Looking For: Dual 30-30 @ 600 'Lytic for a Scott Amp

[Watson A.Name - \Watt Sun, the Dark Remover\]

I'd like to say 'subject says it all' like so many other lamers do, but
it's soooo much easier to just highlight it and copy and paste it into
the body, like this: Looking For: Dual 30-30 @ 600 'Lytic for a Scott
Amp

A friend of mine is fixing a Scott amp and needs a dual 30 - 30 uF at
600 VDC electrolytic, like the old Sprague or C-D twist lock aluminum
cans common in those toob amps. (Notice I avoided that ever so trite
'not uncommon', which should really be the old standard, 'not
unusual').

I have the feeling that it might be easier to clean out the old can and
put a couple individual capacitors inside, or externally. If he were to
use two 60 uF, 350 VDC caps in series for each section, what value
resistor should he put across each of the two caps to balance any
leakags? A hundred k? I see the SMPS caps, which are 220 to 470 at
200V, typically use anywhere from a 330k down to a 150k for the bleeder
resistor. My old Radio Amateur's Handbook shows, for three 100 uFs in
series, a 20k, 10W across each cap. (I don't know why they need to be
that high power, unless a cap were to fail and a lot more of the DC were
to appear across the remaining two caps.)

Any other solutions? Thanks.

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Tim Wescott]

I'd like to say 'subject says it all' like so many other lamers do, but
it's soooo much easier to just highlight it and copy and paste it into
the body, like this: Looking For: Dual 30-30 @ 600 'Lytic for a Scott
Amp

A friend of mine is fixing a Scott amp and needs a dual 30 - 30 uF at
600 VDC electrolytic, like the old Sprague or C-D twist lock aluminum
cans common in those toob amps. (Notice I avoided that ever so trite
'not uncommon', which should really be the old standard, 'not
unusual').

I have the feeling that it might be easier to clean out the old can and
put a couple individual capacitors inside, or externally. If he were to
use two 60 uF, 350 VDC caps in series for each section, what value
resistor should he put across each of the two caps to balance any
leakags? A hundred k? I see the SMPS caps, which are 220 to 470 at
200V, typically use anywhere from a 330k down to a 150k for the bleeder
resistor. My old Radio Amateur's Handbook shows, for three 100 uFs in
series, a 20k, 10W across each cap. (I don't know why they need to be
that high power, unless a cap were to fail and a lot more of the DC were
to appear across the remaining two caps.)

Any other solutions? Thanks.

(450V)^2 / (20k-ohm) = 10W. Hmm. Usually the purpose of a
low-resistance bleeder was for safety, to bring the supply voltage down
to a safe level quicker when the power was off. Inside the can you just
need to overcome and balance the capacitor leakage, which you can find
from the cap datasheet.

Antique Electronic Supply has dual-section caps going up to 525V, but
not 600 (www.tubesandmore.com _not_ www.toobsandmore.com).

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

(450V)^2 / (20k-ohm) = 10W. Hmm. Usually the purpose of a
low-resistance bleeder was for safety, to bring the supply voltage down
to a safe level quicker when the power was off. Inside the can you just
need to overcome and balance the capacitor leakage, which you can find
from the cap datasheet.

Antique Electronic Supply has dual-section caps going up to 525V, but
not 600 (www.tubesandmore.com _not_ www.toobsandmore.com).

Yeah, thanks. From my memories of a long time ago, I can't ever
remember seeing a multisection 'lytic of more than 525V, and anything
above 450V being very rare. I might have seen an oil filled cap in a
large aluminum can that was chassis mounted, rated at something like 8
uF, 600V. But that's not an electrolytic. But hey, those were the
values that he gave me.

 

[Walter Harley]

A friend of mine is fixing a Scott amp and needs a dual 30 - 30 uF at
600 VDC electrolytic, like the old Sprague or C-D twist lock aluminum
cans common in those toob amps. (Notice I avoided that ever so trite
'not uncommon', which should really be the old standard, 'not
unusual').

I have the feeling that it might be easier to clean out the old can and
put a couple individual capacitors inside, or externally.

IME, even if you can find the multisection can caps, they are either
prohibitively expensive, or else they are prohibitively expensive and NOS.
And getting a NOS electrolytic cap is like getting a NOS battery, or a NOS
jug of milk.

