Marantz 23 Tuner Repair And Restoration
This Marantz model twenty three stereo tuner is in need of some repair and restoration work.
This Marantz 23 tuner came to me with the original box and owners manual which are always nice to have.
I have removed the top cover. This Marantz 23 tuner was built in the early 1970''s and appears to be engineered and assembled well.
I have removed the bottom plate to take a closer look at the chassis.
During bench testing I found that I had no audio output from the right channel in stereo mode. In mono both channels worked fine.
Sometimes just reading the circuit operation in the service manual can help you fix a problem.
After reading the circuit description I was able to find on the schematic a circuit that would only affect my issue with the right channel in stereo mode.
The 2SC458 transistors are the chief suspects with the audio issue in this Marantz 23 tuner.
The 2SC458 transistor was used for many years in all brands of audio equipment in the 1970's and 1980's. The 2SC458's are known troublemakers.
If you are working on any vintage stereo repair or restoration and you encounter the 2SC458 they must be replaced.
During this Marantz twenty three tuner repair and restoration there were four 2SC458's replaced
I used the SC1845 transistor as a replacement for the SC458 during this Marantz 23 repair and restoration.
After removing a couple of screws and getting some slack in the wiring I'm now able to get to the artwork side to replace the transistors.
The transistors have been replaced in this Marantz 23 tuner and now the right channel is working fine.
This Marantz twenty tuner is now 45 years old. I will replace all of the electrolytic capacitors. A big physical size difference between the old and the new.
It's usually best to work on one assembly at a time and test as you go unless you are a pro. It's a lot easier to find any problems that way.
Get the assembly that you are working on in a good position to solder. Much less chance of damage to the assembly or the wiring that way.
After reworking an assembly do a short test and make sure that everything is working before moving on to the next task.
I didn't want the soldering iron to touch any of the wiring during this Marantz 23 tuner repair and restoration so I used a screwdriver to keep the wires down.
I'm about done under the chassis of this Marantz model twenty three tuner. Always put the wiring back the way that you found it.
The signal strength lamp has burned out in this Marantz 23. I will change that lamp as well as the tuning lamp to LED's.
The old lamps run on 8 Volts AC. I will construct a circuit that includes the LED, a resistor and a diode.
The LED's should stay working for many years in this Marantz twenty 23 tuner.
It's always a good idea to test out your circuit before you permanently install it.
The LED's are installed in this Marantz 23 tuner and look good.
After 45 years this Marantz 23 tuner was in need of some service. Now it's ready to start it's next 45 years!
This Marantz Model Twenty Three repair and restoration is complete. It's time for some music!