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Colin Wonfor's SECA amp build

Thanks Paul. Now the amp has been on for approx 60 mins the bias is pretty much steady at 150mv and the offset is fluctuating around 2mv. This is without the lid on.
The other channel I cocked up on winding the bias higher than I should have( so used to building Nelson Pass amps which are usually set to 0.47V) and R11 smoked and now reads open circuit. That'll teach me not have the instructions in front of me:eek: Will I have taken out the mosfets as well do you think? It was on for a few minutes only.
 
That's good to know. Shame I didn't order a few extra 0.1R's.

On a happier note the other channel is now playing music through the stunt speakers:D
 
That's good to know. Shame I didn't order a few extra 0.1R's.

On a happier note the other channel is now playing music through the stunt speakers:D

Great work Keith


Nearly at the listening stage.


2mV offset seems more like it.
 
Opps :)

Col reckons the FET's are indestructible.........


They should be I have blown a few, when I set the current to high whoops.
The DC offset you have is great, the first one I did was 12mV, It's OK I still have it.
And it is still ugly.

IMG_20150709_165551370_HDR_zpslyayirf7.jpg
 
I like that build Colin; reminds me of a Ty fighter.

It would seem that I may well have taken out the mosfets as I replaced the 0.1R resistor(thank you Paul) and when I turned on again the magic smoke appeared:eek:. Going to a family gathering today so won't get chance to check things out until tomorrow
 
Is there a way of testing the mosfet's in circuit?

Not easily, unless you disconnect some adjacent components.

For power mosfet, you can measure the resistance between source and drain, with gate connected to source via finger, or gate connected to drain via finger. You should see a massive change in resistance.

If it is always open, or always short, you have a problem.
 
I like that build Colin; reminds me of a Ty fighter.

It would seem that I may well have taken out the mosfets as I replaced the 0.1R resistor(thank you Paul) and when I turned on again the magic smoke appeared:eek:. Going to a family gathering today so won't get chance to check things out until tomorrow

Cheek "Thunderbird 5", The duff fet are normally short cct so yes on meter reading Ohms between Source and Drain S/C
 
This morning I replaced the mosfets and the 0.1R resistor(a big thank you to Paul who very kindlyresistors) and am happy to say that the amp biased up nicely :D Huge sigh of relief.

I haven't listened yet but the amp is warming up nicely with the bias set at 150mv and DC offset fluctuating up and down by a couple of mv but is pretty close to zero.

Will post some pics later after having had a listen.
 
Thanks Paul only listened through the stunt speakers so far. I will try better speakers tomorrow but not in the main system as it's heavy. Note to self; start building monoblocks they'll be easier to lug downstairs:)

A couple of pics:-



 
Damn good actually:cool:

I had a good listen to some vinyl this afternoon; so dynamic and full of detail.

My heatsinks would appear to be overkill as they aren't getting as warm as with the AlephJ
 


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