amp repair?

[Grinder1989 5,000+ posts]

Not everyone wants their repair as cheap as possible. Some want a fantastic repair. Sounds like he really likes his amp. Any shop that only replaces 8 or 9 mosfets in a Memphis 4K is a hack-shop and you'll be lucky if the amp lasts 6 months.

You can't replaced 9 or 8 fets in a 4kw. If one section of the powersupply goes, it takes out 14 fets and possibly the drive transistors (which should always be replaced). As long as the parts are the same, (in a 4kw, 28 064N's are usually replacements for the factory parts) then you can replace that section of the powersupply and the amp will last as long as it's not abused. You should always replace all the fets when a powersupply goes, I'm just stating that you don't *have* to. I have yet to find a good argument that says you have to replace fets in a matching set. Parts are parts.

They all function the same (as long as they are identical part numbers) and I doubt a different batch is going to yield enough of a difference to negatively affect the amp. You have to keep in mind that parts are already made to match up as close as possible. When a powersupply is rebuilt, you should replace all the fets, bad or not. That's what I do, and that's what you do, and every other amp repair shop that has a good guy running it does. I just don't buy that matching part set thing. It's not that it's a bad idea, I just think it's not a necessity. Now if it's a Stetsom, that's a different story lol.

 

[dB-r 10+ year member]

The power supply parts are not near as critical. The output parts in the higher voltage amps (most big Korean Class D's) I have found should match the date codes on all, it will make the amp last longer and run better, less idle current, less likely to Poof on you... Only thing that I see other repair shops doing that I REALLY can't stand is when they mix like ST or Fairchild parts in the same banks with IR mosfets... what a mess that is... LOL....

 

[Grinder1989 5,000+ posts]

The power supply parts are not near as critical. The output parts in the higher voltage amps (most big Korean Class D's) I have found should match the date codes on all, it will make the amp last longer and run better, less idle current, less likely to Poof on you... Only thing that I see other repair shops doing that I REALLY can't stand is when they mix like ST or Fairchild parts in the same banks with IR mosfets... what a mess that is... LOL....

I've not seen a problem with different date codes in the channel. I'm not saying you're wrong, just my observation. I agreed with mix matched parts though. I try to run all IRF. Best parts I know of. I hate fairchild parts. The only amps they're use full in is amps that have adjustable dead time. Otherwise, I run all new IRF.