VOGONS


First post, by Jonas-fr

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Hi,

I've got a Roland SB-55. It's a floppy-based MIDI player, little brother of the mighty SC-55. The SB-55 basically read .MID files on a floppy and plays them through it's MIDI OUT port (it also can record from its MIDI IN port onto a floppy).

The problem with my SB-55 is that when I plug the DC adapter the 3 number LCD screen give me three middle dashes "---" and no buttons seems to be working not even the power button. If I unplug it and replug it the unit seems dead, no status light, nothing on LCD this time, no button reaction. If I unplug it, wait a few minutes and replug it I get the 3 dashes again. One more thing under "the three dashes state" the FDD reacts when I insert a floppy: the main motor spins but the heads don't seek; under the blank LCD state the FDD spins its motor only one second after inserting a floppy then stop it as if it lacked electricity. In both cases the FDD status light is always on (even when the motor stops in the "blank LCD" state).
Since I didn't find a Service Manual for the SB-55 (I'm usually fairly efficient into finding service manuals so I'm guessing it doesn't exist or it isn't public) I looked upon the owner manual in the troubleshooting section but nothing about 3 dashes message. I sent a request to Roland but no answer yet.

Knowing a bit about electronics I've made this diagnostic (it could be one or more of these IMO):
- the floppy drive is dead or the power supply is bad
- the main capacitor (C205 - 16V 2200µF) is dead
- the main EPROM (IC10 - 27C512 EPROM) is dead or it's ROM binary is corrupted
- one or more of the five other small SMD capacitors (16V 47µF) is dead

I replaced the FDD with a working one (with good jumpers configuration) and also with a FDD emulator (HxC based): it didn't change anything

I checked the power supply to the FDD and it gave me 5V so it is OK.

I replaced the main capacitor with a new one: DIDN'T CHANGE ANYTHING

So this is where I am. I never recapped a board with SMD components, I'm not good/precise enough to do it so I let this option as last resort (I still have bought replacement SMD capacitors).

TL;DR I'm now looking for a ROM image of a working Roland SB-55. So if you've got one and are willing/competent to dump it's main EPROM (it's socketed so you don't have to desolder anything, just remove some philips screws to access it, it's very easy!) you'll greatly help me into saving one of these rare beasts! If you've got a working SB-55 but don't have a chip dumper you can send me your chip (I'll pay for the shipping of course and can give you a little extra for the hassle).

Last edited by Jonas-fr on 2017-01-31, 17:04. Edited 1 time in total.

Reply 1 of 29, by Jonas-fr

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Ok I think the issue resides into bad capacitors. I replaced C7 capacitor (it's an ugly soldering job since I don't have tools for SMT) and I gained back some functionnality! The midi file load and plays for a few seconds but stop after that and I got a "dEr" message meaning that my floppy is bad. Since I also tried with a floppy emulator (which doesn't go bad since floppy image is a file and it's load ok with my 486 PC) I think this is because some capacitors are bad too. I'll have to recap the whole thing. I'll try to find someone to do this for me.

In the meantime I dumped my ROM for conservation purpose only and uploaded it here since it's nowhere to be found and can help people to fix broken SB-55! 😉

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Last edited by Jonas-fr on 2016-07-02, 13:05. Edited 1 time in total.

Reply 2 of 29, by Jonas-fr

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Oh by the way, I can't say how I got it but I also found the service manual for the Roland SB-55 which was also not available on the web. Here it is, hope it can help!

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Reply 5 of 29, by kiskadar69

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@derSammler: Thanks for your help. What makes you think that this file is the v1.06? The string "1.006" is also included in the Roland SB-55 v1.03 binary file.

Reply 6 of 29, by DaCiRO

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Jonas-fr wrote:

Oh by the way, I can't say how I got it but I also found the service manual for the Roland SB-55 which was also not available on the web. Here it is, hope it can help!

Did you ever find out was wrong with your SB-55 and did yo manage to repair it?. I am having the exact sam issue that you, my SB-55 only shows the '- - -' message and does not want to play any midi songs. I cannot not even get it to service mode (following the manual that you attached)
Also it seems that these Chinon Fz-354 replacement floppy drives are hard to find these days....

Reply 7 of 29, by jxalex

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before you even heat up soldering iron, switch on oscilloscope and diagnose. Dont swap the capacitors or ICs blindly.

