Pioneer A-27 Repair And Restoration

This Pioneer A-27 solid state integrated amplifier is in pretty good cosmetic shape but needs some repair and restoration.

I have removed the top cover of this Pioneer A-27 integrated amplifier. It's a good idea to take a casual look before powering up unknown equipment.

I have removed the faceplate. There is always a lot of cleaning when you are doing a vintage audio repair or restoration.

Many of the bulbs are burned out in this Pioneer A-27. The bulbs are 40 years old so it's something to be expected.  

The bulbs are still available but I'll be replacing them with LED's. These are used as indicator lights so the light emitted will look the same.  

5mm Led's fit the bulb housing in this Pioneer A-27 just right. A nice snug fit.

With the faceplate off I'll get that cleaned up. Warm water and a little soap works pretty well.

I have removed the bottom cover on this Pioneer A-27 integrated amplifier. The cables and harnesses all look neat and orderly

Many of the individual boards have plug in connectors. This makes the repair and restoration of the Pioneer A-27 easier.

With the individual boards removed from the chassis it makes component replacement easier.

Not all of the boards in the Pioneer A-27 are plug in style. Some are wired point to point.

There is enough slack in the wires to get the boards where you need them to clean the pots and switches with deoxit.

There is also enough slack in the wires to access both the component side and the artwork side which is necessary for component replacement.

I will be replacing 40 year old electrolytic capacitors. These capacitors should be replaced for reliability as well as sound quality.

All of the capacitors replaced will be high temperature rated at 105 degrees centigrade. Which converts to 221 degrees Fahrenheit.

The wiring can only take so many bends and turns before they will break. It's best to find a working position where they can be mostly stationary.

Much of the wiring in the Pioneer A-27 is on the artwork side of the board. It can get pretty tight in here with a soldering iron.

I move the wires that I need to out of the way. I try to give my soldering iron a hole to work in with some space to maneuver.

There are also a good number of wires on the top of several boards that need to be accounted for. 

It's best to check your work as you go. Work on an assembly or two and then make sure the unit is still operating properly before moving on.

I had an issue with the left channel in this Pioneer A-27 integrated amplifier. Intermittent distortion that was audible from time to time.

After troubleshooting I found a bad transistor. Modern test equipment helps with the repair and restoration of vintage audio equipment.

I have another assembly removed. I will clean the pots and switches as well as change out electrolytic capacitors.

Some of the assemblies during this Pioneer A-27 repair and restoration were removed from the bottom of the chassis.

Another plug in style assembly has been removed from this Pioneer A-27 integrated amplifier for component replacement.

Many of the electrolytic capacitors that will be replaced have spent 40 years very near transistors that generate a lot of heat.

The picture below shows what were 40 years ago identical original capacitors. The two on the right were closer to the heat generated by the transistors.

I have started to replace the original capacitors with modern ones. The old ones were rated at 85 degrees centigrade, the new ones 105 degrees centigrade.

The assembly is ready to be reinstalled. All of the electrolytic capacitors have been upgraded to high temperature rated devices.

Some of the capacitors are very close to the heatsinks and will experience high temperatures. Using higher temperature capacitors will increase reliability.

This Pioneer A-27 repair and restoration was made easier by the chassis design. Three of the assemblies are removed by unplugging cables and removing a couple of screws.

The power supply of this Pioneer A-27 integrated amplifier received Nichicon PW high temperature rated capacitors.

It's time to get the assemblies and the cables reinstalled. Then it's time to power up this Pioneer A-27 and start testing out the work that's been done.

The power supply was rebuilt so I need to check the voltages and adjust if necessary.

The voltages all look fine. You should always have the service manual available. The manual will have a procedure for measuring and adjustments.

I will remove the output transistors and heatsinks for service during the repair and restoration of this Pioneer A-27 integrated amplifier.

I have removed the first of the two heatsink assemblies in this Pioneer A-27.

I will clean up the heatsink as well as reseating the power transistors.

New transistor insulators will be installed after cleaning up the old thermal paste and adding new. 

 I have removed the power transistors. The old thermal paste has hardened after more then 40 years of service and needs to be replaced. 

I have the heatsinks cleaned up. I will now install the new thermal paste and insulators along with the original output transistors.

The original power transistors were also cleaned up during this Pioneer A-27 repair and restoration. Hopefully they will last another 40 years.

The first output assembly is all ready to be reinstalled into this Pioneer A-27.

The first heatsink/output transistor assembly has been reinstalled and the second one removed.

It's the same procedure as the first assembly. First cleaning up, installing new insulators, replacing old thermal paste and reseating transistors.

With the heatsink/output assemblies back together this Pioneer A-27 integrated amplifier is getting closer to starting it's next 40 years.

The filter capacitors will be replaced during this Pioneer A-27 repair and restoration. They have started to leak.

None of these 18,000uf capacitors measured over 10,000uf! Even the one's that visually looked fine.

One of the capacitors had started to show some corrosion which is never a good sign for a capacitor.

All 40 year old electrolytic capacitors should be replaced for reliability as well as sound quality.

These old electrolytic capacitors are all ticking time bombs. They all will fail someday. Today? Tomorrow? Year's from now? Who knows.

Let the gunk from a leaking capacitor slowly flow into your equipment and something bad is going to happen. Replace those old capacitors!

The replacement capacitors are manufactured by Nippon Chemi Con and rated at 105 degrees centigrade.. I'll be using 22000uf 80 volt capacitors.

The original filter capacitors were rated at 85 degrees centigrade and were 18000uf 71 volt capacitors.

I had to drill out some holes in the filter capacitors connection plate as the new capacitor screws were slightly larger.

The original filter capacitor brackets along with the rubber spacer worked fine with the new capacitors as the diameter was the same as the old ones.

I have the new filter capacitors installed. This Pioneer A-27 repair and restoration is getting close to completion.

I have reinstalled the fuse board along with dressing the cables back neatly. This Pioneer A-27 is getting ready for it's next 40 years of service.

Any Pioneer A-27 repair and restoration should include the bias/dc offset being checked then adjusted as needed.

Once again before servicing a Pioneer A-27 always have the service manual. The manual will have all the details needed.

Both ground lugs on the back of this Pioneer A-27 were loose. This caused a hum when using the phono inputs.

After loosening the back panel I still couldn't get to the loose ground lugs in the Pioneer A-27 integrated amplifier.

I had to remove the RCA input jack interface board from the back panel. I could then repair the loose ground connectors.

With this section removed it's a great time to clean up the back panel. This Pioneer A-27 repair and restoration is getting closer to completion.

The grounds are now tight, the panel is cleaned up and all of the rear panel RCA jacks have been cleaned with deoxit.

This Pioneer A-27 integrated amplifier is back together. I'll take another look in the chassis to make sure everything is as it should be.

It's time to check out the controls and make sure they are all working properly. Then it will be time to put the top cover on.

This Pioneer A-27 integrated amplifier repair and restoration is complete. It's time for some music!

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