Pioneer SX-1250 Right Channel low when turned on

[gkhashem]

New issue, the right channel is low and/or out when cold. Within a minute or two comes back and seems normal. It will continue normal while the receiver is on from that point on when it comes back it stays on and acts normal. No static , noise, or low volume once she gets going.

No switch other than the volume seems to effect it. All inputs do the same thing. Speakers A and B do it. Nothing seems to cause it. No cracks or pops just a low volume or very little volume.

The speakers wires check out. Then after the warm up all works well. After turning the volume knob back and forth seems to calm down and work.

Do I need just a good cleaning? The unit has supposedly been rebuilt and all seemed well for about 9 months.

Any ideas my for me?

 

[Watthour]

You could try burnishing the relay contacts if that hasn't already been done. Forego the flint or emery paper on the first attempt, and simply use a piece of kraft paper (sacrificed from a grocery bag?) and perhaps a drop of isopropyl alcohol on the paper to dissolve some carbon.

A little bit of resistance there can cause that symptom at low volumes, and get punched through as the power is increased.

 

[gkhashem]

That's what appears to be happening. When you turn up the volume it breaks through and plays. Low volume not much sound from right side. Then you push it up and low volume works.

So speaker relays may be dirty?

 

[zebulon1]

Yes,
Did the restore include a new relay? You can buy new ones.
When you pull the board to clean it, take a picture of the relay. Let us see it.

 

[glen65]

New issue, the right channel is low and/or out when cold. Within a minute or two comes back and seems normal. It will continue normal while the receiver is on from that point on when it comes back it stays on and acts normal. No static , noise, or low volume once she gets going.

No switch other than the volume seems to effect it. All inputs do the same thing. Speakers A and B do it. Nothing seems to cause it. No cracks or pops just a low volume or very little volume.

The speakers wires check out. Then after the warm up all works well.

Do I need just a good cleaning?

Before you start messing around with relays, chemicals or anything else, isolate and "confirm" which section of the receiver is actually responsible for the erratic behavior.
Pull the pre out and main in jumpers. Then drive the power amp (the main in jacks) with an external source for awhile to see how it does on it's own.
If there are no issues driving externally, the amp is OK and the relay is not the problem.

The unit has supposedly been rebuilt and all seemed well for about 9 months.
Any ideas my a DIY guy.

The problem is there are lots of definitions as to what rebuilt actually means.
If you can - take some internal pics. Also take some close ups of the amplifier and power supply PC boards. Thanks

 

[gkhashem]

I think I found it. The filter switched 30mhz and 8 mhz were pressed in. I put them off.

I let the receiver sit for 1 hour turned it on and came back no issues.

Any ideas why this happened? I guess don't look a gift horse in the mouth?

 

[gkhashem]

Tested it again and it was fine so those filters seem to be the issue

 

[ZOOM]

Sounds unlikely. I still think the relay is at fault. This is a problem that comes and goes. Right now, it has gone. It'll most probably be back.

 

[glen65]

I think I found it. The filter switched 30mhz and 8 mhz were pressed in. I put them off.

I let the receiver sit for 1 hour turned it on and came back no issues.

Any ideas why this happened? I guess don't look a gift horse in the mouth?

I had a similar issue arise concerning the filter switches on mine. They get little or no usage. So the mating points in the switch get oxidize causing issues. Try working the switch about 20 times.

 

[glen65]

Sounds unlikely.

Not necessarily, The filter assembly is the last place the audio signal travels before it hits the pre out jacks and into the main amp.

I still think the relay is at fault. This is a problem that comes and goes. Right now, it has gone. It'll most probably be back.

If it does, then it would be wise to drive the main amp externally to isolate and confirm that area is indeed the issue.

 

[petehall347]

clean /deoxit the switches ...

 

[tsd71]

You need to lubricate all the switches, potentiometers, and RCA jacks. Also pay attention to the main - in , pre - out jacks, clean them too.


NOW

 

[gkhashem]

Turned it on again after off overnight. All is fine. This has to be the switch.

For the past few weeks it would act up every time I turned it on after being off more than 10 minutes.

So don't want to argue with the experts but tested it 4 times since and no issues, prior to this it did it every time the unit was cold.

Think I will clean the switches. Not sure if its the 30 mhz or 8 mhz switch.

 

[KingBubba]

IIRC, the filter switches are the last stop in the chain leading out of the pre amp. They were a problem with my 1250 and many others. With the unit off, cycle the switches 50 times and it will wear away some of the corrosion. Deoxit, Faderlube and Caig Gold will be the answer to this issue, but it requires a lot of work to get to the switches. You can try and may have some success going in the front. It is worth the try.

 

[markthefixer]

sometimes it takes several DEOXIT treatments before the "results stick"...

You are reversing 30 years or so of corrosion.

"cleaning" doesn't cut through the corrosion, it just leaves clean corrosion.

Deoxit loosens the bond between the corrosion and the base metal, so it can be scrubbed off by contact friction.

 

[KingBubba]

Glad to hear you are back posting Mark, I hope you are well after your recent issue. Can you shed any light on getting through from the front?

 

[zebulon1]

The only proper way to clean the push button function switches is to remove the board they are attached to. Remove the front face plate, flip the set on it's back front facing you. Remove the screws securing the tone and flat amp boards and lay them on rags placed over the bottom of the chassis. You now can remove the screws for the function switch boards and clean the switches. With the switch in the off/extended position; The straw will go into the front of the switch on either side of the spring. Shoot a short burst of Deoxit in all the switches on the board, then work the dog out of the switches. 50 or more times, think about having to go back and do this again while you work the switches. Then you must follow up with the Fader 5 Lube.

NOTE: When I say remove the board this means leaving the wires attached. There is plenty of slack in the harness to allow for moving the boards out of the way!! :yes:
Pioneer forum mantra: We will never remove the wires! Unless otherwise!!!!

 

[KingBubba]

I suspected as much. There is never anything easy about these old beasts.

 

[zebulon1]

It's worth the time. Big smiles when done. :

I'm half tempted to say rebuild the boards while that deep. But I won't as I realize that's not for everyone or needed. It's just a lot of work and I like to make it worth all the effort.
A good two to three evenings of work. With a Hakko 808 no less!

 

[Audiokingman]

I think I found it. The filter switched 30mhz and 8 mhz were pressed in. I put them off.

I let the receiver sit for 1 hour turned it on and came back no issues.

Any ideas why this happened? I guess don't look a gift horse in the mouth?

Old post, BUT.......the Pioneer SX-1250 does not have 30mHz and 8mHz filters. It has 30Hz and 8kHz filters.