0. have you checked if the supply levels are normal levels and without any ripple in that +5V rail?
1. Check that the chips get 5V which must get that. ALso if there are perhaps some bad joints, reseat cables. Pay attention to any miscolored areas.
2. system clocks.
check that the clocks are running and around ROM there is no bus contemtion, So data is moving as it should on a adress and data bus.

Current project: DOS ISA soundcard with 24bit/96Khz digital I/O, SB16 compatible switchable.
newly made SB-clone ...with 24bit and AES/EBU... join in development!

Reply 8 of 29, by Jonas-fr

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DaCiRO wrote:
Jonas-fr wrote:

Oh by the way, I can't say how I got it but I also found the service manual for the Roland SB-55 which was also not available on the web. Here it is, hope it can help!

Did you ever find out was wrong with your SB-55 and did yo manage to repair it?. I am having the exact sam issue that you, my SB-55 only shows the '- - -' message and does not want to play any midi songs. I cannot not even get it to service mode (following the manual that you attached)
Also it seems that these Chinon Fz-354 replacement floppy drives are hard to find these days....

Sorry for the delay, it was a capacitor issue, I changed them all. Some had leaked and corroded the PCB... Hope you'll be able to save yours too !

Reply 9 of 29, by DaCiRO

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Jonas-fr wrote:
DaCiRO wrote:
Jonas-fr wrote:

Oh by the way, I can't say how I got it but I also found the service manual for the Roland SB-55 which was also not available on the web. Here it is, hope it can help!

Did you ever find out was wrong with your SB-55 and did yo manage to repair it?. I am having the exact sam issue that you, my SB-55 only shows the '- - -' message and does not want to play any midi songs. I cannot not even get it to service mode (following the manual that you attached)
Also it seems that these Chinon Fz-354 replacement floppy drives are hard to find these days....

Sorry for the delay, it was a capacitor issue, I changed them all. Some had leaked and corroded the PCB... Hope you'll be able to save yours too !

Thanks for confirming. It was a capacitor issue on the floppy itself or the main board?. I am finding very hard to pull the cables connected to the main board,.. these don't come out easily, As I pull I am afraid I will end up ripping some of them yet to get o the capacitors on the main board I got to disconnect all the cables first. How did you do it? Disconnecting the cables on the SC-55 is much easier, but the SB-55 seems rather impossible.

Last edited by DaCiRO on 2018-11-05, 15:40. Edited 1 time in total.

Reply 10 of 29, by DaCiRO

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jxalex wrote:
before you even heat up soldering iron, switch on oscilloscope and diagnose. Dont swap the capacitors or ICs blindly. […]
Show full quote

before you even heat up soldering iron, switch on oscilloscope and diagnose. Dont swap the capacitors or ICs blindly.

0. have you checked if the supply levels are normal levels and without any ripple in that +5V rail?
1. Check that the chips get 5V which must get that. ALso if there are perhaps some bad joints, reseat cables. Pay attention to any miscolored areas.
2. system clocks.
check that the clocks are running and around ROM there is no bus contemtion, So data is moving as it should on a adress and data bus.

Thanks for the advice. I do not own an oscilloscope but I can check the power on the lines.

Reply 11 of 29, by jxalex

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DaCiRO wrote:

Thanks for the advice. I do not own an oscilloscope but I can check the power on the lines.

then just use a computer soundcard to probe if there is the ripple, by just decoupling the DC input at first with some capacitor.
but the most important is that check that everything which should get the +5V will get it as it should. 😀

Current project: DOS ISA soundcard with 24bit/96Khz digital I/O, SB16 compatible switchable.
newly made SB-clone ...with 24bit and AES/EBU... join in development!

Reply 12 of 29, by DaCiRO

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Hi I checked and the Power is correct, just in case I connected the floppy drive to an external power source, but no difference. I am wondering if the floppy drive itself is faulty. I get this on-screen error message: '5ur' or maybe instead of a 5 is a capital S 'Sur'...the manuals do not mention anything about this error message which is rather strange since they mention others, ....this has me puzzled.

Reply 13 of 29, by DaCiRO

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OK, to close on the subject.
Two things were wrong. Capacitors and the Floppy drive itself
Capacitors
I replaced the 3 capacitors in the main board, the old ones had leaked badly and there was corrosion in near by components. I managed to scrap it all away, fortunately there was nothing irreversible. The corroded capacitors came out too easily but did so as well the board connecting pads ( 3 capacitors and 4 of 6 pads came out) so I had solder the capacitors to the nearby traces where the pads connected to the board.
whenever I got more time I will undo everything and replace the pads properly.

