[Engineer]

Hi, Vacuumlanders,
I while back I acquired a Pioneer SM-B200 AM(two)/SW/FM stereo,
tube-type receiver in a dreadful state (had to rebuild broken tuning
drives, replace several dead and missing tubes, etc.. looked like it
had been in a landfill.) Finally got it all working except the FM
(still needs a complete alignment when I get the time.) On the way I
found two of the four audio section coupling caps were leaky (6BM8
triode section plate to O/P pentode section control grid.) I replaced
all four, of course.

Now, a few weeks ago I picked up a much better looking SM-B200A
receiver on eBay ("as is", of course) and justified on the premise that
if you have one already then two is better! I tested the tubes, ran it
up on a variac and found a very low B+ of around 178 VDC (off a
210-0-210 transformer) and a bad 120 Hz hum. There were two obvious
faults:
A) a nearly dead reservoir cap at the rectifier cathode (replaced), and
B) three of the O/P tubes had -15 to -16 VDC fixed bias (OK) and one
had only -5 VDC (not at all OK!) This tube was pulling far too much
current. Reason: a leaky 0.05 MFD coupling cap - I've replaced two of
them to date and will replace the other two a.s.a.p. when I can get the
required "round tuit" tool... g Again, FM needs also needs fixing,
has a MPX addition, too... this stuff is sent to try us!

These caps in vintage Pioneer receivers are all of the same general
type. The recent ones I replaced were marked:
"SUZUKI
OIL JCP-D
0.05 uF
WV 400V DC"
(on the grey plastic finish, over aluminum body, one black end.)

The ones I replaced in the first chassis were marked similarly but,
IIRC, the brand was ELNA (same physical size.) This chassis also has
SUZUKI and ELNA brand 0.05 uF and another value caps - all suspect,
IMHO.

In Pioneer tube chasses, these caps are not only used for coupling but
for decoupling, too, all over the place . However, they seem less
dangerous in decoupling service so I have not replaced them (yet!)
It's just crossed my mind that I've had to replace more of this types
"for cause", i.e. failed, than I have the wax covered, paper tubular
caps in real old radios, the one we all replace for insurance, i.e. the
wax ones that are not actually dead yet (but we should still replace
them, of course.)

So, perhaps it is common knowledge, but I conclude that these little
grey, oil filled 0.05's are very bad news! Expunge them!
Cheers,
Roger

[Jon Yaeger]

in article , Engineer at
wrote on 10/8/06 6:15 PM:

Hi, Vacuumlanders,
I while back I acquired a Pioneer SM-B200 AM(two)/SW/FM stereo,
tube-type receiver in a dreadful state (had to rebuild broken tuning
drives, replace several dead and missing tubes, etc.. looked like it
had been in a landfill.) Finally got it all working except the FM
(still needs a complete alignment when I get the time.) On the way I
found two of the four audio section coupling caps were leaky (6BM8
triode section plate to O/P pentode section control grid.) I replaced
all four, of course.

Now, a few weeks ago I picked up a much better looking SM-B200A
receiver on eBay ("as is", of course) and justified on the premise that
if you have one already then two is better! I tested the tubes, ran it
up on a variac and found a very low B+ of around 178 VDC (off a
210-0-210 transformer) and a bad 120 Hz hum. There were two obvious
faults:
A) a nearly dead reservoir cap at the rectifier cathode (replaced), and
B) three of the O/P tubes had -15 to -16 VDC fixed bias (OK) and one
had only -5 VDC (not at all OK!) This tube was pulling far too much
current. Reason: a leaky 0.05 MFD coupling cap - I've replaced two of
them to date and will replace the other two a.s.a.p. when I can get the
required "round tuit" tool... g Again, FM needs also needs fixing,
has a MPX addition, too... this stuff is sent to try us!

These caps in vintage Pioneer receivers are all of the same general
type. The recent ones I replaced were marked:
"SUZUKI
OIL JCP-D
0.05 uF
WV 400V DC"
(on the grey plastic finish, over aluminum body, one black end.)

The ones I replaced in the first chassis were marked similarly but,
IIRC, the brand was ELNA (same physical size.) This chassis also has
SUZUKI and ELNA brand 0.05 uF and another value caps - all suspect,
IMHO.

In Pioneer tube chasses, these caps are not only used for coupling but
for decoupling, too, all over the place . However, they seem less
dangerous in decoupling service so I have not replaced them (yet!)
It's just crossed my mind that I've had to replace more of this types
"for cause", i.e. failed, than I have the wax covered, paper tubular
caps in real old radios, the one we all replace for insurance, i.e. the
wax ones that are not actually dead yet (but we should still replace
them, of course.)

