Sanyo M9998 Restoration.

[SGrant]

I am the original owner of a 1979 Sanyo M9998. I want to use it to feed my cassettes into a computer to digitize them. But first I have to get the box working.

Given what that has entailed so far I'm relieved to see even the experts are challenged by this one. Countless hours of struggling with it have taught me some tips to pass on. Which I will do below.

This site contains quite a few discussions of working on the M9998. So it isn't easy for people looking for guidance to find the most helpful. My post will add to the clutter, but I will add a link to here, on what I thought was the best of them:

Operation Sanyo M9998!

Finally after a long wait I started working on my Sanyo M9998. From the way the PC boards are positioned in the unit I wanted to try the easiest way to reach the deck section. When I tried before it seemed really hard to reach the deck section. Today I found a much easier way to reach the deck...

boomboxery.com

Edit: the older posts are no longer open for additions.

Getting the AM band to work properly is 1 of 2 remaining problems. I have overhauled the band selection switch. At full volume I get almost inaudible white noise from the speakers, and two very faint radio stations. FM works fine.

The other problem is the tape runs at about 80% normal speed. I can't find any mention of a motor speed control in the manual. The pinch roller is clean but slightly convex. I have a new one on order anyway.

Any assistance with these two problems would be greatly appreciated.

 

[SGrant]

Advice for working on the Sanyo M9998.

This is a follow-on from the excellent advice, procedures and photos at:

Sanyo M9998 Resto

I picked this Sanyo up a while back and it’s been sitting in the pile of boxes for repair. I was put off to a degree by its reputation of being a complete bitch to rebelt. Well I’ve got a bit of time off around Christmas and I thought I’d give it a go. I read a few tips on here and dived...

boomboxery.com

Operation Sanyo M9998!

Finally after a long wait I started working on my Sanyo M9998. From the way the PC boards are positioned in the unit I wanted to try the easiest way to reach the deck section. When I tried before it seemed really hard to reach the deck section. Today I found a much easier way to reach the deck...

boomboxery.com

If I have repeated contents from those posts, I apologize.

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Obtain a service manual.

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A headlamp with a tilting lens is very helpful.

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If you need belts, here are their index numbers in the manual, Sanyo part #, and description. I ordered them from turntableneedles.com.

23. 141-2-564T-19100 Square Belt, Counter
30. 141-2-561T-04501 Flat Belt, Main
78. 141-2-564T-20600 Square Belt, Pulley
83. 141-2-564T-18400 Square Belt, Auto Stop

Manufacturer Index Record Player Turntable Accessory, Stylus, Cartridge, Gear

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If you need to clean out belts that have aged into sticky black goo, use alcohol and buy a large box of cotton swabs. Consider wearing gloves and old clothing.

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The Record lever will not depress unless there is a cassette loaded that has the record defeat tabs intact. The tape deck has a switch that detects whether that tab is present, to prevent overwriting recorded tapes. Trying to force the Record lever to engage with no blank tape loaded probably is why so many of these units have broken Record levers.

The Record lever has another complication. It engages a plastic and metal "teetertotter" lever (Parts 73, 74, 75) behind the tape drive assembly that in turn engages a clear brownish plastic thing (#51 Record lever) on the Main Amp PCB Assembly. . The #74/75 lever must be arranged with the metal end on top of the #51 Record lever on the main board. Or Record won't work.

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The screws holding the shields on the Main PCB include red insulating washers. Carefully note their positioning since the manual does not depict this.

