sx-1250 power amp SMOKED help

arranb

Arranb
Hello all and thanks for having me here on audiokarma! I've been doing some research and need some help on something. I just aquired an sx-1250 and am new to rebuilding electronics but have been repairing rc toys and anything else i can. So I replaced multiple caps I found bad in this unit and fired her up. She sounds great and everything was going good until I put the case on and starting hooking up components. For some reason the main fuse blew. After I replaced it i fired it up without a dimbulb and started seeing smoke and a glowing on the right side power board! Ya live, Ya learn I guess. Now I need to replace a bunch of transistors, caps and it looks like a ground strap but I'm not sure. I really need some help determining what the parts are and the strap. I used matts list but didn't see the parts I Burned up. The ground part had broken and I think It may have grounded out on the case causing my problem. Thanks a ton everyone. I can't wait to get my new love going again! Here are some pics I took
 

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that U shaped object is the bias diode .it should have 2 wires attached and tracks the heat from the heatsink ..you might get lucky and find a new one ..otherwise mark the fixer can repair it ..
you are looking at a rebuild and new output transistors to repair it .
 
Picture 2 is the source for all of your trouble. One leg of the temperature comp diode for the bias is broke off. That one little bugger has certainly caused a big headache. The clearly visible damaged components such as the resistors on the amp board are one thing but there will be further damage that is not clearly visible. You're basically looking at a rebuild of the amp board and output transistor replacements. The diode CAN be repaired but I DO have brand new STV-3H diodes if needed.
 
STV-3H-1.jpg
 
Overload, I would rather have new ones. As for the boards I want to rebuild both of them. Can you help me determine all the part numbers I need or direct me on how to find them? The other board did't get damaged but the resistors are hard to read. I'm not even sure if they have any numbers on them. Ya know how i screwed these up? Don't use an impact screwdriver on them.
A dumb mistake I'll learn from I'm sure.
 
Does anyone know if these would work in my unit? I noticed this listing has the power boards but they don't have the stv-3h diodes. Did some models come without them?

http://www.ebay.com/itm/PIONEER-SX1...pt=Vintage_Electronics_R2&hash=item3a997e49e5
The diodes will have been removed. Hang tight and have some patience. Parts lists and great assistance will soon be to follow. In the mean time, get yourself the service manual HERE. IMO, you are better off rebuilding your own boards rather than buying some parted out stuff that may or may not be in working order with the same old caps and such where I'd recommend a rebuild anyways. The auction you linked is being sold as a lot and will likely fetch a few bucks anyways but ya never know. I'm sure there's a few "watchers" :)

A location of where you are on the planet will be a big help so part suppliers and such can be recommended.
 
I agree

I agree and would like to rebuild the ones I have. I already replaced about 25 caps on various other boards. Eventually I'd like to do a complete restoration.
I purchased a new soldering station that I've needed for the last 25 years! I also got a desolder pump and can't understand how I lived without it! This unit is going to stay with me for a long time. Music will never die in my life.

I'm just west of Cleveland Ohio aka The rust belt.

Thanks again for the help.
 
DAMAGE ASSESSMENT!!!!

Better check the outputs with EW's six way test:

http://www.audiokarma.org/forums/showthread.php?t=43186

Before your next Mouser order.
Check every resistor (and diode) on that board! Some will need to be replaced! There are Part numbers for them. Other Senior members may have some suggestions so don't rush an order just yet!

MTF list of 08-20-13:
(Still good as of 10-01-14)

