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sanyo 555 slowdown?

H

harry

Experienced Member
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Oct 19, 2007
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I have recently aquired a sanyo mbc 555, this is quite an early machine, with two single sided 5.25" drives, it is in quite remarkable condition, complete with all original software and manuals, after cleaning both drive heads, and a quick check inside , all seemed well, It boots up very quickly and I can dir the disk, no problem, The drive can be changed over to B: and this too will read first time ok, if I then attempt to load any files, thing start to slow up? and I mean really slow? I can go back to drive A: and try DIR but this will take forever? the drive light is on and the drive is spinning, but it is as if there is no more response,If the machine is left for an hour or two, it will resume normal use and both drives will respond well, but only for a couple of times, and then slow down reading, until no response? other people have had this problem, but no one seems to have a cure? anyone who has used one of these machines and has had the same problem, please let me know if there is a simple cure for this problem...... Harry
 
Hmm..Harry I had a similar problem with my Kaypro II drive which would almost format and verify a disk the first time it was turned on, then get progressivly worse at formatting higher level tracks as time went on.

You can read about that repair here. The problem in this case was a disk clamp, which had developed a greasy "ring" of an unknown substance. This caused the disk to slip during rotation leading to uneven speeds and hence difficulty in formatting higher level tracks.

The point is this symptom used to get worse the longer the machine was used. I'm assuming the greasy ring of comtaminants became more slippery as it heated up. Friction would certainly cause it to heat up if it was sliding on the disk ring.

The drive also needed radial alignment but this would not have caused the non-format symptom, and is unlikely to get worse with use, when started from cold.

My advice would be to check the drive clamps and see if they don't have a similar ring of contaminants causing the disk to rotate at uneven speeds. It's not the only possibility but it is one you could check out.

Tez
 
If you search through these forums, you'll find that a common problem with old 5.25" drives is that the rails that the head assembly slides on need to be cleaned then relubricated. Myself and others have found a silicone based lubricant to be satisfactory. The clean/relube is a worthwhile maintenance activity even if it doesn't rectify the problem.
 
I've got an MBC-555 but in the few times I've used it it didn't have any problems; as others have said I think it's probably a minor problem with the drives instead of a generic problem with the system, but you never know. Clean the heads and rails and see how it goes.

Good luck!
 
sanyo 555 slowdown

sanyo 555 slowdown

Thanks for suggestions, When I clean the drive heads, I always clean and lube the guide rails, ( goes back to looking after my apple II drives I guess) but this
has no effect on the slow down which is happening to both drives, and any software? it is as if the memory is being loaded, or not being accessed properly? or can the interupt control be playing up ? something warms up, or does not reset itself, after quite a short period of time? it only takes about three to four dir requests to start this happening, some of the ram is soldered to the board and some is socketed, would a defective ram show up any errors? or does
the disk contents go to the 8088 first and then to ram? I am confident both drives are working ok due to the initial quick reads on both drives when first booted? am I right in thinking that to read, or activate, the disk, and any files, it needs new interupt, everytime, how can I check if this is happening correctly?
........hair pulling .... harry
 
harry said:
it only takes about three to four dir requests to start this happening
Click to expand...
Okay. What happens if you:
1. Power on unit from cold then do one DIR command, then
2, Wait 5 minutes, then
3. Do a second DIR command.

Obviously (based on your "it only takes about three to four dir requests"), if the DIR command issued in step 3 above is 'slow' then that would indicate to me that your problem is heat induced. Otherwise, if the DIR command issued in step 3 above is 'fast', but then a few more DIR commands then result in 'slow' operation, something else is going on.

If the problem is heat induced, then you may be able to identify the cause using freeze spray (not overdoing it though).

harry said:
I am confident both drives are working ok due to the initial quick reads on both drives when first booted?
Click to expand...
If both drives are from the same manufacturing batch, then both could have the same latent defect. You really should try another drive to quickly disprove the drives as the problem source.

harry said:
but this has no effect on the slow down which is happening to both drives, and any software?
Click to expand...
I noticed the question mark which appears to me that you intended only for the "software" bit of the question.
A useful experiment would be to run a 'speed' program of some sort (e.g. MIPS.COM, SPEED.COM) on start up and see if the speed reported drops with time.
 
sanyo 555 slowdown

sanyo 555 slowdown

Its good to try things, and your suggestion to do one dir, then just leave it
has proved it seems a warming up error, or a loss of voltage perhaps, as leaving it on gives the result of not being able to do the second dir, I left it running with the directory on screen, with the flashing A: prompt for 10mins, when I then tried the drive, it would not respond? I guess I will have to start some checking, any ideas?
....... Harry
 
I also have a 555, but, fortunately, it works fine.

However, I would go with Tezza on this one and clean both sides of the diskette clamping mechanism. Any lubricant type contamination here would cause the spindle to spin, but the diskette NOT to spin and would worsen as friction caused the lubricant to thin.

