On Tue, 26 Jan 2010 05:17:53 -0600, "Mark Zacharias"
wrote:

"N_Cook" wrote in message
...
Mark Zacharias wrote in message
...
"N_Cook" wrote in message
...
In 1963 JVC VN900 amp, circuit designation STV-3, probably a triple
diode
for bias seting, any info on it?. Parts listing absent from the manual,
just
68C on black body 4x7x10mm that looks like a slotted opto device but
instead
of square bottomed notch , semicircle curved, as though for locating
on
a
rod, but mounted on pcb here.




I tried to email you some data on that diode but it bounced. You can
email
me at



and reverse the domain to read "sbcglobal"

and I'll resend.

BTW I think the VN-900 was closer to 1970...

I own one, also a VN-700...

Mark Z.


Presumably about 1973 made, from www cites, although I can find no
indicator
inside the amp.
Can't find 6303 as an ELNA type number , so maybe old stock caps used.
Those 2SC960 with great bolt down mounting flanges, that are not bolted,
floating in mid air look mighty strange also , no package pic/type number
found for them, somewhere between TO3 and TO37 but flanges twice as thick
but TO5 size cap .
Amp serial number 046017**




As a teenager in the '70's I used to like these models, (the VN-900 and
VN-700) but now as a technician I find they are really kind of junky as
regards the amp section and overall quality, compared to the Pioneer,
Kenwood, Marantz etc of the time.
Seems like they put a little too much of the manufacturing cost into the SEA
tone section.
Also, I find one can clean the controls until you are blue in the face, yet
within a couple months they are acting up again. I seem to have much better
luck on this with other brands.
My VN-900 has low level noise problems I have so far been unable to resolve.
Coupling caps, power supply, signal transistors, no luck. Had to set it
aside for some future date...

Mark Z.


Mark,

We used to have problems with noisy resistors in Japanese amps of that
vintage. In a pinch, for testing purposes, we'd stack 3 silicon
diodes to sub for a STV-3. If the STV3s aren't available these days,
perhaps mounting the diodes to a piece of aluminum and attaching it to
the heatsink might suffice. Chuck