Sansui BA-5000 Repair And Restoration
This Sansui BA-5000 is more then forty years old and is in need of some service.
This Sansui power amplifier weighs more then 100 pounds so you will get a workout just moving it around.
This Sansui BA-5000 is scratched up a bit and some of the cover screws are missing or are not the correct screw type.
I have begun to take the covers off and I can see that there will be plenty to clean up in this Sansui BA-5000 power amplifier.
I notice that the bias transistor that is normally attached to the power transistors heatsink is loose and wrapped in electrical tape.
This type of issue is why you should always give any unknown piece of vintage audio equipment a visual look before powering it up.
The other channel also has the bias transistor wrapped in electrical tape and is hanging loose.
Powering up this Sansui BA-5000 with the bias transistors in this unknown condition could cause severe damage in short order.
Once again doing a visual check during any vintage audio repair or restoration is a must before even thinking about applying power to the unit.
With this Sansui BA-5000 power amplifier sitting vertically with the bottom covers removed I can see another issue.
I can see something wrapped in.....You guessed it, some more electrical tape.
After unwrapping my latest Christmas present I find that I have a resistor.
I find that this resistor is part of the fan circuit. I've got more important issues then the fan circuit at this point. I'll figure this out later.
Still looking from under the chassis of this Sansui BA-5000 I can see the regulated power supply assembly.
I'm happy to see the original tie wraps as installed by the factory in 1976. This means no one has messed with this area of the BA-5000.
The original filter capacitors along with the original rectifiers are also as they left the Sansui factory in Japan many decades ago.
This Sansui BA-5000 power amplifier has no power switch. It was bypassed at some point in the past.
One of the speaker posts are broken off at the back of this Sansui BA-5000.
After removing the protective cover from the fan I can see plenty of grime to clean up from it.
After removing the fan from the heatsink assembly I get my first look at the grime that is clinging to the output transistors.
Any vintage audio repair or restoration involves a lot of cleaning and it's obvious this Sansui BA-5000 is going to need some cleaning.
I can tell that some of the power transistors are not original with transistors having manufacturing date codes from 1985.
There seems to be a mix of the original Sanken output transistors along with a variety pack of other brands/types.
This heatsink/output transistor assembly will need to be removed from the Sansui BA-5000 for further inspection and cleaning.
I have now removed the heatsink/output transistor assembly. I can clean out the part of the chassis that this assembly normally occupies.
I live in Florida and in the winter months I will sometimes work outside as the temperature is usually pretty nice with low humidity.
What better place to start cleaning this assembly then outdoors. I've leave the mess out here.
If the sun starts getting hot I'll move my portable table to another area.
I've started to remove the power transistors from this Sansui BA-5000 power amplifier.
I'll test each output transistor. Then I'll decide if any replacements will be needed for this Sansui BA-5000 repair and restoration.
I have written the output transistor results out on paper. I used a Peak DCA Pro for testing of the transistors.
Some of the transistors tested poorly and others looked like they were hit with a hammer.
The Sanken transistors will be kept but the others will be replaced.
The picture below shows all of the output transistors that were installed in this Sansui BA-5000 power amplifier.
With the output transistors removed from the heatsinks they can be cleaned up.
I'll remove the F-2516 and F-2517 connector boards for inspection and cleaning.
Some of the original emitter resistors were replaced at some point in this Sansui BA-5000's life.
I have the connector boards removed from the heatsink so that I clean the heatsink up well.
There is decades of dirt and grime to clean up in every corner of this Sansui BA-5000.
Looking much better now. This Sansui BA-5000 will be ready to start it's next 40 years.
Now it's time to flip the heatsink assembly over and clean up the transistor mounting side.
I've cleaned off the old thermal grease and the heatsink is ready to have the power transistors mounted.
I'll be using On Semi MJ1193/MJ1194 replacement transistors for the outputs. These are well suited for the Sansui BA-5000.
New output transistor insulators and thermal grease will be added.
I have reinstalled the output transistors along with the new insulators and thermal paste into the heatsink assembly.
Sometimes it's best and easiest to take what you can to the sink for cleaning with dish soap and warm water.
The fuse panel is cleaned up and will be reinstalled during this Sansui BA-5000 repair and restoration.
Now it's time to work on the F-2518 driver board during this Sansui BA-5000 repair and restoration.
The transistor hanging with the red wires is the bias transistor. These red wires and this transistor type 2N2222 is not original.
Before I figure out the bias transistor I'll be changing out the old electrolytic capacitors along with transistors, and diodes that have a history of failing.
This capacitor is not leaking. Some of the electrolytic capacitors were held in place with glue during assembly in Japan. That's the brown stuff.
