It all makes sense now. So the driver transistors drive 1&3 and 2&4 on this amp. So essentially I'm only replacing the three transistors in that one bank..?
Since I've exhausted my supply of power FETs it's Digi-key time again. IIRC these were the expensive ones. At the rate I'm going through them, might as well order 20 or so.
Since I've exhausted my supply of power FETs it's Digi-key time again. IIRC these were the expensive ones. At the rate I'm going through them, might as well order 20 or so.
According to the information you provided, yes.
Yes, only replace 3 FETs in one of the four banks if all others survived.
Yes, only replace 3 FETs in one of the four banks if all others survived.
Hello Adelphia,
I am a student of Perry's and just repaired an A8000V Audiobahn and found these posts helpful. I hope you get yours up and running soon. My repair was a little more involved, but I opted to go with the TIP35C and TIP36C for the audio drivers and found that they were very similar to the D718 and B688 BJT's. The A8000V produces about 50 rail volts however.
Along with two failed audio drivers, I also had Power supply troubles and had to replace 2 PowerSupply FETs, 2 Rectifiers, and repair shorted wiring in the transformer.
Good luck with the repair. Your in good hands.
Cheers!
Mack
I am a student of Perry's and just repaired an A8000V Audiobahn and found these posts helpful. I hope you get yours up and running soon. My repair was a little more involved, but I opted to go with the TIP35C and TIP36C for the audio drivers and found that they were very similar to the D718 and B688 BJT's. The A8000V produces about 50 rail volts however.
Along with two failed audio drivers, I also had Power supply troubles and had to replace 2 PowerSupply FETs, 2 Rectifiers, and repair shorted wiring in the transformer.
Good luck with the repair. Your in good hands.
Cheers!
Mack
Mack, thanks for the comment. It has been quite the uphill battle with this one, but I'm confident I can get it working again. Many of the challenges I faced were a result of "beginner" errors, like powering up the amp with all it's fuses, or without the transistors clamped. A smaller iron and thinner solder is next on the list.
Congrats on repairing the A8000V. I also have an A8002T which is similar in output to yours, just two channel. They seem to be good amps under normal use, I've used this brand for years with good luck until now.
I'll post back after replacing the bank of FETs, hopefully after that it will be final testing and closing it up!
Congrats on repairing the A8000V. I also have an A8002T which is similar in output to yours, just two channel. They seem to be good amps under normal use, I've used this brand for years with good luck until now.
I'll post back after replacing the bank of FETs, hopefully after that it will be final testing and closing it up!
Well it appears I have a working amp again. I quickly found out that soldering to the legs of these is much more difficult than the outputs.
I'm thankful that the board has a layout of the underneath traces on top. I found troubleshooting much easier by putting my meter on something adjacent to the FETs (that they're connected to) when measuring voltage or resistance. After the last episode, it's obvious they lie waiting to unleash hell should you touch their two legs together.
This whole event started when attempting to find out why the chassis of the amp was arcing at vehicle ground. After replacing these components, with the power on, I put my meter against negative input (ground) and the amp chassis, and read 0 volts. Is this the correct way to test this? I want to be sure that when I reinstall, I won't have the arcing problem.
Also on the rail cap.. Will any 2200uf 63v component do? I tried finding them online at Newark but they all were direct ship from the UK, costing an additional 30$ plus a 2-3 week wait. I found a substitute (also 2200uf 63v) in their 10,000 page catalog that was about 2$ and they had it in stock. Will I have any problems?
I'm thankful that the board has a layout of the underneath traces on top. I found troubleshooting much easier by putting my meter on something adjacent to the FETs (that they're connected to) when measuring voltage or resistance. After the last episode, it's obvious they lie waiting to unleash hell should you touch their two legs together.
This whole event started when attempting to find out why the chassis of the amp was arcing at vehicle ground. After replacing these components, with the power on, I put my meter against negative input (ground) and the amp chassis, and read 0 volts. Is this the correct way to test this? I want to be sure that when I reinstall, I won't have the arcing problem.
Also on the rail cap.. Will any 2200uf 63v component do? I tried finding them online at Newark but they all were direct ship from the UK, costing an additional 30$ plus a 2-3 week wait. I found a substitute (also 2200uf 63v) in their 10,000 page catalog that was about 2$ and they had it in stock. Will I have any problems?
