SX-626 TURN ON THUMP Wrong Cap and other Questions

[moondogtn]

I picked this up a while back and really liked the sound of it. This is the 1973 version from what I can tell. I had planned on doing a complete recap later until I noticed a bit of crackling on right channel after it warms up. So, I figure I would go ahead and take care of all in one swoop. I ordered parts and started looking at tuner board.


SHOULD BE AWE-011 C61 0.47 50 CEA 0.47 50 667-ECQ-V1H474JLW
is actually 5 ufd 50V speco brand.

SHOULD BE AWE-011 C66 2.2 16 CSSA 2.2 50 647-UKL1H2R2MDDANA
is actually 2.2 ufd 35 volts orange color brand unknown.

I guess my question is...should i replace these using values on documentation? I purchased from original owner. He never said anything about repairs but I never asked him either.

Thanks for any info. BTW, I can post pics if anyone is interested.
Bill

 

[slimecity]

You are generally best to go off the values actually mounted on the board unless they are blatantly wrong due to some after-factory work.

Are you sure the first cap isn't ".5" mfd? If it is this value, then it will be fine. If it is actually "5" mfd and it looks like its been put in later, I would agree to replace it with proper value. "Speco" sounds suspect to me....

The second value may also be fine, despite the doc's stating this cap should be 50V, a 35V cap may have instead been deemed sufficient depending on factors including the actual voltage present at that point in the circuit (and also obviously, cost). The fact that the second cap is orange suggests to me it may be a factory cap, that's what a lot of JP equipment had from this vintage for signal-path caps.

If you are planning on doing a general recap then I would include these but otherwise wouldn't worry too much if they are bulging, haven't shorted etc.

The crackling you are getting is more likely related to either dirty contacts/pots etc or a failing small signal transistor than caps BTW.

 

[moondogtn]

sx-626 transistors




Please post what transistors you used in that channel.

for posterity, I worked up a list:
sx-626 power amp

q1,q2 2sc732 input 50v 0.15a 0.4w 200-700hfe 150mhz
512-KSC1845FTA (ln)to-92 ecb 120v .05a .5w 100mhz 300-600hfe $0.05 ea

q3,q4 2sc497 vas 100v 0.8a 0.6w 40-240 50mhz
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

q5,q6 2sc497 driver npn 100v 0.8a 0.6w 40-240 50mhz
512-KSC2690AYS to-126 ecb 120/a160 1.2a 1.2w/20w 175mhz 35-320hfe $0.40

q7,q8 2sa497 driver pnp 100v 0.8a 0.6w 40-240 50mhz
512-KSA1220AYS to-126 ecb 120/a160 1.2a 1.2w/20w 175mhz 35-320hfe $0.39 (R=60-120, O=100/200, Y=160/320)

q9,q10,q11,q12 2sc793 output npn 100v 7a 60w 30-200hfe 30-200 9mhz
863-MJ21194G npn to-3 250v 16/30A 250W 8-75hfe 4mhz $5.87 / digikey $5.88

q13 2sc893 anti-thump delay 150v 0.05a 0.6w 40-240hfe 40-120mhz
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

I double checked. It's a 5. There is also a 2.7Kohm resistor on bottom of board running parallel to R40 which is 2.2kohm which measures what it should in circuit, about 1.2kohms.

I should probably just skip the tuner board but since I was here decided to do it first as it was on top.

I have cleaned and lubed controls. I assumed it was transistors and not pots. I planned to replace the problematic transistors.

Transistor subs that I had were from markthefixer..see above as I was working from my phone.

Also, plan on swapping pots to bourns.

Let me know thoughts before I proceed.

Bill

 

[moondogtn]

Any other thoughts on this?

I may just install what manual calls for to see what it changes. If nothing, I will leave them.

 

[slimecity]

Looks fine. Do things in stages and power up in between each only using a DBT. I'd recommend start with caps, then trimpots then transistors.

 

[markthefixer]

I picked this up a while back and really liked the sound of it. This is the 1973 version from what I can tell. I had planned on doing a complete recap later until I noticed a bit of crackling on right channel after it warms up. So, I figure I would go ahead and take care of all in one swoop. I ordered parts and started looking at tuner board.


