• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

SX-838 troubleshooting assistance please

Thanks so much for the quick, detailed response.

There is one local supply house about 10 miles from here, so I'll check there for the cap. I was there about 2-3 weeks ago, and seem to remember a lot of NTE packaging. :(



markthefixer said:
unfortunately, that is a vulnerable cap, and a low noise to boot. eventually it will need to be changed out. and we can't go with a 25v cap. So order up a poly film 0.47 at 50v on some other order in the future...

2.2 uf will leave you with a lot of mic rumble coming through... the ukl part of the spec would be a match and the 50v part of the spec would be a match..

lamps:
http://www.dgwojo.com/index.php?p=1_2_Products

http://www.vintage-electronics.cc/vlamp.html

they are "fuse lamps" , and the stereo lamp is 8v 50ma and 4mm or so...
Click to expand...
 
Just curious, what's the supply house? You may PM me if you don't want to be public with the name of the place. Glad you basically have it running OK!
 
rBuckner said:
Just curious, what's the supply house? You may PM me if you don't want to be public with the name of the place. Glad you basically have it running OK!
Click to expand...

I don't mind mentioning them in public - I've only been there once, and the fellow I dealt with was very helpful.

Pacific Electronics, in Dublin, CA
 
Got the cap, and found a stereo repair place that had the fuse lights and the little bi-lead bulbs. Life is good!

Now..... should I be concerned with the tuner board caps? I presume fooling with those is fraught with danger, but can they be safely ignored? And what about the filter caps - I haven't replaced them, either......
 
Uncle Bambi said:
Got the cap, and found a stereo repair place that had the fuse lights and the little bi-lead bulbs. Life is good!

Now..... should I be concerned with the tuner board caps? I presume fooling with those is fraught with danger, but can they be safely ignored? And what about the filter caps - I haven't replaced them, either......
Click to expand...

I would leave the tuner alone unless it's broke or not good enough. If I were living where you do, if it got KFOG okay I'd be happy!

About the main filter caps I've heard both schools of thought:

Don't replace them because they are larger and tend to not dry out and fail like little ones, which is true in my experience.

Do replace them since they handle alot of ripple current which can lead to failure. I have only seen one fail once in my experience, on a mid 70's Pioneer SX-939 (which is older than yours). That was like a 70 watt/ch model or so. Another reason given is that it makes for better bass as newer caps have lower ESR and can source instantaneous current better. Some truth to that if you're REALLY pushing the power limits. (I'm donning the flame suit now...).

What I do is replace them if they have any suspicious look to them at all or if the receiver is a higher power model, say 60 watts/ch or more. For sure I don't recommend going higher in capacitance value any more than you have to. It's fine going higher in voltage rating. One other thing to keep in mind is that new caps of the same value are going to be smaller than the original. I usually use cut up pieces of various PVC plumbing fittings to make up the difference. Some folks use weather stripping but I don't as it WILL rot out sooner or later.
 
Measure the dc voltage at the terminals of the two big capacitors, then measure the AC voltage at the same spot. If the AC voltage is larger then the DC voltage, you need a blocking capacitor in series with your meter leads.

a 0.1uf ceramic disc cap will be fine. As long as the voltage rating of the capacitor is greater than the DC voltage that needs to be blocked.

If the DC to DC and AC to AC voltages are similar for both caps, there are no problems, as a dual cap failure is very rare.

As for the tuner, there is no underneath access without removing or lifting it, so it is best to leave it be until you are ready and have made arrangements for it to be aligned afterward.
 
Thanks, Mark.

Just wanted to conclude the thread by posting a couple pics of the receiver lit up and doing what it was meant to do. BTW - changing that little bi-lead bulb for the FM selector was a right bastard to do. The only thing I could not fix was the light at the end of the dial station indicator - I couldn't figure it out....

P1000525.jpg


P1000528.jpg
 
Last edited:
Ok - I have to resurrect this thread, as very intermittent issue has cropped up. I've been listening to this receiver via both FM and CD daily since I finished repairing it 2-3 weeks ago.

Twice this week, while listening to the radio at low volume, the receiver cuts out for a second and goes dead, and then comes back with a "thump" and continues on its merry way. This last time, I thought I heard the relay click, but it happened so fast I cannot be sure.

Both times were during FM listening and never under high volume with CD's, but frankly it is such a rare occurrence that it could just be coincidence. I did not re-cap the tuner or replace the large filter caps.

