Another SX-850 cuts in/out

I used this for a few years, it started cutting out then back in on the left channel. Stored it and used my SX-650 for 18 months, now trying to get the SX-850 fixed up. When I turned it on after storing it, it took about 10 minutes to start and then it cycled in and out of protection about every 10 seconds. After about 30 minutes, it stayed on 2-3 minutes at a time, but then went into protection for about 10 seconds before coming back on. On FM, when it is in protection, the FM signal is still strong. So, after reading a lot and getting a manual, I cleaned the switches and controls with De-Oxit, but it still cycles. I have sound in both channels when using FM or Aux, but with Phono, I only have both channels when in MONO. When in Phono and stereo, I only have the right channel. If I let it sit for a weekend, it takes a long time to start (Several minutes). If I turn it on and let it run awhile, then turn it off and turn it back on a few minutes later, it comes on normally (about 4 seconds) then starts cycling in and out of protection

Readings on the power board AWR-101C are:
pins 6,7 +51.0 VDC
pins 8,9,10 +35.9 VDC
pin 11 +27.2 VDC
pin 13 -12.9 VDC
pin 14 -49.8 VDC
pin 15 -17.9 VDCBoard

Readings on the Protection Board:
pin 1 -15 to +34 MV
pin 3 -7 to +25 MV

pin 2 -12.9 VDC
pins 10,11 +35.9 VDC
pin 9 +8.8 VDC
pin 12 +7.2 VAC

These readings look OK based on everything I've read in various threads. Now, I need some guidance on what steps to take next. I know enough to follow basic instructions, but am not an electronics wizard. I appreciate any suggestions. Thank you.

You have two separate problems.

First you need to rebuild the protection board awm-062. I am doing this off the top of my head: replace q1 and q2, c1 and c2 (0.22uf), then c3 and c4 probably 330 uf and c6 100uf? and c5 4.7uf?.
then replace Q6 and Q7.
leave q3,q4,q5 alone...
add the diode

edit:
http://www.audiokarma.org/forums/showthread.php?p=4403583

edit2: fark it, all the old lists are confusing, here's the best new list.

awm062 board parts

Q1-Q2 2SC869-C
512-KSC2310YBU TO-92 ecb 150v .05a .8w 100mhz 40-240hfe $0.11 ea

Q3, Q4 2SC945-Q
512-KSD1616AGBU to-92 ecb 60v 1a 0.75w 160mhz 135-400hfe $0.09

Q5 2SA733-Q
512-KSB1116AGBU to-92 ecb 60v 1a 0.75w 160mhz 135-400hfe $0.09 (Y,G=200/400)

Q6 2SC945-Q
512-KSD1616AGBU to-92 ecb 60v 1a 0.75w 160mhz 135-400hfe $0.09

Q7 2SC1384-R
512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40

C1, C2 0.22uf
598-DSF050J224 CDE Metallized Polypropylene Film Capacitors 0.22uF 50V 5% $0.14

C3, C4 330uf 6v 647-UPW1A331MPD 330uf 10v $0.20 ea

C5 4.7uf 25v 647-UPW1H4R7MDD 4.7uf 50v $0.12

C6 100uf 16v 647-UPW1H101MPD 100uf 50v $0.22

don't forget to add the 1n4004 flyback diode to pins 9 (anode) and 10(cathode).

512-1n4004 conventional rectifier 1a 400v $0.06 ea

Click to expand...

the phono (awf-011) is also a rebuild (assuming clean switches and good input from the TT).


edit fark it, all the old lists are confusing, here's the best new list.

The phono amp is labeled awf-011 on the board, on the underside of the unit, taking it off the nylon supports should give you enough slack to replace the components listed below - which will result in the best possible performance.

here's the updated mouser.com parts numbers:
Q1, Q2 2sa725 to-92 bce
512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

Q3, Q4, Q5, Q6 2sc1313 to-92 bce
512-KSC1845EBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

C1, C2 1uf 25v CSSA
647-UKL1H010KDDANA 1uf 50v low leakage $0.18 ea
OR
667-ECQ-V1H105JL 1uf 50v stacked film metallized polyester - preferred, best possible sound - $0.68 ea

C7, C8 330uf 6v CEA
647-UPW1A331MPD 330uf 10v standard upw

C11, C12 3.3 25v CEANL
647-UKL1H3R3KDDANA 3.3uf 50v low leakage ****xx BACK IN stock xx******
use
647-UKL1H4R7KDDANA 4.7uf 50v low leakage ** no detrimental effects upon substitution **


C17 100uf 35v CEA
647-UPW1H101MPD 100uf 50v standard upw

C18 220uf 25v CEA
647-UPW1V221MPD 220uf 35v standard upw

here's day67's thread:
http://www.audiokarma.org/forums/sho...d.php?t=176402
study it, it has LOTS of valuable information.

