68C diode from 1963

N

N_Cook

Guest
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.
 
N_Cook <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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.
Click to expand...
Just found a side ref to it in the manual, a varistor, part number
E03094-002
circuit symbol 3 triangles in a row, like 3 diodes without 2 of the cathode
bars,
not skew Z over a resistor, or back to back triangles
Probably varistor diode but no useful data found yet , whether varistor or 3
diodes or varistor and 1 diode or whatever, or that symbol found elsewhere
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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.
Click to expand...

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

mark_zacharias@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.
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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@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.
Click to expand...

All received, thanks.
Next task - to learn Japaneso
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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@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.
Click to expand...
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
 
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
 
In article <hjkei3$f2m$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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@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
Click to expand...
Some diodes intend for temperature compensation used actual transistor
B-E junctions, to get a better match to the "real" transistors over
temperature.

Isaac
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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@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.
Click to expand...
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**
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjmgpk$rdm$2@news.eternal-september.org...
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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@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**
Click to expand...
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.
 
On Tue, 26 Jan 2010 05:17:53 -0600, "Mark Zacharias"
<mark_zacharias@sbclobal.net> wrote:

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

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
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:003e02f5$0$28396$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjmgpk$rdm$2@news.eternal-september.org...
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@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@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.
Click to expand...
This VN900 originally had sun damage rack and pinion pivot switch (pink
noise sw), metal actuating pin heated up relative to plastic and cracked the
plastic. Also worn pot. They went to a High St repairer and a 2SD188 went
C-E short on one channel on initial powerup and they gave up.
And for good measure had coffee poured into it, in its very distant past,
when the owner was a student.

Have ground off the pivot rivet and got the switch dissassembled, metal
ground down a bit to give some slack and hopefully capillary superglued back
as one. Will probably replace o/p pair with 2955/3055 before wasting
anything more contemporaneous.
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
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Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@news.eternal-september.org...
Click to expand...

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.
Click to expand...
Placed switch pivot in a plastic bag and glue passed 1lb load on end of pin.
Next the vol control, quad ganged pot with bass comp CTs, not many of them
around no doubt. To disassemble requires grinding off the swaging on the end
of the shaft, presumably drill + maybe tap for screw and pad/washer to
refit.
A grey small electro on the main board has leaked at some time

SEA (punningly in blue print on front) stands for Sound Effects Amplifier ,
from the user manual, me thinking Selective Equalisation Adjustment
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:003e02f5$0$28396$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjmgpk$rdm$2@news.eternal-september.org...
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@news.eternal-september.org...
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.
Click to expand...

All the nuts for the VN 900 ,TO3 were loose, not to point of dropping off ,
but not as tight as I would expect, so worth checking your one, compressed
nylon insulator/spacers?. Sw rebuilt , quad pot graphited paste pushed in
for the moment, won't know whether requires rebuilding until I can get some
power on it.
 
so far not broken an age-hardened hookup wire.
Easier to work on than a lot of 70s stuff, can remove sw and pots etc with
room to manoeuvre, wired in place. And the edge-connectored multiple cards
makes it a lot easier, presumably can swap between channels for diagnostic
purposes if required.
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
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Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
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Click to expand...

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.
Click to expand...
As far as intrusive noise.
Anyone know why +74V DC rail to a preamp ? producing low current shot noise?
Particularly the third transistor in,
250V rating 2SC1103 and associated Rs would be my guess at noise source.
Assuming its not bleed over from the pink noise generator
 
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Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
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Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@news.eternal-september.org...


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.


As far as intrusive noise.
Anyone know why +74V DC rail to a preamp ? producing low current shot
noise?
Particularly the third transistor in,
250V rating 2SC1103 and associated Rs would be my guess at noise source.
Assuming its not bleed over from the pink noise generator
Click to expand...
Definitely not bleed over, the noise varies too much in nature and
intensity. I suspect the internal wiring to the back panel could be an
issue - they used individual (cheap) shielded phono cable and if you look
you'll see the grounds don't tie together at the rear panel (not all of them
anyway).
I am also suspicious of an oily residue on the tone board. Perhaps someone
tried to clean the controls with WD40 or the like and made a mess of it.
It's definitely a preamp issue, as the main amps work fine when divorced
from the preamp section.
I noticed the higher than usual voltages. Not being a old radio guy, the
idea of "noisy resistors" still bothers me a bit (even though I acknowledge
it is a known phenomenon), although if it's due to their resistance
shifting, I can definitely see them causing noise in a given circuit.

