Setting out to refurbish my Sanyo M9998. I bought it new back around 1979. As the original owner, I have the Owners Manual, mics, mic brackets and AC power cord. And purchase and repair documents. I want to use it to play cassettes and feed the output into a computer to digitized them. It's in nice shape, but... - tape drive does not work - dial lamp is burned out - AM band won't switch on - volume control is very noisy I obtained a Service Manual and got to work. First impression is that the manual stops giving instructions after you have the chassis out. No help getting at the belts. Second impression is that it looks really good inside. Third impression is there is a good reason people don't like to work on these things and so few of the units have working tape drives. The box is absolutely crammed. Good thing the people who designed the early personal computers didn't learn their craft from the people who engineered these stereos. By contrast computers are extremely organized and easy to work on. It's going to be great fun putting it back together. Fourth impression is that disassembly has to go deep into the guts to change the belts. It appears from the records the belts were last changed in 1985. It seems odd it is so difficult to do something that likely needs doing every 10 years or less. The tape counter belt seems ok but I'll change it anyway. The two capstan belts are loose (shot). The motor drive belt has degraded into some horrid black sticky goo. I have guidance from Mister X for cleaning the controls: Question 1: where can I source a dial indicator lamp? I think they are called "pea" lights, and the Sanyo part number is 4-612T-12600. Question 2: there is a source on eBay for belt kits. Is this the best source for the needed belts? Question 3: is there anything that should be lubricated?
Sanyo M9998, I looked it up on Google and checked out the images, not bad I could like that design Indicator bulbs, sometimes called grain of wheat bulbs, search e-bay. If you want to keep it 100% authentic with no LED upgrades that is. And places like Digikey and Mouser that have incandescent indicator bulbs for instrument panels etc,. Like Mr.X said in the other thread, belts can usually last 20 to 30 years. I think there was a rationale for rubber formulations to be the way they are for performance and functionality over longevity. fixyouraudio.com has some explanation on belt formulations if I remember correctly. All these boom boxes and stereos appear to have been designed with little thought to ease of belt replacement. Perhaps with CD on the horizon the manufacturers expected / hoped the consumers would merely buy new boxes and throw the old ones away. Landfill fodder. Imagine the hundreds of thousands... nay... millions of boom boxes, cassette decks, walkman's etc,. that fill the landfills. A veritable "layer" of Japanese audio devices
The M9998 has a mythical grail following, it's one of the early best looking boomboxes every made but they are very hard to find, especially with both mics. I still remember one of Arkays Long Posts of hunting one in Hong Kong with that German Guy that had the huge wall of boomboxes. 20 years ago, most of us normal people never saw one of these wonders but it got plastered on the radar with that post. Of course Radio R probably had three or more. Fix your Audio sponsors the website, I've also used Turntable Needles for belts. (I think I posted that in your other thread). TN has one of the best belt/parts search engines for belted audio machinery. https://www.turntableneedles.com/ If you can't find the light, maybe reach out to dgwojo on Audio Karma, he's the lighting guru and I think he's on ebay. https://audiokarma.org/forums/index.php?members/dgwojo.441/ I use mainly DeOxit for the volume and other switches. The company also makes Fader Lube for sliding switches like EQ's, they might have carbon or other materials that react badly with DeOxit. This should get rid of scratchy volume and other clicks and pops. Any sliding metal parts for the tape deck will need some lube, search around the site for the recommended lubes, I use something like white silicone (I haven't done one since last year). Personally I love the builds, some are very tough and some are almost impossible to service. It's boggling how they assembled these to begin with and it's one of the reasons they were so expensive when new. The whole industry really changed in the 80's and parts became more modular with circuit boards and plug in connectors. Speedy assembly was huge and anything to make the process quicker was adapted.
When I bought the M9998 CD's weren't on the horizon yet. Good to hear the belts last longer than I thought. My receipts show I had them replaced just 6 years after I bought the box, so perhaps they have been improved over time. Thanks for the links about belt formulations and bulbs.
Thanks for the links, background and perspectives. Greatly appreciated. Before the M9998 I had a Sanyo M9980, but sold it when I got the M9998. The band selection switch is a sliding switch, and the box has no equalizer. I have a bottle of "Robins" Head & Guide Lubricant RC-2-22. From Robins Industries Corp. Flushing 56, NY. $1.00. Sheesh, I must have had this since I got my first tape recorder in 1964! The bottle itself must be a collector item. Still 1/3 full too. And a spray can of Radio Shack contact and head cleaner. Must be 40 years old. Maybe it still has pressure. My M9998 also still has the original battery tubes. And in perfect condition since I never put batteries in it. It also has the little black plastic RCA jack covers, but they've cracked from aging. It's a shame that accessories such as microphones and owner manuals almost always get lost as these boxes change hands. Like original cargo covers are never included with used suv's.
