Just by tryin to measure R543 black lead on ground and positive on one leg makes my amp oscillate.
I wouldn't call that oscillation. It's 40mV noise. Don't worry about that yet.Ok. Just wondering because it dissapears when i remove CN6. It is so wierd somethime when i power up i come off protection mode and DBT goes out and i got 7mV dc on output. Then sometimes my DBT lights up a little bit and i get 300mV on output then next time it's okay gain.
As soon as i connect input DBT ligts up, with a 1K signall. Removing input and i'm back to stable. Fun! 2 pics of my output:
View attachment 1416857
View attachment 1416858
The problem is quite honestly that you seem to lack basic understanding on how to use an oscilloscope correctly, which makes trying to help you quite frustrating.
Put the scope aside for a second, plug everything in and check EVERY voltage in the schematic with the input grounded (or at least disconnected). Then let’s see what we can see!
Sorry about that i Just got it för 1week ago. I will try to understand it in parallell to this.
Well that is my problem i'm only able to measure voltages att certain areas. Just touching will cause problems. Maby i'm able to test voltages for every position if i turn it off every time i move the probe. If i power up the amp with a probe with i can hook then i'm ablte to meausre but i dare to just inject a probe it does not like it.
Well that is my problem i'm only able to measure voltages att certain areas. Just touching will cause problems. Maby i'm able to test voltages for every position if i turn it off every time i move the probe. If i power up the amp with a probe with i can hook then i'm ablte to meausre but i dare to just inject a probe it does not like it.
Measure with a hight input impedance multimeter. If you’re using the scope, make sure the switch on the probe is set to 10x. But use a multimeter instead!
If it goes into failsafe mode from you just touching a test point, you’ve got big problems.
If it goes into failsafe mode from you just touching a test point, you’ve got big problems.
CN6 powers the relay 501 that allows power from cn13 to reach the preamp section. So pulling either plug, turns off the power to the preamp, making your reading go away.
I see you went along the +80v rail, and saw the transition to 45v them 15v didn't happen. You found the zener 507 down. Perhaps in that order. You didn't look at the -80v rail, which should go through the same 45v 15v to power the opamp, which the zeners likely regulate. There is a good chance the opamp is dead, if zener was open circuit.
I think you are in the right area, and need to keep probing, and get results together. We will have a better idea of what happened, if you don't start cleaning up the crash scene before completing this documenting.
The opamp now fitted has 50% more gain, and 50% higher slew rate than the 082 that should be in there. It's bandwidth is vastly greater. Oscillation wouldn't be a surprise, and an 082 costs one gold coloured coin. Add to this the fact the opamps power regulation here failed, and I would be changing it for the right part. The other opamp gets the same failed power supply. The state it failed in, needs to be known. So if you have replaced that zener, it's a problem.
Looking at that opamps job of bias correction, this job is gaining clarity.
I see you went along the +80v rail, and saw the transition to 45v them 15v didn't happen. You found the zener 507 down. Perhaps in that order. You didn't look at the -80v rail, which should go through the same 45v 15v to power the opamp, which the zeners likely regulate. There is a good chance the opamp is dead, if zener was open circuit.
I think you are in the right area, and need to keep probing, and get results together. We will have a better idea of what happened, if you don't start cleaning up the crash scene before completing this documenting.
The opamp now fitted has 50% more gain, and 50% higher slew rate than the 082 that should be in there. It's bandwidth is vastly greater. Oscillation wouldn't be a surprise, and an 082 costs one gold coloured coin. Add to this the fact the opamps power regulation here failed, and I would be changing it for the right part. The other opamp gets the same failed power supply. The state it failed in, needs to be known. So if you have replaced that zener, it's a problem.
Looking at that opamps job of bias correction, this job is gaining clarity.
@njswede
This is useful
http://bilder.hifi-forum.de/max/588...er-amp-stages-and-voltages-marked_1006636.png
It almost looks like they are doing the same breakdown
This is useful
http://bilder.hifi-forum.de/max/588...er-amp-stages-and-voltages-marked_1006636.png
It almost looks like they are doing the same breakdown
Thank you! I was thinking that too so I replace both op-amps to new but same ones. No difference. Maby I should try going back to original ones and try?CN6 powers the relay 501 that allows power from cn13 to reach the preamp section. So pulling either plug, turns off the power to the preamp, making your reading go away.