So, perhaps it is common knowledge, but I conclude that these little
grey, oil filled 0.05's are very bad news! Expunge them!
Cheers,
Roger


I've rebuilt a number of Pioneer, Sansui, and Kenwood receivers.

I replace ALL of the grey coupling / bypass capacitors. If you take them
out of circuit and measure the leakage under high voltage, you will find
that virtually all of them are bad.

For that reason, rebuilding these vintage Japanese receivers is a very
time-consuming process. Sometimes barely worth the effort . . .

Jon

[Bob H.]

I've rebuilt a number of Pioneer, Sansui, and Kenwood receivers.

I replace ALL of the grey coupling / bypass capacitors. If you take them
out of circuit and measure the leakage under high voltage, you will find
that virtually all of them are bad.

For that reason, rebuilding these vintage Japanese receivers is a very
time-consuming process. Sometimes barely worth the effort . . .



Indeed, I did some work on a Sansue 500 ( a lot of hours), and still
had a ways to go. After a couple years of eyeing my Sansui and Pioneer
amps, I ended up parting them out for the very nice iron they possess.
I don't see the justification in effort on these amps, as there are a
bunch of other classics which are much more reasonable to work on, and
worth more.

Bob H.

[Sander deWaal]

"Engineer" said:


So, perhaps it is common knowledge, but I conclude that these little
grey, oil filled 0.05's are very bad news! Expunge them!
Cheers,
Roger



They're universally used in Japanese amps of that era, and they're
leaky wthout exception.
I routinely replace them *all* before even turning the amp on.

A notorious firestarter is the one that's soldered across the power
transformer from one mains lead to ground.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Engineer]

Thanks for the comments... pity about the Pioneer chasses.

I think I may be going through a "bad cap" spell. Another project on my
bench is the refurbishing (and improving!) a Heathkit A-9C amplifier.
It's full of green SANGAMO tubular caps. The worst ones seem to be the
0.05 uF, marked:
"SANGAMO
Type 33
..05-600
..05-600
..05-600"

The larger, green 0.1 uF ones may not be so bad, but who knows? They
have rounded ends and are marked:
"SANGAMO
Type 33
..1-600
..1-600"

Anyway, I've replaced two, so far (coupling to 6L6 control grids.)
They tested OK out of the circuit but at low voltage (on a Fluke 111.)
IIRC, they were putting a couple of hundred mV positive (above ground,
not cathode) on the grids - but I was not paying attention so did not
write it down!
Cheers,
Roger

[Bob H.]

Engineer wrote:
Thanks for the comments... pity about the Pioneer chasses.

Actually, the Pioneer chassis was so well built that I spent hours
stripping all the stuff off of it, and putting it and the cage on ebay
for a few bucks in order to avoid trashing it. All I got was one
deadbeat bidder. Hey, I tried...

BobH.

[Engineer]

Bob H. wrote:
Engineer wrote:
Thanks for the comments... pity about the Pioneer chasses.

Actually, the Pioneer chassis was so well built that I spent hours
stripping all the stuff off of it, and putting it and the cage on ebay
for a few bucks in order to avoid trashing it. All I got was one
deadbeat bidder. Hey, I tried...

BobH.

Bob,
Yes, they look so good that you can't trash them!
BTW, got any bits left? I'll pay the mailing... g
Very best.
Cheers,
Roger

[Bob H.]

I should have posted them. They're gone now. I'm condensing my toobie
shop into 1/3 the space, so a lot of stuff had to be compressed or
parted out. I've got my remaining classic stuff shoe-horned into
shelves. Between that, an extension, and a rental house restoration,
I've been away from DIY for almost a year, now. Back to it soon.
I do have a Bogen amp chassis if you'de like it. It is the heavy guage
screen cover type with a standard sized case. It's in the shed now.

cheers,
Bob H.


Engineer wrote:
Bob H. wrote:
Engineer wrote:
Thanks for the comments... pity about the Pioneer chasses.

Actually, the Pioneer chassis was so well built that I spent hours
stripping all the stuff off of it, and putting it and the cage on ebay
for a few bucks in order to avoid trashing it. All I got was one
deadbeat bidder. Hey, I tried...

BobH.

Bob,
Yes, they look so good that you can't trash them!
BTW, got any bits left? I'll pay the mailing... g
Very best.
Cheers,
Roger