Looks like Antique Radio Supply has multisection cans going up to 525V.
Gee, I wonder if he actually needs the full 600. Can he disconnect the
power transformer and measure the unloaded AC voltage? Multiply by 1.4 and
add 10%, for absolute worst case of overvoltage, no load, and no rectifier
sag, I think.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

in message

IME, even if you can find the multisection can caps, they are either
prohibitively expensive, or else they are prohibitively expensive and NOS.
And getting a NOS electrolytic cap is like getting a NOS battery, or a NOS
jug of milk.

Looks like Antique Radio Supply has multisection cans going up to 525V.
Gee, I wonder if he actually needs the full 600. Can he disconnect the
power transformer and measure the unloaded AC voltage? Multiply by 1.4 and
add 10%, for absolute worst case of overvoltage, no load, and no rectifier
sag, I think.

Thanks for the info. I asked him what the output tubes were, and he
said e wasn't sure. So I'm not sure if he really wants to delve into
this project. Like as in spend time on it other than just replace the
capacitor.

You know, some people look at this kind of thing as a waste of time, and
if they can't just get it done in a few minutes with a new part, then
it's gonna end up in the scrap metal pile. ;-/

 

[Walter Harley]

Thanks for the info. I asked him what the output tubes were, and he
said e wasn't sure. So I'm not sure if he really wants to delve into
this project. Like as in spend time on it other than just replace the
capacitor.

You know, some people look at this kind of thing as a waste of time, and
if they can't just get it done in a few minutes with a new part, then
it's gonna end up in the scrap metal pile. ;-/

I just fixed up an early-60's McIntosh receiver for a friend, that needed a
new cap or two. Tubes in the receiver section, semiconductors elsewhere.
Beautiful sounding unit; measured better than .01% THD+N at rated power, if
I remember! And "rated power" according to the service manual (imagine
that, a service manual for a piece of consumer equipment!) meant continuous
sine wave power into a 4 ohm load; I tested it, and it lived up to the
claim. It just sat there singing away, no problem.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

in message

I just fixed up an early-60's McIntosh receiver for a friend, that needed a
new cap or two. Tubes in the receiver section, semiconductors elsewhere.
Beautiful sounding unit; measured better than .01% THD+N at rated power, if
I remember! And "rated power" according to the service manual (imagine
that, a service manual for a piece of consumer equipment!) meant continuous
sine wave power into a 4 ohm load; I tested it, and it lived up to the
claim. It just sat there singing away, no problem.

Macs were notoriously conservative. I remember listening to a pair of
Macs driving Bose 901s, and seeing the meters peak at +3, so I guess
they were putting out a thousand watts(!)

Odd that the receiver you worked on was solid state but with tubes in
the receiver - must've been from the '70s. But at least it wasn't a
room heater. I've got a Scott RS250 receiver stashed somewhere that
someday I'll fix when I get the time and inclination.

Well, I've strayed from the subject far enough. Maybe I should've
xposted to rec.audio.tech or something.

 

[Walter Harley]

Macs were notoriously conservative. I remember listening to a pair of
Macs driving Bose 901s, and seeing the meters peak at +3, so I guess
they were putting out a thousand watts(!)

IIRC this one had supply rails around 40V. So, it could in principle dump
250W avg sine into a 4 ohm load, per speaker, or 125 for an 8 ohm load. It
was rated for 40W per channel (regardless of load) - obviously a rating
based on heat dissipation ability, rather than supply capability. Don't see
that very much these days!

Odd that the receiver you worked on was solid state but with tubes in
the receiver - must've been from the '70s. But at least it wasn't a
room heater.

It sure looked older than '70s; I would have guessed mid 60's. A lot of
point to point wiring with terminal strips, small PCB's here and there for
individual subcircuits. Multi-section can electrolytics. Supply ripple
rejection based on multistage R-C filtering, rather than regulation. No
IC's anywhere. Carbon comp resistors, some mica capacitors. (There, see,
we *are* talking about components!)

And despite being solid state, it was definitely a room heater, even with no
load. I'd guess (based on warmth) that its quiescent power consumption was
around 30W.

I don't remember what the output transistors were - that would have helped
date it.