I see you went along the +80v rail, and saw the transition to 45v them 15v didn't happen. You found the zener 507 down. Perhaps in that order. You didn't look at the -80v rail, which should go through the same 45v 15v to power the opamp, which the zeners likely regulate. There is a good chance the opamp is dead, if zener was open circuit.
I think you are in the right area, and need to keep probing, and get results together. We will have a better idea of what happened, if you don't start cleaning up the crash scene before completing this documenting.
The opamp now fitted has 50% more gain, and 50% higher slew rate than the 082 that should be in there. It's bandwidth is vastly greater. Oscillation wouldn't be a surprise, and an 082 costs one gold coloured coin. Add to this the fact the opamps power regulation here failed, and I would be changing it for the right part. The other opamp gets the same failed power supply. The state it failed in, needs to be known. So if you have replaced that zener, it's a problem.
Looking at that opamps job of bias correction, this job is gaining clarity.
I will also do new measument on all point possible, just scared to short stuff
Both 506 and 507 are replaced with 1N965BCN6 powers the relay 501 that allows power from cn13 to reach the preamp section. So pulling either plug, turns off the power to the preamp, making your reading go away.
I see you went along the +80v rail, and saw the transition to 45v them 15v didn't happen. You found the zener 507 down. Perhaps in that order. You didn't look at the -80v rail, which should go through the same 45v 15v to power the opamp, which the zeners likely regulate. There is a good chance the opamp is dead, if zener was open circuit.
I think you are in the right area, and need to keep probing, and get results together. We will have a better idea of what happened, if you don't start cleaning up the crash scene before completing this documenting.
The opamp now fitted has 50% more gain, and 50% higher slew rate than the 082 that should be in there. It's bandwidth is vastly greater. Oscillation wouldn't be a surprise, and an 082 costs one gold coloured coin. Add to this the fact the opamps power regulation here failed, and I would be changing it for the right part. The other opamp gets the same failed power supply. The state it failed in, needs to be known. So if you have replaced that zener, it's a problem.
Looking at that opamps job of bias correction, this job is gaining clarity.
https://eu.mouser.com/ProductDetail.../1N965B-TR-PBFREE?qs=u16ybLDytRYm6a86SaMKNA==
Just want to point out that all these components that I’m using are successfully installed and working on two Denon Poa 6600. But obviously not one mine so I’m missing something or it comes down to the problem area with all problematic traces. 🙂
Just want to point out that all these components that I’m using are successfully installed and working on two Denon Poa 6600. But obviously not one mine so I’m missing something or it comes down to the problem area with all problematic traces.
That’s a great breakdown i will use it to beep my traces once again@njswede
This is useful
http://bilder.hifi-forum.de/max/588...er-amp-stages-and-voltages-marked_1006636.png
It almost looks like they are doing the same breakdown
So active feedback is what that thing is? Not sure what's wrong with good old feedback. One of those 80s HiFi gimmicks?@njswede
This is useful
http://bilder.hifi-forum.de/max/588...er-amp-stages-and-voltages-marked_1006636.png
It almost looks like they are doing the same breakdown
The amp might actually work without them
The 15v zeners are interesting. The lower one was broke, and the voltages found suggest the top one was acting like a piece of wire. This is the bias trim power supply. Explaining how the offset is floating about, and initialising how it feels fit.
It's really not obvious to me what could blow the zeners. 50v rails come through 1.8K resistors, so 30mA is about all they could get. Both failed though. I think I'm stuck.
We should get a look at this other thread, where these part swaps worked. These input fets are wrong, and seem to control tr502 and tr503 which have not passed what they should be doing. There really are a lot of questions, and I'm afraid I have lost hours on this, while my own amp needs attention. Another biasing job in fact. Which is why I have some affinity to this thread, but I'm really stretched out here mentally, as I can't even point to where I learned any of this stuff. I simply haven't, so don't have a lot more to give.
