Hi again,
Sorry for stupid questions, but it's first time I open a MTX amp.
Problem: one of the power supply fets is blow (P60NE06-16). I changed all four fets with STP60NF06L.
1st question) Is it right ? The amplifier works, but idle current is about 3 Amps ... I think it's too high, but I don't have any specification.
Over the power supply, there are 3 resistance (2 of 1,5 Kohm and 1 of 1 Kohm) very hot because the voltage on them are about 30 V (more or less)
2nd question) I changed them with 7 W components ... Is it enough or there is another damage (around the 1 Kohm resistance there are some transistor and they are a little bit hot too ...) ?
Thanks
Giovanni
Sorry for stupid questions, but it's first time I open a MTX amp.
Problem: one of the power supply fets is blow (P60NE06-16). I changed all four fets with STP60NF06L.
1st question) Is it right ? The amplifier works, but idle current is about 3 Amps ... I think it's too high, but I don't have any specification.
Over the power supply, there are 3 resistance (2 of 1,5 Kohm and 1 of 1 Kohm) very hot because the voltage on them are about 30 V (more or less)
2nd question) I changed them with 7 W components ... Is it enough or there is another damage (around the 1 Kohm resistance there are some transistor and they are a little bit hot too ...) ?
Thanks
Giovanni
The STP60NF06L is a logic level FET. That could be part of the problem. It's also possible that this is one of the older amps that had power supply FETs that ran hot no matter what transistor was used. Post a photo of the board.
Hi Perry,
photos of the MTX board are attached
As I said, the amp works properly (I tested it with two speaker, front / rear separately and in bridge mode also), but with idle current around 3 A (3,3 A exactly) and three resistances (they are green in the second picture because I changed them with 7W components ... original was 2 or 3 W maximum) extremely HOT.
Thanks for your suggestions
Giovanni
photos of the MTX board are attached
As I said, the amp works properly (I tested it with two speaker, front / rear separately and in bridge mode also), but with idle current around 3 A (3,3 A exactly) and three resistances (they are green in the second picture because I changed them with 7W components ... original was 2 or 3 W maximum) extremely HOT.
Thanks for your suggestions
Giovanni
Attachments
It appears that the resistors you replaced are in the regulator circuit. If so, this amp like the 2300, has problems with those resistors running very hot. They don't generally fail but they can cause heat stress damage to the board.
This is similar to the amps that had power supply FETs that ran very hot at idle. With a standard drive circuit, I'd be more concerned about the logic level FETs. They should not be a problem here but since I've never tried those in an amp like, I can't say definitively if standard FETs would work better.
Since there are only 4 FETs and FETs like the IRF3205 are readily available, I'd suggest replacing them. If nothing else, you'll know for certain if they are the problem.
This is similar to the amps that had power supply FETs that ran very hot at idle. With a standard drive circuit, I'd be more concerned about the logic level FETs. They should not be a problem here but since I've never tried those in an amp like, I can't say definitively if standard FETs would work better.
Since there are only 4 FETs and FETs like the IRF3205 are readily available, I'd suggest replacing them. If nothing else, you'll know for certain if they are the problem.
A report of some test I made during the week end, when supplier are closed (and the weather is rainy).
I changed power supply FETs with 4 x P60NE06-16 (not new but working, taken from another amp "sleeping" in my garage) ... nothing different. Idle current remains 3,3 A, resistances are hot as always.
I disconnect all secondary circuits (removing from the circuit all "double-diodes"): idle current has become 2,2 A. In my opinion it is a little bit higher, but I don't know where a problem can be.
Thanks for your help
Giovanni
I changed power supply FETs with 4 x P60NE06-16 (not new but working, taken from another amp "sleeping" in my garage) ... nothing different. Idle current remains 3,3 A, resistances are hot as always.
I disconnect all secondary circuits (removing from the circuit all "double-diodes"): idle current has become 2,2 A. In my opinion it is a little bit higher, but I don't know where a problem can be.
Thanks for your help
Giovanni
There may not be a problem that can be resolved.
The resistors will get hot if they are a part of the regulator circuit.
The resistors will get hot if they are a part of the regulator circuit.
- Status
- Not open for further replies.