I need to clean SX 1250

[sendust]

Hi guys i just picked up a 1250 thats working well and appears to be all original, I am having some issues with the right channel on all settings am fm phono etc, a loss of sound and clarity. I want to clean pots etc to make sure all connections are clean. i have removed the lower metal casing and see the area i wish to clean is below the front two boards, picture attached. My question is should i loosen the boards to get below them to access pots etc or am i barking up the wrong tree. thanks for any advice.

 

[KingBubba]

Start with the front faceplate. The tuning knob is held on by a 1.5mm Allen wrench. Be very careful with this or you are screwed. Turn to upside a give it on drop of penetrating oil or similar. Leave it over night before you start. Trust me, if you strip it, you will have some real issues. Good luck in the first step.

 

[sendust]

Start with the front faceplate. The tuning knob is held on by a 1.5mm Allen wrench. Be very careful with this or you are screwed. Turn to upside a give it on drop of penetrating oil or similar. Leave it over night before you start. Trust me, if you strip it, you will have some real issues. Good luck in the first step.

First step was already completed, i should have mentioned that..face plate is off and i sprayed detox 5 into the upper switches and pushed them in and out about 10 times.

 

[sendust]

I read the service manual and removed the screws holding the front section as per photos, i cleaned everything with compressed air then shot some detoxit d5 into pots etc, worked them a bit and now will wait for an hour or two, work again and reassemble unless there is something else i should look at in this area. thanks

 

[savatage1973]

Not necessarily something that you should look at, but you might want to blow out the controls a final time with compressed air and apply some Faderlube--DeOxit F5 before reassembly. Don't know where you are, but if you don't have any on-hand and don't want to wait for it to ship, any Guitar Center location carries it.

 

[zebulon1]

I know this sounds goofy but when the channel cuts out, mess with the switches as mush as possible. Try to see if the switches have any impact on the dropping. The signal runs through every one of the switches and pots.
Try the volume by increasing the gain.
Remove the jumpers from the back and clean/polish them as well. A pipe cleaner with Deoxit for the jack.

 

[sendust]

I know this sounds goofy but when the channel cuts out, mess with the switches as mush as possible. Try to see if the switches have any impact on the dropping. The signal runs through every one of the switches and pots.
Try the volume by increasing the gain.
Remove the jumpers from the back and clean/polish them as well. A pipe cleaner with Deoxit for the jack.

I dont think it sounds goofy, i did try all switches and i found that increasing volume brought it back for a while, this is why i am hoping it just needs cleaning, i did all pots and switches and cleaned all rca connections. I will let the unit it for a while and will try later hoping this works.

 

[savatage1973]

If the issue is more prevalent at low volumes, and clears up when you increase the volume, check the speaker relays. Contacts may be dirty, corroded or burnt--won't give a good connection until after the power is high enough to establish continuity.

 

[sendust]

Cleaned the unit, waited a few hours, started it up and it sounds amazing, the issue so far appears to be a poor connection issue. I have always been a huge marantz fan owning several units but i must admit i really like the sound of this unit, amazing bass and great clarity.

 

[kevzep]

Replace the speaker relay, that will undoubtedly be the issue. Switches and Controls are a bit more random when cutting in and out...

You really should do the unit some service, get rid of those old caps and dodgy transistors too...

I have one under the knife at the moment and the main caps on this one are almost toast.....as are a lot of the other ones I am pulling out...

 

[zebulon1]

Replacing the relay is an easy job on the 1250. Of course if you have the proper tooling. The relay resides on the protection board which is removable.
By increasing the gain the extra power over comes the crusty points in the relay.

 

[sendust]

Replacing the relay is an easy job on the 1250. Of course if you have the proper tooling. The relay resides on the protection board which is removable.
By increasing the gain the extra power over comes the crusty points in the relay.

Im in the process of ordering some parts, it seems most people feel at this age it should be recapped even if it is in working condition.

 

[kevzep]

Im in the process of ordering some parts, it seems most people feel at this age it should be recapped even if it is in working condition.

You don't have to replace the caps, but as they have been in service for some 45 years or so, they are now drying up and turning into resistors or in some cases as risk of shorting out.
Its preventative maintenance, it like you take your car in for a service, they change the oil and filters etc etc, there's nothing wrong with the car, its working, and probably working just fine, but we take it in and service it all the same to ensure years of trouble free motoring.
Amplifiers and electrolytic caps are the same.

 

[zebulon1]

More important than all the caps is the stabilizer board. If any reliable operation of the older 1250 is desirable, rebuilding the board is required. The caps can wait.
Also: The large filter caps have a history of venting. An easy visual check will confirm that.

 

[sendust]

More important than all the caps is the stabilizer board. If any reliable operation of the older 1250 is desirable, rebuilding the board is required. The caps can wait.
Also: The large filter caps have a history of venting. An easy visual check will confirm that.

What should be replaced on the stabilizer board? and do you have a parts list that matches mouser? thanks for your help with this

 

[sendust]

I realize once caps etc are replaced ,the power amplifier will need to be re adjusted , i see in the service manual it shows attaching 5.1 k ohm resistor to power in jacks, is this needed ? if so i will make a few to plug in, im only asking because some on the info in manuals are incorrect. thanks

 

[kevzep]

I realize once caps etc are replaced ,the power amplifier will need to be re adjusted , i see in the service manual it shows attaching 5.1 k ohm resistor to power in jacks, is this needed ? if so i will make a few to plug in, im only asking because some on the info in manuals are incorrect. thanks

Oh yes I saw that too, I think, its to effectively "mute" the amplifier whilst adjusting the Bias and DC offset, not a big deal.
I'm not sure if the regular guru's here do that or not, but its pretty simple to do if thats the go.

 

[kevzep]

More important than all the caps is the stabilizer board. If any reliable operation of the older 1250 is desirable, rebuilding the board is required. The caps can wait.
Also: The large filter caps have a history of venting. An easy visual check will confirm that.

You are of course absolutely right, when I say re-cap, it means a full refurb, sometimes I am not always clear and speak in my own shorthand.....
Best place to start though as you said..

The SX1250 I have on the bench has the Main Filter caps venting. So they have to go, and whilst I'm at it, then might as well do the rest, caps and transistors everywhere.....

My client wants to keep the output transistors though because he thinks its part of the Pioneer sound.....and who am I to argue.

 

[zebulon1]

You are of course absolutely right, when I say re-cap, it means a full refurb, sometimes I am not always clear and speak in my own shorthand.....
Best place to start though as you said..
The SX1250 I have on the bench has the Main Filter caps venting.

I knew what you were getting at
The 1250 is a perfect set to restore in phases.

 

[kevzep]

I knew what you were getting at
The 1250 is a perfect set to restore in phases.

All good, I think we are all ambassadors for saving all this classic gear.....

There is quite a lot to on the 1250, so as you say, definitely a good one to do in phases........speaking of which, I am about to head back into the one I am doing...