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mike49504 19th December 2009 06:27 AM

rockford fosgate power 650 mosfet
Im working on this amp alot of things are wrong with it.

my question is wondering if this amp needs sill pad under the fets?
They are using 540's and 9540's in the outputs but i recieved the amp with no sil-pad just tons of heatsink grease

Perry Babin 19th December 2009 06:49 AM

The heatsinks are hard anodized and if the coating is in good condition, it doesn't require any additional insulators.

Double-check the solder connections for all of the heatsink mounted semiconductors (especially the rectifiers). They tend to break but appear to be OK unless you look carefully or move the semiconductor body.

The transistor against the side of the heatsink is for the fan. Make sure it's tight against the heatsink and there is sufficient compound between the transistor and the sink.

mike49504 19th December 2009 06:56 AM

Ok thanks Perry,

Next question is he said when it did work the left channel had low output op amp maybe?

Perry Babin 19th December 2009 07:04 AM

Dirty switch, gain set lower than the other channels, bad input signal line connection...

It's rare that an op-amp is defective causing low gain. Generally, they'll have too much DC offset or the signal is clipped.

If you try to remove any op-amp, cut the legs free from the body of the op-amp, heat the legs from the top (not touching the board with the iron) and remove the legs. Desolder the pads from the side of the board that has the most copper. Never touch the pads with the iron. Apply enough new solder to allow you to heat the solder connection without touching the pads. These old boards are very sensitive to heat.

Email me if you want the schematic diagram.

mike49504 19th December 2009 08:03 AM

Ok another question when the amp was brought to me it has no fuse's in it wondering where i can get the fuse's and wondering if you might have a part number??

Perry Babin 19th December 2009 08:19 AM

AGA 7 1/2 was the original. Many people changed them to larger fuses because they blew the originals. If the amp isn't abused, the 7 1/2 amp fuses will provide the best protection.


You can find better deals but you can buy these if cost isn't a major concern.

Perry Babin 20th December 2009 05:08 AM

A friend purchased the AGA7.5 fuses from the following company. They were a fraction of the price at Mouser. They are not available from the online catalog but if you go to page 2 of the 'Product Catalog', you'll see them. Email them or call them to order.

Terminal Resolutions has Wire Terminals, Automotive Wire, Battery Terminals & Electrical Supplies
Product Catalog

mike49504 20th December 2009 02:49 PM

Thanks Perry,

i found the fuse's also at a hardware store where i live bought a box of 20 for $10.00.

My next question is that this amp blows the a06's and a56's when you hook a speaker up to the amp.

wondering what do i check?

Im gonna replace all the outputs in this amp also since when i got the amp i noticed all of the are out of different amps like 3 have one date code then 3 more have another date code and some are new

Perry Babin 20th December 2009 07:03 PM

Which A06s/56s is it blowing?

Does it blow them if you power it up with no speakers?

Any time you have to replace blown outputs in these amps, you should also replace the driver transistors. Even if the outputs are not blown, I'd suggest that you replace the drivers since you're replacing all of the outputs.

mike49504 20th December 2009 07:58 PM

It only blows them with the speakers hooked up its blowing on the left channel. its the a06 that blowing and it connects to the irf540

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