wantmoretoys
New Member
I was wondering if anyone has a list of what to replace in order to recap a pioneer sx-434. I dearly love this little receiver, and would like to make it the best sound it can be. Any help is appreciated.
Pioneer sx-434 would like to recap
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xlbee: got a link????? Nothing in Digital Doc's on the 434. the AKDatabase is incomplete. I'll upload a copy of the manual to Jailtime for inclusion.
Wantmoretoys: The FULL Service Manual, with Parts lists, and schematics is @ www.hifiengine.com. Free registration.
Basically you will replace all Electrolytics on the AF BOARD(See manual). The Parts list will give you sizes and voltages. Also download the PIONEER Tuning Fork Articles for their explanations of the coding of Capacitors as it applies to the manuals. (see attached).
Study the schematic, and the ACTUAL boards, and compare the parts on the board with what is listed. If there is a discrepancy, go with what is on the board.
When you dis assemble, try and keep the main output transistor heatsink attached to the main board. It supports the outputs. Between each pair of outputs are your bias DIODES. STV3H. (D1&D2). These are extremely fragile. If you break them, they are unobtainable. Save the remains and contact Mark the Fixer. He can probably repair them. If the outputs need to be replaced they can be replaced with the heatsink in place.
Tuner: If the tuner is working leave alone, other than the few caps that Mark the Fixer will allude to.
Nichicon UKL and UPW caps are the commonly recommended caps . The orange caps on the board are low noise. Those get replaced with UKL's. The rest can be UPW's. Keep it simple with regard to the parts and gather a baseline sound. Then you can substitute fancy stuff, although IMO the 434 really doesn't need or benefit from them.
Mouser has most every part you need to overhaul the 434. A full recap should run about $25-30.00, plus shipping if you get exact amounts.
If Q-10-11-12-13 are 2sa725's replace them with KSA992. the 725's get noisy and it's best to replace them. Watch the pin orientation. Locate the datasheets and compare the pinouts.
Larry
Wantmoretoys: The FULL Service Manual, with Parts lists, and schematics is @ www.hifiengine.com. Free registration.
Basically you will replace all Electrolytics on the AF BOARD(See manual). The Parts list will give you sizes and voltages. Also download the PIONEER Tuning Fork Articles for their explanations of the coding of Capacitors as it applies to the manuals. (see attached).
Study the schematic, and the ACTUAL boards, and compare the parts on the board with what is listed. If there is a discrepancy, go with what is on the board.
When you dis assemble, try and keep the main output transistor heatsink attached to the main board. It supports the outputs. Between each pair of outputs are your bias DIODES. STV3H. (D1&D2). These are extremely fragile. If you break them, they are unobtainable. Save the remains and contact Mark the Fixer. He can probably repair them. If the outputs need to be replaced they can be replaced with the heatsink in place.
Tuner: If the tuner is working leave alone, other than the few caps that Mark the Fixer will allude to.
Nichicon UKL and UPW caps are the commonly recommended caps . The orange caps on the board are low noise. Those get replaced with UKL's. The rest can be UPW's. Keep it simple with regard to the parts and gather a baseline sound. Then you can substitute fancy stuff, although IMO the 434 really doesn't need or benefit from them.
Mouser has most every part you need to overhaul the 434. A full recap should run about $25-30.00, plus shipping if you get exact amounts.
If Q-10-11-12-13 are 2sa725's replace them with KSA992. the 725's get noisy and it's best to replace them. Watch the pin orientation. Locate the datasheets and compare the pinouts.
Larry
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Recap lists were recently added into the AK database and the one that the OP is requesting is there.
You will find it on this page:
http://akdatabase.com/AKview/thumbnails.php?album=88
And if you are interested in having more "Tuning Fork" guides, they are here:
http://www.audiokarma.org/forums/showthread.php?t=249745&highlight=tuning+fork
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Ok. MEA CULPA! I forgot about those. However I will add that the list should be vetted by MTF before ordering.
Thanks
Larry
Thanks
Larry
cnh2
Super Member
With all the vintage Pioneer gear on this site. Pioneer ought to think about getting a few of the old guys out of retirement sending them to L.A., Chicago and N.Y. and opening up shops to refurb all these units.
Now I know, there are a lot of DIYers here. But the percentages are probably "low" and most people can't handle the tough jobs.
Considering what prices Pioneer silver faces draw on the used market. There has to be some "money" in all this.
My two cents. Or probably more like 100-500 dollars in repairs depending on your Pioneer. lol
I have an SX-838 in the shop. Been there for three months (slow turnover with my guy). Problems in the pre-amp stage for those of you Electronic Scientists. Though I guess I own enough "vintage" receivers, now, to try "butchering" a few without losing much. And I do mean "butchering", I've used a soldering gun perhaps once or twice. Don't like the darn things!
cnh2
Now I know, there are a lot of DIYers here. But the percentages are probably "low" and most people can't handle the tough jobs.
