Pioneer SX-1050 Receiver Repair And Restoration

This Pioneer SX-1050 will power up but there is no output to the speakers.

This Pioneer SX-1050 repair and restoration will include cleaning the pots and switches. Some disassembly is always needed to do this job.

I have removed the faceplate on this Pioneer SX-1050 receiver for cleaning and to allow better access to the controls for cleaning them.

Any vintage audio repair or restoration involves a lot of cleaning. This Pioneer SX-1050 is no exception.

The soft start relay is engaging but the speaker protection relay shown in the lower left of the picture below is not operating.

After troubleshooting I determined that there was an issue being caused by the 090 protection board itself and not something external.

The problem was solved by replacing a 32 volt zener diode that had failed. After replacing the diode the speaker relay operated fine.

I'll replace the speaker relay. It's still working properly but after 40+ years while I'm working on this Pioneer SX-1050, I'll change it out.

Most of the parts are still available to repair or restore vintage audio equipment. This Omron relay is a perfect replacement for the original.

When you need a relay for a vintage audio project Omron probably still makes a relay that you can use for a replacement.

I'll be replacing the 40 year old electrolytic capacitors as well as transistors that have a history of failing on the equalizer assembly (phono).

The four transistors shown with the orange dots need to be gained matched during this Pioneer SX-1050 repair and restoration.

I keep a lot of the small signal transistors in stock and I may have to test several to get the gain (hFE) of the transistors to match up.

The signal transistors shown in the picture below are very inexpensive. They cost about 5 cents a piece when purchased 100 at a time.

I'm now ready to replace the capacitors and transistors on the equalizer assembly. This work will help get the best sound out of your vinyl records.

I'll use an Atlas DCA Pro to gain match the transistors. Modern test equipment is very helpful when repairing or restoring vintage audio equipment.

The equalizer assembly is accessed from the bottom of the chassis. There are four small tabs that are compressed to remove it.

There is enough slack in the cables to move the equalizer assembly into a position to make component replacement possible.

I have begun to replace the components on this Pioneer SX-1050 receiver's equalizer assembly. Always use good quality replacement parts.

I used Nichicon and Panasonic capacitors. I have also used audio grade capacitors at all points in the signal path for the best sound quality.

I have completed the capacitor and transistor replacements on this Pioneer SX-1050 receiver's equalizer assembly.

Next up for restoration is the flat amplifier assembly. There is enough slack in the wires to get the assembly where you need it.

With the flat amplifier out of the chassis the controls can be cleaned properly with deoxit or your favorite cleaner.

The flat amplifier has a variety of electrolytic capacitors and transistors that will be replaced during this Pioneer SX-1050 repair and restoration.

Any capacitors in the signal path will be replaced with audio grade capacitors. The smaller value capacitors will be replaced with film capacitors.

Film capacitors will give you a lower noise level and are superior to electrolytic capacitors when in the signal path.

The cost of film capacitors is slightly more then electrolytic capacitors but it's only $25 extra in parts cost for an entire Pioneer SX-1050 restoration.

I have replaced the necessary capacitors and transistors on the flat amplifier during this Pioneer SX-1050 repair and restoration.

Nichicon muse series audio grade capacitors were used in the signal path. Nichicon PW series capacitors were also used on the flat amplifier.

Next I'll do the update of components on the tone amplifier assembly during this Pioneer SX-1050 repair and restoration.

The tone amplifier assembly in the Pioneer SX-1050 receiver has a cover that needs to be removed for better access.

The tone amplifier assembly has a good amount of slack in it's wiring. Getting the assembly into a workable position is not to difficult.

Again in this assembly it's more 40+ year old electrolytic capacitors and transistors prone to failure or noise that will be replaced.

In this tone amplifier assembly I'll replace some of the small electrolytic capacitors with film capacitors are I did on the flat amplifier assembly.

All that is left to do on the tone amplifier assembly is to replace the tantalum capacitors. They are blue in color. They are also known trouble makers.

With all of the new components installed I'll give the tone amplifier assembly one final look before reinstalling it into this Pioneer SX-1050.

I'll update the power supply assembly(B) which is located at the bottom of the chassis in this Pioneer SX-1050 receiver.

There are four plastic tabs that need to be compressed and after removing some wiring from the channel guides you will have access.

There are three electrolytic capacitors that need to be replaced on this assembly during this Pioneer SX-1050 repair and restoration.

The picture below shows the voltages that the three capacitors are subjected to on the power supply assembly(B), 24 volts and 76 volts.

The original capacitor rated at 25 volts will be replaced with a capacitor rated at 50 volts.

