Hello all.
I just got a pioneer SX-348, to test out and see how it sounds compared to my other stuff (It's all tubes!). I couldn't find the service manual so I don't have any clear way to fix it except replace caps and hope that works.
I need to order new caps for it probably though I haven't checked them yet. To my knowledge all the tubes are fine, but some caps have shorted and the output tubes glow cherry red, a good sign to turn it off.
I was wondering, if I might be able to use the phono preamp and tuner amp section if I just remove the output tubes. IIRC tube gear is generally designed to withstand being turned on without the tubes being in place, so a dead tube won't destroy the whole thing?
- keantoken
I just got a pioneer SX-348, to test out and see how it sounds compared to my other stuff (It's all tubes!). I couldn't find the service manual so I don't have any clear way to fix it except replace caps and hope that works.
I need to order new caps for it probably though I haven't checked them yet. To my knowledge all the tubes are fine, but some caps have shorted and the output tubes glow cherry red, a good sign to turn it off.
I was wondering, if I might be able to use the phono preamp and tuner amp section if I just remove the output tubes. IIRC tube gear is generally designed to withstand being turned on without the tubes being in place, so a dead tube won't destroy the whole thing?
- keantoken
KT,
Replace those OEM oil caps. with Soviet surplus K40 PIO (paper in oil) stock. I suspect you have the same issue of electrically leaking parts, just like the contemporary Sansui tubed units exhibit.
Mica and ceramic caps. tend to hold up, but ceramic caps. in the direct signal path is a "no no".
BTW, have you tried contacting Pioneer? Perhaps they have documentation in the archives.
Replace those OEM oil caps. with Soviet surplus K40 PIO (paper in oil) stock. I suspect you have the same issue of electrically leaking parts, just like the contemporary Sansui tubed units exhibit.
Mica and ceramic caps. tend to hold up, but ceramic caps. in the direct signal path is a "no no".
BTW, have you tried contacting Pioneer? Perhaps they have documentation in the archives.
Okay, I just found a good page. Problem with this sort of thing is, I can never find a page that tells me what the caps look like. I've never found a page on how to identify different caps, I'm just supposed to know somehow.
The obvious ones are marked "suzuki oil jcp-a" at 400WV. Can I assume all film, mica and ceramic types are dipped package and lima bean types?
The shop I got it from recommended getting these caps:
Bob's Antique Radios - Supplies
Probably not like the soviet caps, but I have real budget issues. Maybe I could go more expensive if someone knows a good source?
- keantoken
The obvious ones are marked "suzuki oil jcp-a" at 400WV. Can I assume all film, mica and ceramic types are dipped package and lima bean types?
The shop I got it from recommended getting these caps:
Bob's Antique Radios - Supplies
Probably not like the soviet caps, but I have real budget issues. Maybe I could go more expensive if someone knows a good source?
- keantoken
Get me a list of cap needs. You could also use my B&K mutual conductance
tester, but you would have to get to Dallas. Have a Sico tester that checks
only for "emission". Basically wires all internal parts like a diode, and check
that is works like a diode. Mostly to see if the cathode coating still emits?
You can rig something like that fairly easy...
tester, but you would have to get to Dallas. Have a Sico tester that checks
only for "emission". Basically wires all internal parts like a diode, and check
that is works like a diode. Mostly to see if the cathode coating still emits?
You can rig something like that fairly easy...
Wow, you're right, it's SX-34B! I think the 6BM8 tubes are okay, it's just been sitting for a while. One channel actually worked.
KenPeter, tomorrow I will go to a shop and get a "capacitor analyst", which measures capacitance, I think ESR, and leakage at 100V. I can use it to test caps. I will write down all the obvious oil caps. The two PSU caps are 150V, 100uF, which I happen to have several scavenged switching supply caps that should work (KME pair of 100uF/200V, Marcon pair of same, ambiguously marked pair of 200V/470uF, a soon to be unsoldered Rubycon pair of 470uF/200V, and 5 small Teapo caps, hardly worth mention. I'm betting on the KME pair). I've also got photoflash caps, but I think these have better uses elsewhere...
What about those film caps rolled up in clear plastic? Do those need to be replaced?
- keantoken
KenPeter, tomorrow I will go to a shop and get a "capacitor analyst", which measures capacitance, I think ESR, and leakage at 100V. I can use it to test caps. I will write down all the obvious oil caps. The two PSU caps are 150V, 100uF, which I happen to have several scavenged switching supply caps that should work (KME pair of 100uF/200V, Marcon pair of same, ambiguously marked pair of 200V/470uF, a soon to be unsoldered Rubycon pair of 470uF/200V, and 5 small Teapo caps, hardly worth mention. I'm betting on the KME pair). I've also got photoflash caps, but I think these have better uses elsewhere...