Some amplifiers have the chassis ground tied directly to the heatsink. If that's the case with your amp, the only reason it would arc is if you had a bad ground connection on the amp (ground terminal to vehicle).
Check all of the components (amp disconnected from power source) to see if their tabs are shorted to the case.
With the amp powered up, at idle, did you measure any DC voltage on the sink (black meter probe on the ground terminal of the amp)?
Look for the capacitor at mouser. What are its dimensions?
Check all of the components (amp disconnected from power source) to see if their tabs are shorted to the case.
With the amp powered up, at idle, did you measure any DC voltage on the sink (black meter probe on the ground terminal of the amp)?
Look for the capacitor at mouser. What are its dimensions?
I discovered the arcing problem. One of the power FET tabs was contacting the amp chassis.
This amp normally has a wire that connects ground to amp chassis, but it is a ring terminal that is clamped to chassis when the cover is installed. Since I've done all the testing thus far without the cover, this was left disconnected.
I'll check mouser for the capacitor. I don't have the exact dimensions of the capacitor, does this make a difference? There's ample room in the cap location for any size 2200uf/63v cap.
On a positive note, the amp played beautifully to and from work, about an hour each way. It got hot to the touch but never entered protection.
This amp normally has a wire that connects ground to amp chassis, but it is a ring terminal that is clamped to chassis when the cover is installed. Since I've done all the testing thus far without the cover, this was left disconnected.
I'll check mouser for the capacitor. I don't have the exact dimensions of the capacitor, does this make a difference? There's ample room in the cap location for any size 2200uf/63v cap.
On a positive note, the amp played beautifully to and from work, about an hour each way. It got hot to the touch but never entered protection.
The capacitors are not critical. If you can give me the dimensions, I will try to find suitable replacements for you.
Perry, do you need measurements in width & height?
As car audio has become a significant hobby, I plan on attempting amp rebuilds in the future. I want to make sure I have all necessary equipment.
I took note of the solder size I should use (rather than the larger one i used for this rebuild).
The soldering iron I have now (and used for this rebuild) is an American Beauty (?) Little something or other (?) can't remember the name, 65w iron with a huge (almost flat-tip screwdriver looking) tip. Without having to purchase a new one, the only other option I have is a Tenma 21-7930 adjustable station which I can obtain from work.
I have a plethora of passive components to work with.
I must admit, I have no experience with desoldering. Is this a necessary part of amp rebuilds? On this amp, I simply cut the bad components metal legs at the surface of the PCB and soldered the new component to them. I have the right desoldering braid, just not sure how to use it.
As car audio has become a significant hobby, I plan on attempting amp rebuilds in the future. I want to make sure I have all necessary equipment.
I took note of the solder size I should use (rather than the larger one i used for this rebuild).
The soldering iron I have now (and used for this rebuild) is an American Beauty (?) Little something or other (?) can't remember the name, 65w iron with a huge (almost flat-tip screwdriver looking) tip. Without having to purchase a new one, the only other option I have is a Tenma 21-7930 adjustable station which I can obtain from work.
I have a plethora of passive components to work with.
I must admit, I have no experience with desoldering. Is this a necessary part of amp rebuilds? On this amp, I simply cut the bad components metal legs at the surface of the PCB and soldered the new component to them. I have the right desoldering braid, just not sure how to use it.
Yes, diameter and height.
The Tenma iron will work better than what you have. If you have to buy a new one, I'd recommend the Weller WES51.
Desoldering braid is OK for cleanup and SMD work but it's relatively expensive. I'd suggest that you buy an Edsyn DS017 (under the name Hirschmann at MCM). The desoldering pump is much more efficient when desoldering large numbers of parts.
When desoldering components like transistors, apply new solder to each leg, lay the iron across all 3 legs. When the solder melts, the transistor will fall out. Then desolder the pads with the desoldering pump. For resistors, pull gently on one leg while heating the solder. It will pull free when the solder melts.
To desolder with braid, you lay the braid on top of the solder and apply pressure to it with the iron. When the solder melts, it will be wicked into the braid.
The Tenma iron will work better than what you have. If you have to buy a new one, I'd recommend the Weller WES51.
Desoldering braid is OK for cleanup and SMD work but it's relatively expensive. I'd suggest that you buy an Edsyn DS017 (under the name Hirschmann at MCM). The desoldering pump is much more efficient when desoldering large numbers of parts.