The 15v zeners are interesting. The lower one was broke, and the voltages found suggest the top one was acting like a piece of wire. This is the bias trim power supply. Explaining how the offset is floating about, and initialising how it feels fit.
It's really not obvious to me what could blow the zeners. 50v rails come through 1.8K resistors, so 30mA is about all they could get. Both failed though. I think I'm stuck.
We should get a look at this other thread, where these part swaps worked. These input fets are wrong, and seem to control tr502 and tr503 which have not passed what they should be doing. There really are a lot of questions, and I'm afraid I have lost hours on this, while my own amp needs attention. Another biasing job in fact. Which is why I have some affinity to this thread, but I'm really stretched out here mentally, as I can't even point to where I learned any of this stuff. I simply haven't, so don't have a lot more to give.
Oh I see they’re committing a big no-no in the bias control circuit. The trim pot is on the high side, so it it goes open, the output stage goes boom. 😀
Totally understand mate! No worries. I will have a go on measuring voltages today and we if I can beep around to see if I am missing something.The amp might actually work without them
The 15v zeners are interesting. The lower one was broke, and the voltages found suggest the top one was acting like a piece of wire. This is the bias trim power supply. Explaining how the offset is floating about, and initialising how it feels fit.
It's really not obvious to me what could blow the zeners. 50v rails come through 1.8K resistors, so 30mA is about all they could get. Both failed though. I think I'm stuck.
We should get a look at this other thread, where these part swaps worked. These input fets are wrong, and seem to control tr502 and tr503 which have not passed what they should be doing. There really are a lot of questions, and I'm afraid I have lost hours on this, while my own amp needs attention. Another biasing job in fact. Which is why I have some affinity to this thread, but I'm really stretched out here mentally, as I can't even point to where I learned any of this stuff. I simply haven't, so don't have a lot more to give.
Maby I will remove 0.1uf cap between pins 8an4 and try without them or try 0.01 uf instead. At this point I feel I got nothing to loose. Any one more whiny big thanks for helping me!
I guess you have new ICs and zeners so have your 15v rails back, for both chips. Both of which are changed, and likely have decoupling caps.
Have we seen an oscillation though. I have not looked at the scope pics, but trust njswede had that approach covered, and seemed to see nothing.
What we can see, is starting at the beginning, stage 2 doesn't seem to be coming good, and stage 1 that controls it, isn't original. It's usually best to start at the beginning, because what follows, can't work without it. I don't know what this stage does, I have read nothing, but it has a connection back to the main amp, so it can't be ignored. It's some sort of feedback. It's fundamentally important looking. To my untrained eye.
Have we seen an oscillation though. I have not looked at the scope pics, but trust njswede had that approach covered, and seemed to see nothing.
What we can see, is starting at the beginning, stage 2 doesn't seem to be coming good, and stage 1 that controls it, isn't original. It's usually best to start at the beginning, because what follows, can't work without it. I don't know what this stage does, I have read nothing, but it has a connection back to the main amp, so it can't be ignored. It's some sort of feedback. It's fundamentally important looking. To my untrained eye.
Good day! So today i did some more measurements and i hope this will help us out. As i said i'm having trouble in certain areas to insert probe without it start to go crazy and relay clicks in. The right part of the amp in steady to insert probe but not the left side, in some areas i'm not able to have probe connected and power on correctly. Is there any more measuremeants that would be good?
And don't mind the purple lines that is just med checking my traces.
(And im using a Ectech 355 multimeter)
And don't mind the purple lines that is just med checking my traces.
(And im using a Ectech 355 multimeter)
Not sure which node is “not able to come of protection when probe is inserted”. Can you clarify?
Which mode is the multimeter in? Looks like you have a “Low Z” mode. You do NOT want to be in that mode!
In certain areas i power on amplifier with probe hooked to leg and when i power on the amplifier does not come of protectinon mode becuase amp is drawing crurrent and DBT is glowing.Not sure which node is “not able to come of protection when probe is inserted”. Can you clarify?
My 2 cents from Finland. Try to find this book somewhere, you will find it's very helpful and practical. My copy have a message from Bob Pease and it seems you don't have "middle-sized trouble", sorry can't help any more.
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