Salas hotrodded blue DCB1 build

Is there any issue with adding wiring so that the mosfets reach the heatsinks?

I've only seen designs that have their heatsinks bolted directly to the mosfets that are soldered to the PCB. My enclosure will be just wider than 90mm to accomodate the transformer.... Other designs have shown the mosfets bolted to the base plate of the enclosure -- are they hotrodding like that?
 
Is there any issue with adding wiring so that the mosfets reach the heatsinks?

I've only seen designs that have their heatsinks bolted directly to the mosfets that are soldered to the PCB. My enclosure will be just wider than 90mm to accomodate the transformer.... Other designs have shown the mosfets bolted to the base plate of the enclosure -- are they hotrodding like that?

Mine are wired with short lengths of magnet wire. No problems :)
 
Last edited:
diyAudio Chief Moderator
Joined 2002
Paid Member
That is oscillation potential territory. Extending is adding inductance, at least solder the gate resistor with very short pin to the gate -after- any attempted extension cable, and restore continuity with a jumper where the resistor was on PCB. Was not intended like that, nor scoped like that, grey zone.
 
Thanks!

The issue for mounting monster heatsinks and transformer in a box are mechanical --the 80 va transformer is over 90mm wide and bending the pins on the mosfet is not enough to make them reach the sink with a box that is 90mm wide internally.

So, instead of fins sticking out from the surface of the box, the box can be made larger by making the fins flush or in the same plane as the sides of the box. The footprint of the enclosure can be thought of as a barbell or dog-bone. The heatsinks may be bolted directly to the floor and become the middle front and back side of the enclosure.

One end now has enough room for the transformer.

--------------------------------------

If the pins of the mosfets can be bent to reach the heatsinks which are at the sides of the board and bolted to the top/bottom of the enclosure, then all problems are solved.

If the pins can't be bent, then a thick 10mm aluminum bar needs to be added as a heat spreader, though I worry about the thermal efficiency losses.
 
Last edited:
Member
Joined 2011
Paid Member
it's back and not kicking

No rest for me. I'm experiencing something I can't grasp control off. Low frequency attenuation is back three months later after the fix. It's a recurring problem, that was curred in different ways earlier. This time I'm more certain it's a DCB1 problem. A passive, two mono attenuators based pre shows more slam and bass and overall better balance in lows.

Checking connections, soldering, usual procedures since yesterday.
 
Member
Joined 2011
Paid Member
You wouldn't guess what has worked for me. Cleaning both sides of pcb. I live in ex industrial area and building. It's quite dusty here and the pre was still in an open case. The underside collected dust as it was sticky after cleaning with isopropyl alcohol from last time. Wiped good as I could and voila.
 
Picked up the transformer today! Potted 80 VA from Sumr in Toronto.

Now to order the heatsinks and the rest of the parts. Then, either make a box -- or stuff it into rectangular aluminum tube, a la Peter Daniel.

heatsinkusa looks like the best source.

80VA for a DCB1? A bit big. I believe that ~25VA is sufficient. Anyways, it can't hurt if you use the right fuse! :D

Do
 
thanks!

if I go for >800mA version would it be enough to cool IRFPs with these outer heatsinks? the box looks to be quite decent and well made, outer heatsinks seems to be an advantage as well.

It measures about 160mm inside, so would it be ok to extend the legs of mosfets to 50mm to fix them on the heatsinks?
 

Attachments

  • case.jpg
    case.jpg
    66.7 KB · Views: 343
Last edited:
Member
Joined 2006
Paid Member
I think that Chassis is okay. Just will need to mount Mosfets off at least one side of the board. Might be a little overkill, but so what?
I have plenty of the boards and kits left, I ordered much more than I needed since with lower numbers per normal GB cycle, I just stocked up to keep prices normal.