What about those film caps rolled up in clear plastic? Do those need to be replaced?
- keantoken
Here is a list of oil and lytic caps:
8x .05uF/400V oil (marked jcp-a)
2x .02uF/400V oil (marked jcp-a)
2x 100uF/150V lytic polar
Elna elyt 50uF 25V (marked 40 SV)
2x 10uF/20V very small polar, may not be caps, wired in series. I'm assuming 10m means 10uF.
Elna elyt can 250V 20/20/40uF
Elna elyt can 350V 20/20/20uF
- keantoken
8x .05uF/400V oil (marked jcp-a)
2x .02uF/400V oil (marked jcp-a)
2x 100uF/150V lytic polar
Elna elyt 50uF 25V (marked 40 SV)
2x 10uF/20V very small polar, may not be caps, wired in series. I'm assuming 10m means 10uF.
Elna elyt can 250V 20/20/40uF
Elna elyt can 350V 20/20/20uF
- keantoken
KT,
You want K40 Soviet surplus as the replacement "oilers". Acquire 8X 0.047 μF. and 2X 0.022 μF. parts, all at 400 WVDC. "Flea Pay" is a likely source for those items.
It's likely that some or even all of the OEM Carbon composition resistors have drifted and/or gone noisy over time. Those parts can be replaced by inexpensive Xicon Carbon film stuff from Mouser. Never decrease the wattage rating of resistors.
Unless they have started to physically degrade, wirewound resistors don't need attention.
OEM film caps. can be replaced by 716P series Orange Drop parts.
You want K40 Soviet surplus as the replacement "oilers". Acquire 8X 0.047 μF. and 2X 0.022 μF. parts, all at 400 WVDC. "Flea Pay" is a likely source for those items.
It's likely that some or even all of the OEM Carbon composition resistors have drifted and/or gone noisy over time. Those parts can be replaced by inexpensive Xicon Carbon film stuff from Mouser. Never decrease the wattage rating of resistors.
Unless they have started to physically degrade, wirewound resistors don't need attention.
OEM film caps. can be replaced by 716P series Orange Drop parts.
Okay, I plan on buying Vishay/Sprague "Orance Drop" to fill in the dead PIO caps. Is this okay?
Vishay polypropylene capacitor
- keantoken
Vishay polypropylene capacitor
- keantoken
Well, I replaced those oil caps with Sprague Orange Drop 715P, and it's ALIIIIVE. Sounds kinda weird though. I think there is something wrong with the receiver, some stations blend together and others distort when not fully tuned. The treble is harsh, and I hope I can remedy this. I didn't replace the 20nF oils in the preamp because they didn't show short and I wanted to test the output stage, but I will get to them next, and if that doesn't clear things up then I'm stumped. There is hum present regardless of volume at the same level for both channels.
There was also some occasional crackling going on... One channel was totally dead, then it went POW and startled me, and happily sang along afterwards...
Something tells me I'm about to spend an inordinate amount of money on this...
- keantoken
There was also some occasional crackling going on... One channel was totally dead, then it went POW and startled me, and happily sang along afterwards...
Something tells me I'm about to spend an inordinate amount of money on this...
- keantoken
Helloooooooooo.
Well, it seems to sound better today than it did yesterday. A few things bother me:
1: When I hit the amp, the speaker crackles. I can also hear something "sing" inside even when the speakers are off, a lot like how you can hear the stylus on turntables.
2: One output tube glows brighter than the rest. Not sure what this means.
There seem to be very subtle clipping-type distortions affecting the bass and midrange.
It sounds yummy, like gummy lifesavers. Needs some work though, it has many cheap ceramics in the signal path it looks like, mixed with the occasional mica (?). Guitar really shines, but treble is like a dull razor.
- keantoken
Well, it seems to sound better today than it did yesterday. A few things bother me:
1: When I hit the amp, the speaker crackles. I can also hear something "sing" inside even when the speakers are off, a lot like how you can hear the stylus on turntables.
2: One output tube glows brighter than the rest. Not sure what this means.
There seem to be very subtle clipping-type distortions affecting the bass and midrange.
It sounds yummy, like gummy lifesavers. Needs some work though, it has many cheap ceramics in the signal path it looks like, mixed with the occasional mica (?). Guitar really shines, but treble is like a dull razor.
- keantoken
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