Considering what prices Pioneer silver faces draw on the used market. There has to be some "money" in all this.
My two cents. Or probably more like 100-500 dollars in repairs depending on your Pioneer. lol
I have an SX-838 in the shop. Been there for three months (slow turnover with my guy). Problems in the pre-amp stage for those of you Electronic Scientists. Though I guess I own enough "vintage" receivers, now, to try "butchering" a few without losing much. And I do mean "butchering", I've used a soldering gun perhaps once or twice. Don't like the darn things!
cnh2
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The amount of time it takes to do it right, and pay for the skill, would make it cost prohibitive. The guys doing it now ain't in it for the money. I would love to clear minimum wage on these.
and to think that most of the labor could have been avoided by judicious component materials choices - stuff I see corroded in Pioneer equipment that in "commercial" equipment is just as old and in pristine shape. switch contact material and jack contact material that is not corroded black - it is still shiny.
gold contacts are appropriate for preamp signals - current density is low enough, and actuation life counts are also usually in the range.
varox84
Active Member
Hi guys, Im recapping a sx 434 as practice (this is my first time) to take on better amps in the future and im reviving this thread to ask the following: how can I know which wire is positive and which one is negative on the SX 434 filter caps? there is no aparent indication of this but maybe I just fail to see how to tell.
I would appreciate your help. Thanks!
Varox
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I would appreciate your help. Thanks!
Varox
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bktheking
Gitter Done!
Your question is two fold- Black mark on the cap post in the pic indicates negative (of the cap itself) so in your case the orange wire- however in this arrangement is it to provide a negative voltage to the rail, the other cap should be opposite to the one in the pic. The black wire is essentially the ground but it is wired in this arrangement for a purpose- to supply - and + to the rail.
So when replacing these caps, just make sure you wire the appropriate wire to the proper lead of the cap- 1 cap will be orange to the negative, black to positive, the other cap will be red wire to the positive and black to the negative.
So when replacing these caps, just make sure you wire the appropriate wire to the proper lead of the cap- 1 cap will be orange to the negative, black to positive, the other cap will be red wire to the positive and black to the negative.
varox84
Active Member
So, my first recap experience has been very instructive so far. Ive learnt for example that I should finish one board and try whether it goes well. This of course I did not do. So far I have recapped the power supply, the amp board, changed 4 transistor on the amp board and the two filter caps.
I tested the unit and I get no sound but a hum through my speakers. I get this for every function, so aux, phono and tuner give me this hum which only stops when I set it on the speakers off position.
From the parts I tampered with, where should I start troubleshooting? I checked the position of all the caps and Im positive I soldered them correctly and in the correct position. Should I solder the old transistors back and check? or the filter caps?
I have a multimeter but wouldnt know how to use it to find the problem. As usual all sugestions are welcome.
Thanks a lot
I tested the unit and I get no sound but a hum through my speakers. I get this for every function, so aux, phono and tuner give me this hum which only stops when I set it on the speakers off position.
From the parts I tampered with, where should I start troubleshooting? I checked the position of all the caps and Im positive I soldered them correctly and in the correct position. Should I solder the old transistors back and check? or the filter caps?
I have a multimeter but wouldnt know how to use it to find the problem. As usual all sugestions are welcome.
Thanks a lot
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Bill S
Thread Killer
Speaking from experience, I'd first check the transistor data sheets for the ones you replaced and note/compare the lead orientation (ECB, EBC, etc). Then, re-check your work on those parts per the board diagram. Check capacitor installs as well - make sure polarity is OK on those.
varox84
Active Member
Thanks for your responses, Ive already checked the data sheets of the replacement transistors and compared with the service manual. Both transistors have the same orientation so I just soldered the new ones exactly the same as the old ones.
These replacements I used as per the replacement list available on the ak database:
AWK-034: Q10: 2SA725: KSA992FBU
AWK-034: Q11: 2SA725: KSA992FBU
AWK-034: Q12: 2SA725: KSA992FBU
AWK-034: Q13: 2SA725: KSA992FBU
The new filter caps are significantly smaller than the originals which were wire wrapped. What I did is not what you would call tidy. So thats one thing that might have gone wrong. Transistors is my second guess. And I am pretty comfortable with how I worked the caps in.
These replacements I used as per the replacement list available on the ak database:
AWK-034: Q10: 2SA725: KSA992FBU
AWK-034: Q11: 2SA725: KSA992FBU
AWK-034: Q12: 2SA725: KSA992FBU
AWK-034: Q13: 2SA725: KSA992FBU
The new filter caps are significantly smaller than the originals which were wire wrapped. What I did is not what you would call tidy. So thats one thing that might have gone wrong. Transistors is my second guess. And I am pretty comfortable with how I worked the caps in.
