Solved Weak Output In PANASONIC TWO-IN-ONE Model RX-M70
This was brought by a recently added customer with the complaint that the output was weak in all modes; i.e., Tape & Radio. I checked the set in front of him and found it to be true. I took up the set for service as soon as I could get some gap. Paucity of time because of other activities, have increased my backlog. But I am right now not in a position to evade acceptance on one pretext or other like before because of financial strains being presently experienced and that is the naked fact and I am not ashamed to admit it! Having said that let me come back to our main subject of this article.
I opened the set, during which I noticed that the set had undergone service before, though the customer seemed to say otherwise. A few screw legs were found broken as the set had been forced open due to potter wasp building nests on the screw holes. It took some efforts for finally opening the set to see the condition inside. There was not much dust collection, but corrosion and rust formations were found in many places. I dismantled the entire set to carry out my usual service.
As I noticed that a few capacitors were corroded, I happily replaced all the electrolytic caps (Totally 24 numbers) as usual. Did a retouch of all the solder joints.
As you can see, this set had three speakers; one woofer, one midrange and one tweeter. I am giving an extract of the circuit diagram that I could download:
The midrange speaker was driven by IC202, AN7141 and woofer by IC201, LA4192 with bridged output to drive a mono speaker. The tweeter was connected parallelly to the midrange. Over all it was a good circuit for a mono set like this. It should give a good output with segregations of frequencies. The cause for the low output might have been due to filter capacitors that were found corroded and also the clogged switches such as function, band and recording switch of tape.
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I cleaned and lubricated all of them including the connectors and headphone socket as well. Then when I applied power, the output was very good and I really loved it. The three bands; Medium, Short and FM and the tape worked very well. I applied IPA on the belts when the mechanism was running to clear off dirt and dust and to increase its grip.
I played the cassette that came with the set a couple of times running both the A & B sides, enjoying the nostalgic songs of yester years!
The testing was done keeping the boards on the table, as I had removed the woofer for cleaning inside:
Then fixed the speaker, board and mechanism back in its place and played tape and radios for some more time.
Then fixed the front cover on the available screw legs. Did some more tests before passing it over to delivery section.
Mission accomplished with satisfaction that got added to the collection.
This article was prepared for you by Parasuraman Subramanian from India. He is 76 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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Albert van Bemmelen
April 11, 2026 at 2:55 pm
No doubt cleaning, lubricating and replacing those 24 capacitors in this Panasonic RX-M70 set took a good amount of time before it was back in good working condition. And I hope it helped you to solve any present financial strains that no doubt do happen in these stressful economic times! Especially after the recent absurd high gas prices at the pump.
Parasuraman S
April 11, 2026 at 9:56 pm
Yes, Economy hits us very badly, that too when we have other pressing needs! But only when we swim against opposite currents, we gain power and strength! Many thanks for your expert comments, dear Albert!
Yogesh Panchal
April 11, 2026 at 3:30 pm
Good Job!Sir,
Revived the unit for at least for more 10 years with proper maintenance...
Parasuraman S
April 11, 2026 at 9:58 pm
Let us hope so. The customer is very happy and still spreading praises to all known circles and is responsible to sprout new customers for me! Many thanks for your comments, dear Yogesh Bai!
Mark J
April 12, 2026 at 2:41 am
Parasuraman nice repair and restore.
Parasuraman S
April 12, 2026 at 11:51 am
Many thanks, dear Mark!
MP
April 12, 2026 at 11:10 pm
What greatly aroused my interest to read the article was the radio brand name. It evokes sweet memories. And so I couldnt agree more with you when you wrote ...... the output was very good and I really loved it. I, heard such like sound in 1990 from a sister radio. Ever since, that instant refuses to leave my thoughts. The sound was remarkable: a deep bass and a pleasantly superb general audio from a hi-fi system that made one not to feel like listening to a lower rated sterio radio. When I'm feeling really low I prefer doing vigourous exercices that make my body and mind to feel relaxed after drinking a lot of water. It also brings about a sound sleep. Rest is important for good health. No overwoking !
Parasuraman S
April 13, 2026 at 5:38 pm
Many thanks for your comments!
Boris
April 13, 2026 at 9:40 pm
Ha, my father has the same exact radio. He bought it in Doha on its way back after a couple months of work in the emirates, some 25 years ago. Still going strong, except the cassette door which often does not open...
Thank you for another nice article!
Parasuraman S
April 14, 2026 at 7:06 pm
Use WD40 and clean any rust formations in the spring. Use silicon grease at the hinges of the door. Apply WD40 on the mechanism buttons ensuring that they do no spill over to the belt, pinch roller, play well and other rubber parts. Then press it down one after the other several times in order to smoothen the mechanism. Many thanks!
Boris
April 30, 2026 at 8:41 pm
Thank you very much for your suggestions Parasuraman, will definitely follow them, the issue now is getting the door to open... I'd prefer not to open the whole chassis for now, since the rest is working very well.