Click to expand...

The parts lists are posted many places on here, and somebody should be able to help you by linking to them and the repair threads.

The boards are easily accessible, get the service manual for both the 850 and it's brother the 950, they use those same boards (awm-062 & awf-011).

Thanks for detailed info

Thanks for your very detailed and informative info. Looks like I have quite a bit of work "fun" to do starting with getting the components. I have read many of the posts here and have gathered quite a bit of the info needed. I have not done much work with solid state components, so may have questions after I get the components and start soldering. Thanks again!

For info, I could not get the link to day67's thread to work, but found the info at this link. Nor sure how to hyperlink it. Also am sure TT works both chanels as tested it with another amp. On SX850 neither phono1 or phono2 worked on left channel in stereo mode. Thanks again for info, will get a SX-950 manual also and study more before I go too fast.

http://www.audiokarma.org/forums/showthread.php?t=176402&highlight=day67

Quick Question about C1,C2 on Protection Board

I received the parts from Mouser today and started working on the Protection Board. I removed C1 which is a .22mf Electrolytic cap. When I went to install the new cap, I noticed it is a poly film cap. Is the 598-DSF050J224 CDE the correct replacement since there is no (+) or (-)? Thank You, I am taking this one step at a time and appreciate your help.

spadad128 said:

I received the parts from Mouser today and started working on the Protection Board. I removed C1 which is a .22mf Electrolytic cap. When I went to install the new cap, I noticed it is a poly film cap. Is the 598-DSF050J224 CDE the correct replacement since there is no (+) or (-)? Thank You, I am taking this one step at a time and appreciate your help.

Click to expand...

That is correct, the replacement cap is not sensitive to polarity, and can be installed either way.

Thanks, Mark, for the immediate response. I will turn my soldering iron back on! Actually, this is the first board I've tried to repair so it will take me awhile. I'm trying to be extra careful and double check everything as I go.

Beautiful! Finished work on Protection Board and brought her up slowly on a variac. Relay kicked in at about 80VAC and FM started playing clearly without cutting out. I'm delighted with results. Now will get to work on preamp board. Mark's info gave me confidence I could do this and made it really easy to order the parts. The info on this forum is invaluable.

Success...I think!

Today I finished with the caps and transistors on the preamp board. Turned it on and Phono1 and Phono2 sounded very good and both channels worked. The only issue I had was after it was on about 10 seconds, there were a few rather loud pops in the left speaker. I turned it off and then turned it back on and it popped 2 times then the popping stopped completely. I let it run for about 2 hours with no additional problem. Then I turned it off and let it set for 3 hours. When I turned it back on, it sounded fine and I havn't been able to get it to act up again. I rechecked all the voltages and they were the same as my first post, except the Protection Board pins 1 and 3 changed to a steady +9 mv on both channels. Are the pops anything I should worry about, and if so, what should I look for? Or, should I button it up for now and see if anything else develops? Thanks for guiding me through this, I really appreciate your help.

Oops! Spoke too soon. Turned it on tonight and again have pops in left speaker. Quite a few this time so turned it off to do more research.

Those pops aren't a good thing.... I'd leave it alone until Mark has a chance to chime in.

ok, so far you have done the protection board and the phono preamp? correct?

do the pops occur if the pre-out / amp-in jumpers are pulled?

if they go away it's the 2sa725's in the flat amp. (most likely)

If they continue, it's the 2sa726's in the power amp. (less likely)

either one uses ksa992's, get ksc1845's as well, they are useful in various places...

512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea
512-KSC1845EBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

OK, ready for more fun

Yes, I have rebuilt the protection board and phono preamp boards using all the parts you recommended.

the unit pops with the pre-out / amp-in jumpers in or out. Either way, it pops.

If I start it by using a variac at 90V, it plays without pops.

So, I think I need to tackle the power amp Q1,Q2,Q3,Q4 but will also order enough for the flat amp board just in case. Will also order some KSC-1845's as you suggested.

Taking a quick look, it looks like I can get to the power amp board by following the instructions in the manual to take out the screws for the heat sink and shield plate, then tip the heat sink forward and remove the shield. If I do that, can I drop the board low enough to get to the 2sa726's without removing any of the wires?