Any non-lubricating contact cleaner should do it and, if the drive is belt driven, I'd give the belt, the motor pulley and the "flywheel" all a shot too.
 
sanyo 555 slowdown

sanyo 555 slowdown

I have now cleaned both drives around the clamp wheels, checked to see if there is any residue on the disk, these are spotless, yet both drives behave exactly the same, is there any tests I can do in dos, or in basic, to check if any of the system has a malfunction, ...... Harry
 
Chuck(G) said:
Are these drives belt-driven or direct-drive?

If the former you might check for a slipping belt on startup.
Click to expand...
-------
Direct drive TEAC FD-54-Bs, at least in mine. One unusual thing about these boxes is the linear power supply; I wonder if the 12V could be dropping for some reason.
 
MikeS said:
-------
Direct drive TEAC FD-54-Bs, at least in mine. One unusual thing about these boxes is the linear power supply; I wonder if the 12V could be dropping for some reason.
Click to expand...

Could be.

If the OP does a couple of DIRs and then lets the drives turn off (i.e. wait a couple of minutes), is the startup again delayed at the next DIR?

The simplest thing would be to try another known-good drive.
 
sanyo 555 slowdown?

sanyo 555 slowdown?

Thanks for replies, making a test disk from the zip files from druid6900 will not be that easy at the moment, but I have checked the 12v and 5v supplies, at start up and after the machine has almost come to a standstill , all are still spot on, 12.07v, unchanged, 4.98v unchanged, my two drives are teac fd-55A-OO-U
direct drive units, condition is as new! as is the whole machine, one thing I have found is the end of the 8088cpu, gets very hot very quickly, this is opp , end to pin 1, this end is much hotter than the rest, and heats up very quickly,
not sure if this is normal ? I just cant quite see both drives malfunctioning, at the same time, with the same slow response, if one drive had gone bad and the other reading ok , it would make more sense , as there is no floppy control card,
is this done by the 8088? or the interupt controller first?
 
The floppy controller's still there--but, like much of the strangeness of the Sanyo MBC-55x, is a Western Digital 1793 clone (which ought to make the TRS-80 people feel warm and fuzzy)! No DMA controller. Serial I/O was via an Intel 8251 USART (not a NS 8250 UART). Theoretically, the MBC550 could do synchronous comm, although I don't know of anyone who actually did.

Note that your drives need to provde a "drive ready" signal on pin 34, so just any old 360K drive will not work.

But your 8088 getting warm sounds pretty ominous, especially considering that it's being run at 3.58 MHz.
 
Chuck(G) said:
The floppy controller's still there--but, like much of the strangeness of the Sanyo MBC-55x, is a Western Digital 1793 clone (which ought to make the TRS-80 people feel warm and fuzzy)! No DMA controller. Serial I/O was via an Intel 8251 USART (not a NS 8250 UART). Theoretically, the MBC550 could do synchronous comm, although I don't know of anyone who actually did.

Note that your drives need to provde a "drive ready" signal on pin 34, so just any old 360K drive will not work.

But your 8088 getting warm sounds pretty ominous, especially considering that it's being run at 3.58 MHz.
Click to expand...
You're amazing as always, Chuck; where did you find all that info?
If I have some time I'll dig mine out & see if the CPU gets warm.
 
MikeS said:
You're amazing as always, Chuck; where did you find all that info?
If I have some time I'll dig mine out & see if the CPU gets warm.
Click to expand...

Remember FormatQM and ConFormat? Support calls for "it doesn't work on my machine". I was amazed at how far vendors would stretch the truth when they called a system "PC Compatible". :sigh:
 
8088 heat

8088 heat

The thing should only dissipate 2~2.5 W
Just out of curiosity, what's the clock generator ? A 8284 ?
I'm wondering if the clock is unstable or runaway, and maybe that's driving the 8088 into some sort of overload.
Does OP have another system OP can drop the suspect 8088 into and see if it still heats up ?
patscc
 
sanyo 555 slowdown?

sanyo 555 slowdown?

I must thank you guys for your input, It would be good to know if any other machines heat up the 8088 as quickly as mine ? unfortunately the only other similar machine I have (sanyo mbc 4050) is running an 8086, I don't have anything else to swap or test with, I think I will try and find a replacement 8088 and see what happens, so close yet so far! ..... Harry
 
harry said:
I must thank you guys for your input, It would be good to know if any other machines heat up the 8088 as quickly as mine ? unfortunately the only other similar machine I have (sanyo mbc 4050) is running an 8086, I don't have anything else to swap or test with, I think I will try and find a replacement 8088 and see what happens, so close yet so far! ..... Harry
Click to expand...

You may also want to look for an 80C88--it's pin-compatible and lower-power CMOS.
 
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