I've got a few Sanyo's from the 70's running around here including a M9980, another beautiful boombox. I keep thinking of starting a thread of the five best looking boomboxes for each year and Sanyo would definately be in the mix. I think anybody that was into tape decks still has some Radio Shack Cleaner around, that place had almost everything to get electronics cleaned up and running although I don't think they ever carried belts. I'd probably just put the Robins on a display shelf, the good part might have evaporated and the rest will just be a nasty goop. Were you doing a lot of recording on the machine? I always felt like this machine was aimed at musicians to record their live work.
After countless hours working on the box, 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. After installing 4 new belts, the tape runs but 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 suggestions would be very welcome.
I remember on the old forum mentioning a local shop to me selling one of these Sanyo M9998 for sale. The guy running the record shop had one new/boxed and wanted £100 for it. It wasn't really my thing although I loved the fact it was new and working perfectly. He also had a couple of Aiwa mini-combo's for sale also which I was more interested in. If anyone on the site wanted it I could acquire it on their behalf but there was no takers. I let them both go and bought some records instead! Looking at their prices now I wish I'd bought both.....
After replacing the belts, the problem with cassettes slowing to a stop turned out to be sticking 40-year old cassettes. Not the motor. Its remaining problem is the AM band does not work. I have thoroughly ensured the band selector switch is not the problem. When I touch one vom probe to ground and the other probe to pin labelled "B" on transistor Q104, and with the band selection set to AM, it plays AM stations as normal and the station dial changes stations. Touching the probe to a few other places adjacent in the circuitry did not play any AM. It didn't matter if the vom was turned on or off. If I reverse the probes I get no AM. So is the vom acting as an antenna or jumpering a broken connection? I tried using a jumper between Q104 - B and ground. No AM. So the vom must be acting as an antenna. Which would mean something wrong between the antenna and Q104. In the circuit diagram Q104 is at upper center near the book binding. In the photo of the circuit board, Q104 is between the AM antenna and the osc with the red adjuster.
Odd that yours shows signs of plenty of use but still has the cassette door sticker. For an update on mine, I replaced the Q104 transistor. That didn't fix it. But elsewhere I have been advised that 2SC930 transistors may be a variety of things, many of which won't work. So I have to try to find a "genuine" Sanyo 2SC930D. Touching an ohmeter probe to the B pin on the transistor may be putting enough current into the transistor to activate it. Because the AM band works normally in that circumstance, with both tuning and amplification, suggests the problem is not in the upstream or downstream, tuning or amplification areas. Unless the circuit providing current th the base of Q194 contains a defect.
Thanks for your update. I'm going to get to that sanyo sometime soon. Meanwhile, I'm out here taking a break from working on my c100 Conion. Here's a picture of what I'm playing. It's also a Sanyo MR-U4GP I'm playing a saga cassette.
This video has to do with mostly Older Sanyo motors in boombox's for those that are looking for the speed adjustment as there is NOT any speed adjustment! One you view this poorly titled video you will understand about the Older motors found in cassette decks that do Not have 'any' speed adjustment for pitch or speed. The GOVERNATOR - How vintage DC tape recorder motors work! I hope this video gives you a better under standing about the older motors.
Another M9998 compare video of mine. Sanyo M7770K M7880K M7300K M7790K M7830K M-X520 (M-X720K-was sold) M-9998K Sale compare (that phone number is no good anymore)
Sanyo m9940k on top of the m9998k I'm going to start working on my 98 k shortening it but I wanted to show you the picture of this because I have so many Sanyo. Not now but recently I realized but I didn't understand it. Why both of these models on top have the exact same model number but it doesn't explain why they have different woofer colors so that was just plum interesting to me. Both of the m9940k work perfectly. They run on 6D batteries, and they sound really really good for their size. decentman4you2007@gmail.com Once again, I'll answer any questions.
It turned out the M9998's cassettes drive problems actually were the fault of the cassettes I was using for testing. They were Ampex, probably from 1979, like the box. The magnetic coating rubbed off the mylar backing so easily the capstan and pinch roller could not maintain traction on the tape. The tape drive works fine with intact tapes. I checked out disassembling the motor to lubricate it, but it looked too challenging to proceed. I did put a bit of lubricant where the spindle exits the case, which may have helped. I had only started investigating replacement motors when I determined the cassette problem. Still, the AM band has defied repair. Apparently there are all sorts of bogus 2SC930D transistors which won't work. Good luck with the 9940's. They've got to be easier to work on than the 9998. I'm now using the M9998 as my home stereo. It's wired to external speakers, and I can control music playing on my phone, via an FM transmitter dongle on the phone, to the M9998's FM tuner. The music on the phone includes all my cassettes in mp3 format, so I don't need to use the tape drive.