The two original capacitors rated at 80 volts will be replaced with capacitors rated at 100 volts.

The higher voltage rating of the replacement capacitors should allow them to run well inside their specifications.

With the new capacitors installed in the power supply assembly(B) this Pioneer SX-1050 is closer to completion.

The electrolytic capacitors on the power supply assembly(A) will be replaced. This assembly is located near the rear of the chassis.

This assembly is removed from the top but first you must get enough slack in the wiring from the bottom of the chassis.

After getting enough slack I can get the power supply assembly(A) into a position where I can replace the capacitors.

This is a fairly small board but there are several electrolytic capacitors to replace.

I have replaced the capacitors with high quality Nichicon PW series. This Pioneer SX-1050 repair and restoration is coming along.

I'll now reinstall the power supply assembly(A) back into the chassis of this Pioneer SX-1050 solid state receiver.

I have removed the heatsink assembly from this Pioneer SX-1050 solid state receiver for service.

There is decades of grime to clean up from the heatsink area as well as the power transistors.

I have started to remove the power transistors from the heatsink assembly. I will clean up the old thermal compound.

I will also clean up the old thermal compound from the power transistors.

These are the original power transistors that left Japan 40+ years ago. Hopefully they will make it another 40 years.

With the power transistors and the heatsink cleaned up I'll reinstall the power transistors into the heatsink.

I'll apply new thermal compound and install new insulators. This will help the transfer of heat from the transistors to the heatsink.

During this Pioneer SX-1050 repair and restoration I also cleaned up the backside of the heatsink assembly

I'm ready to reinstall the serviced heatsink/power transistor assembly into this Pioneer SX-1050 receiver.

With the heatsink assembly removed I can change the electrolytic capacitors on the power amplifier assembly.

With the heatsink removed there is enough slack in the wiring so that I can get to both the front and the rear of the assembly.

Same story on the power amplifier assembly, those 40+ year old electrolytic capacitors need to be replaced.

Be careful with the bias transistors shown below that attach to the heatsinks. The wires can break very easily.

The two 22,000uf, 80 volt original filter capacitors will be replaced in this Pioneer SX-1050 solid state receiver.

With the filter capacitors removed from the chassis it's a great time clean up the decades of grime.

I will use 22,000uf, 100 volt capacitors as replacements that have the exact dimensions as the originals.

It's a good idea to take pictures so that you can be sure that you wire up the new capacitors correctly.

Both the original and the new filter capacitors were screw type but the new capacitors screws were a slightly larger diameter.

The screws for the new capacitors would not fit thru the ring connectors in the Pioneer SX-1050. I drilled them out slightly to fix the issue. 

This was not a big deal but you run into things like this as there are no longer OEM parts for a Pioneer SX-1050.

The replacement filter capacitors have been installed. Hopefully these will help this SX-1050 operate well for many more decades.

I found that the sealed volume control needed cleaning that required it to be removed.

 

Many times the sealed volume controls like the one in this Pioneer SX-1050 receiver do not require cleaning but this one did.

The left and right channels would come and go as you turned the volume. Many flakey issues can be fixed by cleaning with deoxit.

I had to unsolder the volume control and loosen two screws on the volume control. You are better off not to remove the screws.

With the two screws loosened you separate the case enough to get your deoxit straw into the opening.

Once again just loosen the screws and leave a couple of turns on the nuts. You can destroy your control if it comes apart. 

Also at the back of this Alps volume control there is a label and it looks like a solid back panel.

You can cut thru at the center as that part of the volume control is hollow and is only hidden by the paper label making it easier to Deoxit.

I used a piece of a self adhesive label to cover the hole back up to keep dirt out of it in the future.

This Pioneer SX-1050 repair and restoration required some soap and water. The picture below shows the inside of the bottom cover.

The knobs needed to be cleaned up. Many times vintage audio equipment has just been sitting around for years.

A little dish soap and an old tooth brush works well on cleaning up the knobs

I'll clean up the faceplate of this Pioneer SX-1050 solid state receiver with dish soap, warm water, rags, Q-tips etc.

I have reinstalled the cleaned up faceplate and knobs. This Pioneer SX-1050 receiver is looking better.

This Pioneer SX-1050 is looking better but any vintage audio repair or restoration should include bench testing.

I'll use a Sound Technology 3200A audio analyzer along with a signal generator during bench testing.

Both channels of this Pioneer SX-1050 tracked very close to each other at various volume control settings.

This Pioneer SX-1050 easily met it's distortion specifications at varying frequencies and power output levels.

This Pioneer SX-1050 receiver repair and restoration is complete. It's time for some music!

 


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