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Sanyo MBC-550-2

C

ChrisCwmbran

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Oct 11, 2011
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483
Location
Cwmbran, Wales, United Kingdom
I have a Sanyo MBC-550-2 which has been upgraded to have a second FDD. Overall the unit is intact and fairly rust free however one of the floppy drive mechanisms is very stiff. On examination inside one of the drives appears to be a Teac FD-54B-02 and the otherone I think might be a Mitsubishi drive. Each drive has differing corrosion though. On the Teac drive there are specs of rust on a lot of the shiny metal and the other drive which has a cast alumium chassis seems to be covered in a white powdery oxide:

IMG_20120525_121035.jpgIMG_20120525_121052.jpg

I'm guessing I need to strip these drives and deal with each one differently. Does anyone have any suggestions? Does anyone know of documents that would cover the strip down and re-assembly of them?

It's the non-TEAC drive where the lever on the front is so stiff that I dont dare try to fully turn it.

Thanks in advance all!
 
Avoid taking it apart if you can as head alignment is difficult. If it's just the disk release handle that stiff, working in a tiny drop of oil at the various contact points might help - I had a similar issue with an IBM drive, the sticking actually was in the plastic-to-plastic contact in that case, resolved with some grease :)
 
I understand exactly what you are saying. and I will certainly have a look at lubricating the mechanism. I am concerned however that the drives will corrode more and that the dust/corrosion might destroy floppys used in it.
 
Can't advise on the floppy situation, but if you need Sanyo DOS 2.11 to get the thing running give me a yell as I have two bootable copies - just need to image them.
AFAIK the hardware was so odd that the normal io.sys in MS-DOS doesn't work.
 
SpidersWeb said:
Can't advise on the floppy situation, but if you need Sanyo DOS 2.11 to get the thing running give me a yell as I have two bootable copies - just need to image them.
AFAIK the hardware was so odd that the normal io.sys in MS-DOS doesn't work.
Click to expand...

From what I remember, the 550 doesn't even have a normal BIOS--part of DOS loading is that a BIOS is loaded before the system.

Very strange system--and one of the few 8088 boxes that are actually slower than a 5150.
 
Chuck(G) said:
From what I remember, the 550 doesn't even have a normal BIOS--part of DOS loading is that a BIOS is loaded before the system.

Very strange system--and one of the few 8088 boxes that are actually slower than a 5150.
Click to expand...
Strange indeed; nice looking though, with that silver case & keyboard and those chrome plated floppy drives. Also the only PC clone I've seen with a linear power supply; almost like they took an old silver VCR and stuck a PC into it.

It has a certain unique charm... ;-)
 
SpidersWeb said:
Can't advise on the floppy situation, but if you need Sanyo DOS 2.11 to get the thing running give me a yell as I have two bootable copies - just need to image them.
AFAIK the hardware was so odd that the normal io.sys in MS-DOS doesn't work.
Click to expand...

I wouldn't mind a copy of those IIRC I only had Dos 1.25 with my MBC, mind I do have a complete set of original floppies including the Micropro stuff Wordstar etc.

Cheers.

Phill.
 
Once you get the drives working, if you find access is slow or erratic, take a look at this thread I did a month or so back: http://www.vintage-computer.com/vcf...-Flaw-identified-in-Sanyo-MBC-55x-motherboard

Short summary, on every board I have looked at so far, Sanyo installed a tantalum capacitor backwards (it is even backwards on board markings). If the capacitor fails as a result, it slows down/blocks disk access. Removing the capacitor seems to be enough to remedy the situation. It is part of an extra delay that slows down how fast the disk can be accessed on spin-up, but none of the software I tried needs the delay. Removing the capacitor removes the delay.

Also, I should point out that only the 12V portion of the supply is linear - the 5V output is an inductor based switching supply. It just looks more like a completely linear supply because of the huge line frequency transformer. I found out the hard way that the huge transformer has a fuse in it that is a pain in the ass to deal with if it blows (with some creative drilling and soldering, it is possible to bypass it though). The power supply will run happily from battery if you disconnect the transformer and put ~14-20V DC in its place (or less if you don't need to operate 12V devices). But, I don't think the negative supply rail will operate then, but it isn't important unless you use rs-232.

It really is a neat machine, especially for experimentation/hobby projects because of the ample room left inside the case and the extreme long lifetime of most components used. I have a lot of plans for what I will do with mine once I find the time and get some more pressing projects done.
 
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excellent post Brad. Although I had heard that the S* had a linear supply, it puzzled my how a computer board could run off non-switching 5vdc.

there's a line to a site w/images for the S* here: http://groups.yahoo.com/group/tandy2000/. The most recent post/s in fact.

MY S* IS HERE IN MY CAR. Ran out of space in the last of my storage units. Had to put it somewhere, didn't I!

It would be nice if there was a solution to dissolve aluminum/pot-metal type oxidation. Perhaps some sort of electrolysis, which would require dismantling the drive. WD40 for the stuck components. Work it, work it.

Good luck w/your S*. Yes it certainly does have it's charm. Seems to be sort of a prototype or inspiration for the Tandy 1000. Same video modes, neither has DMA IINM.

You should work on changing the crystal in yer Sanyo there Brad LOL. Why o why they made it slower the 4.77! But in reality it may be the same crystal used in vanilla pc's, because 3.58 is also a subdivision of the color burst frequency (don't make me do the math). It's divided by 4 in the S*, by 3 in peecees.
 
Sanyo mbc 550 / 555 software disk images available.

Sanyo mbc 550 / 555 software disk images available.

I have made images of several sanyo mbc 550 / 555 disks including the sanyo specific dos. You can get them at:

http://www.eriscreations.com/sanyo/

and if anyone has any software for this machine please contact me if you can provide a copy of it. I'm adding to the archive as i have time.

Gerry
 
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