Any ideas, or should I just wait for it to die? I'm more worried about speaker damage than anything else...... :(
 
Uncle Bambi said:
Ok - I have to resurrect this thread, as very intermittent issue has cropped up. I've been listening to this receiver via both FM and CD daily since I finished repairing it 2-3 weeks ago.

Twice this week, while listening to the radio at low volume, the receiver cuts out for a second and goes dead, and then comes back with a "thump" and continues on its merry way. This last time, I thought I heard the relay click, but it happened so fast I cannot be sure.

Both times were during FM listening and never under high volume with CD's, but frankly it is such a rare occurrence that it could just be coincidence. I did not re-cap the tuner or replace the large filter caps.

Any ideas, or should I just wait for it to die? I'm more worried about speaker damage than anything else...... :(
Click to expand...

ARGG.... :scratch2:

Is it heat related? I know that is hard to say by your description....
Maybe try disconnecting one speaker and run it.....

Tough one....
 
goat67 said:
ARGG.... :scratch2:

Is it heat related? I know that is hard to say by your description....
Maybe try disconnecting one speaker and run it.....

Tough one....
Click to expand...

Hmmm..... if it were heat related, I would expect it to warm up and go into protect until it cooled down, not go dead, come right back, and continue on for the rest of the day - no?

FWIW - I've been driving it at pretty high volume since I posted last, playing CD's. So far, it has been flawless.
 
Uncle Bambi said:
Hmmm..... if it were heat related, I would expect it to warm up and go into protect until it cooled down, not go dead, come right back, and continue on for the rest of the day - no?

FWIW - I've been driving it at pretty high volume since I posted last, playing CD's. So far, it has been flawless.
Click to expand...

please detail everything done to the protection circuit first...

it does do the delay time, correct? on power up and upon fault?
 
markthefixer said:
please detail everything done to the protection circuit first...

it does do the delay time, correct? on power up and upon fault?
Click to expand...

On the Protection board, all these were replaced:

c1 0.22 10 cssa 0.22 10 667-ECQ-V1H474JL3
c2 0.22 10 cssa 0.22 10 667-ECQ-V1H474JL3
c3 330 6 cea 331 6 647-UPW1A331MPD
c4 330 6 cea 331 6 647-UPW1A331MPD
c5 4.7 25 cea 4.7 25 647-UPW1E4R7MDD
c6 100 16 cea 101 16 647-UPW1E101MED
Q1 2sc869 512-KSC2310YBU
Q2 2sc869 512-KSC2310YBU
Q3 2sc945 512-KSC945CLTA
Q4 2sc945 512-KSC945CLTA
Q5 2sa733 512-KSA733CLTA
Q6 2sc945 512-KSC945CLTA
Q7 2sc1384 512-KSC2383YBU


On power-up, the delay time is noticeably quicker than my other Pioneer SX receivers - about 2-3 secs before it clicks on and is ready for use. Upon fault, in and out in about the same time - maybe a little less. The last time it went quiet, I thought I heard the relay click (but could not be sure - it happened fast), and then it came right back on with a mild "thump". I subsequently played it on FM for at least a couple of more hours before turning it off to go run errands.

Like I said - it's only happened a couple of times since I announced "mission accomplished" :).

Today, I've listened to about 4 CD's back-to-back at pretty good volume without issue.
 
FWIW - This weekend I played about 6 CD's back-to-back at some pretty high volume, figuring that if it were heat related then that would make the problem show up.

Nope..... ran fine, all day long. Could it be the FM section? Like I said - I did not re-cap on the tuner board.
 
rBuckner said:
Just a wild idea but maybe it was a glitch in the power line? Did any digital clocks go flashing?
Click to expand...

Digital clock? What's that? :)

Except for the computer, pretty much everything in my office is analog. No digital clocks here. Other parts of the house, but not here. :D But - no, I did not have to reset any clocks, and my workstation (that I was actively working on) did not hiccup when it happened. So, I'm pretty sure it is a problem in the unit.

FWIW - if it is the tuner section giving me issues, it's not too big a deal... assuming it stays there. Local FM is pretty much crap anyway, so this unit will be playing CD's mostly while I work on my bikes in the garage. Well... maybe an odd ballgame or two......
 
You must log in or register to reply here.
Back
Top Bottom