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To repeat previous advice:
- write down and number every step
- apply masking tape to screws, numbered by step
- apply numbered tape to component, connector and screw locations
- take photos before and after you remove or disconnect anything
- also take pictures of things you don't disassemble, such as the cassette bay,

Reassembly involves some critical actions not needed during disassembly:

- do not force the chassis back into the front case. There are several things besides misplaced wiring that can obstruct the chassis. Forcing the chassis into place will only break things.
- the chassis will not go all the way in if the head assembly is not retracted. If it is engaged and the levers won't retract it, just push it down away from the capstan.
- the tape control levers are both mechanical and electrical.
- Stop/Eject, Rewind, Play, and Fast Forward tape control levers engage metal knobs on the bottom of the AMSS assembly #107. These in turn engage white plastic levers that in turn engage electrical switches. The default and spring-loaded position of these white levers is wrong for assembly. You have to rearrange all 4 of them to the non-default position. This is tricky to do. Symptoms of having this wrong include that the levers are stuck or jam, the tape drive malfunctions, and the dial lamp is on whenever the unit has power. (Because these levers light up the dial lamp when engaged or jammed on.) The service manual does not seem to depict these parts or how to arrange them.
- tape counter reset button can fail to clear its opening on the case. I chamfered the inside of the case where it interferes so the button will slide into the hole even if not perfectly aligned.

 

[SGrant]

M9998 Belt Replacement

In the course of at least 7-8 rounds of assembly and disassembly I came to believe the belts can be changed without removing the Main PCB Assembly #109 and its two emf shields, and the AMSS PCB #107.

- open the case and disconnect 7 connectors on rear panel, a hidden connector on lower left side of the Main PCB Assembly, connector on top of Tuner/Pre/Switch PCB Assembly #101, two yellow wires beside the AM aerial, brown/blue wires, and red/white/blue AMSS wires from AMSS board.
- unscrew the OCS PCB #110 from the right speaker bay.
- unscrew the chassis and slide it out of the front case. There are 5 screws, of 3 differnt kinds. Note which is which and where they came out of because during reassembly the rear case uses some of the available holes.
- unscrew the Volume PCB Assembly #102 and fold it aside. This is also handy for using contact cleaner on the 5 potentiometers.
- unscrew, fold aside and secure with tape, the cassette bay lamp bracket.
- remove 2 tape drive assembly screws from the bottom of the chassis
- remove 2 small screws from the sides of the AMSS Assembly, that secure it to the tape drive assembly
- remove 2 screws from the upper front of the tape drive assembly
- slide the tape drive assembly out of the front of the chassis
- the tape drive assembly has 2 tabs or lugs #138 affixed by the screws that attach Shield Plate, Mechanism #85 to the top of the tape drive chassis. I left these off because they don't seem to be used for anything and interfere with reinstalling the tape drive.
- there are still a few parts that have to be removed to replace the 3 inner belts. The tape counter's 4th belt is easy.

 

[SGrant]

History of my Sanyo M9998

Back in 1976 I bought an old stepvan and camperized it to live in. At the time only a handful of people were doing this and it made sense because I lived in one place but worked in two places and didn't have a car.

For a sound system in the van I bought a Sanyo M9980. THE audio business in Vancouver in that day was Commercial Electronics. They served high-end audiophiles who, at the time, were dismayed by the emergence of portable stereos. So I figured that if Commercial Electronics was going to carry portable stereos, they would carry the best.

The M9980 worked fine in the van because I could plug it right into the van's 12v electrical system. I installed a set of speakers up in the front with a switch to change input from the dashboard AM radio or the Sanyo.

After a few years I wanted something better so in 1979 I bought the M9998 for $600 from Commercial Electronics, and sold the M9980. The M9998 had outputs for the external speakers.

After I moved out of the van the M9998 came along as my home sound system, powering a set of external floor speakers. I never put batteries in it. That the M9998 did not have removable speakers was the only thing I didn't like about it. Along the way I had the belts replaced once by Commercial Electronics and once by a genuine Sanyo repair shop. I must have done them once myself because I recall what the inside looked like and was dismayed that such a fine machine looked so messy inside.

Years passed. I didn't realize it was anything special until it showed up on Stereo2go's original "10 Holy Grail" ghetto blaster list. It was different from most of them. Smaller, all-black and relatively plain looking. But it was set up to be used as an amp and PA system, and had superior specifications and sound.

