I've been working on a bass 8k (power supply seems identical to MD8000.1 so I've been browsing repair posts for those as well). I've replaced IC9, IC3, and IC1 and any accompanying SMDs that needed replaced. I replaced both power supply, output fets, and gate resistors. With the rectifiers pulled to isolate the power supply I can't get it to build a square wave on powerup. IC1 builds a perfect 40khz square wave, IC3 not so much, it tries to build a very odd signal initially and then goes flat once the amp goes through it's power up cycle. While testing R150 went up in smoke. I'm running out of ideas and looking for some guidance. I will be buying Perrys book as soon as I have the funds as well
Any help is greatly appreciated, I have a lot to learn and am very appreciative of any guidance and tips. Thank you!
Any help is greatly appreciated, I have a lot to learn and am very appreciative of any guidance and tips. Thank you!
Do you have a clean square wave into both inputs of IC3?
To eliminate any confusion, the 'book' is not a paper type book. It's viewed with a web browser.
To eliminate any confusion, the 'book' is not a paper type book. It's viewed with a web browser.
Only on both inputs of IC1, but not IC3 (IC1 also has nice clean 40khz output as well)
And understood, I should have phrased it differently
And understood, I should have phrased it differently
Remove IC3. Confirm that you read 5.6k ohms between pin 3 of IC3 to pins 5 and 7 of IC3.
If you do, power up. Do you have drive to pads 2 and 4 of the IC3 location?
If you do, power up. Do you have drive to pads 2 and 4 of the IC3 location?
Yes 5.6k ohms between pin to pin 5 and 7
With the amp powered up there is no drive to pad 2 or 4. Pin 6 does show DC voltage
With the amp powered up there is no drive to pad 2 or 4. Pin 6 does show DC voltage
It's con3. I don't think it will make a difference but desolder it. It will be two individual pads. Confirm that there is no bridge between them. Does that get you drive from the MCU to IC3.
There are people here who work on these amps on a daily basis and could offer suggestions. Hopefully someone will step up and do so. I think the MCU may be damaged but don't replace it (or even order one) on that statement.
I'm going to ask someone who works on these if they know if the failure of the driver could damage the MCU. The lack of series resistors seems strange in this design.
I'm going to ask someone who works on these if they know if the failure of the driver could damage the MCU. The lack of series resistors seems strange in this design.
From the replies, it appears that the failure of the driver IC can cause the MCU to fail. Email Taramps to get a price on the MCU and shipping. Don't order it yet, just get a price. Maybe someone here will volunteer to sell you one that they have located in the US.
If you can get to talk to a technician (I had no luck) ask them if they believe that the MCU has failed.
I found a few amp repair livestreams from a Taramps tech who's stated it's common for the MCU to fail when IC3 fails so that seems to be the issue
I guess for them (servicing their own amps) the destruction of the MCU is irrelevant. Not so much for those who have to pay for shipping from Brazil.
It seems like they'd protect the MCU. Two Zener diodes and two resistors would likely protect it.
It seems like they'd protect the MCU. Two Zener diodes and two resistors would likely protect it.
If/when you get a chance, measure the resistance of the failed driver from pins 2 and 4 to pins 5, 6 and 7. No hurry. It's not even critical that you do this. It's simply to satisfy a curiosity of mine.
Pin 2 to 5: Open
Pin 2 to 6: Open
Pin 2 to 7: Open
Pin 4 to 5: Open
Pin 4 to 6: Open
Pin 4 to 7: Open
(Edited to correct measurements)
Pin 2 to 6: Open
Pin 2 to 7: Open
Pin 4 to 5: Open
Pin 4 to 6: Open
Pin 4 to 7: Open
(Edited to correct measurements)
Last edited: