SX-838 Recap?

nathan stuch

New Member
Hi all, I'm an new to this as a member and look forward to much learning.

My question is for the 838 I have had for about 15 years now and its starting to crackle a little so I figured its time to clean and "maybe" repair anything? I have read about Electrolytic Capacitors need changed after about 30 years and was wondering if you guys had any suggestions on updating at least the two main 8000fu 50v caps to increase sound quality and longevity?

I also have a nice 3900 that works well so I have a unit to listen to music on and time to freshen up my "little 838 buddy"

Thanks much.

Nate in Omaha.
 
Hi Nate, welcome to AK

The 2 big eacps I do not think are causing the crackling. causes can be
2sa725,726 transistors (bjts)
dirty, tarnished contacts
leaky ecap's in the signal path, sky blue Sanyo's
regulated power supply
the last to do is usually the big ecaps unless they show signs of leakage or measure out of spec
all service extends the life if done properly.
 
Thank for the reply.

I have not pulled the unit apart yet to check...Plan on doing that this weekend. I picked up DEOXIT and will commence to cleaning. I was only going to change caps if needed or if there was any that would make it sound better than it does.

Thanks much.

Nate.
 
I was only going to change caps if needed or if there was any that would make it sound better than it does.

Cleaning the potentiometers (volume, balance, treble, bass) and the switches (power, speakers, mono/stereo, loudness) should clear up any static... normally heard when adjusting the knob or switch. Excellent first step, regardless.

Replacing the electrolytic caps will 1) give the unit more life and 2) quite often improve the quality of the sound (by returning it to original ecap performance as these degrade with the decades).

When @rcs16 said "2sa725,2sa726" the point was to replace the small signal transistors that are known to "go noisy" over the years. This isn't the only source of static-y noise, but it is a common source of static noise even when you aren't adjusting knobs of switches. The bad transistors (there are only a few models know to go bad) add random pops and crackles into the signal that is being amplified.

Good luck! Let us know what you decide to do and how it goes.
 
On the X3X series (434 thru 939 and the 1010) the #1 transistor on the TOP TEN MOST WANTED LIST is the 2sc1451, followed by the 2sa725 and 726 @#2 & #3.. The 1451 WILL die dramatically(think Drama Queen) and has taken out board components in a cascading failure mode, up to most of the amplifier board components with it. Symptoms are usually what I call "Rice Krispies",(snaps, crackles, pops that are NOT mitigated by cleaning controls). The 2sa725 and 726 will exhibit similar symptoms but normally don't take out most of a board in a cascading failure.
 
use fader lube on the pots, only if they are scratchy, and use only enough to clear up the problem
2sc1451 replacement is KSC3503
 
Thank you all for the education. Since Im going to have it opened up, I will just go ahead and change out the 2sa725 and 726 and the "1451" just as a precaution/preventative maintenance to keep it going for another 45 years. I will let you all know what becomes of it and thanks for all the help.

Nate.
 
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