs of anything.
Anyway, way early on when I bought the amps I started looking into potential subs for all of the transistors just in case that I needed them and ordered large quantities from Mouser.
So at this point I have backups on hand but have not changed any of the above mentioned parts.
But in case that they are needed I am getting some N-channel JFETs ready.
James
edit: Concerning R529 &532. The schematic shows them as 2.2 ohms /1w. This has to be a typo, there are 2.2k ohm 1w parts there.
From my notes R529, 532 both measured at 2224 ohms.
R530, 531, 1.8k ohms measured at 1811 and 1806 ohms respectively.
So all 4 resistors are very nominal.
Posting this because of my low +/-47.8v.
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