Also, before I place the order, should I also get caps for the amp and flat boards while they are out? I can do the research to find threads which list the parts, just looking for your recommendation.

Thank You!

be careful of the thermal diodes connected to the amp board but mounted on the heat sink - the leads love to break - unobtanium - but i do fixe$... unscrew them and tuck them away safely without bending the leads within 1/4 inch of the body of the diode.

never disconnect wire wraps, the harnesses can be freed up enough to give more board clearance.

Stand it on it's side, I use plywood strips as feet secured through the bonnet mounting screw holes using the bonnet screws.

since the board is exposed and you are ordering parts, yes. caps... post the list you find... here's the latest
http://www.audiokarma.org/forums/showpost.php?p=4183930&postcount=10
the WHOLE list, from that post:
http://www.audiokarma.org/forums/attachment.php?attachmentid=242895&d=1291238079

before pulling anything be sure about knowing capacitor polarity and correct insertion, as well as the only correct way of six ways any transistor's leads are installed FOR THAT TRANSISTOR.

we have lots to talk about before you pull the trigger on the order or twist any more screws.

Thank you MAXZ28 and markthefixer.

I want to do some more research through some of the old threads. I have seen several of MTF's thermal diode posts including epoxy repair and one on fragile wires, as well as how to identify various transistor configurations. But, I need to review them all again and print the ones I do not already have printed. (I believe you want to be certain I know about ecb, bce etc, and I have read several links that were very helpful when I rebuilt the protection and phono preamp boards. But, if there is more, let me know. When I get parts from Mouser, I print out the specification sheets and that helps, but I am a beginner on transistors).

I understand capacitor polarity (or think I do), but will be glad for info on correct insertion. I will not turn any screws until after I get back to you with a parts list and/or other questions. I was hoping to avoid the amp board, but with your help think I can work my way through it. Thanks again, Mark.

Taking me longer than planned - work got in the way!

Recap of what has been done so far: Replaced all transistors and electrolytic capacitors in Protection Circuit board (AWM-062) and the Equilizer Amp board (AWF-011). Added 1N4004 flyback diode. Unit Pops in left speaker with the pre-out / amp-in jumpers either in or out. Plan to replace all electrolytic caps and transistors in Power Amp board (AWH-059) to fix pops. Also plan to order caps and 2sa725's for Flat Amp board (AWG-038) but will wait to install them until after Power Amp board rebuilt to make sure that stops the pops.

Power Amp Board Parts
awh-059 c1 647-UKL1H2R2KDDANA
awh-059 c2 647-UKL1H2R2KDDANA
awh-059 c3 647-UKL1H010KDDANA
awh-059 c4 647-UKL1H010KDDANA
awh-059 c5 647-upw1v330mdd
awh-059 c6 647-upw1v330mdd
awh-059 c11 647-UPW1E331MPD6
awh-059 c12 647-UPW1E331MPD6


awh-059 Q1 512-KSA992FBU
awh-059 Q2 512-KSA992FBU
awh-059 Q3 512-KSA992FBU
awh-059 Q4 512-KSA992FBU
awh-059 Q5 512-KSA1142YSTU
awh-059 Q6 512-KSA1142YSTU
awh-059 Q7 512-KSC2682YSTU
awh-059 Q8 512-KSC2682YSTU
awh-059 Q9 512-KSC2073TU
awh-059 Q10 512-KSC2073TU
awh-059 Q11 512-KSA940
awh-059 Q12 512-KSA940

Flat Amp Board Parts

awg-038 c1 647-UKL1H2R2KDDANA
awg-038 c2 647-UKL1H2R2KDDANA
awg-038 c5 647-UKL1E4R7KDDANA
awg-038 c6 647-UKL1E4R7KDDANA
awg-038 c13 647-UPW1V221MPD6
awg-038 c14 647-UPW1V221MPD6
awg-038 c17 647-UKL1H100KDDANA
awg-038 c18 647-UKL1H100KDDANA
awg-038 c23 647-UKL1E4R7KDDANA
awg-038 c24 647-UKL1E4R7KDDANA
awg-038 c25 647-UKL1E101KPDANA
awg-038 c26 647-UKL1E101KPDANA
awg-038 c27 647-UPW1H101MPD


awg-038 Q5 512-KSA992FBU
awg-038 Q6 512-KSA992FBU

BOM
647-UKL1H2R2KDDANA 4
647-UKL1E4R7KDDANA 4
647-UPW1V221MPD6 2
647-UKL1H100KDDANA 2
647-UKL1E101KPDANA 2
647-UPW1H101MPD 1
512-KSA992FBU 2
647-UKL1H010KDDANA 2
647-upw1v330mdd 2
647-UPW1E331MPD6 2
512-KSA992FBU 4
512-KSA1142YSTU 4
512-KSC2073TU 2
512-KSA940 2
512-KSC1845EBU 6

