Bad caps and fets in Hifonics mono amp

[KriszXJR]

Hi
I have a class D mono amp.
It was protected (red led light) and some seconds red light too off.
Four IRFP264N fet and four 680uF/120V cap is bad in amp section.
I can order IRFP4229 fets and 470uF/200V caps (in correct dimensions 18x35mm).
My question is, this components are good for my amp?
Replace only the the bad caps or all?
I was removed bad components, and now the amp no protect and the relay clicking.
But on speaker output -84V. (and all fets legs)
Thanks!
Happy New Year!

 

[timwebb]

i never seen a hifonics use 264n for outputs. im sure the driver for that side is shorted as well

 

[nigelwright7557]

You need to check the amplifier section mosfets too.
Just changing power supply mosfets could end up blowing them again straight away.

In my experience if the amplifier mosfets have gone then it often takes the class d chip with it. I always change class d chip and mosfets.

 

[KriszXJR]

Is this a DWM3640 board?
Pin 5 and 18 text is +12V but have -72V.
If HR-0, SP-R, HL-0, SP-L pins volage -83, the two IRS21844S is bad?
Without driver board the HR-0 -4V, HL-0 0V, SP-R 0V, SP-L -4V.
Perry please help me!
Thanks!

 

[Perry Babin]

The driver IC virtually always fails when the FETs it's driving (directly - no driver transistors) fail. You can check it as shown below. None of the probe/pin combinations should be below 1000 ohms (most should read in the mega-ohms range). This isn't definitive because some can read high but be defective but most defective ICs read low resistance for at least one of the combinations shown.

That's not the same as the boards marked 3640 but the circuit is likely to be the same.

 

[KriszXJR]

U2:
11-13 1,3k
11-12 1,6k
12-13 0,3k
5-7 6,2k
6-7 3,3M
5-6 3,3M
U1:
11-13 1.3M
11-12 6,2M
12-13 3,1M
5-7 6,2k
6-7 3,3M
5-6 3,3M

 

[Perry Babin]

U2 appears to be defective. It could be causing the low 5-7 reading on U1. Remove U2 and re-check.

 

[KriszXJR]

Ok, thanks!
But I will order the fets and caps.
Can you answer for my first question?

 

[Perry Babin]

If you're referring to the substitute parts, I'd suggest using the exact replacement value capacitors and part number FETs.

 

[KriszXJR]

How much value C4 cap on driver panel? (Near U1)
I resoldered the driver panel, and i noticed broken cap.

 

[KriszXJR]

Perry You know how much value C4 ?

 

[Perry Babin]

No but I'll measure one on a similar board when I get back to the shop.

 

[Perry Babin]

C4 is a 1nF (1000pF) cap on the driver board I have here. I don't know the voltage rating. 50v should be enough.

 

[KriszXJR]

I replaced U1-U2 (IRS21844s) and U5 (lm293), U3 (tl072c), U4 (lm311), D1 and D2s and C4 cap on driver board.
And four bad output fets. (irfp4229)
After power on (with 15A fuse) broken again.
U2 irs:
11-13 5k
11-12 5k
12-13 120ohm
5-7 6k
5-6 6k
6-7 40ohm
U1 irs:
11-13 3,4M
11-12 6M
12-13 3,5M
5-7 6k
5-6 3,3M
6-7 3,3M
(This amp similar with Autotek MM2000.1, MB Quart DSC2000.1 and ? Emphaser EA1800D)
-4V on speaker output (without driver board).

 

[KriszXJR]

Without driver board...
Why is defective the IRS21844s?

 

[Perry Babin]

I can't read the circuit board designations. For the op-amp nearest the 15v regs with the two diodes just above pins 7 and 8, which pins on that op-amp connect directly to the diodes?

 

[KriszXJR]

NE5532 pin7 connect to diode K
Common anodes, and another diode catode at rca shield.
5,1V zeners, if i good see...

 

[Perry Babin]

If you solder a bridge between pins 6 and 7, does the 4v DC go away?

 

[KriszXJR]

No

 

[Perry Babin]

What's the DC voltage on pin 7 of that op-amp?

What's the DC voltage on the au-in pad for the driver board?