SHOULD BE AWE-011 C61 0.47 50 CEA 0.47 50 667-ECQ-V1H474JLW
is actually 5 ufd 50V speco brand.

SHOULD BE AWE-011 C66 2.2 16 CSSA 2.2 50 647-UKL1H2R2MDDANA
is actually 2.2 ufd 35 volts orange color brand unknown.

I guess my question is...should i replace these using values on documentation? I purchased from original owner. He never said anything about repairs but I never asked him either.

Thanks for any info. BTW, I can post pics if anyone is interested.
Bill

The c66 2.2uf 16 to 35 v could be factory - using what they had, going up in voltage is harmless

The C61 .47 versus 5uF, go with the five I have seen it before, that is the stereo indicator light switch/driver and I suspect that on weak stereo signals it flickered a lot - putting a lot of wear and tear on the stereo indicator lamp.

The resistor, leave it as well, sometimes the service manuals that hit the streets hadn't caught up to what they making in the factory. And the service bulletins updating the changes have been lost to the mists of time. Plus then there's WHICH manual survived to be scanned.

BTW the awe-011 is the 1971 model's tuner. The 1973 tuner was done almost completely with integrated circuits instead of transistors.

 

[larryderouin]

The 1973 Service manual will tell you (on the 2nd or 3rd page) what serial #'ed units are using the 1973 model. You have to figure out the model based on the IC Sticker on the back panel. It will have one of 5 designations as below.





If your IC (KUW, KCW, FVZW, NBW, FW) serial # falls below the serials listed, use the 1971 manual. I would go thru the manuals and note the board # of each board and use the manual that meets your needs for the boards. The AWE-011 Tuner board is used in the 1971 model so use the 1971 manual. Manual Here Scroll down to SX-626 and pick the 1971 manual.

 

[moondogtn]

Slide, Mark and Larry, I appreciate the responses. I haven't had any time to get to this. Also, I must have been confused about which version I had. I was looking at correct manual. I finally got a chance to work on it today. Tuner board is recapped.

For C66, I used a 4.7 50 Volt cap.

I also replaced Q19 2SC968 using KSC2383 since my stereo lamp stays lit no matter what... no matter what is selected. It has been that way since I got it a few months back. If receiver is powered up, so is the stereo indicator lamp. I tested the original and it seemed intermittent so I was hopeful this would resolve the issue. Pin 5 of the board which goes to stereo indicator showed that I had a constant 10 Volts. I will dig deeper. First things I will be checking are Q18,20

Thanks again for the advice.

Bill

 

[moondogtn]

I tested several transistors on tuner board.
Q13, 15, 18, and 20. All were good. Q15 was a 2sc738 rather than a SE3001 like the prints show.
So, I didn't make any progress on the stereo lamp always being on. I read several threads and not one of the constant stereo lamp issues was ever corrected from what I gathered.

I will continue working through and return to that once the rest of the work is complete.
AWR-006 is the power supply.

AWR-006 C5 100 35 CEA 100 50 647-UPW1H101MPD
AWR-006 C9 330 25 CEA 330 50 647-UPW1H331MPD6
AWR-006 C10 330 25 CEA 330 50 647-UPW1H331MPD6
AWR-006 C12 100 16 CEA 100 50 647-UPW1H101MPD

I also replaced transistors
AWR-006 Q1, Q3 originals were 2SD313 replaced both with KSC2073

My next question in regards to this board.
AWR-006 Q2 2SC945 Should I replace using KSC1845 or KSC2383? Why? I am trying to figure out what it is doing in the circuit so that I can learn. Thanks

Bill

 

[rcs16]

ksc945c is what you want to use to replace the original NEC 2sc945 center collector part. ksc045cg is the higher hfe, also comes in lead formed CGTA or straight leaded CGBU,
ksc945 is 150mA collector I, ksc1845 is only 50mA andksc2383 can be used if you need higher I and Pd

 

[moondogtn]

Rick, I actually have a KSC945CYTA that I can throw in there. Last night I installed a KSC2383. For some reason, I thought that needed to be beefed up a little hence my question. I will try to work on it tomorrow so that I can remove the 2383 and install the 945. Thank you again! I appreciate it. I just wish I could get that pesky stereo indicator to work properly....nuisance.

