fet replacement for 1178

hi,

the 1178 uses a special dual transistor ic (npd5566)

I can't find any specs about that part...


is there a complementary part like a single transistor for that ??



thanks,
mat

More or less educated guess: check for 2N5566. Expensive, but easy to get.

Samuel

See also this thread:

http://www.diyaudio.com/forums/showthread.php?postid=155182

thanks,

I don't need that dual transistor in "one package", but maybe there is a common replacement single transistor for that?? (bf245?)

mat

Brad once mentioned the 2N4393 here.

Samuel

[quote author="matthias"]hi,

the 1178 uses a special dual transistor ic (npd5566)

I can't find any specs about that part...


is there a complementary part like a single transistor for that ??



thanks,
mat[/quote]

I've heard about this one: 2N5566 --> http://www.vishay.com/docs/70254/70254.pdf

Friendly

Fly

I guess 2 matched BF245 will do the job?

steff

thank you !!

I can't find a really close single substitute. The BF245 is low C and low gm by comparison. The 2N4393 (and higher Idss versions 4392, 4391) are somewhat lower C and gm but within hooting distance at least.

The U310, E310 etc. have lower breakdown voltage but a better gm/Cin ratio. Two of them in parallel would be pretty close to half of a 5566 if the voltage is tolerable.

BTW the difference among the series (5564, -65, -66) is not drain current and Vgs off as is often the case with FETs but rather goodness of d.c. matching (-5566 is the poorest).

I'd have to see the circuit.

here's the manual with schematic...

http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/UREI-1178 manual.pdf

Hello, can someone know what types are the CR11,12,13,14 diodes on 1178's meter amp ???

cheers fotis

Hi Matthias,

have an original NPD dual fet for the 1178 (National Semi). If you need really one, I can send it to you.

Milos

[quote author="matthias"]here's the manual with schematic...

http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/UREI-1178 manual.pdf[/quote]

Ah yes. Plunkett told me about this a bit in fact; his contribution, principally, was to get a bit more range out of the design by driving the source of the FET as well as the gate.

I would say that the FET is by far the most critical part in the whole system. The use of the dual part is for matching of the two channels, but given the absence of an identical single I would make a special effort to get the exact replacement if at all possible.

[quote author="FotisGR"]Hello, can someone know what types are the CR11,12,13,14 diodes on 1178's meter amp ???

cheers fotis[/quote]

Most likely 1N4148's, but they don't look ultracritical.