Denon POA 6600 Thread

[Bratwurst7s]

Yes... Re-bottled it all and put a Miller lite label on it.

When I was flying to Arizona they had Miller Light on the menu. And only 2 other choices.
So I told the Steward that I guess that I will take one of those Ale thingys (and I am not fond of Ale) because there was nothing better.

He replied that he had some Bittburger Pilsner if I would prefer that. Does a bear crap in the woods?
So I enjoyed some Bittburger.
I would drink toilet water before a Miller lite. (From the tank, OK?)

,
James

 

[Soundscape]

TR502/TR503: I could not safely get at E or C on these. B is +12.63 on both.

I'm thinking either TR502,503, or 506 have an open junction.

 

[Bratwurst7s]

I'm thinking either TR502,503, or 506 have an open junction.

I took another break, will work on again it later today or tomorrow.

I was suspecting TR506 also, removed and tested (good) and replaced with new. Gonna check 502,503 next, woke up and realized that I can get at E & C on them by way of the nearby resistors.

If they are bad I have another worry, because they are new.

,
James

 

[Soundscape]

I took another break, will work on again it later today or tomorrow.

I was suspecting TR506 also, removed and tested (good) and replaced with new. Gonna check 502,503 next, woke up and realized that I can get at E & C on them by way of the nearby resistors.

If they are bad I have another worry, because they are new.

,
James

This reminds me of a different piece I had with similar issues with. Replaced some trannies in the V-amp ckt, secondary failures from shorted outputs etc. It came out of protection, but still had high base voltages.
I took it off the DBT and damaged a pre-driver tranny that I already replaced earlier. I found some open emitter resistors, then replaced the pre-driver tranny again, and it worked.

 

[Bratwurst7s]

I'm thinking either TR502,503, or 506 have an open junction.

Damn good call. My respect. I had already pulled and checked TR504, 505 and 506, all were good.

Today I did some simple resistance checks and did not get continuity between the base of TR502 and R508. De-soldered, cleaned and re-soldered the resistor, as well as a number of other connections in that area, all looked good.

Pulled TR502 and 503 and cleaned the pads. The pad for the base of TR502 was broken and lifted right off when I cleaned it.


Got some repair work to do.

,
James

 

[Soundscape]

Damn good call. My respect. I had already pulled and checked TR504, 505 and 506, all were good.

Today I did some simple resistance checks and did not get continuity between the base of TR502 and R508. De-soldered, cleaned and re-soldered the resistor, as well as a number of other connections in that area, all looked good.

Pulled TR502 and 503 and cleaned the pads. The pad for the base of TR502 was broken and lifted right off when I cleaned it.
View attachment 3229043View attachment 3229044

Got some repair work to do.

,
James

Cool... Hopefully that's all it is... and will be singing soon.

I can be compensated with beer & blunts.

 

[Soundscape]

If it still won't bias...or more importantly, displays some bias voltage at null when it should be zero, let's talk more. We're getting close either way.

 

[Bratwurst7s]

Well, this project turned into one of me doing some of my worst work ever, and in the end much of it was unneeded and complicated by several very dumb mistakes.

Dumb mistake number 3, or 4, or was it 5. I took the easy way out when "repairing" the broken trace "eye" on TR502. By way of using a new transistor and bending a lead over to complete the trace. Since it looks like 502 and 503 are a complimentary pair that meant replacing 503 again with a match to 502.



This was a mistake. Don't do this.
After re-installing the board and powering it up on the dbt it was clear that I had caused more damage than I had fixed, I was getting crazy voltages all over the place. This was naturally very depressing and I walked away for a week. No, make that 2 weeks.

 

[dr*audio]

Damn good call. My respect. I had already pulled and checked TR504, 505 and 506, all were good.

Today I did some simple resistance checks and did not get continuity between the base of TR502 and R508. De-soldered, cleaned and re-soldered the resistor, as well as a number of other connections in that area, all looked good.

Pulled TR502 and 503 and cleaned the pads. The pad for the base of TR502 was broken and lifted right off when I cleaned it.
View attachment 3229043View attachment 3229044

Got some repair work to do.

,
James

Bad solder joint with a void around the component lead at the top of the top picture. Reflow it.

 

[Bratwurst7s]

So this last Monday I went back to it, removed TR502/503 again, and repaired/reinforced most of the traces connecting 502/503 to the surrounding parts using the snipped off tinned copper leads from some caps that we always save. I realized today that I only took one photo of that, on my cell phone. So I will retrieve that and post it. As an example of what not to put oneself into a position of needing to do. I am certainly not proud of it.

Anyway, after doing that I was back to seeing exactly the voltages that I was getting in late April. Then got an intestinal bug and fever for Tuesday and Wednesday. Got back to the amp on Thursday, and finally, way late, the (very) Dim Bulb on my shoulders brightened up a bit and I did what I failed to do in April and checked the rail voltages in the output section.

