A friend of mine recently asked me to take a look at his Marantz 2238b receiver. When I met him to pick up the receiver, he said overall it “sounded bad” and one of the channels was possibly out.
Thankfully the receiver simply needed a good cleaning and some lights replaced. See before and after in the video below:
I wrote a post on how to replace the lights and clean a Marantz 2215b receiver and even though the 2238b isn’t that much different, I went ahead and documented my steps with photos for this post. Read on if you’d like to try this yourself.
Please note – I am still teaching myself how to repair vintage audio gear and would not consider myself an expert. This guide is not meant to repair all vintage audio gear, only point out how to handle cleaning and replacing lights.
If you are a beginner and want to follow this guide, please take your time and go slow. There are some steps that I will not include because they require soldering knowledge. But everything else just requires a screwdriver, some Deoxit, new lights, (a lot of) patience and a steady hand.
Let’s begin.
FIRST THINGS FIRST: UNPLUG THE UNIT!!!
These receivers pack enough of an electrical punch to cause serious injury so please unplug the unit before following any of the steps below. We can’t be held responsible for any damage to your equipment or more importantly yourself so please unplug the unit and if any of the steps below feel dangerous to you, please have a professional handle instead.
Let’s Replace Those Lights!
With the unit unplugged, we need to remove the top of the unit which is easily handled by unscrewing four screws on each side of the unit. In the photo above I have already removed two from the left side.
Also, there are four screws on the top of the unit to remove: two in the front, two in the rear. See photo below with screws circled…
Remove the cover and you’ll find the above view of the unit…
First, let’s replace the lights for the Signal Strength and FM Tuning meters on the left side of the unit.
In the photo below you will see two plastic tabs circled.
PLEASE NOTE: Both of these tabs snapped off when I attempted to unhook the light’s base. I was able to glue them back after I replaced the lamps but it took some patience.
What you need to do is remove the lamps from their casing. As you can see, it should be as simple as sliding them up and out of the plastic tabs mentioned above but remember, these are over 40 years old and those pieces get fragile with age. Hopefully they will not break on you.
Once you have them released from those tabs, simply pull the piece back to reveal the bulbs as shown in the photo below. In this case both bulbs are burned out.
All you have to do now is replace them with your bulb of choice. In my case I had some extra LED lights lying around as replacements in the photo below.
Now, simply secure the lights back in place and you are ready to move to the tuning dial lamps!
The best way to approach the tuning dial lamps is by removing the board from plastic pieces very similar to the ones for the meter lights. I’ve circled the spots in the photo below. I was able to take a screw driver to one end of the green circuit board and push slightly up until it came loose. Thankfully, none of the plastic holders broke on me like they did on the meters!
Once the circuit board is free, simply tilt backwards to reveal the lamps as shown below:
Simply replace each with a new bulb…
Once the lights are replaced, insert the circuit board back into place.
Please note, since this is a beginner’s guide, I’m not including how to replace the tuner pointer light, stereo light, etc., as those require soldering.
Lastly…where do you buy lights? I use www.dgwojo.com where I email David the name of the unit and model number and he provides me with the options needed.
Cleaning Pots. Eliminate Scratchy Sounds For Good!
To eliminate scratchy sounds on your receiver, you need to clean all of the potentiometers or “pots”. These can vary from knobs you turn to buttons you push or slide.
The Marantz 2238b has the following pots and switches to clean:
Five pots to clean: Bass, Mid, Treble, Balance and Volume (the most important).
Eight push button selectors to clean: FM Muting, FM 25, Tape 1 Monitor, Mono, Hi Filter, Loudness and Speakers 1 – 2. The most important button to clean is the Tape 1 Monitor.
Below are instructions on how to access and properly clean.
First, with the power still unplugged from the receiver, remove the bottom casing from the unit. You might want to keep a bowl or container close by to keep the screws safe as they have a tendency to run away. I count twelve total screws.
The secret to clean pots is in the sauce and you will want to have a can of Deoxit on hand to spray into the pots to clean. Deoxit can be found at your local Guitar Center or simply via Amazon.
Buy Deoxit from Amazon and help support this site.
I do not recommend using any other cleaner besides Deoxit. Please do not take any liberties here and try something different. Deoxit is the only product to use.
Where do I spray? In the photo below you will see all of the pots to clean.
Spray right into the openings of each pot as shown below. You do not have to spray a lot. A little squirt goes a long way with Deoxit.
After you spray the Deoxit in, simply turn the volume knob on the front of the unit back and forth, back and forth many times to work the Deoxit in. I usually go back and forth about 100 times which sounds like a lot but since I have the unit open I may as well get her as clean as possible.
To clean the push button switches on the front of the unit, you will need to locate the circled area in the photo below. Once the Deoxit is applied, I simply the push the button in and out around 100 times to make sure it cleans properly.
The most important push button switch to clean is the Tape Monitor one. A dirty Tape Monitor switch can cause all sorts of problems, including a loss of sound. Just remember to not keep the switch activated when you eventually power the unit back on or you will not have sound.
Congratulations, you have cleaned all of the pots and switches needed.
WARNING: DO NOT POWER THE UNIT UP TO TEST FOR 24 HOURS.
I usually give the Deoxit PLENTY of time to dry before I power the unit back up to test. Even though Deoxit dries quickly, it’s still liquid based and we know how electricity and liquids mix. So, pat yourself on the back for all the work so far and just be patient, knowing you can power her up the next day.
One last piece of advice, before you plug the unit back in and power her up to test everything, go ahead and turn the volume knob all the way down and make sure your balance knob is correctly centered. Just give the unit a quick eyeball to make sure you will not blow yourself (or your speakers) away when you turn the unit back on.
If everything was cleaned properly, the unit should light up nice and bright from the new lights and the scratchy sounds should be eliminated. If so, turn the unit back off, unplug again and reinstall the bottom and top covers.
If this doesn’t fix the problem, take the unit to a professional for repair. These instructions are meant for a beginner to clean the unit, not attempt a professional repair.
In the video I posted above, all that was needed were clean pots and new lights to get the unit playing properly again. These vintage units can still need a lot of adjustments or to be recapped for optimum use, but for now at least this will get it playing. Any further maintenance or repair should be taken to a professional.
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