When desoldering components like transistors, apply new solder to each leg, lay the iron across all 3 legs. When the solder melts, the transistor will fall out. Then desolder the pads with the desoldering pump. For resistors, pull gently on one leg while heating the solder. It will pull free when the solder melts.
To desolder with braid, you lay the braid on top of the solder and apply pressure to it with the iron. When the solder melts, it will be wicked into the braid.
Thanks a bunch for that advice. Is there any certain size or shape tip I'm looking for for this type of electronics repair if I used the Tenma station?
You mentioned the desoldering braid as being expensive. Price is not a concern for this. Could you explain further on the desoldering pump? I've never seen or used such a thing. How does it work?
I hope to have the cap dimensions for you in the AM. Again, I appreciate all the help.
You mentioned the desoldering braid as being expensive. Price is not a concern for this. Could you explain further on the desoldering pump? I've never seen or used such a thing. How does it work?
I hope to have the cap dimensions for you in the AM. Again, I appreciate all the help.
I don't know what's available for the Tenma. These are the dimensions of the tip I generally use:
0.02" T x 0.093" W x 0.625" L
The desoldering pump is a spring loaded plunger. When you press the release, the plunger is pulled up by the spring and the vacuum it creates pulls up the molten solder with it. Don't by a cheap or small desoldering pump. Only buy the DS017 or the static dissipative version of it.
If you do a lot of work, desoldering braid gets expensive. The desoldering pump uses nice cheap air to do the job.
0.02" T x 0.093" W x 0.625" L
The desoldering pump is a spring loaded plunger. When you press the release, the plunger is pulled up by the spring and the vacuum it creates pulls up the molten solder with it. Don't by a cheap or small desoldering pump. Only buy the DS017 or the static dissipative version of it.
If you do a lot of work, desoldering braid gets expensive. The desoldering pump uses nice cheap air to do the job.
Perry- Could you explain the expected temperature of an amp to get? Should it be too hot to touch, or should I be able to rest my hand on it? When I play for 20+ minutes at high volumes the amp gets (what I consider) dangerously hot to where I cannot hold it for more than a second or two.
The amp does have a protection circuit, using a thermistor underneath the board sandwiched to the heatsink. The only problem I see with this design is that it is on the power supply side of the board, which does not get as hot as the audio output side. This was typical even when the original audio components (output transistors) were installed.
I measured voltage at the emitter resistors when the amp reaches this temperature and none read > 0.001V.
I'm still debating using thermal epoxy to mount CPU heatsinks to the base of the amp. I'm just leery of the replacement output transistors going bad due to excess heat, which I assume killed the originals. This amp seems to have a faulty protection circuit because I've never seen it once go into thermal protection.
Other than it pounds away with a single sign of any problems.
The amp does have a protection circuit, using a thermistor underneath the board sandwiched to the heatsink. The only problem I see with this design is that it is on the power supply side of the board, which does not get as hot as the audio output side. This was typical even when the original audio components (output transistors) were installed.
I measured voltage at the emitter resistors when the amp reaches this temperature and none read > 0.001V.
I'm still debating using thermal epoxy to mount CPU heatsinks to the base of the amp. I'm just leery of the replacement output transistors going bad due to excess heat, which I assume killed the originals. This amp seems to have a faulty protection circuit because I've never seen it once go into thermal protection.
Other than it pounds away with a single sign of any problems.
It's normal for the amplifier to get hot. If the voltage across the emitter resistors remains low, I believe it's simply getting hot due to normal power dissipation.
Most amps shut off at 180-200°F. That's far too hot to hold your hand on.
Did you try lifting it up off of the mounting surface and using a second fan to force air under the heatsink?
You could extend the wires on the thermistor and move it to the sink next to the output transistors.
Most amps shut off at 180-200°F. That's far too hot to hold your hand on.
Did you try lifting it up off of the mounting surface and using a second fan to force air under the heatsink?
You could extend the wires on the thermistor and move it to the sink next to the output transistors.
Amp is working great. I installed the correct cap in the meantime. I've been using it non-stop on a 60 minute drive to and from work and it really shines. I'm more than content with the output, and even though the amp does get hot after 30+ minutes, it has never entered protection.
Now I have a new problem in that the subwoofer has split one of the enclosure joints.. But that's a topic for another thread..
Again, many thanks Perry and others for the generous help provided!
Now I have a new problem in that the subwoofer has split one of the enclosure joints.. But that's a topic for another thread..
Again, many thanks Perry and others for the generous help provided!
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