Heatsinks

Hello Brendon
Not to much progress, weekend weather fantastic. Spend it riding my bike all over the city. 17 degrees, unheard of in late november.
I think my HS worries are over for the moment. My next concern is matching mosfets. I believe at one time Nelson Pass sold matched pairs, no longer the case. Anyone out there aware of a source for matched pairs.
Gustavo
 
Matching FETs

Gustavo,

Matching mosfets is very time consuming (more time than matching 1% resistors). When I ordered the FETs for my BLS pre-amp I also ordered a batch of IRFP-240 (for another SoZ project at my other home in Canada and of course.. for back-up).

For the 4 channel pre-amp, I ordered 30 IRF610 and most of them matched - even found quad set matches.

You have my e-mail so let me know if you need any.

re: jduncan

IRF9610 are P-Chan devices. I assume they're not for the BLS pre-amp project? Only 1 IRF9610 mosfet is required in the pre-amp which goes in the power supply board.
 
OK, after taking out the mosfets I want myself, I now have these additional IRFP240's available...of course I'd prefer it if someone wants to take most/all of them but just contact me anyway.

Vgs
4.29
4.27
4.38
4.33
4.42
4.30
4.38
4.32
4.30
4.27
4.34
4.32
4.36
4.29
4.18
4.28
4.40
4.29
4.14
4.27
4.28
4.16
4.14
4.39
4.41
4.37

From an initial purchase of 50, I took the 24 which were between 4.20 and 4.26.

Cheers,

Joseph
 
need them matched pairs

I need to buy some irf 240 or 244 matched pairs
Minimum of 2 pr. but 4 would give me some back-ups
I'm making a SOZ

Anyone still have some from their Pass projects? I guess I'm too lazy or overwhelmed to want to match 'em.

Actually I'm just in a big hurry to hear these amps!


Thanks,
Mark
 
Easy and not time consuming

Matching FET's as per NP's instructions is easy, not time consuming. I did my 200 devices (4 types) in about 2 hours including setup.

Number the devices (with a small sticky label or a marker).

Put the results into Excel or other spreadsheet

Sort by Vgs (at appropriate current).

Make a cell with difference between Vgs lines.

Use the odd ones as current sources?

This is unlikely to cost you much more than buying pre-matched ino the exact quantity that you need.


Petter