Pioneer SX-535 channel question

[jghamp001]

I have a Pioneer SX-535 that is in overall nice condition, except there is no sound through one channel on either A or B setting.
I am going to clean the pots and switches, but I opened the case and noticed a coil on the amp board (I think) looks burnt where it meets the board. Is this my problem?

 

[ivandezande]

That's just glue. Deoxit things and see where that gets you.

 

[dly66]

Welcome to Audiokarma.

Have you checked the protection fuses on the back panel? Should be under a square cover on the back panel next to the AM antenna mount. An SX-535 was my first restoration project. When I got it sounded like it had a major head cold. Was recapped and a lot of transistors replaced and its fidelity returned. I pulled it off the shelf to use as a reference.

If a fuse is blown you can replace it but don't hook up speakers to the unit. Check the DC at the speaker terminals first. When output transistors blow they often short collector to emitter which can put a large DC voltage on the speaker terminals which can quickly fry woofer voice coils. Creates a contest for which fails first, woofer voice coil or the protection fuse. Fried a woofer one time not checking for DC on the outputs on a unit new to me with unknown history. It was putting out 35 Vdc across the speaker terminals on one channel.

For reference below is a picture of the amp board out of mine. It has been recapped and a number of transistors and several resistors replaced.

Fortunately these are very repairable, plenty of information on this site for recapping one and replacing transistors. Plenty of helpful people can chime in and help someone fix them too. A common vintage low power Pioneer receiver. Nice looking and solidly built.

 

[jghamp001]

That's just glue. Deoxit things and see where that gets you.

Thanks for looking at it, I’ll go ahead and deoxit and see if that helps then

 

[jghamp001]

Welcome to Audiokarma.

Have you checked the protection fuses on the back panel? Should be under a square cover on the back panel next to the AM antenna mount. An SX-535 was my first restoration project. When I got it sounded like it had a major head cold. Was recapped and a lot of transistors replaced and its fidelity returned. I pulled it off the shelf to use as a reference.

If a fuse is blown you can replace it but don't hook up speakers to the unit. Check the DC at the speaker terminals first. When output transistors blow they often short collector to emitter which can put a large DC voltage on the speaker terminals which can quickly fry woofer voice coils. Creates a contest for which fails first, woofer voice coil or the protection fuse. Fried a woofer one time not checking for DC on the outputs on a unit new to me with unknown history. It was putting out 35 Vdc across the speaker terminals on one channel.

For reference below is a picture of the amp board out of mine. It has been recapped and a number of transistors and several resistors replaced.

Fortunately these are very repairable, plenty of information on this site for recapping one and replacing transistors. Plenty of helpful people can chime in and help someone fix them too. A common vintage low power Pioneer receiver. Nice looking and solidly built.

View attachment 1375715

Welcome to Audiokarma.

Have you checked the protection fuses on the back panel? Should be under a square cover on the back panel next to the AM antenna mount. An SX-535 was my first restoration project. When I got it sounded like it had a major head cold. Was recapped and a lot of transistors replaced and its fidelity returned. I pulled it off the shelf to use as a reference.

If a fuse is blown you can replace it but don't hook up speakers to the unit. Check the DC at the speaker terminals first. When output transistors blow they often short collector to emitter which can put a large DC voltage on the speaker terminals which can quickly fry woofer voice coils. Creates a contest for which fails first, woofer voice coil or the protection fuse. Fried a woofer one time not checking for DC on the outputs on a unit new to me with unknown history. It was putting out 35 Vdc across the speaker terminals on one channel.

For reference below is a picture of the amp board out of mine. It has been recapped and a number of transistors and several resistors replaced.

Fortunately these are very repairable, plenty of information on this site for recapping one and replacing transistors. Plenty of helpful people can chime in and help someone fix them too. A common vintage low power Pioneer receiver. Nice looking and solidly built.

View attachment 1375715

 

[jghamp001]

Thanks for pointing out the protection fuses. I opened that up and they look good to me. I’ll try Deoxit and see if that helps.

I was worried that glue was something serious and would need to take it to a shop

 

[dly66]

Deoxit can do wonders. I have used it on ones I have and some I would check for someone locally who sells on Ebay and it can many times get missing elements back in action.

If you have a Guitar Center nearby they stock the cans of D5. People complain about the new integrated straw but the one I have has been okay for me. Parts Express still sells the old can design with separate straw which IMHO was better. Keep in mind you try to find the holes and openings so it gets to the contact surfaces inside and then work the controls and switches to help wipe away the corrosion. Probably to do one good shot and work each control/switch multiple times, wait a bit and do the process a second time. Then leave it to dry for a while.

I believe this generation of Pioneer was sold from 1974-1976 according to hifiengine so its over 40 years old. The next generation was the silver faced x50 series.

In older stuff bad solder joints, such as at the function selector switch, can kill things too. I think the function selector joints tends to be a problem since it gets snapped from one extreme to the other with some force many times over the unit's life. Might scan the boards for poorly soldered joints or ones you can see lines or rings in the solder joint. Have fixed lost channels several times by finding and touching up/redoing bad solder joints.

 

[dly66]

There was this brown glue used back then to hold down components and it does make it look like something went wrong or a capacitor is leaking. When someone was gluing in some caps in yours they may have dripped some on the amp board. Glue was often used with some of the bigger capacitors, most of which would be on the power supply board.

 

[Bobby E]

I just bought the same unit with the same issue with no sound in the right channel. I was ok using the mono until I realized I was missing a channel of the stereo mix. I corrected this by using an RCA plug mono adapter which converted the stereo from the turntable into a mono mix to the left channel than I could hear both right and left mixes together. I’m not electrically inclined so this was my band-aid solution but it worked for me. I got the RCA mono plug at Radio Shack years ago.