And found zero volts on the +80v line. This was easily traced back to... ...wait for it... ...F002.
A 10A 125V fuse.
That I should have checked 2 months ago.
Which caused me to do a bunch of useless flailing around that did nothing but waste time and cause damage. You might note that I am a bit upset with myself at the moment.

,
James

 

[Bratwurst7s]

Bad solder joint with a void around the component lead at the top of the top picture. Reflow it.

I did re-solder it, and a large amount of other connections on Monday.

Thursday I express ordered some 10A fuses. They arrived yesterday. Replaced both F001 & 002.

Powered up on DBT, all voltages showed correct and symmetrical where they should be. Took it off the DBT, dialed in the idle current and the amp sat cool and stable. Just like that.

,
James

 

[Bratwurst7s]

Today the amps went in the rack. They now produce music. Very nice music.



I could have been this far in April if I wasn't so dumb.

In any case, they both work now. The amp with the replacement MJE13032G/33G drivers is on the right, I can't hear any difference in sound. Note that at this point the original op-amps are installed.

,
James

 

[Bratwurst7s]

I still have a 3rd, damaged, one of these. So I still have a bit more fun ahead, but first there are two Yamaha AX-1090's, my turntable, and some other stuff that needs to get done.

,
James

 

[Bratwurst7s]

As promised, a photo of some less than spectacular work.


,
James

 

[Bratwurst7s]

After about 5 hours of use I am very happy with how these amps sound.

Using the 4 little Marantz MA500 amps was a useful interim solution but they were severely limited by the load that I was putting them under, effectively a 2 ohm load. They were like having a little car that had 500hp and 4" wide tires.

I have been listening at quite "spirited" levels and the Denon's don't break a sweat. The sound remains very clean and clear regardless of the volume. I have the feeling that I could blow the windows out long before the amps give up.

I will run them this way for a couple of weeks and then I will try them with an OPA1656 in IC501 and a LME49720 in IC502.

,
James

 

[Soundscape]

So this last Monday I went back to it, removed TR502/503 again, and repaired/reinforced most of the traces connecting 502/503 to the surrounding parts using the snipped off tinned copper leads from some caps that we always save. I realized today that I only took one photo of that, on my cell phone. So I will retrieve that and post it. As an example of what not to put oneself into a position of needing to do. I am certainly not proud of it.

Anyway, after doing that I was back to seeing exactly the voltages that I was getting in late April. Then got an intestinal bug and fever for Tuesday and Wednesday. Got back to the amp on Thursday, and finally, way late, the (very) Dim Bulb on my shoulders brightened up a bit and I did what I failed to do in April and checked the rail voltages in the output section.

And found zero volts on the +80v line. This was easily traced back to... ...wait for it... ...F002.
A 10A 125V fuse.
That I should have checked 2 months ago.
Which caused me to do a bunch of useless flailing around that did nothing but waste time and cause damage. You might note that I am a bit upset with myself at the moment.

,
James

Congrats sir ya fixed a fine amp. We've all made mistakes but at the end of the day you fixed the bitch. Also, ya did better work than ANY of my local stereo shops.
Celebrate and enjoy the music mr Bratwurst.

 

[Soundscape]

I will run them this way for a couple of weeks and then I will try them with an OPA1656 in IC501 and a LME49720 in IC502.

you have bigger stones than I...and I don't say that to all the guys. IMO...if it works haul ass.

If I may. What's the DC offset at the speaker terminals?

 

[Bratwurst7s]

you have bigger stones than I...and I don't say that to all the guys. IMO...if it works haul ass.

If I may. What's the DC offset at the speaker terminals?

They show 2mV. I think that this is because of some kind of magic happening in the DC servo section because I have never seen such a thing before. The second amp was showing that a half hour (run time) before it burned.

,
James

 

[Soundscape]

They show 2mV. I think that this is because of some kind of magic happening in the DC servo section because I have never seen such a thing before. The second amp was showing that a half hour (run time) before it burned.

,
James

Dude, 2mV is outstanding and a rewarding testament for your labor. Nice.

The second amp was showing that a half hour (run time) before it burned.

Getting my POA's confused bro. Is this the 3rd or 5th? Lol

 

[Bratwurst7s]

Dude, 2mV is outstanding and a rewarding testament for your labor. Nice.



Getting my POA's confused bro. Is this the 3rd or 5th? Lol

Well, the thing is that they both showed 2mV before reworking them, and 2mV after. I have never seen an amp before that only had 2mV DC offset but I have also never before had an amp that had that DC servo thingy in it.

I haven't started working on the 3rd one yet. That probably won't happen until after Summer. Got too many other projects that got backed up by this one.