Working on a couple of tough-dogs.
One of them is an audiobaun A6004T. Keeps burning outputs, but it might be user error... It had shorted outputs QA11, QA12, both a 2SC4467 and 2SA1694.
Also had both drivers shorted, and top blown off of QA10 i think it was? then RA40, RA41 and RA42 open and burnt to a crisp. figured everything else out via the other 3 channels. With outputs removed, other 3 channels work fine. no problems.
So i replaced all those parts, and checked everything else for opens, shorts, etc etc. the differential and VAS stages all test fine. its odd... But i do not have these exact output transistors, all i have are the TIP35C, TIP36C pairs, as most amps use them.
So i used those. The channel sounds fine within the first 2 or so seconds on powerup, then it starts to cut in and out between protect for a few seconds before the output transistors short completely, and hold it into protect. Replacing the outputs, same exact thing happens. It might be me, not being able to sub out the 2SA/2sC outputs for the TIP set....
Thats the first amp.
Moved second amp to new thread.
One of them is an audiobaun A6004T. Keeps burning outputs, but it might be user error... It had shorted outputs QA11, QA12, both a 2SC4467 and 2SA1694.
Also had both drivers shorted, and top blown off of QA10 i think it was? then RA40, RA41 and RA42 open and burnt to a crisp. figured everything else out via the other 3 channels. With outputs removed, other 3 channels work fine. no problems.
So i replaced all those parts, and checked everything else for opens, shorts, etc etc. the differential and VAS stages all test fine. its odd... But i do not have these exact output transistors, all i have are the TIP35C, TIP36C pairs, as most amps use them.
So i used those. The channel sounds fine within the first 2 or so seconds on powerup, then it starts to cut in and out between protect for a few seconds before the output transistors short completely, and hold it into protect. Replacing the outputs, same exact thing happens. It might be me, not being able to sub out the 2SA/2sC outputs for the TIP set....
Thats the first amp.
Moved second amp to new thread.
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i wouldnt know becuase it only lasts about 8 seconds before the outputs go bye bye. emitter resistors get hotter than a firecracker as well towards the end. When the amp is first on though, it sounds ok, but i cant turn it up becuase if i turn it up, the sound starts kicking the amp into protect before eventually it kicks itself in and out of protect on its own at idle, before outputs short.
Is the emitter of QA8 connected to the base of QA10?
If so..
1. short legs 1 and 2 of QA8
2. connect your multimeter (set to DC volts) across one of the emitter resistors in that channel
3. clamp all transistors
4.insert a 10 amp fuse in the B+ line and power the amp up.
If the DC voltage across the emitter resistor is more than 0.000v for more than ~1 second, shut down the amp and post the results.
If so..
1. short legs 1 and 2 of QA8
2. connect your multimeter (set to DC volts) across one of the emitter resistors in that channel
3. clamp all transistors
4.insert a 10 amp fuse in the B+ line and power the amp up.
If the DC voltage across the emitter resistor is more than 0.000v for more than ~1 second, shut down the amp and post the results.
Ok, i put the right outputs inside there, $11 bucks later. its still pulsating between protect and power.... Also on powerup, both emitter resistors shoot up to about .258V on poweron, then back to 0v, then .258, kinda in an oscillating fashoned.
I still dont trust using the 10amp fuse either. also i dont want to short out any pins for the simple fact that i cant get to much. its really compact in there.
I still dont trust using the 10amp fuse either. also i dont want to short out any pins for the simple fact that i cant get to much. its really compact in there.
Alongside the drivers being shorted, there was a top blown off of one transistor, so that made a total of 3 transistors excluding the outputs that had to be replaced. All the rest of them test fine, even against the other channels. within spec.
Unfortuantely, which could be the cause of my entire problem, i didnt have the exact drivers on hand either. :-(
Could be my whole problem, as i pulled these drivers from another board that worked but had shorted power supply turns.
The original drivers were:
2SA1023
2SC1027
Transistor that blew its top off was:
QA8, 2SC3198.
Replaced the drivers with:
2SB1238
2SD1859
replaced QA8 with a 2SC945.
This is all that I had on hand. anything wrong with these figures so far? thanks.
There was also a handfull of resistors that were open or burned, so i replaced those as well. both 2.2ohms and the 220ohms bridging between the two were all blown open. I checked all other resistors and diodes they are all fine
Unfortuantely, which could be the cause of my entire problem, i didnt have the exact drivers on hand either. :-(
Could be my whole problem, as i pulled these drivers from another board that worked but had shorted power supply turns.
The original drivers were:
2SA1023
2SC1027
Transistor that blew its top off was:
QA8, 2SC3198.
Replaced the drivers with:
2SB1238
2SD1859
replaced QA8 with a 2SC945.
This is all that I had on hand. anything wrong with these figures so far? thanks.
There was also a handfull of resistors that were open or burned, so i replaced those as well. both 2.2ohms and the 220ohms bridging between the two were all blown open. I checked all other resistors and diodes they are all fine
http://www.bcae1.com/temp/unknownaudiobahn01.swf
This may be close to what you have. It's from a smaller 2 channel amp.
This may be close to what you have. It's from a smaller 2 channel amp.
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