Pioneer SX-1980 - Repair And Restoration

This Pioneer SX-1980 is in good cosmetic condition but after 40 years it's in need of some repair and restoration. 

I have begun to disassemble this Pioneer SX-1980 receiver. A classic piece of stereo equipment from the 1970's. 

A bit dusty but not bad. This Pioneer SX-1980 solid state receiver chassis should be an easy clean up.

 This is where the Pioneer SX-1980 needs some repair and restoration attention, the power supply.

The power supply assembly inside the Pioneer Sx-1980 fry's itself as you will see in the next picture.

Hmmm.....I wonder if those dark area's were from years of heat? The answer is yes.

Transistors needed to be replaced during this Pioneer SX-1980 repair and restoration. Amazing they lasted almost 40 years with the heat generated. 

All back together after replacing the transistors and capacitors in the power supply.

I used Deoxit to clean the pots, switches, and contacts.

Tie wraps work well for a third hand.

More transistors and capacitors to be replaced during this Pioneer SX-1980 restoration.

Same Here......Replace those parts.

Ready to be reinstalled.

Another assembly out for part replacement and cleaning.

More work here.

An important part of this Pioneer SX-1980 repair and restoration will be to clean the push button switches along with the toggle switches.

You must remove the switches and pots from the chassis to properly clean them.

Fortunately in the Pioneer SX-1980 receiver the removal of the necessary boards is not that difficult.

There is a good amount of slack in the cables that allows the Pioneer SX-1980's boards to be accessed.

Once removed you can clean the switches and pots correctly with less of the mess that deoxit can make.

Try not to bend the boards around too much. The wires are wire wrapped to pins and these can break if bent back and forth.

The push button switches are one of the leading causes of intermittent sound issues in the Pioneer SX-1980 solid state receiver.

I used cardboard to stop the deoxit spray from going anywhere it shouldn't when cleaning the push button switches.

You can tell when you have got the deoxit spray where you need it. The deoxit will seep from the small holes near the contacts of the switch.

Work the switches 20-30 times each. This will take some time and patience but this Pioneer SX-1980 repair and restoration requires it.

All of the front panel boards have been removed from the chassis. You can move these into position as needed.

I used modern test equipment to help match transistor gains during this Pioneer SX-1980 repair and restoration.

I also used modern components where it made sense. Vintage audio repair and restoration requires some research before beginning a project.

Here I have cleaned the switches and upgraded components in the filter amp.

 I have started to reinstall the boards I had removed for service back into this Pioneer SX-1980 receiver.

The last two assemblies are ready to be reinstalled. This Pioneer SX-1980 repair and restoration is getting closer to completion.

I've got everything back together and I will power up this Pioneer SX-1980. I'll make sure all is well before moving on.

There is a issue with the FM reception in this Pioneer SX-1980 receiver and I have removed the protective covers for access.

Always review the service manual before you attempt to "play around" with the FM section of the Pioneer SX-1980.

I use a ST 1000A to help me with FM issues. Just like everything in life having the proper tools to do a job can not be overstated.

After following the FM adjustment procedures in the service manual I can now tune and lock FM stations along with having good sensitivity and selectivity.

I'll be replacing the four 22,000uf 100V filter capacitors during this Pioneer SX-1980 repair and restoration.

The Pioneer SX-1980 receiver has screw type connectors on the filter capacitors that are accessed from the bottom of the chassis.

You remove the filter capacitors from the top of the chassis. Don't forget to clean up the dirt before installing the new capacitors.

I have installed two of the new filter capacitors. The original capacitors are about 40 years old and it's time to replace them.

The four filter capacitors have now been replaced with new Nippon Chemi-Con 22,000uf 100V capacitors.

I have hooked up the wiring of the new filter capacitors at the bottom of the chassis. This Pioneer SX-1980 is getting ready to start it's next 40 years.

The Pioneer SX-1980 receiver powered up fine with the new capacitors. This repair and restoration is one step closer to completion.

Now it's time for some bench testing. After 2 hours of warm up I have adjusted the SX-1980's idle current and DC offset.

The service manual for the Pioneer SX-1980 has a procedure for amplifier adjustments.

I was able to adjust the idle current and DC offset to specifications. This should always be done before bench testing.

I will use a signal generator that can provide varying frequencies for testing of this Pioneer SX-1980 receiver.

I use 8 ohm 300 watt load resistors on the test bench. This receiver will push them to their limits.....and maybe beyond.

The ST 3200 audio analyzer shows that the power output of this Pioneer SX-1980 is very even for both the left and right channels.

I worked my way up in power output and supplied frequencies taking measurements as I went.

This Pioneer SX-1980's power versus distortion stayed pretty much the same through the audio range.

The volume control also stayed within 1% - 2% between channels throughout it's range. Below shows 84.1 watts left and 84.8 watts right.

The power meters were calibrated during this Pioneer SX-1980 repair and restoration.

The adjustment pots for the meters are on the left side of the chassis.

This Pioneer SX-1980 solid state receiver met it's amplifier power/distortion specs. Any vintage stereo restoration should include bench testing.

This Pioneer SX-1980 restoration is about complete. I'll leave it running on the test bench for a few hours to make sure all is well.

135 capacitors and transistors were replaced in this Pioneer SX-1980.

Always use respected names for your replacement components. Just pennies more for the piece of mind.

I've put the covers back on this Pioneer SX-1980 solid state receiver and after one final check it will be done.

Now it's time for some music. This Pioneer SX-1980 repair and restoration is complete.