I believe I am about to fix the popping and static in my channel with this resistor. What ohm is R121 please? PLEASE 
An externally hosted image should be here but it was not working when we last tested it.
With the Fluke at amp ground, and no rca's, one channel is a tad different at idle with no input.
As far as what I have to work with, pretty much whatever I need. I just DO NOT repair audio and I need all the counseling I can get. Techtronix 442 is a dual trace, and the TENMA 72-7290 has counter, generator, DMM and PS. I have my Fluke 87 III as well.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
As far as what I have to work with, pretty much whatever I need. I just DO NOT repair audio and I need all the counseling I can get.
Techtronix 442 is a dual trace, and the TENMA 72-7290 has counter, generator, DMM and PS. I have my Fluke 87 III as well.An externally hosted image should be here but it was not working when we last tested it.
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Actually q33 just went hot potato on me with a little smoke, but I cut it off almost instantly so it got real hot but I think it is still alive. It's the only one that got hot. No foreseeable reason so can I assume that is the final that was going out and causing the trouble? Nothing else in the row got warm. The amp was only on for about ten seconds total, and I was probing the orange capacitor with my flukes + and the negative connected to the amp ground with the meter on DCv. Unless it has dc bias or something from the fluke, which I doubt.
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Look at the signal on the cap. Do you see the same characteristics as you do on the speaker terminals of the defective channel. This is to determine if the channel is being driven with a pulsing signal or if the pulsing is due to something else.
Did you check the output transistors carefully?
Did you check the output transistors carefully?
Well I'm starting out here from scratch and here is where I am at.
The voltage measurements from earlier up there were with no channels driven, but I had a sub connected to one channel (just noticed).
I switched the sub and plugged the rca's in so the sub was now on the bad channel and attempted to take a reading and got the response from the q33 of an intense quick heat. I have never had an issue with the amp smoking before, but I have always had the backing in place so the outputs have always been firmly against the shell, and in this case they were floating so what this tells me is that q33 is the only transistor I can find that is running hot.
Symptoms are popping, scratching sound at the sub "randomly" sometimes a minute apart from each other and weakness in the channel (flutters out on low notes with even a little volume).
So it appears Q33 would be to blame if all the drivers there get the same signal?
The amp is on RIGHT NOW playing fine through the good channel and the bad channel is cold until a speaker load is placed on it and Q33 gets HOT and FAST.
Can I assume Q33 at fault? Should all those drivers get the same signal making it easy to pinpoint q33 as faulty?
If not, just tell me where to go from here and I'll do it. Thanks so much.
The voltage measurements from earlier up there were with no channels driven, but I had a sub connected to one channel (just noticed).
I switched the sub and plugged the rca's in so the sub was now on the bad channel and attempted to take a reading and got the response from the q33 of an intense quick heat. I have never had an issue with the amp smoking before, but I have always had the backing in place so the outputs have always been firmly against the shell, and in this case they were floating so what this tells me is that q33 is the only transistor I can find that is running hot.
Symptoms are popping, scratching sound at the sub "randomly" sometimes a minute apart from each other and weakness in the channel (flutters out on low notes with even a little volume).
So it appears Q33 would be to blame if all the drivers there get the same signal?
The amp is on RIGHT NOW playing fine through the good channel and the bad channel is cold until a speaker load is placed on it and Q33 gets HOT and FAST.
Can I assume Q33 at fault? Should all those drivers get the same signal making it easy to pinpoint q33 as faulty?
If not, just tell me where to go from here and I'll do it
. Thanks so much.Do all of the outputs match (has anyone replaced any of them)?
It's possible that Q33 is leaking or otherwise defective but it's also possible that it's threshold is slightly lower than the 3 in parallel with it. You could remove it and check it to determine if it's leaking.
Do you have any of the shunts like the ones you use on computers? If so, placing them on the 2-pin headers near the outputs should prevent the outputs from overheating unless one is defective.
It's possible that Q33 is leaking or otherwise defective but it's also possible that it's threshold is slightly lower than the 3 in parallel with it. You could remove it and check it to determine if it's leaking.
Do you have any of the shunts like the ones you use on computers? If so, placing them on the 2-pin headers near the outputs should prevent the outputs from overheating unless one is defective.
Shunts - no
Replaced - Does not look like it.
Here's a picture:
http://diymobileaudio.com/gallery/watermark.php?file=8569
Q33 appears to be stock.
Replaced - Does not look like it.
Here's a picture:
http://diymobileaudio.com/gallery/watermark.php?file=8569
Q33 appears to be stock.
Yes 33 was HOT, smoking (literally) hot. On the other side of the board the transistor equal to Q32 on the other side is brown from heat and has been driven good and hard, but that channel is perfect. This side 32 is clean and 33 is overheating. That's why I figured they should all be getting equal signal in that row and might point to 33 being bad. Figured I'd get an idea before I pulled the transistors out to check them while we are just talking here.
Very interesting given that one's heat signs. Anywho, that channel works so I'll worry with it if it ever gives me flack. I've seen mouser referenced here a lot, is that where I need to go to get this particular Q33 or is there a better source? I may buy in some bulk since my 600.2 uses the same outputs.
Mouser is generally a good source but it appears that they're out of stock on the 6491s. They have Central Semiconductor 6491s in stock but I have no confidence on CS parts.
Try Future
Electronic Components from the Best - Future Electronics
or Digikey
DigiKey Corp. | Electronic Components Distributor | United States Home Page
Try Future
Electronic Components from the Best - Future Electronics
or Digikey
DigiKey Corp. | Electronic Components Distributor | United States Home Page
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