Can I just check, I have a new Transformer I want to use for convenience (has other useful voltages for my pre-amp remote volume and led volume resistors. It's 2x15VAC but on UK system runs to 18.3VAC.
With 18.3VAC hotrodded DCB1 running at 9.14 DC, how big should my MOSFET sinks be? Will normal small cast sinks do the job? Like these I have on at the moment:
AAVID THERMALLOY|ML524-30-B|HEAT SINK BIG CHIEF TO247/218 | Farnell United Kingdom
Many thanks
Lucas
With 18.3VAC hotrodded DCB1 running at 9.14 DC, how big should my MOSFET sinks be? Will normal small cast sinks do the job? Like these I have on at the moment:
AAVID THERMALLOY|ML524-30-B|HEAT SINK BIG CHIEF TO247/218 | Farnell United Kingdom
Many thanks
Lucas
Hi Salas,
Well, it's those standard Hotrod 5W 10R Dale resistors. Is that what you mean, or do you want me to take a measurement from somewhere?
I'm guessing it will be fairly hot with 18vAC transformer, right.
My last one worked great - it was 14vAC, but this new 18vAC one has some other useful secondaries for this amp, and is R-core so low EMI (It's a small box).
Thanks
Lucas
Well, it's those standard Hotrod 5W 10R Dale resistors. Is that what you mean, or do you want me to take a measurement from somewhere?
I'm guessing it will be fairly hot with 18vAC transformer, right.
My last one worked great - it was 14vAC, but this new 18vAC one has some other useful secondaries for this amp, and is R-core so low EMI (It's a small box).
Thanks
Lucas
At ~ 200mA it will create 3W per CCS MOSFET if it will reach 24VDC on the filter caps. Those sinks will go +19C over in box ambient.
Hmmm - they're 35v caps, so just about within spec.
Bottom line is "no, those sinks are in no way big enough." Right?
19C over ambient could mean 49C in mid-summer highs. That's not good for those mosfets is it?
Bottom line is "no, those sinks are in no way big enough." Right?
19C over ambient could mean 49C in mid-summer highs. That's not good for those mosfets is it?
They could hold in England not in Greece. But enclosed, I doubt you would have 30C ambient. It accumulates from radiated. If it hits 55C+ on sink in the end is unhealthy even if those MOSFETS are TO-247 proven dogs, which they are.
OK, so I'll put some vents on the lid above the fets and try not to worry about it too much. Worst case scenario is a burnt out chip, right. OK, maybe the house burning down is worse than that, but let's not go there...
Thanks once again Salas.
Thanks once again Salas.
Get a cheap IR laser spot thermometer gun from Ebay. Very useful for all stuff hot or cold. So you will know in your build.
I recommend the Raytek MT6. It's identical to the Fluke model (I've been told Fluke actually owns Raytek) except for the fact that its gray instead of yellow, and $40 cheaper. I've got one and it works like a charm.
Lucas could you not just fasten them to the chassis floor. Thats what I did with mine and they barely get warm using the 10R resistors.
Too rich for my blood. I'll get a cheap HK one if at all I think. Thanks for the advice though.
For a pure buffer only build (no volume pot) are there any considerations or additional parts I should use?
Irfp150
Well, I managed to bust my pair of IRFP240...But I could easily get some IRFP150: could it be an alternative?
Thanks.
Well, I managed to bust my pair of IRFP240...But I could easily get some IRFP150: could it be an alternative?
Thanks.
I put two IRFP9140 on the P-side if it makes a difference. I saw the combination 9140/150 once or twice in amps, that's why I ask.