Kenwood KAC-X201T will not turn on

[spooney]

picked this amp up cheap from somebody online knowing it didn't work.I don't see any fried components and the fets and output transistors all appear ok.This amp will not turn on at all.this is the first time i've ever tried to troubleshoot an amp with a problem of this nature.I was hoping maybe Perry or someone else could maybe point me in some directions.

[Perry Babin]

If the amp won't power up, confirm that you have power to the FETs and the third leg of the FETs is grounded.

If those are OK, post the power supply IC number and the voltages on the pins.

[spooney]

The FETS all appear to be ok but I'm getting no voltage on any of the pins of the c494 IC.

[Perry Babin]

What's the DC voltage on the 3 pins of Q101?

What's the DC voltage on the base of Q403?

Check these with power applied to the amp (including remote). Use the ground terminal as the reference (black meter lead connection).

[spooney]

on pin 1 of Q101 i've got 12.7 volts , pin 2 has .4 volts but slowly drops , and pin 3 has 12.7 volts as well. As for Q 403 I'm unable to find it so far.Could it possibly be Q405?

[spooney]

quick question for you Perry.This amplifier internally consist of three seperate boards.Theres the main board,the preamp board,and a small board near the fan.Do I need to have the fan board plugged in to get proper measurements from the amp or can I leave it unplugged as it makes it difficult to work on with all three boards plugged together

[Perry Babin]

Doesn't the fan board have the gain controls?

If so, the gain may be very low without it.

If you try it, make sure that you have a relatively small fuse or current limiter in line with the B+ source. Sometimes, when components are removed from a circuit, the circuit becomes unstable and oscillates (which could cause damage to the amp). I don't think it will happen here but you should be careful when you initially power it up.

[spooney]

was the voltage on Q101 what I should be expecting?And what about that Q403?I don't see it on the board.I see a Q405 though. I've yet to get this amp to actually power up.

[Perry Babin]

Sorry I missed one of the posts. I only read the last one.

The center leg should have ~12v on it but the transistor (Q101) is not being driven on by Q403 (small surface mount transistor near Q101). When properly driven 'on', the voltage on the third leg will be ~0.6v less than the voltage on the first leg and the voltage on the first and second legs will be nearly identical.

[spooney]

ok i think i see it now.I'll get some voltage measurements from it and check back.Thanks Perry