This is for one sx-1250 amp board:
sx-1250,power,amp,
sx-1250,awh-048l,C2,10,16,ceanl,,10,50,647-UKL1H100KDDANA
sx-1250,awh-048l,C5,220,16,ceanl,,220,16,647-UKL1C221KPDANA
sx-1250,awh-048l,C11,0.22,10,csza,,0.22,50,667-ECQ-V1H224JL
sx-1250,awh-048l,C15,470,80,ACH-038,,470,100,647-UPW2A471MHD
sx-1250,awh-048l,C16,470,80,ACH-038,,470,100,647-UPW2A471MHD
sx-1250,awh-048l,q1,2sa750,,,,,,512-KSA992FBU
sx-1250,awh-048l,q2,2sa750,,,,,,512-KSA992FBU
sx-1250,awh-048l,q3,2sc1439,,,,,,512-KSC3503dstu
sx-1250,awh-048l,q4,2sc1439,,,,,,512-KSC3503dstu
sx-1250,awh-048l,q5,2sa858,,,,,,512-KSA1381ESTU
sx-1250,awh-048l,q6,2sa858,,,,,,512-KSA1381ESTU
sx-1250,awh-048l,q7,2sc1904,,,,,,512-KSC3503dstu
sx-1250,awh-048l,q8,2sa899,,,,,,512-KSA1381ESTU
sx-1250,awh-048l,q9,2sd610,,,,,,512-KSC2073TU
sx-1250,awh-048l,q10,2sb630,,,,,,512-KSA940TU
sx-1250,awh-048l,q11,2sc869,,,,,,512-KSC1845FTA
sx-1250,awh-048l,vr1,500 ohms,offset,25 turns,,,,652-3296P-1-501LF
sx-1250,awh-048l,vr2,500 ohms,idle,1 turn,,,,652-3386H-1-501LF

Output #'s 863-MJ21193G (PNP) and 863-MJ21194G (NPN), four each
 
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Does anyone know if these would work in my unit? I noticed this listing has the power boards but they don't have the stv-3h diodes. Did some models come without them?

First that auction has ended. Second the diodes are ESSENTIAL, and it depends upon the seller whether or not they include the diode. Plus that board could be a ticking time bomb, and not a turn key solution.


Zebulon1's parts list is all the caps, all driver transistors but NOT the outputs, and the trimpots. We need to include the diodes and resistors. YOU arranb need to find ALL the damaged resistors, and discover and post their parts designation from the board layout diagram in the service manual (download it here, size ~ 64MB ), so we can include parts numbers for THEM too...

Testing each resistor that doesn't look burned is necessary, by using the ohmmeter setting on your DMM, and lifting one of the resistors leads out of the circuit pattern to eliminate interference.

We have extensive lists that I will provide, that only need to be cut and pasted into the mouser.com parts list importer (free registration required).

It will take me a bit of time to figure out which other resistors that, while they test good, should be preemptively replaced.

After we are completely finished, IF you get a new STV-3H diode, I ask that you send me the busted STV-3h diode rather than throwing it out. I fix them and if successful, hold on to them for the future. Don't actually charge for THEM, just the standard charge for the repair. In effect you are donating it to a future AK'er...

edit : the german seller has more stv-3h diodes!!! auction # 380416094305 This is your BEST bet. Good price too. Works out to about 10 bucks, shipped. I have bought from them - it is a smooth transaction. :D



You should move your thread (probably just start a new one with what you posted in vintage solid state) about your blown amp board over here, in a NEW thread - yes - I checked - and you haven't yet. After you start the thread I will make a copy of this post and it's information in the new thread.

THIS (in your own thread) is where you will get the most effective help. INCLUDING parts sources and parts numbers in a literally cut and paste format.

With all the blown resistors I see on the board, you are going to need plenty of help, mostly in parts numbers, which are ALREADY known and researched. You blew some of those 0.5 ohm 5 watt big white rectangular resistors, and that caused the flameout of the 4 resistors in a row you featured in one photo. Almost every medium to high powered transistor in that channel including the outputs IS fried, and those that survived, were racing to destruction, are damaged, and should be replaced to avoid a re-run of the fireworks when you turn it back on..

As to why - you probably broke the thermal bias diode wire - on both pictures the second wire's hole is unpopulated - and if the wire is busted off at the diode, you are either going to have to find another (we call them unobtanium) - or send it to me for grinding and flexible lead replacements (I have a "service" that repairs these parts FRAGILE wires).
 
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edit : the german seller has more stv-3h diodes!!! auction # 380416094305 This is your BEST bet. Good price too. Works out to about 10 bucks, shipped. I have bought from them - it is a smooth transaction. :D

I would be tempted to buy a few of those for my parts bin, but as of yet, I have never needed to replace one.