Eventually it was replaced by a home stereo that could play CD's. Then I found the M9998's tape player didn't work, again. More years passed. It came back into use as a home stereo because the Sony home stereo was a piece of junk and I can feed my phone's mp3's into the Sanyo.

More years pass. I think of selling the Sanyo but never get around to it. It ages into a vintage item. I have a bunch of cassette tapes I wanted to convert to mp3. I bought a $20 gizmo off eBay designed to do this. It was so crappy I thought it was defective. I returned it for another one, which was just as bad. So much for that idea.

More years pass. I get tired of my mp3 collection and again think about digitizing the cassettes. I consider buying a vintage but pristine walkman. However I realized instead of buying more stuff it makes more sense to fix the Sanyo and use it for the digitizing.

As the original owner I still have the Owners Manual, external microphones with brackets, AC power cord and purchase receipt. It has the little black RCA jack covers but they are cracked. The rewind and fast forward caps, and the radio tuning parts seem to be in new condition. It has never had batteries in it so the tubes etc. are in perfect condition. The only things I don't have are the original packaging and the tape drive door sticker.

 

[SGrant]

Overhauling M9998 radio band selector switch

Since the FM worked properly, checking this switch seemed like the place to start restoring the AM band. Which seemed totally dead but later I found to emit almost inaudible white noise and two very weak stations at full volume.

There seems to be zero chance of finding a replacement switch if it's broken. I desoldered its 26 pins, which were very awkward to access because I didn't want to completely remove the Main PCB. I removed the switch, pried open the metal case tabs to free up the switch's component board. The switch contains a gear that moves horizontally a plastic slider with 6 tiny "springs" that saddle and slide along two rows of contacts. A ball bearing between the gear and a piece of springy metal provide the luxurious dedent action.

There was thin blackish surface corrosion on some of the parts. More like discoloration than corrosion. I cleaned up everything, coated the parts with dielectric grease so this never happens again, bent the case tabs back and soldered the switch back in place. This took me just 5 hours.

I assumed everything in the switch would fit together only one way. I was wrong. Take a picture into the end of the switch and note the band selection before removing it. This will record where the slider should be positioned for the band.

Now the band selector switch only selected mono FM, and at the AM position. Because it turns out the band selector switch can in fact be reassembled incorrectly. And the only way to fix it is to disassemble the unit again and desolder and pry open the switch. But I was getting faster at assembly and disassembly. Repeating the process took less than an hour. But the AM band still didn't work properly.

I used an old soldering iron and braided copper wire for desoldering. I have a solder sucker but it seemed useless. I was running out of 40-year old wire braid so bought a new reel. The packaging is still the same but the braided wire is now finer and about half the thickness it used to be. I found that twisting the braided wire into a longitudinal spiral worked vastly better than using it flat.

 

[SGrant]

According to the discussion link, the M9998 has no motor speed adjustment.

https://boomboxery.com/forum/thread...aybe-i-get-it-for-4000-m90.27987/#post-353264

 

[thinkchronicity]

A Sanyo labour of love....i can relate. The no AM thing: have you inspected/tested the tuning capacitor? I had the same problem on a Goldstar where wax had migrated into the AM gangs, ultimately destroying and shorting them. Just a thought.

 

[thinkchronicity]

Not sure about gaining back 20% loss of speed....but...a thicker walled drive belt will raise the tempo.

 

[SGrant]

Not sure about gaining back 20% loss of speed....but...a thicker walled drive belt will raise the tempo.

So far as I know nothing in this unit has ever been lubricated (with the exception that I just did the band selector switch).

I'm going to check the various spindles etc. to see if they need lubrication or are jammed. Check the spindle brake for proper operation and see if the motor spins as it should.

Finding a motor belt for it wasn't too difficult, finding a thicker one might be. Before I do that I will install a new pinch roller.

 

[SGrant]

A Sanyo labour of love....i can relate. The no AM thing: have you inspected/tested the tuning capacitor? I had the same problem on a Goldstar where wax had migrated into the AM gangs, ultimately destroying and shorting them. Just a thought.

