Earthquake PH2000

[mike49504]

I got another one of theese in for repair..

Theese amps use the SSP45N20A's for the outputs..

When i opened this amp up someone has IRFP260N's in it for the outputs..

Does anyone know if this is a factory mod or did someone put the totally wrong outputs in it ??

 

[Perry Babin]

The solder connections are often a good indication of what's been flow soldered and what's been hand soldered.

You may also be able to see the impression of the TO-220 transistors on the sil pads if they were originally in the amp.

 

[mike49504]

I cant tell since the sil pad was not orginal.. And also really couldnt tell if the solder was orginal ..

The guy sid he had someone fix it before..

So i will just put it back to the other outputs..


The orginal outputs are the SSP45N20A's So will the IRF3415's work in this ?

 

[Perry Babin]

I don't know if the 3415s would work. They may work if the rail voltage never exceeds ±75v. The IRFP260N is readily available.

 

[mike49504]

Ok i replaced the outputs in this amp i put them back to the SSP45N20A's

Also replaced all drivrs for the outputs...


Amp still has 70 volts on output terminals.. Thats measured directly across them..


Any ideas where to look next ?

 

[Perry Babin]

I don't have any information on this amp. I'd need a MUCH better photo to help.

Read the photo section of the basic repair page. The camera that I used there was a very old Nikon. I'm sure that the S3000 can do much better if you take the time to learn to use it.

 

[mike49504]

Heres some better pics of the board..

 

[Perry Babin]

If Q20 is an MPSA92, remove it. Does that eliminate the DC on the speaker terminals?

 

[mike49504]

Removed Q20 still have the 70 volts on speaker terminals

 

[Perry Babin]

If Q22 is connected to the bases of the drivers for the high-side FETs, pull it. Does that eliminate the DC?

 

[mike49504]

With Q20 and Q22 removed i still have the 70 volts on outputs

 

[Perry Babin]

What is the DC voltage across pins 1 and 3 of the high-side FETs?

If you have two meters, connect a meter across the speaker terminals while you're measuring the DC voltage across the legs of the FET to see if the DC voltage across the speaker terminals drops.

 

[mike49504]

High side fets have 0.91 volts measured dirstly across legs 1-3

 

[Perry Babin]

If you have less than 1v and you still have 70v on the speaker terminals, you either have shorted/leaky FETs or something else is shorted to the positive rail.

 

[mike49504]

With all of the outputs removed I get 81 volts on the output terminals still...


Would a shorted inductor cause this and still make the amp idle fine or do i need to look at other cause's?

 

[Perry Babin]

Unless the inductor is shorting to the board, it cannot cause there to be DC on the speaker terminals.

If you connect a dummy load resistor across the speaker terminals, does the amp draw excessive current or does the DC simply drop to 0v?

 

[mike49504]

If i connect a 1 ohm resistor across the speaker terminals the DC goes away and amp still idles fine..

 

[Perry Babin]

That would seem the indicate that something is leaking current and not shorted. Is there any leaked electrolyte on the board?

What is the rail voltage?

What is the driver voltage (emitter of Q20)?

 

[mike49504]

Ok something is not right with this amp now..

I have - 70 volts of rail but only 5.6 volts of positive rail and now i have 5.6 volts on the output terminals..

Im thinking the rectifer is bad..

 

[mike49504]

Ok now i have both + and - 71 volts of rail..

It doesnt appear that any caps are leaking..

So now i have to go thru this amp to find out whats leaking ..


For some reason i only have 9.8 volts on the outputs now