Bill

 

[markthefixer]

Try a 0.47uf cap in that c61 pesky stereo light, while I have seen other units where 4.7uf helped, it's the only change in the area, and
while the others went from flickering to behaving, it could be that other things changed it back to original operation and the
4.7uf is now too much - this is just for a test.

As for the 945 vs the 2383, it's a wild call, more current drive under overload conditions can be nice, but under overload it's more like which smokes first. Hard to say.

 

[moondogtn]

Mark, I swapped C61 to .47 and no apparent change. I will swap back to 4.7 if you feel that is better.

Rick, i went ahead and installed the KSC945CYTA on Power supply board.

Tomorrow, i plan on moving forward to preamp.

Bill

 

[moondogtn]

To maybe save someone some trouble if they decide to order parts without confirming what was installed like I did. I wanted to mention something that I discovered. It could be common knowledge but I wasn't aware of it. I knew there were different versions of this receiver and thought the way to designate was serial number and tuner board.

Initially, I was using the tuner board awe-011 as a guide for choosing which transistors needed replaced. I understand that I should have confirmed the parts on the boards.
For another point of reference, the serial number on this unit is SF3717893 and it is a 120 volt KUW unit so I was assuming I should use the 1971 manual.

While working on head amp, I noticed that I did not have 2sc870 and 2sc871 but rather 2SC1312 installed on the board. It was then that I noticed the board number was actually W21-004-B so it was the 1973 manual that worked for this one. Luckily the 1845 would work here.

I plan to utilize these KSC1845 on the control amp board to replace the 2SC1312.
and the KSA992 to replace the 2SA725s.(edited to show correction)

I appreciate all the help just wanted to mention the odd discrepancies based on all the previous threads regarding designations and choosing manuals. I know I read somewhere on this model to use the corresponding board number to choose which version manual to use. This would seem to be wise.

Bill

 

[kramden]

Curious, was the stereo indicator checked before any work was done? Ie: when you found the 'crackling'.

 

[moondogtn]

Yes, Stereo indicator has been on since I first acquired the unit.

I am also beginning to wonder if FM stereo is actually working or not?

 

[kramden]

Plug in some headphones (if the unit is operational) and give a listen. You should be able to clearly hear the difference between monaural and stereo stations. If the stereo light stays on when you change the band to AM, could someone have hardwired the lamp to a ps voltage?

 

[moondogtn]

Kramden, I was able to power up until today. Unfortunately I cannot do that at this point. I recapped power amp board, replaced Q13 with KSC2383 and was hoping to get the new trimmers installed but I am out of time, parts, and energy for the night.

I have been checking it between each section and feel like I found the issue in EQ amp. . I let it play the other night for some time and no crackling.

I am not planning on replacing other transistors in power amp unless someone knows of any problem children. Also, I don't have any 1220s for the 2SA497s and don't really want to wait. I may order some from mouser if recommended since I don't have circuit board to create standoffs for pots. I may try come up with some other way to mount those though. Ideas welcome.

BTW, the FM stereo indicator light stays on no matter which input selection is made. I don't think its hardwired as I traced it out. I plan to revisit it once I get this completed.

Thanks again for ideas and help.

Bill

 

[larryderouin]

Bill; When you check for MONO vs. Stereo, it would probably be best to try an NPR station that plays classical all the time as they tend not to use compression as much and the stereo is much more defined vs. Mono. Most commercial stations in the Baltimore are so compressed it might as well be mono for what little stereo does get thru to be decoded. IT sounds like the MPX circuit is either non functional or some ham handed person got in there and "tweaked the pots" on the board.

Larry

 

[moondogtn]

Larry, I appreciate that thought and will attempt. I went ahead and mounted pots directly to board. So, I need to adjust trim pots, add jumpers for C3,C4 and repair phono jacks before I power it up.

Honestly, it does seem like someone was in here before me but not certain what all they touched. The tuner and the power amp from what I can tell.

I will hold off on replacing driver? transistors until the KSA1220 arrive. I have decided to replace them all but outputs.

I feel like I am learning slowly but still learning. Thanks for all the input gentlemen.

Bill