I'm classified as an amateur with these matters, so please bear with me.

I found this comment by Superduper back in a 2015 thread.

Search results for query: "Could be the AM RF amp burned out"

boomboxery.com

"Could be the AM RF amp burned out which is fairly common on Sanyos since the transistors they used are not as durable over time; or could be failure in the AM local oscillator or mixer circuit, or less likely the IF amplifiers; and of course the all-on-one qualifier: any number of things. Typically, if you are getting very quiet AM, the issue is most likely in the IF stages or if the issue is no AM but you do get white noise, the RF section."

Is the "AM RF amp" also known as the AM preamp?

I don't know enough to identify the IF and RF sections, let alone the tuning capacitor. The experts on these units commonly "recap" them. I assume that means wholesale replacement of capacitors. But these electronics have different types of capacitors. Do they mean they replace just the electrolytic capacitors?

And some say they are wary of the Niobium capacitors. Can you replace Niobium capacitors with others of the same specifications but different and more durable chemistries?

Along those lines, am I correct that you can replace a capacitor with one of a higher voltage rating as long as the uF or pF rating is the same? It's hard to find electrolytic capacitors with the exact same specs as these old ones.

Since the FM band works perfectly, (and the unit has the great sound they are reknown for) I think it's safe to assume the AM band problem is between the AM antenna and the amp. Looking at the circuit diagrams in the manual, it appears that those areas contain the capacitors listed below. Are the "IF" and "RF" circuits within those areas?

C151 ceramic 150pf +-50% 50v

C131 bc con 0.0047uf +-25% 25v
C153 ceramic 0.01uf +80-20% 50v
C132 styrol 120pf +-5% 50v
C133 bc con 0.01uf +-25% 25v
C134 ceramic 7pf +-0pf 50v
C327 ceramic 0.0022uf +-50% 50v
C302 ceramic 0.022uf +80-20% 50v
C303 electrolytic 10uf 16v

C323 al electrolytic 0.1uf +40-20% 10v

C753 {haven't found this one)

C151 ceramic 100pf +-20% 50v
C101 ceramic 20pf +-10% 50v
C102 ceramic 16pf +-10% 50v
C103 ceramic 0.022uf +80-20% 50v
C104 ceramic 0.022uf +80-20% 50v
C106 ceramic 12pf +-10% 50v
C107 ceramic 5pf +-.25pf 50v
C108 ceramic 30pf +-10% 50v
C109 ceramic 8pf +-.5pf 50v
C110 ceramic 330pf +-10% 50v
C112 ceramic 0.022uf +80-20% 50v
C113 ceramic 0.022uf +80-20% 50v
C114 ceramic 0.022uf +80-20% 50v
C115 ceramic 13pf +-10% 50v
C116 ceramic 4pf +-.25pf 50v
C117 ceramic 0.047uf +80-20% 50v
C301 ceramic 220pf +-20% 50v
C304 bc con 0.022uf +-20% 25v
C305 ceramic 0.0022uf +-20% 50v
C306 ceramic 0.01uf +80-20% 50v
C307 ceramic 2pf +-.25pf 50v
C308 bc con 0.047uf +-20% 25v
C309 ceramic 2pf +-.25pf 50v
C311 ceramic 1pf +-.25pf 50v
C312 ceramic 33pf +-10% 50v
C313 electrolytic 1uf 25v
C314 ceramic 220pf +-20% 50v
C315 ceramic 220pf +-20% 50v
C316 ceramic 220pf +-20% 50v
C317 electrolytic .47uf 50v
C319 electrolytic 1000uf 10v
C320 bc con 0.015uf +-20% 25v
C321 bc con 0.01uf +-20% 25v
C322 ceramic 30pf +-10% 50v
C324 ceramic 0.047pf +80-20% 50v
C325 ceramic 0.047uf +80-20% 50v
C326 ceramic 0.022uf +80-20% 50v
C327 ceramic 0.0022uf +-20% 50v
C328 ceramic 0.01uf +80-20% 50v
C329 ceramic 0.01uf +80-20% 50v
C330 electrolytic 220uf 10v