Mark Z.
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
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Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@news.eternal-september.org...


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.


As far as intrusive noise.
Anyone know why +74V DC rail to a preamp ? producing low current shot
noise?
Particularly the third transistor in,
250V rating 2SC1103 and associated Rs would be my guess at noise source.
Assuming its not bleed over from the pink noise generator





Definitely not bleed over, the noise varies too much in nature and
intensity. I suspect the internal wiring to the back panel could be an
issue - they used individual (cheap) shielded phono cable and if you look
you'll see the grounds don't tie together at the rear panel (not all of
them
anyway).
I am also suspicious of an oily residue on the tone board. Perhaps someone
tried to clean the controls with WD40 or the like and made a mess of it.
It's definitely a preamp issue, as the main amps work fine when divorced
from the preamp section.
I noticed the higher than usual voltages. Not being a old radio guy, the
idea of "noisy resistors" still bothers me a bit (even though I
acknowledge
it is a known phenomenon), although if it's due to their resistance
shifting, I can definitely see them causing noise in a given circuit.

Mark Z.
Click to expand...
I put some manky oily residue (not all over) down to a leaky nearby cap ,
replaced , but tested ok.
Perhaps a breakdown product of that dark phenolic 60s type pcb, like "dolls
disease" in soft plastics. I'm wondering if the SEA board , populated with
70s Si Tr and Rs &cs ,along with the main caps, is a hang over from earlier
60s model.
 
On Thu, 28 Jan 2010 05:46:00 -0600, "Mark Zacharias"
<mark_zacharias@sbclobal.net> wrote:

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjrieg$vft$1@news.eternal-september.org...
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
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Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjjk1l$64m$1@news.eternal-september.org...


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.


As far as intrusive noise.
Anyone know why +74V DC rail to a preamp ? producing low current shot
noise?
Particularly the third transistor in,
250V rating 2SC1103 and associated Rs would be my guess at noise source.
Assuming its not bleed over from the pink noise generator





Definitely not bleed over, the noise varies too much in nature and
intensity. I suspect the internal wiring to the back panel could be an
issue - they used individual (cheap) shielded phono cable and if you look
you'll see the grounds don't tie together at the rear panel (not all of them
anyway).
I am also suspicious of an oily residue on the tone board. Perhaps someone
tried to clean the controls with WD40 or the like and made a mess of it.
It's definitely a preamp issue, as the main amps work fine when divorced
from the preamp section.
I noticed the higher than usual voltages. Not being a old radio guy, the
idea of "noisy resistors" still bothers me a bit (even though I acknowledge
it is a known phenomenon), although if it's due to their resistance
shifting, I can definitely see them causing noise in a given circuit.

Mark Z.
Click to expand...

The noisy resistor problem in the preamps of Kenwood receivers of the
early 1970s was fairly common (If I remember correctly, they were
emitter resistors). The company I worked for didn't carry JVC
receivers so I don't know if they had this problem. Chuck
 
In article <hjrieg$vft$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:003e02f5$0$28396$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hjmgpk$rdm$2@news.eternal-september.org...
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:00cec390$0$8066$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
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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.


As far as intrusive noise.
Anyone know why +74V DC rail to a preamp ?
Click to expand...
With bipolar transistors, the way to get low noise is to run low emitter
current. Low emitter current means high Rbe (intrinsic base resistance).
High Rbe means low gain (for gain determination, Rbe in in series with
the external emitter resistance). In that environment, one way to
recover some stage gain is to run a high collector resistor, and that
calls for a high rail voltage.

Isaac
 
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