AKAI M-10 Reel to Reel tape recorder

[abhi1981]

Hello everyone
Recently got an Akai M-10 for around $141 (Rs. 12000) after a lot of haggling 
Play, FFWD, REW, auto reverse works, but no sound on playing a tape. Tape counter works, belt is loose. I checked the amp by aux cable through line-in, and one channel is working.
VU meters are a bit sticky due to corrosion build-up. Lights are working.
Opened it and there was tons of dust inside. And a lot of wax  from a capacitor  .
Regarding the leaky cap, what should be a suitable replacement for it? These 2uf 250v caps come in lots of sizes - ceiling fans have large ones, but same one in an air conditioner indoor unit is quite small.

[abhi1981]

Some more pics

[abhi1981]

Did some googling.
All the motor run capacitors have two values - one for 60Hz and the other for 50Hz. I need only 50Hz, but not sure which value .

Used google to translate the Japanese text on the cap. It color dots represent the value of that terminal.

[wasedadoc]

Did some googling.
All the motor run capacitors have two values - one for 60Hz and the other for 50Hz. I need only 50Hz, but not sure which value .

Used google to translate the Japanese text on the cap. It color dots represent the value of that terminal.
(Attachment Link)

Should be simple enough to trace which capacitors are brought into play by the 50/60 selector on the back.

[coppice]

Recently got an Akai M-10 for around $141 (Rs. 12000) after a lot of haggling 

Isn't inflation wonderful. That's more than it cost new.

[abhi1981]

Checked the schematics, the 50Hz switch is just shorting the 1uf and 2uf pins of this cap, and the other two caps. This makes it a 3uf cap. The switch has already been factory set to 50Hz.
A 3uf ceiling fan cap should work. A similar modification has been done in this video -
I'll change this cap and clean the switches and then see whether there is sound.

[abhi1981]

A 3uf ceiling fan cap worked. Also cleaned all the switches with contact cleaner.
Now there is sound from tape playback, but right channel is still dead.

[abhi1981]

Changed all the capacitors. Lubed the motors. Fixed the VU meters. Fixed everything mechanical. Now its working perfectly mechanically, but extremely noisy during playback and recording. Lot of hissing and popping and hum at higher volume.
Should I change the marked transistors on the preamp board? What should be the replacement for these?
(pic shows the board with the old caps)

[quadtech]

https://youtu.be/QJwuqaDuuqI?si=vB9Fu04xP1KJrLmK

https://youtu.be/0ikjHpZevQs?si=E7hev2Ak_63_Nitv

Did you replace the main filter capacitor. The YouTube links show a comprehensive restoration including the replacement  capacitors and transistors.

[abhi1981]

Thanks for posting the video links. Very comprehensive.
I have changed each and every electrolytic capacitor present in this machine.
I have not changed the box type capacitors.

[abhi1981]

Just found out that those box capacitors are 0.1uf-120ohm snubbers. 
I'll change them with X2 ones.

[David_AVD]

With all tape recorders that have a mechanical record switch, clean it (spray contact cleaner and exercise) as one of the first steps.

Because they sit in the playback position 99.9% of the time they are often oxidised and a cause of audio issues.

[quadtech]

With all tape recorders that have a mechanical record switch, clean it (spray contact cleaner and exercise) as one of the first steps.

True. and also check/clean for contact corrosion in the headphone / monitor jacks

[abhi1981]

With all tape recorders that have a mechanical record switch, clean it (spray contact cleaner and exercise) as one of the first steps.

Because they sit in the playback position 99.9% of the time they are often oxidized and a cause of audio issues.

Thanks for your suggestion. That was the first thing I did.
But what I have learned from my experience is that contact cleaners do not work on hard oxidized surfaces.  At the most they flush away dirt and other soft residue. Black hard carbon has to be scraped clean or by using hard chemicals - like acids.
The best way to clean switches is to disassemble them and scrape the contacts clean. But sometimes it is impossible to disassemble a switch due to its design, then contact cleaner is the only option.

[Jeff L]

Regarding squeel on playback-- are you familiar with SSS? Certain makes of (old) tapes degrade with age and stick/release stick when going through the transport path.  *Tapeheads. org* has lots of info./ lists of tapes to avoid.

[abhi1981]

No, its not SSS. The squeal was coming from the speakers at full volume. Since then I have changed all the remaining transistors. The problem seems to have gone. Playback and recording is good. But, sometimes while recording, the left channel dies. Cleaned the record slider switches, but the problem remains.

The only thing left was the AA072D ICs. Pins 7 and 8 of the left  IC was kind of open (12 meg). It should measure 470 ohms. Upon desoldering, I found that it was working again. Maybe the heat of solder rejoined the connection inside. I reinstalled it and recording worked fine for sometime. But. now its back to square one. I have ordered the parts for making a replacement IC. I'll test again after installing the replacement ICs.

The whole metal body of the recorder has a little bit of mains voltage on it. Not enough to give a shock, but I can definitely feel it vibrating under my finger. Is this normal or is there a leak somewhere??