C501 electrolytic 2.2uf 25v
C502 bc con 0.047uf +-25% 25v
C503 al electrolytic 0.47uf +40-20% 10v
C504 al electrolytic 1uf +40-20% 10v
C505 al electrolytic 1uf +40-20% 10v
C506 styrol 0.001uf +-5% 50v
C507 electrolytic 1uf 25v
C508 mylar or bc con 0.01uf +-20% 50v
C510 electrolytic 1uf 25v
C511 electrolytic 1uf 25v
C512 electrolytic 470uf 16v

To replace capacitors I have to bite the bullet and completely remove the Main and Tuner boards, something I have so far avoided doing. Sigh.

I'm very grateful for the advice and guidance.

 

[thinkchronicity]

Regarding tape speed again, you should add a drop of oil to the motor pulley shaft - that's one bearing done. The other might need doing, but that involves taking the motor apart (videos on YT about this).
Also, the main rail voltages might be drooping a bit due to old (power supply section) filter caps. You could try running the unit on batteries or AC adaptor and see how the speed changes.

AM preamp is not a term i've heard used. Basically, Q101 is the rf "front end" of the circuit, amplifying the tiny signal from the rod antennas using a FET transistor. Next, in a line going to the right on the schematic, we have Q103 and Q104. This is the mixer/converter section which cleverly creates a constant frequency (the intermediate frequency) ready to be filtered and amplified by the four IF stages, that's Q301,302,303,304.
All the transistors have the working voltages indicated on the base, emitter and collector. I would be checking all those for starters. The FET Q101 has a box down the page with voltages in, but tbh i'm not totally sure why they have 'dx' (which means on receive mode) and 'local' - maybe someone can chip in on that.

As you're getting some signal on two AM stations, the polyvaricon tuning capacitor is probably ok. Easy to spot though: typically a white or clear plastic box with a shaft coming out of it going to the tuner flywheel, string & tuner knob.

Don't know about niobium caps sorry. Wholesale recapping normally means just the electrolytics because these are kinda chemicals in a tin can that degrade over time and with use (heat). You may well have an out-of-spec cap on the radio board, but i think better to find it rather than the replace everything approach. You can go higher in voltage as long as capacitance and temp ratings are the same.

 

[BoomboxLover48]

I am the original owner of a 1979 Sanyo M9998. I want to use it to feed my cassettes into a computer to digitize them. But first I have to get the box working.

Given what that has entailed so far I'm relieved to see even the experts are challenged by this one. Countless hours of struggling with it have taught me some tips to pass on. Which I will do below.

This site contains quite a few discussions of working on the M9998. So it isn't easy for people looking for guidance to find the most helpful. My post will add to the clutter, but I will add a link to here, on what I thought was the best of them:

Operation Sanyo M9998!

Finally after a long wait I started working on my Sanyo M9998. From the way the PC boards are positioned in the unit I wanted to try the easiest way to reach the deck section. When I tried before it seemed really hard to reach the deck section. Today I found a much easier way to reach the deck...

boomboxery.com

Edit: the older posts are no longer open for additions.

Getting the AM band to work properly is 1 of 2 remaining problems. I have overhauled the band selection switch. At full volume I get almost inaudible white noise from the speakers, and two very faint radio stations. FM works fine.

The other problem is the tape runs at about 80% normal speed. I can't find any mention of a motor speed control in the manual. The pinch roller is clean but slightly convex. I have a new one on order anyway.

Any assistance with these two problems would be greatly appreciated.

Operation Sanyo M9998!