This glue should be removed when replacing the capacitor. It has shown over time that it can damage the circuit board or surrounding components.
The glue will usually comes off fairly easy. An X-acto knife, small screwdriver or even a finger nail will work.
The transistors will be replaced on the driver boards with modern equivalents.
There is plenty of dirt to clean up even on the back side of the boards.
In certain circuits in the Sansui BA-5000 power amplifier audio grade replacement capacitors should be used.
The connector pins with be cleaned with Deoxit during this Sansui BA-5000 repair and restoration.
The other driver board in this BA-5000 will get the same updates.
Any suspect components like this resistor that shows heat damage will be replaced.
The filter capacitors in this Sansui BA-5000 tested out okay. They need to be replaced after more then 40 years of service but will stay for now.
The F-2521 power supply will be rebuilt during this Sansui BA-5000 repair and restoration.
Taking pictures before removing any assembly is always a good idea so there are no mistakes when reinstalling.
I have removed the F-2521 power supply for electrolytic capacitor and transistor replacement as well as connector pin cleaning.
With the F-2521 power supply removed from the chassis it's a good time to look at the artwork and solder joints of the assembly.
I'll be using Nichicon PW series capacitors in the power supply. 80 volt rated original capacitors will be replaced with 100 volt.
Notice the size difference between the old and new capacitors. In addition Nichicon PW series capacitors are rated at 105 degrees centigrade, the originals 85.
The original regulator transistors will be replaced with new On Semi MJE15032G transistors.
I've completed the component change of the F-2521 power supply.
The rebuilding of the power supply during this Sansui BA-5000 repair and restoration is an important step to making the unit reliable.
I have reinstalled the F-2521 power supply back into the chassis of the Sansui BA-5000.
Now I will remove the Sansui BA-5000 faceplate so that I can clean it as well as to access more assemblies.
Dirt and grime find way to get in. Even the meter assemblies will need to be cleaned.
Now I will need to remove the F-2520 buffer amplifier board for inspection and to replace almost 45 year old components.
The buffer amplifier board is attached at the front of the Sansui BA-5000.
The buffer amplifier comes out fairly easy once you remove the faceplate, cables and screws.
Once out of the chassis I'm able to inspect the buffer amplifier. I can see that the gain controls have been drilled out for cleaning at some point.
I'll also inspect the artwork side for any issues. If nothing else this buffer amplifier's artwork side needs a good cleaning.
From what I can tell this Sansui BA-5000 buffer amplifier has not been out of the chassis sense it left Japan in 1976.
This Sansui BA-5000 power amplifier repair and restoration will take many hours to complete but I feel this unit is worth the time.
I will use replacement capacitors at a minimum that meet the voltage specifications but many times the replacements will be higher rated.
This original capacitor in the picture below was fairly near a power resistor. The dark spot shows the heat that it was subjected too.
This original capacitor in the picture below was directly across from a power resistor. It was subjected to very high temperatures for decades.
I have replaced the electrolytic capacitors with modern high temperature rated ones. Each is rated at 105 degrees Centigrade, 221 degrees Fahrenheit.
Many of the transistors were replaced with modern low noise versions along with the connectors pins being cleaned.
Now the F-2515 meter amplifier assembly with be serviced during with Sansui BA-5000 repair and restoration.
I have removed the first of two meter amplifier assemblies from the meter housing and will upgrade the components.
The meter amplifier assemblies will have electrolytic capacitors, transistors and diodes replaced.
The Sansui BA-5000 has some diodes that have a history of failing. They are the green and black components shown in the picture below.
I have made up the equivalent diode by combining two modern diodes.
I'll check the artwork side of this F-2515 meter amplifier assembly for any issues.
I have completed the component upgrades on this Sansui BA-5000 power amplifier meter assemblies.
I'll clean up the connector pins with liquid Deoxit D100 and a Q-tip. Then they will be ready to be reinstalled on the meters.
I'll clean up the back of the meters before I reinstall the upgraded meter amplifier assemblies.
There is no better time to clean the front while I am holding the meter assembly in my hand.
This Sansui BA-5000 power amplifier repair and restoration involves a lot of cleaning. Almost 45 years of grime to take off.
This Sansui BA-5000 is looking better and better but there is still a lot to do.
I reinstalled the upgraded meter amplifier assemblies into this Sansui BA-5000 power amplifier.
I then reinstalled the upgraded buffer amplifier assembly. This Sansui BA-5000 repair and restoration has one area completed.
For all the work that I've done so far to the BA-5000 I have yet to apply power to it. There were just to many issues to take a chance.
I have rebuilt the power supply, buffer amplifier, meter amplifier, and the driver assemblies. I will see if I can check those areas first.