647-UKL1H010KDDANA (1uf 50v) and 647-UPW1E331MPD6 (330uf 25V) not in stock at Mouser, but may be able to find close subs, I haven't checked yet. Also 512-KSA1142YSTU's are no longer available. All of these are for the Power Amp board. The 6 KSC1845EBU's are from MTF's suggestion, but I'm not sure what they are for or if 6 is a reasonable quantity.

I have the SX-850 on end mounted to a plywood base for stability but have not turned any more screws yet. I've also read the posts MTF suggested and am familiar with them. I know this board will be more challenging than the other two boards, so will go step-by-step as I receive further advice.

Couple of questions:
1. do I really need to replace all the transistors in the Power Amp board or is this overkill?
2. do I need to discharge any capacitors before I start work?
3. are there items I should delete or additional items I should purchase when I place the order with Mouser?

Thanks very much for your help on this project.

spadad128 said:

647-UKL1H010KDDANA (1uf 50v) and 647-UPW1E331MPD6 (330uf 25V) not in stock at Mouser, but may be able to find close subs, I haven't checked yet. Also 512-KSA1142YSTU's are no longer available. All of these are for the Power Amp board. The 6 KSC1845EBU's are from MTF's suggestion, but I'm not sure what they are for or if 6 is a reasonable quantity.

I have the SX-850 on end mounted to a plywood base for stability but have not turned any more screws yet. I've also read the posts MTF suggested and am familiar with them. I know this board will be more challenging than the other two boards, so will go step-by-step as I receive further advice.

Couple of questions:
1. do I really need to replace all the transistors in the Power Amp board or is this overkill?
2. do I need to discharge any capacitors before I start work?
3. are there items I should delete or additional items I should purchase when I place the order with Mouser?

Thanks very much for your help on this project.

Click to expand...

647-UKL2A0R1KDD there were others but I am suspicious about cut leads that are too short etc due to the low price.

647-UPW1E331MPD different dimensions, should be no problem...

512-KSA1142OSTU

the 1845's would be for 4x 2sc1313 in the phono amp, 2x 2sc1885 in the flat amp, 2x 2sc1312 in the tone amp. The 992's are 30 years better quieter technology, and their mirror twin is the c1845... the whole signal chain will be improved - and without changing the "sound"... we have done it many many times.

1. the entire list is included for those repairing blowups - you just need to do the 726's - you COULD do them all with no ill effects and the cost is minimal, but.... then you are remounting/regreasing to-220 drivers (a940,c2073) and such... messy... and would need to spend 5 to 10 bucks for (NON-CONDUCTIVE!!) thermal compound - which, as I come to think about it, may be a good idea, as you may want later to "freshen up" the output transistor mountings IF you are going to run it hard...

2. a 10 ohm resistor with clip leads for cap discharge, but if it's been off for say 1/2 an hour - don't worry.

3. phono amp, flat amp, tone amp caps? You're in there, save on shipping costs...

Thanks again - exactly what I needed

OK. I think I've got the picture and will increase the KSC1845's to 8 instead of 6. I'll also order the caps for the tone, flat amp, and power supply boards while I'm at it. I've already replaced caps in the phono preamp board. Good suggestion, may as well do it right for a couple of bucks worth of caps.

For the amp board, I'll just replace the 726's. That seems reasonable to me. I will also get some non-conductive thermal compound, although I don't run it hard for fear of shattering glass. I'll have the grease when/if I need it for this or something else. The other part I'm going to order is Q5, Q6 and Q7 for the Power Supply board as this seems to be a weak link based on all the threads I have read.

The spreadsheet you attached with all the capacitor information was perfect and saved me a bunch of work. Thanks, Mark, for all you do to help us out.

Normally at this point I would post a list of all the parts you mentioned. Can't right away, but if you post the list before closing the order I'll check the list, and if you don't know what transistors replace what, post the aaa-999 board number, part number (c9, q3 etc) and part number or values to make it quicker and I'll check/upgrade the list to eliminate any problems I spot.

List of Parts

I've been working on a revised list and will have it finished soon. I will post a new list tomorrow for your review before I place the order with Mouser. I certainly appreciate your checks, especially for the transistors.