Finally after a long wait I started working on my Sanyo M9998. From the way the PC boards are positioned in the unit I wanted to try the easiest way to reach the deck section. When I tried before it seemed really hard to reach the deck section. Today I found a much easier way to reach the deck...

boomboxery.com

I was also wondering why the above link I started was abruptly stopped. I ran into another problem where the tape plays for 5 minutes and then slow and stops. I came back to post about it, and it was stopped for updates.

 

[SGrant]

A Sanyo labour of love....i can relate. The no AM thing: have you inspected/tested the tuning capacitor? I had the same problem on a Goldstar where wax had migrated into the AM gangs, ultimately destroying and shorting them. Just a thought.

Initial response to your suggestions. Wax?! I had no idea it can be a problem. Shows what little I know. In fact the unit has a largish blob of wax on this board. I had assumed it was put there for some reason during manufacture. There is a smaller blob under the base of the baby blue capacitor.

 

[thinkchronicity]

The wax suggestion was a red herring after not reading all your text properly. Your board looks fine: no wax near the tuning cap. It's laid over sensitive components to prevent microphonics and hold everything steady. Things are easily perturbed at high frequencies.

 

[thinkchronicity]

Should be 12.4v across the motor when running. What's it doing?

 

[Superduper]

Make sure that the tuner select switch, which you "rebuilt" is actually conducting properly. There are several gangs, you will need to ensure that they are in fact switching properly. Dielectric grease is definitely the wrong type of grease to apply, because it is an "insulating" grease and can cause connectivity problems, especially with regards to the low tension spring contacts inside the switches. A far better product to apply is surface conditioner such as Deoxit gold GL100 which has the consistency of oil, not grease.

Wax is installed at the factory to "set" certain components from moving including coils and sometimes screws. The reason is that the actual physical component placement or spring "shape" can affect tuner alignment. If you are working at or near the tuner, be advised that it is very common to accidentally touch one of those coils and deform them, as they are made of very soft copper. If you do that, you will affect the tuner alignment. The only capacitors that need or warrant replacements are the electrolytic ones as they do have a set lifespan. The other types of capacitors are all very reliable and do not fail on any predictable timeline. Leave those alone, not only are they almost certainly ok, some such as the styrol ones are not easy to find and almost all of the non-electrolytic caps can have some affect on the tuner alignment. To be honest, if you don't know your way around a tuner: RF section, IF sections, MPX section, AM section, FM section, local oscillator, mixer, discriminator, detector..... etc. You really shouldn't be poking around there.

As for the motor, there is no speed control that we are aware of on the 9998. Over time, the entire rotating assembly can build up additional rotational resistance and the belt tension is critical. The only sure way of having the proper belt tension is to use factory belts which of course are no longer available. The best thing to do is to rebuild the entire rotating system and clean every part to ensure friction is not a factor but it's probably easier to just find a new replacement motor that has an internal speed adjustment.

 

[SGrant]

Superduper: I'm certainly venturing beyond my depth. I'll go over the tape drive system before looking at replacing the motor. Thinkchronicity mentioned the thickness of the belt may be a factor. I certainly thought it was rather thin and if it is stretching between motor and capstan it would slow the tape. But I'm not going to dig into that stuff until the new pinch roller arrives. It's due in January and every time I dismantle this thing it raises the likelihood of collateral damage. 8 times so far.

I sprayed some contact cleaner into the band switch thinking it might dilute the dielectric grease. No change in the tuning symptoms. The FM and FM afc still work fine. I'd like to avoid removing the band selection switch a 3rd time unless absolutely essential. That I can get a couple of AM stations (weakly) might indicate the switch is ok.

Thinkchronicity, I'll see if I have a compatible power supply. I may even still have the original. I can't quite bring myself to buy 10 D cells just for a test. I'll check motor voltage next time I get in there.

As for the transistors, Q101 has a bit of deposit or corrosion along its top seam. Since I don't work with these things I don't know if the deposit signifies anything. I don't think the deposit came from somewhere else.