I will use a variac for the first power up. You don't want to power up the Sansui BA-5000 for the first time on full line voltage.
I will also use a dim bulb tester along with the variac. The bulb will burn brightly if the Sansui BA-5000 is drawing excessive current.
I will use meter's to monitor voltage and current to try and prevent any damage if there is an issue.
I found that the power supply voltages were correct and the Sansui BA-5000 was not drawing excessive current.
These preliminary tests were done without the power amplifier assembly installed in the Sansui BA-5000.
I ran a 1000HZ sine wave from a signal generator into the Sansui BA-5000 RCA input jacks. I monitored the output at the driver assembly.
The signal out of the driver assembly looked good on the oscilloscope and could be adjusted correctly with the gain controls.
Verifying that the voltages look good and that I am able to pass a signal from the RCA inputs out through the driver assembly I'll move on.
I noticed after powering up the Sansui BA-5000 power amplifier that one of the six fuse type lamps was burned out.
The original lamp has a blue gel cap molded to the lamp. My replacement is just a clear lamp.
I cut the original gel cap with an X-Acto knife off of the original burned out Sansui BA-5000 lamp.
I then fit the gel cap over the replacement fuse type lamp.
The replacement lamp now looks just like the original and it lights up just like the originals Only needing one replacement lamp this was the way to go.
I will clean up the lens assemblies on this Sansui BA-5000 so that the light from the fuse lamps is strong and even on the power meters.
I will now replace the two electrolytic capacitors on the F-2519 power supply board along with cleaning the connector pins.
I have replaced the two capacitors on the F-2519. This Sansui BA-5000 repair and restoration is moving forward.
Once again I'll look for any issues on the artwork side of the F-2519. After 45 years solder joints can cause problems.
A new Omron soft start relay will be installed in this Sansui BA-5000 power amplifier. The exact relay is still available for purchase.
The soft start relay plugs into a connector on the Sansui BA- 5000 so that makes changing it out easy.
Behind the relay are two 3.9 ohm power resistors who's job it is to take the current surge for a second or two as the BA-5000 is turned on.
The resistors checked out fine and will be reinstalled.
With the surge resistors, relay socket, and new relay installed this section of the Sansui BA-5000 power amplifier is ready for service.
The picture below shows the resistor that sits between the output transformer and 8 ohm speaker tap of the left channel.
It goes without saying that this resistor got very hot! What happened? Who knows?
The capacitor was shorted, the resistor measured good but I replaced it anyways.
This burnt resistor caused me some concern for the output transformer so I applied about 25 volts AC to the 2 ohm tap and took measurements.
The AC voltages measured at the 4 ohm tap and 8 ohm tap both increased as expected. So it appeared the output transformer was working correctly.
The BA-5000 was the only solid state amplifier that Sansui ever made that used output transformers.
One of the main reasons that the BA-5000 can drive nearly any speaker is the output transformers. It's also why it weigh's so much.
Now it's time to figure out the mystery of the bias transistors in the tape. This one has a 2SC984 transistor with broken wires.
This one has a 2N2222 transistor under the tape. The bias transistors operating properly are critical to the Sansui BA-5000.
After experimenting with different bias transistor types I settled on the KSC2383 to use as the bias transistor.
I used as much of the original wiring as I could to construct the new bias transistors for this Sansui BA-5000 power amplifier.
With the driver cards installed I was able to adjust the bias high or low of the 180mA specification with the bias current staying stable.
I did notice that the right channel DC offset was high at 80mv. This was caused by a defective 2SA798 transistor.
The transistor tester showed a large gain difference between the two half's of the 2SA798 transistor. Gained matched KSA992's replaced it.
I found a used power switch from a Pioneer Spec 4 on eBay that I will use for the missing power switch on the Sansui BA-5000.
The pioneer Spec 4 power switch works fine and looks good. A lot better then no power switch at all.
Where tie wraps were cut new ones were installed and all routing of the wiring was done neatly.
I'll now do some bench testing before I put this Sansui BA-5000 power amplifier totally back together.
This Sansui BA-5000 checked out fine on the test bench so I have reassembled the amplifier.
There is no reason that this BA-5000 amplifier can not be operating properly for many more decades after it's repair and restoration.
This Sansui BA-5000 will never be cosmetically perfect but that is a large reason why vintage audio equipment appeals to me.
This Sansui BA-5000 was not shown much respect for a long time but with some work 45 years later this amplifier is still ready for everyday service.
I'm sure the engineers that designed the Sansui BA-5000 never thought that almost a half century later the amplifier would still be in use.
This Sansui BA-5000 power amplifier repair and restoration is complete. It's time for some music!