Hi guys
I am currently stumped on another Memphis MCD1000 with all outputs removed even the rectifiers removed for some reason when turned on I am getting a red to green light flickers alittle bit of noise in the transformer coils and 2 of the 8 power supply fets for some reason same locations on board they get very hot within seconds doesn't matter which fet I place there if removed others tend to heat up I even tried swapping the wires on the coil for each bank for fets with no luck they still getting extremely hot fast replaced the main power supply capacitors 3300uf 25v power supply gate resistors because I checked the voltage to each fet and the reading will give a 12.21v and fluctuate between 10v constantly if the driver board is removed it seems to hold voltage on each rail i replaced all bjt a1266 on the driver board with bd140 with no luck nothing appears to be shorted i even removed the audio riser boards with the same result flashing lights is there something i am missing here i am beginning to wonder if theres a short in the transformer coil but not sure how i would test that
I am currently stumped on another Memphis MCD1000 with all outputs removed even the rectifiers removed for some reason when turned on I am getting a red to green light flickers alittle bit of noise in the transformer coils and 2 of the 8 power supply fets for some reason same locations on board they get very hot within seconds doesn't matter which fet I place there if removed others tend to heat up I even tried swapping the wires on the coil for each bank for fets with no luck they still getting extremely hot fast replaced the main power supply capacitors 3300uf 25v power supply gate resistors because I checked the voltage to each fet and the reading will give a 12.21v and fluctuate between 10v constantly if the driver board is removed it seems to hold voltage on each rail i replaced all bjt a1266 on the driver board with bd140 with no luck nothing appears to be shorted i even removed the audio riser boards with the same result flashing lights is there something i am missing here i am beginning to wonder if theres a short in the transformer coil but not sure how i would test that
Did you verify new BD140's were all in working condition? Check connection of the power card to the board?
I'm know Perry would be much better at helping you track down this issue but maybe start checking voltage on all 16 pins of the TLX94. It's usually his first Method and it is VERY helpful!
I'm know Perry would be much better at helping you track down this issue but maybe start checking voltage on all 16 pins of the TLX94. It's usually his first Method and it is VERY helpful!
Please break up large paragraphs. If you can't decide on where to break the paragraphs, leave a blank line between sentences.
You need to take the time to be more specific. You checked the voltage in the FETs and read 12v. On which leg?
With the PS driver board out of the amp, does it draw excessive current?
Do any of the PS FETs get hot?
You need to take the time to be more specific. You checked the voltage in the FETs and read 12v. On which leg?
With the PS driver board out of the amp, does it draw excessive current?
Do any of the PS FETs get hot?
You checked the voltage in the FETs and read 12v. On which leg?
Drain (middle legs) of 3205 fets fluctuating (while driver card installed)
With the PS driver board out of the amp, does it draw excessive current?
No excessive current
Steady volts at 12.21
And PS fets get extremely hot when the PS driver board is installed without the PS driver board installed the PS fets are cold
Drain (middle legs) of 3205 fets fluctuating (while driver card installed)
With the PS driver board out of the amp, does it draw excessive current?
No excessive current
Steady volts at 12.21
And PS fets get extremely hot when the PS driver board is installed without the PS driver board installed the PS fets are cold
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Also PS driver board has been ruled out replaced the board with a known working PS driver board the power light will light up but there is a high pitched noise coming from the transformer coil
Each PS Fet 3205 heats up extremely if each PS fet in line is removed one by one and continued testing the next PS fet heats up really hot
The only thing i can come up with is there is a short in the transformer or the board beings one of the resistors has burned through the board
Each PS Fet 3205 heats up extremely if each PS fet in line is removed one by one and continued testing the next PS fet heats up really hot
The only thing i can come up with is there is a short in the transformer or the board beings one of the resistors has burned through the board
I ended up replacing the C3198 transistors near the fuses on the main board and that seemed to fix that problem the PS fets are no longer getting hot there is no flicker on the lights
But now when the riser board near the RCA jacks is connected there is noise from the transformer and the grn led light will flicker i am assuming something else is shorted out also the PS fets are not getting extremely hot there cold
When the Board near the RCA jacks is removed the grn led stays lit like normal the PS fets are cold
But now when the riser board near the RCA jacks is connected there is noise from the transformer and the grn led light will flicker i am assuming something else is shorted out also the PS fets are not getting extremely hot there cold
When the Board near the RCA jacks is removed the grn led stays lit like normal the PS fets are cold
I wouldn't know Perry all output fets are removed to test that and with the card near the rca jacks is placed in the amp the grn light is flickering causing noise to the transformer
So I figure if the amp green led is flickering and the transformer is making noise I didn't feel safe putting in output fets
But like I said when that card near the rca jacks is not connected the amp now will power up and all PS fets are cold and there is no noise coming from the transformer
I also tried another known working board near the rcas with the same result transformer noise and flickering has to be something on the main board I would guess in the preout section of the amp
I replaced pretty much everything in the transformer (Power Supply) side when it comes to transistors even tried a different A1023 near the fuse to be sure right next to the blown C3198 transistors unless its the rectifiers or the 7815 7915 transistors only thing I havnt touched
So I figure if the amp green led is flickering and the transformer is making noise I didn't feel safe putting in output fets
But like I said when that card near the rca jacks is not connected the amp now will power up and all PS fets are cold and there is no noise coming from the transformer
I also tried another known working board near the rcas with the same result transformer noise and flickering has to be something on the main board I would guess in the preout section of the amp
I replaced pretty much everything in the transformer (Power Supply) side when it comes to transistors even tried a different A1023 near the fuse to be sure right next to the blown C3198 transistors unless its the rectifiers or the 7815 7915 transistors only thing I havnt touched
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Install the outputs to see if the amp works.
As a side note, this is for the synchronization of the audio and PS oscillators. The amp will work with this transistor out. I've only had one amp in the shop with this problem and the owner was in a hurry to get it back so I never chased down the reason it caused the problem. Several other people have had the same problem and removing this transistor is what they did to get the amps working. As far as I know, no one has ever determined why it causes a problem.
As a side note, this is for the synchronization of the audio and PS oscillators. The amp will work with this transistor out. I've only had one amp in the shop with this problem and the owner was in a hurry to get it back so I never chased down the reason it caused the problem. Several other people have had the same problem and removing this transistor is what they did to get the amps working. As far as I know, no one has ever determined why it causes a problem.
Hey Perry do you think this could be a shorted ic on the preout side of the amp beings the TL072CP has 6 volts on pins 4 and 8 I checked a working mcd same style 1000 and it reads 15 volts so for some reason it seems that the TL072CP is not getting the full power from somewhere on the amp just not sure where
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