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From: N_Cook on 25 Jan 2010 11:32
1N4148 at 7mA would be more like -2.3mA per deg C so 3 x 1n4148 looks
suitable

No other datecodes found, so presumably ELNA QEY 6303 is a type number for
6800uF 63V electros.
Light grey cement/epoxy? cased resistors are more 70s than 60s
Some strange-to-me 2SC960 bolt-downable (but not here, like the varistors)
packages , different to my 1977 databook listing, but all types in here are
Si not 60s Ge


From: isw on 26 Jan 2010 00:26
In article <hjkei3$f2m$1(a)news.eternal-september.org>,
"N_Cook" <diverse(a)tcp.co.uk> wrote:

> Mark Zacharias <mark_zacharias(a)sbclobal.net> wrote in message
> news:00cec390$0$8066$c3e8da3(a)news.astraweb.com...
> > "N_Cook" <diverse(a)tcp.co.uk> wrote in message
> > news:hjjk1l$64m$1(a)news.eternal-september.org...
> > > 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
> >
> > mark_zacharias(a)labolgcbs.net
> >
> > 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.
> >
>
> I was taking 6303 on the Elno main caps as datecode , dark brown phenolic
> pcb board, wire-wrap type wiring and some strange transistor packagings as
> being consistent with 1963 but will burrow again
>
> Not that 150A package but
> Imax 120mA, Vr max 50V, Ir max 10uA, and at 7mA, 1.65V forward V, -7mV per
> degree C
>
> As one 1n4148 is about -1.6mV per deg C then 3 in series would be about
> right forward V but not enough thermal response at -4.8mV , is Ge more
> thermally responsive ? or some sort of NTC thermistor in there as well

Some diodes intend for temperature compensation used actual transistor
B-E junctions, to get a better match to the "real" transistors over
temperature.

Isaac
From: N_Cook on 26 Jan 2010 05:40
Mark Zacharias <mark_zacharias(a)sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3(a)news.astraweb.com...
> "N_Cook" <diverse(a)tcp.co.uk> wrote in message
> news:hjjk1l$64m$1(a)news.eternal-september.org...
> > 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
>
> mark_zacharias(a)labolgcbs.net
>
> 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**



From: Mark Zacharias on 26 Jan 2010 06:17
"N_Cook" <diverse(a)tcp.co.uk> wrote in message
news:hjmgpk$rdm$2(a)news.eternal-september.org...
> Mark Zacharias <mark_zacharias(a)sbclobal.net> wrote in message
> news:00cec390$0$8066$c3e8da3(a)news.astraweb.com...
>> "N_Cook" <diverse(a)tcp.co.uk> wrote in message
>> news:hjjk1l$64m$1(a)news.eternal-september.org...
>> > 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
>>
>> mark_zacharias(a)labolgcbs.net
>>
>> 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.

From: Chuck on 26 Jan 2010 11:12
On Tue, 26 Jan 2010 05:17:53 -0600, "Mark Zacharias"
<mark_zacharias(a)sbclobal.net> wrote:

>"N_Cook" <diverse(a)tcp.co.uk> wrote in message
>news:hjmgpk$rdm$2(a)news.eternal-september.org...
>> Mark Zacharias <mark_zacharias(a)sbclobal.net> wrote in message
>> news:00cec390$0$8066$c3e8da3(a)news.astraweb.com...
>>> "N_Cook" <diverse(a)tcp.co.uk> wrote in message
>>> news:hjjk1l$64m$1(a)news.eternal-september.org...
>>> > 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
>>>
>>> mark_zacharias(a)labolgcbs.net
>>>
>>> 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
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