I know I just jinxed myself.:D
 
Markthefixer and everyone else thank you so much for your help! I've downloaded manuals but couldn't read them at all. Most weren't complete eaither. Now I see what q1 and so on mean. I ordered the sv1's from your link provided. I will test resistors and learn to make the list. I'm new at this so I may have a few more questions. I Hope I'll be able to help someone else in the future as you guys have helped me! What's your thoughts on just replacing everything on the board? even if I find some that are still good. For what it costs is it worth it to just do em all?
 
here's #1
checking r34 22 carbon film. How do I determine the new part number? I don't see the voltage and is the 22 for ohms? I'll get the hang of this with a little help. thanks
 
Free Hi Res Service manual:

http://www.kallhovde.com/pioneer/sx-1250smhires.pdf

Resistors have a component number starting with "R". Look at the Board layout image and find the location of the resistor on the board. Remember you are looking at it from behind (from the trace side) so resistor and other component locations will be opposite from the image.

Post the values you read in parentheses after the resistor component number. I have a list of Mouser part numbers for the 1250's amp board and will post those after you do your evaluation. I have been wanting MTF to look at them. This will be a good opportunity to have him check the selections out.

Pioneer SX-1250
Power Amplifier Assembly (AWH-048) Resistor List:

R1: 3.3K Carbon Film: (my reading)
R2: 220K Carbon Film:
R3: 82 Carbon Film:
R4: 47K Carbon Film:
R5: 47K Carbon Film:
R6: 82 Carbon Film:
R7: 62K Carbon Film:
R8: 200K Carbon Film:
R9: 100 Carbon Film:
R10: 100 Carbon Film:
R11: 16K Carbon Film:
R12: 16K Carbon Film:
R13: 1.5K Carbon Film:
R14: 62K Carbon Film:
R15: 220 Carbon Film:
R16: 220 Carbon Film:
R17: 1K Carbon Film:
R18: 47 Carbon Film:
R19: 47 Carbon Film:
R20: 620 Carbon Film:
R21: 100 Carbon Film:
R22: 100 Carbon Film:
R23: 10K Carbon Film:
R24: 100 Metal Oxide: 1W
R25: 100 Metal Oxide: 1W
R26: 1K Metal Oxide: 1W
R27: 1K Metal Oxide: 1W
R28: 0.5 Wire wound: 5W
R29: 0.5 Wire wound: 5W
R30: 22 Carbon Film:
R31: 22 Carbon Film:
R32: 0.5 Wire wound: 5W
R33: 0.5 Wire wound: 5W
R34: 22 Carbon Film:
R35: 22 Carbon Film:
R36: 4.7 Metal Film: 1W
R37: 4.7 Metal Film: 1W
R38: 10 Metal Oxide: 2W
R39: 10 Metal Oxide: 2W
R40: 1.2K Carbon Film:
R41: 1.2K Carbon Film:
R42: 13K Carbon Film:
R43: 13K Carbon Film:
 
If you have trouble reading the free manuals, one recourse is to purchase one. DO NOT get them off Ebay. 99.99999994% of them are 3rd and 4th genreation copies of the same ones. Jeez you'd think someone could be a bit original!

Anyway, one guy I know that has extremely legible, and COMPLETE Manuals is Rick Stout @ www.stereomanuals.com . He also does reproductions that are as good or better in most cases than the originals. I've bought manuals from him for going on 6 years now and haven't had one I couldn't read. The schematics are fantastic, FOLDOUT, and done on professional grade copiers, not some HP Ink Jet at home from a pdf.

These are what I would consider concours grade. MTF calls them his GOLD STANDARD manuals. But they ain't exactly cheap. But if you plan on keeping it and want a manual that will stand up to repeated use, go for it.

I scan mine and put them away in a 3 ring folder. Then use the scans on my computer. This way I have manuals that are worth the effort IF/WHEN I ever sell any of my gear.

He has 2 versions....128page OEM version for $36.00 and 78 page non OEM version for $22.00.

NO AFFILIATION WITH STOUT and ASSOCIATES. VERY SATISFIED Customer.
 
here's #1
checking r34 22 carbon film. How do I determine the new part number? I don't see the voltage and is the 22 for ohms? I'll get the hang of this with a little help. thanks

You just TOLD me the Pioneer part number from the board (that's ALL I need!!)

R34

Just this ^^^ for all the bad resistors....

I HAVE most of the replacement numbers already, I just have to look them up...

as for replacing ALL the parts, the sub 0.1uf caps and most of the 1500 ohm and higher resistors should be just fine.

