Digital Designs M5A

[caraudioguy2100]

Amp came in with 4 power supply fets blown .

Nothing else is wrong with the amp .

Since this amp has 6 banks of fets can I replace just the one bank of fets that blew ?

 

[Perry Babin]

The FETs were pushed to their limits, enough to have some fail. The surviving ones were pushed as hard as the ones that failed. Is it worth the risk of having injured FETs for the cost of a few extras?

 

[caraudioguy2100]

I’ll replace them all .
Next Question I have is the power supply filter caps are made by capxon and the rail caps are samyoung .

I’ve heard these caps are junk . Wondering since I have the amp apart should I replace the caps since I already have brand new Nichicons ?

I know people replace caps for no reason but wondering if it’s wise to replace them with a better quality cap or just leave them

 

[Perry Babin]

If you're unsure what to do, pull several of the originals and check them for value and ESR. If they're within spec. Tell the owner and let him decide whether the added cost is worth it to him.

I'd also suggest testing the ones you have to use as replacements to see if they measure better than the ones you pull to check.

 

[caraudioguy2100]

So I should replace all 24 power supply fets correct ? The original drivers are C3228,A1275

Are the BD139,140 still the best replacements for the drivers ? Or is there something better ?

In the image im does it appear the drivers are defective or possibly a diode since the drive isn’t being pulled back to ground ?

scope set to 5us 5volts/div

 

[Perry Babin]

Better? It would depend on what a person would use as the most important properties of the driver. The BD transistors are proven good PS drivers.

Yes. At the very least, the PNP driver appears to be open/defective.

 

[caraudioguy2100]

After replacing the drivers here is what I get now . Does the drive appear to be ok ?

Scope set to 5us 5volts/div

 

[Perry Babin]

That looks OK.