This is the 2nd Ample Audio A 1100 DX car amp
I've gotten in for service this month with a "ghostly" protect
problem.

Get this; Amp instantly goes into protection upon power up.
Okay, that's not unusual but, NO shorted mosfets in power
supply or Audio section.( I even pulled the rectifiers out of
circuit to isolate the PS)

No pri/sec shorts in Xformer. No leaky or shorted "totum pole" trans.
Swapped out the TL494 pulse wave chip. (checked all transistors in PS)

The PS does try to gernerate square waves, I can see them appear briefly
at the gates of the PS mosfets and at the secondary of Xformer.

Admittedly, I am NOT a car amp Guru, but I have repaired enough of them
to know my way around in there and I'm scratching my head.

Hopfully, someone out there has seen this or has more ideas.

TIA, humbley,
RIck

(TA7205) writes:

This is the 2nd Ample Audio A 1100 DX car amp
I've gotten in for service this month with a "ghostly" protect
problem.

Get this; Amp instantly goes into protection upon power up.
Okay, that's not unusual but, NO shorted mosfets in power
supply or Audio section.( I even pulled the rectifiers out of
circuit to isolate the PS)

No pri/sec shorts in Xformer. No leaky or shorted "totum pole" trans.
Swapped out the TL494 pulse wave chip. (checked all transistors in PS)

The PS does try to gernerate square waves, I can see them appear briefly
at the gates of the PS mosfets and at the secondary of Xformer.

Admittedly, I am NOT a car amp Guru, but I have repaired enough of them
to know my way around in there and I'm scratching my head.

Hopfully, someone out there has seen this or has more ideas.

TIA, humbley,
RIck

The square wave phenomenom implies that the amp is going into oscillations.
Is there a feedback loop problem? What was the frequency of the square
wave?

--RY

--
Randy Yates
Sony Ericsson Mobile Communications
Research Triangle Park, NC, USA
, 919-472-1124

Randy Yates writes:

The square wave phenomenom implies that the amp is going into oscillations.
Is there a feedback loop problem? What was the frequency of the square
wave?

I retract this - I realized after I sent it that you stated the *PS* (power
supply) generates these. I presume it's a switcher and this is an indication
that it is functioning normally?
--
Randy Yates
Sony Ericsson Mobile Communications
Research Triangle Park, NC, USA
, 919-472-1124

"TA7205" wrote in message

This is the 2nd Ample Audio A 1100 DX car amp
I've gotten in for service this month with a "ghostly" protect
problem.

Get this; Amp instantly goes into protection upon power up.
Okay, that's not unusual but, NO shorted mosfets in power
supply or Audio section.( I even pulled the rectifiers out of
circuit to isolate the PS)

No pri/sec shorts in Xformer. No leaky or shorted "totum pole" trans.
Swapped out the TL494 pulse wave chip. (checked all transistors in PS)

The PS does try to gernerate square waves, I can see them appear
briefly at the gates of the PS mosfets and at the secondary of
Xformer.

Admittedly, I am NOT a car amp Guru, but I have repaired enough of
them to know my way around in there and I'm scratching my head.

Hopfully, someone out there has seen this or has more ideas.

Disconnected the inputs and outputs to see what happens to the bare amp?

"Randy Yates" wrote in message

Randy Yates writes:

The square wave phenomenom implies that the amp is going into
oscillations. Is there a feedback loop problem? What was the
frequency of the square wave?

I retract this - I realized after I sent it that you stated the *PS*
(power supply) generates these. I presume it's a switcher and this is
an indication that it is functioning normally?

For future reference - just about every after-market power amp costing more
than about $30-50 has a switchmode power supply.