Carvin PB 150 FETs

[lowell]

the 2 inner FETs on this module are measuring short to the speaker jack on all three leads. I figure that I should replace the outer 2 xistors too but the schematic says N/U... what does that mean? Anyone know what these are?

[Mark Black]

My guess is the schematic might apply also to a lower-powered version of the amp, in which case the "NU" would mean "Not Used". Carvin could probably clarify...

Be sure and measure the gate drive resistors, as well as any dull matte-finish resistors ("flame-proof" or "fusible" types).

I would also replace the zener diodes Z1 & Z2, regardless of whether they test bad as they may have been stressed (and they're cheap).

Good luck!

[Enzo]

I'd say NU means not used. You are asking about a Carvin PB150 amp and showing a FET100 schematic. I suspect in the FET100 those two transistors were not mounted. They use the same board for other models, and in some of those the parts are installed, such as in yours.

I agree with Mark on all those other parts too.

[lowell]

thanks guys will do... Enzo, this is what Carvin sent me for a schematic when I asked for the PB150. Confusing, but maybe the guy who sent it didn't know.

[Enzo]

Or it is as I suggested, the same board used in more than one model. You could always call them and verify, like MArk said. But if you ignore the NU does it work out? I mean does it match otherwise?

[ivey]

Former Carvin Tech:

In 1992 I lived in Vista, California and moonlighted at both Carvin and Counter Point Electronics.

I still have all of my files from Carvin.

I know that this thread is very old, but in case it is visited by those looking for additional inform, I am inputting the following information on the Carvin FET100 Power Module.

a> The first set of PCB board was incorrect and traces were cut to correct the problem at assembly.
b> The power module was design to use the IRF631 Mosfet. A 150 volt unit. We used 4 units to give 60 watts RMS and 100+ watts music.
c> International Rectifier, stop producing the IRF631 units because they was slow movers and no other sells were done but to Carvin, which only used 30, 000 every two years or so, Carvin switched to the 15N20, in 1993 when the stocks of IRF631 ran out. And later 20N20.
d>The first run of products that used the FET100, were given a heatsink that proved to be too small, and did not do the cooling job. I left Carvin before that issue was resolve.
e> The 15N20 was superior to the 20N20, but a better deal was stuck for the 20N20 units.
f> Bias was set 200ma at about 28 volts.
g> The first units used MR752 rectifiers, later they were switch 1N5806
h> Custom units used 5532 IC's and later LM833 IC's.


Ivey

[danieldialatone]

"I know that this thread is very old, but in case it is visited by those looking for additional inform, I am inputting the following information on the Carvin FET100 Power Module."

Thanks a million, Ivey. This totally saved me from having to search further. yeah... too bad about those 15n20's!! they are a bit hard to find. i found the 20n20's but before i totally give up looking for the 15n20's in what way were the 15n20's superior? over all sound or reliability?

[ivey]

The 15N20 resisted wafer shorts better and were not prone to EDS as are the 20N20's. The IRF 631 are still available, but you will have to spend a $250.00 dollars on semiconductors. You can order 5 line items at $50.00 dollars per line item at Rochester Electronics. They have 687 units of the IRF 631 and 2000 of the 15N20.

But I have a sweeter deal for you. At "All Electronics" you can purchase STW60N10 at $2.00 each, which are far superior to them all. So get them while their hot.

I have laid out a PCB design of the Fet100, to use IRF630's, at 89 cent a copy. And I will post it; it is done Express PCB. So it will be easy for everyone. The lay out is simple, single sided, not two sided as Carvin did, which I felt made repairs a bitch. Because we sold thousands of those units, and people abused them.

So remember, you can use IRF 630's in that setup, with no problems. You will need 4 units. So it is about a $3.60 mod. Well not really, because it was design to use the IRF 600 line any way. In fact, if you put in six IRF 630 and bias them. You will get 180 watts rms and 300 watts music power. Use a good large heat sink and your golden.

If Carvin is still using that small heat sink (because they ordered 500,000 of them) to get a better deal. Just make a new one. And use the one you got as central mount. Even thou it was design to use TO220's, you can mount 4 TO218's on it.

When I am able to, I will draw up and submit the first production drawings of the FET100.

Take Care

Ivey

[danieldialatone]

thanks man. if you ever come through Chicago, lunch is on me.