Testing the voltages on Q303 and Q304 requires removing the circuit boards from the chassis and providing power to them without causing more damage. I think that's above my skill level. Q103 has something mounted on one leg, visible in the photo. And its gate leg has insulation on it. So checking it would also require removing the boards from the chassis. Q101 and Q104 are easily accessible from the component side. Q301 and Q302 will be a challenge to check on the component side, but possible.

 

[SGrant]

I tried two 12v power supplies, and both had the same result: humming from the speakers and nothing else. Not even the dial light. One power supply was a multiple voltage. The other has a home made "Sanyo M9998" label on it. Made in China. But I doubt it's the original because Japan probably was not buying such things from China in the '70's.

Back on 120v ac, I played a cassette again. I let it run longer than before and it definitely was slowing down. I stopped it before it ground to a halt. Presumably a stretchy motor belt would run slow but maintain speed. This points the finger at the motor lubrication or condition.

 

[Superduper]

Back on 120v ac, I played a cassette again. I let it run longer than before and it definitely was slowing down. I stopped it before it ground to a halt. Presumably a stretchy motor belt would run slow but maintain speed. This points the finger at the motor lubrication or condition.

FYI, this is a 15V boombox. Using a 12V power supply won't supply sufficient voltage to the motor. And if it's a small switching type of supply, it might not even have enough current capacity for this type of use. You can tell if it's a switching or linear supply by it's weight. A linear supply with sufficient current is going to weigh probably a couple pounds at least. Also, switching supplies emit lots of noise that can affect the radio, AM especially. As for the dial light not illuminating, be advised that the M9998 has a dual winding transformer with a special smaller winding specifically reserved for the dial lamp. When operating on AC (internal power supply), the 2nd winding lights up the dial lamps continuously. On any other power source, that winding isn't operating so the dial lamps will only illuminate if you depress the light button. In fact, the factory supply outputs MORE than 15V. That is apparent when you look at some of the voltage specs near the motor. You can see at least one 15.5v spec.

I do not recommend opening up the band switch again. Using dielectric grease (by definition is an insulator) is wrong but opening up the switch more than once invites disaster as the clips that hold the switch together tend to fail from bending fatigue and could very well snap off. If you read what I suggested, it was to "verify" that the switch had continuity. You can verify this with a simple ohmmeter probing the switch lead pads. Using contact cleaner can thin out the grease, but it's probably not going to exit that switch unless you flood it by a lot. Unfortunately, some of the volatile solvents in the contact cleaner will evaporate but the grease is going to just resettle at the bottom of the switch.

If adding a drop of oil to the motor improves speed, just be advised that this isn't a lasting repair. The factory motor used oil-lite type bearings which are impregnated brass. When friction heats it up, it will secrete oils. When cooled back, the oil is reabsorbed (google oilite). Unfortunately, I don't think you can just oil the bearings and get them to absorb some if they've dried out. Relying on oil is just going to mean that the speed will always be fluctuating and never stable, and will be a maintenance nightmare. Far better if all rotating assembly is properly cleaned of oxidation, rust, contaminants. Aside from only a few spots (which might be identified in the service manual), everything else should be clean and dry.

The FET Q101 has a box down the page with voltages in, but tbh i'm not totally sure why they have 'dx' (which means on receive mode) and 'local' - maybe someone can chip in on that.

"dx" in the sanyo refers to the switch setting for "local/dx", in this case local is local and dx is distant, with regards to stations and sensitivity, and only applies to FM. BTW, Q101 and 103 shouldn't even have any effect on AM. That's because the FET Q101 only is for the FM (rod antennas). In fact, the AM portions usually don't even mix with the rest of the circuit until further down. AM and FM front ends have different circuitry and have different IF frequencies (10.7mhz for FM, 455khz on AM, typically). On the M9998 tuner schematic, the AM specific portion is shown in the lower 1/2 of the schematic.

 

[SGrant]

Thanks for the expert info and guidance, Superduper. I definitely was not trying a linear power supply. Molded into the case at the External DC port is: "12~15V".