3 Cheers for FREEDOM!!!   Congratulations, can't wait to see what you will craft.



Yes, the FETs most certainly have gone off to better pastures. Anything else to check for or just replace them?
Already ordered based on the parts list, the 4410, now I see the ones on the board were 3710.  Big difference between 4410 and 3710?

Those are the crap pads in place right now .

These ceramic pads are nearly here, been waiting 4 weeks, www.ebay.co.uk/itm/371144914592?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT .
Get your farnell pads instead?

Will get me rectangular Alu supports, do it right.

Also I have rearranged the PSU which has with this simple mod will force the PSU board to close down in constant current mode. Less chance of smouldering FET,s

Change R10 to 1K and R11 to 10K, Change R13 to 1K and R10 to 10K as in this circuit.

Update on the repairs, new FETs arrived.

Fumbling in the dark with this, please do chime in with any thoughts.

Still keeps popping the right side fuse, measured D5-8, the next thing after fuses, AC to DC rectification I would assume, not on chart but what else could it be.

The left set does not conduct(Mohms in both directions) and the right side ones do.
Unclear on exactly why a half working rectifier would roast fuses, still, these diodes died when the short drew a large current that's for sure.

Is half wave rectification enough to bust a fuse? Maybe when I replace the diodes I get both fuses burning out, wouldn't that be something

Going to order a few 6A20G swap all 4 out and cross my fingers nothing else is fried, the 4-5 day wait for parts is tremendously frustrating, but this will get fixed dammit.

If the diodes have gone short, that would blow fuses. Is your AC in from the transformer the voltage you expect to see?

To late spare diodes plus on there way by pigeon post.

Go Tommi go, I like the results you have with the heat sinks clever man, I thought of using Peltier Pads to remove the heat from the FETs but then the heat sink would get much hotter.

For those who fancy some light reading and suffer from insomnia like me :-  

en.wikipedia.org/wiki/Thermoelectric_effect



en.wikipedia.org/wiki/Thermoelectric_cooling


www.britannica.com/science/Peltier-effect


Fantastic stuff.

Now you tempt me with another 7W, I wants it so bad, how am I going to resist. I barely have 1 working channel as it is.



Will it work well with the PSU board later?



I dont have insomnia but I get obsessively interested and keep going until I drop, effectively the same.

Cooling things is almost a hobby in itself for me, I can ramble on forever, apologies for the wall of text.
I would love to toss around ideas on cooling, who knows, I might come up with something useful.

What is really great about peltiers is the pinpoint precision you get if you throw enough power at the problem.

I remember looking at a peltier controller circuit. The thing is, every time you stop feeding power the heat seeps back, so you need to always have a current going through the peltier. A PID that controls Voltage somehow or PWM with a positive DC offset would probably be best.
If you ever want a FET at a precise temperature for some form of testing, peltiers are perfect for that.

Heatpipes on the other hand are amazing at moving heat away from a concentrated source, I think that's a big part of the temps I am getting with relatively little heatsink mass.
Heatpipes contain water/ethanol/acetone under vacuum that boils at a specific temperature, the vapour spreads the heat along the pipe near instantly, usually they are set for 35-50C depending on what type of heatpipe you select. There are specialized ones too for odd applications like satellites with helium or some other gas in them to operate well in the void of space. 
Anyhows, there are reasonably priced 10 and 20cm ones on ebay and you can easily buy or drill a plate to fit them directly on the FETs, as long as you have good cooling on the other end they will be magical. 
www.ebay.co.uk/itm/6mm-Heatpipe-for-DIY-Fanless-PC-Passive-CPU-Cooling-System-220mm-/171806190750?hash=item2800726c9e:g:lJwAAOSwZd1VZvH9

Here is a pad to attach the heatpipes. www.ebay.co.uk/itm/DIY-Aluminum-Thermal-Mounting-Radiator-Pad-for-3-x-6mm-Heat-Pipes-/171816661141?hash=item2801123095:g:JnQAAOSw~OdVccha

If you wanted to cool a FET quickly and spread the heat onto a heatsink then heatpipes are a good solution, there are even flat ones, you just cant drill into them or they wont work. 
www.ebay.co.uk/itm/HEAT-PIPE-ULTRA-FLAT-1TX100L-MM-Part-AMEC-THERMASOL-MHP-1220A-100A-/271932773766?hash=item3f5074d586:g:NEcAAOxyBjBTPxmi

A side note , TEGs, more heat resistant peltiers used to generate electricity instead , I really want to build one for our cabin in the woods, generate electricity with the thermal differential AND heat the cabin. www.ebay.co.uk/itm/TEG-Power-Thermoelectric-Generator-Wood-Stove-/221382596452?var=&hash=item338b6e5764:m:mE-Ah0y1F7FpiEcpHB3r1MA

I better not tell you about peltier's then, space parts are above my pay grade so to speak ;-)

They are a very useful invention.


This is shaping up to be the amp of a lifetime, there is no way I am ever parting with this one.

It sounds great AND it scratches that tweaking and upgrading itch nicely.
This is exactly what I would do to a PC, tweak it to the enth degree , see what it can do.

Just bumped up the bias to 295mV, took proper temp measurements with room at 20C, heatsink 29C, package 51.2C, No worries with heat at all.


As for being able to tell, so far this amp is destroying all the mass market systems I have ever heard. I must say that might not mean much, I have not spent a day with any premium equipment +2K, best I have at hand is a Marantz PM6005 and tannoy mercury speakers. Right now with 1 20y old JPW 510 it sounds amazing.
So exciting to hear what happens with the mod and PSU board.

Wouldn't that be something , trek to the HiFi store with my mystical wooden box, show them what's what hahaha.


I might need to ask you  for guidance on the mod, I dont feel too sure about peeling off bits of PCB.

James,s Seca is spectacular, I have read that thread so many times, when he gets the tri-amp setup going I will aspire to copy him as best I can.

Whenever I can I will make the trek, it's about 1000km south of here.

Haha, he has some Tannoy Canteburys, I will never own a pair but would be nice to have a listen.