Floppy Drive
The floppy drive was (is) also damaged, and I suspect is due to one or more of the 3 capacitors in it being faulty. The visible issue is that the main axis of the floppy motor does not spin so might be, I guess, that the capacitor near by is bad, or the little ball bearing that connects the end motor axis to the floppy metal body is either damaged or stuck due to stone dried lubricant or lack of lubricant..... I am still troubleshooting this part.

In the meantime I was able to find a replacement 2DD floppy drive and once installed the SB-55 came back alive again!!. ...Issue is though that the floppy is white so it does not blend too well with the dark grey body of the SB-55,... the white button sticks out like a sore thumb,..and it just drives my eyes to it like if I was enchanted,...I barely get to notice the rest of my module set anymore due to this 😀 ....will pain that to dark bluish-grey sometime when time allows.

Not: I mentioned before that I was also getting an error message 'Sur' (which is not listed in the operations or maintenance manuals). It must be be an abbreviation for 'Surface', and I am pretty sure it comes out when the SB-55 can't read the floppy due to not being formatted or the format being damaged. For me If goes away when I re-format the floppies (initialize them) on my Win98 PC or formatting them in the SB-55 itself by following the process sated in the manual to do so
"...While holding CLEAR insert the disk with the protecting floppy tab set to Write and press REC..."

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Reply 14 of 29, by Drummer

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Hello there.
Well, directly to this topic. Three months ago I experienced the same problem. After a bit of investigation, I decided to consider the whole situation from another point of view. So i decided to check the POWER ON RESET circuirty and...Voilà, as the French generally say...I fixed the malfunctioning removing the capacitor on the reset integrated circuit and substituting it with another, brand new, tantalium solid.It probably depends on the liquid contained in the elettrolitic capacitor which, after a certain number of years, degrades and deeply modifies the performances of these kind of components. Then, as a further action for considering the entire problem solved, I also replaced all the other polarized capacitors.

Ah, by the way: the error message (SUR) experienced by another reader doesn't indicate an error on the surface of a floppy disk but an extra increase of the temperature of the circuitry controlling the FDD. It happens the same when I use a cleaning floppy for more than 10 seconds...

Hope this helps. And sorry for my italian English..

Reply 15 of 29, by saifbadri

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Hi, my wife used a 12v DC instead of 9v DC to power our SB-55 and now it has black screen. only a small amber light inside of the disk drive bay (you have to open the disk lever to see it)
I was looking at the service manual above (thanks for that btw) and I'm not sure which component I need to take a look at. finding a used one is not possible looked everywhere...
can someone please provide any advice thanks here is the power circuit diagram attached.

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Last edited by Stiletto on 2020-02-03, 19:32. Edited 1 time in total.

Reply 17 of 29, by derSammler

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saifbadri wrote on 2020-01-31, 21:09:

Hi, my wife used a 12v DC instead of 9v DC to power our SB-55 and now it has black screen.

Normally, the SB-55 can work fine with an input voltage of 12V, as the input voltage is always regulated down to 5V, no matter if you feed in 9V or 12V. But considering it's age, the voltage regulator probably just failed. Open the unit and check the 5V rail with the PSU connected and the unit turned on. If there are no 5V or they are much lower, replace the voltage regulator.

Reply 18 of 29, by saifbadri

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gdjacobs wrote on 2020-02-01, 02:23:

Does it function or is there more wrong than the display?

No its not working at all. Only gaint sound then the disk stops. Hitting play or clearing it as roland recommended not helping. The power led is off too...
Is this a symptom of a bad rom?

Reply 19 of 29, by saifbadri

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derSammler wrote on 2020-02-01, 08:53:
saifbadri wrote on 2020-01-31, 21:09:

Hi, my wife used a 12v DC instead of 9v DC to power our SB-55 and now it has black screen.

Normally, the SB-55 can work fine with an input voltage of 12V, as the input voltage is always regulated down to 5V, no matter if you feed in 9V or 12V. But considering it's age, the voltage regulator probably just failed. Open the unit and check the 5V rail with the PSU connected and the unit turned on. If there are no 5V or they are much lower, replace the voltage regulator.

Thanks got another freind who recommended this on discord. I will test that today. Caps look fine so I hope its just the regulator. I tried applying 5v to the logic inputtaping into ground and 5+ but got the same results. Maybe its a bad eprom...