Pioneer SX-838 - how important is a recap?

[Texas Tom]

Hi everyone. I bought a Pioneer SX-838 a couple of years ago. I did check a few things when I got it home. It had broken volume knob and sounded terrible. I put it on the shelf and forgot about it.

About two weeks ago, I pulled it out and dug in. I replaced the broken volume knob/pot and thoroughly cleaned potentiometers and switches multiple times.

Tried it again and it sounds really good! A few days ago, I checked the DC offset and Idle Current today.
They were almost perfect to specs!
All the lights work as well!

I know many of you would recommend re-capping, but since there was basically no drift, how serious is the need to do so?

 

[spark1]

Well, if you think it sounds really good, why spend the time and money?

I only "re-build" units that I intend to keep. Replace electrolytics, deep clean switches and pots, replace any parts known for becoming problematic with age. I do this to assure the until will performan as good as it can.

 

[ivandezande]

Hi everyone. I bought a Pioneer SX-838 a couple of years ago. I did check a few things when I got it home. It had broken volume knob and sounded terrible. I put it on the shelf and forgot about it.

About two weeks ago, I pulled it out and dug in. I replaced the broken volume knob/pot and thoroughly cleaned potentiometers and switches multiple times.

Tried it again and it sounds really good! A few days ago, I checked the DC offset and Idle Current today.
They were almost perfect to specs!
All the lights work as well!

I know many of you would recommend re-capping, but since there was basically no drift, how serious is the need to do so?

The only caps that are a true issues here are the small blue Sanyo ones. I see some on the protection board, which speaking of, that drive transistor dies and a fly back diode should be added.
Also, see those small metal can transistors on the amp board? Those eventually will put your amp in protection and maybe fry some speakers.
Not to mention every small signal transistor in there is getting leaky and noisy.

Obviously you can just use it until there’s an issue, but it’s not performing to what it should be and don’t let anyone tell you it is. All vintage electronics are time bombs of some sort. Gotta change the oil on a car, even though it’s still “running fine”.

 

[spark1]

By that logic, all electronics are time bombs!

Doing a full rebuild as preventive maintenance - and potentially to improve sound quality - makes sense if you plan to keep it. Otherwise, nope.

 

[drp1003]

Hello, I own a Pioneer SX-939; it is the second on the list of these types of Pioneer receivers. The SX-1010 being the TOTL model. I rebuilt mine a few year ago after I purchased a kit off Ebay from a seller who went by the name of PEACE LOVE AND MUSIC, but I think now goes by the name Affinity for Artifacts. This Ebay seller has a very good reputation here on AK, and is also - I think - a member (but don't quote me on that).

My SX-939, before I rebuilt it sounded horrible; it was noisy as heck.

Try this: without playing any music and being very careful, hook up some cheap speakers, turn on your SX-838 and turn up the volume all of the way, and listen for noise. Do this in AUX mode. And then do it again in PHONO mode. The PHONO should sound pretty loud compared to AUX (it is PHONO after all).

Does AUX sound static-y and noisy and generally bad? Again, PHONO should sound louder, but it should not sound bad, ie. clicks and pops and static-y.

You said you cleaned the switches and pots? Even so, how does it sound with the volume turned up all the way (again, please make sure you are not playing any music through the receiver when you do this)? Does it sound static-y and noisy and kinda loud?

After I rebuilt my SX-939, and did this noise test - the one I just described to you - my receiver was very very quiet. It still made a hisssssssss sound, but it was still very quiet.

The kit came with all the goodies: transistors, electrolytic caps, diodes, and stuff I cannot even remember at this moment. An extensive kit to be sure, well worth the investment if you plan on keeping the receiver. These receivers are great. I love my SX-939 and will keep it until I am dead.

A 50 year old receiver is gonna need to be rebuilt. It's inevitable.

 

[mrk229]

Hi everyone. I bought a Pioneer SX-838 a couple of years ago. I did check a few things when I got it home. It had broken volume knob and sounded terrible. I put it on the shelf and forgot about it.

About two weeks ago, I pulled it out and dug in. I replaced the broken volume knob/pot and thoroughly cleaned potentiometers and switches multiple times.

Tried it again and it sounds really good! A few days ago, I checked the DC offset and Idle Current today.
They were almost perfect to specs!
All the lights work as well!

I know many of you would recommend re-capping, but since there was basically no drift, how serious is the need to do so?

As @ivandezande said if you spot any of the sky blue Sanyo caps "they gotta go".

The power supply boards on most Pioneers have components that run very hot. The solder joints on those components should be at the very least reflowed. I like to remove the old solder and then resolder. Inspect the joints on the larger resistors and the regulator pass transistors. Look for dull grey color, grainy looking joints or "halos".

A halo-like ring around a component lead on a solder joint indicates a fractured joint, often caused by mechanical stress, vibration, or temperature changes that lead to movement and a physical break in the connection. This halo is a visual sign of a bad, compromised joint, not necessarily a "cold" or "dull" joint, but a sign of stress and fatigue that requires re-soldering for a reliable connection.

While you are there replacing caps may be a good idea as they all get heat soaked from the hot parts around them.

The 838 does have a lot of transistors that are known to go bad or fail in various ways over time and as @spark1 said if it is a keeper then a rebuild might be something to seriously consider.

Keep in mind a lot of the direct fit parts used in rebuilding these are getting harder and harder to find.

@drp1003 mentioned a kit, that can be a good way to go if you don't want to take the time to build a BOM and source the parts yourself. I would only buy a kit from the eBay seller he mentioned. He supplies very complete kits with quality parts, they typically come with helpful instructions if you need them.

 

[EastPoint]

Caps need to go, most transistors as well. The 838 is full of crappy transistors, those are more important than the regular electrolytics (other than the blue Sanyo caps, which are also terrible).

 

[ohm470k]

I agree with everyone else on those little blue Sanyo bas*****. They are always way off from the original value. I usually do all caps on all my vintage gear for longevity's sake and because I enjoy the process. Check dlucy's, i think it's his, list for the known bad small signal transistors and get them out of there. That, along with your thorough cleaning, should give you many years of enjoyment with it.

 

[Texas Tom]

Sorry for my late response. I appreciate all the advice. I will update this as I move forward.