But, Zeb, you forced my hand (leaving me little time to double check it for completion) with the resistor list ( that's ok :D ):

R2 220K 1/4W RD1/4PS 224JNL 660-CFS1/4CT52R224J
R4 47K 1/4W RD1/4PS 473JNL 660-CFS1/4CT52R473G
R5 47K 1/4W RD1/4PS 473JNL 660-CFS1/4CT52R473G
R7 62K 1/4W RD1/4PS 623JNL 660-CFS1/4CT52R623G
R8 200K 1/4W RD1/4PS 204JNL 660-CFS1/4CT52R204J
R14 62K 1/4W RD1/4PS 623JNL 660-CFS1/4CT52R623G
R1 3.3K 1/4W RD1/4PS 332J 660-CFS1/4CT52R332G
R3 82 1/4W RD1/4PS 820J 660-CFS1/4CT26A820G
R6 82 1/4W RD1/4PS 820J 660-CFS1/4CT26A820G
R9 100 1/4W RD1/4PS 101J 660-CFS1/4CT52R101G
R10 100 1/4W RD1/4PS 101J 660-CFS1/4CT52R101G
R11 16K 1/4W RD1/4PS 163J 660-CFS1/4CT52R163G
R12 16K 1/4W RD1/4PS 163J 660-CFS1/4CT52R163G
R13 1.5K 1/4W RD1/4PS 152J 660-CFS1/4CT52R152G
R18 47 1/4W RD1/4PS 470J 660-CFS1/4CT52R470G
R19 47 1/4W RD1/4PS 470J 660-CFS1/4CT52R470G
R23 10K 1/4W RD1/4PS 103J 660-CFS1/4LT52R103J
R42 13K 1/4W RD1/4PS 133J 660-CFS1/4CT52R133G
R43 13K 1/4W RD1/4PS 133J 660-CFS1/4CT52R133G
R15 220 1/4W RD1/4PSF 221J 660-CF1/4CT52R221G
R16 220 1/4W RD1/4PSF 221J 660-CF1/4CT52R221G
R17 1K 1/4W RD1/4PSF 102J 660-CFS1/4CT52R102G
R20 620 1/4W RD1/4PSF 621J 660-CFS1/4CT52R621J
R21 100 1/4W RD1/4PSF 101J 660-CFS1/4CT52R101G
R22 100 1/4W RD1/4PSF 101J 660-CFS1/4CT52R101G
R30 22 1/4W RD1/4PSF 220J 660-CFPS1/4CT52R220G
R31 22 1/4W RD1/4PSF 220J 660-CFPS1/4CT52R220G
R34 22 1/4W RD1/4PSF 220J 660-CFPS1/4CT52R220G
R35 22 1/4W RD1/4PSF 220J 660-CFPS1/4CT52R220G
R40 1.2K 1/4W RD1/4PSF 122J 660-CFS1/4CT52R122G
R41 1.2K 1/4W RD1/4PSF 122J 660-CFS1/4CT52R122G
R36 4.7 1W RN1H 4R7K 594-5073NW4R700J
R37 4.7 1W RN1H 4R7K 594-5073NW4R700J
R24 100 1W RS1PF 101J 279-ROX1G100R
R25 100 1W RS1PF 101J 279-ROX1G100R
R26 1K 1W RS1PF 102J 660-MOS1CT52R102J
R27 1K 1W RS1PF 102J 660-MOS1CT52R102J
R38 10 2W RS2P 100J 660-MOS2CT52R100J
R39 10 2W RS2P 100J 660-MOS2CT52R100J
R28 0.5 5W RT5B 0R5K 71-CP5-J-0.47
R29 0.5 5W RT5B 0R5K 71-CP5-J-0.47
R32 0.5 5W RT5B 0R5K 71-CP5-J-0.47
R33 0.5 5W RT5B 0R5K 71-CP5-J-0.47


f 1%, g 2%, J 5%, K 10% , none 20%
carbon film = RD NL = low noise
metal oxide film = RS (no NL on these)
metal film = RN (no NL on these)
cement cased wire wound = RT


I did NOT provide a cut and paste resistor list, because not all of the resistors will be replaced.


edit - checked, in stock, valid numbers...
 
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Zeb, hi-red manual download link already provided and HIDDEN in deference to Grumpy....
Bad blood you know...

Zebulon1's parts list is all the caps, all driver transistors but NOT the outputs, and the trimpots. We need to include the diodes and resistors. YOU arranb need to find ALL the damaged resistors, and discover and post their parts designation from the board layout diagram in the service manual (download it here, size ~ 64MB ), so we can include parts numbers for THEM too...
 
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