Roland VA-3 boot issue - Page 1
Forum section: electronics / repair

author: frisc0
author_rank: Regular Contributor
timestamp: August 17, 2021, 10:11:23 pm
content: Hi,My nephews Roland VA-3 keyboard has the issue at power on, it won't boot; during play suddenly it crashed and refused to reboot again. I want to have a go at repairing it, if possible. It's a keyboard with few buttons but a touch screen lcd to operate it. At power on the lcd lights up white/grey color and 3 buttons with red leds light up. A few seconds later the color of the lcd changes to yellow/orange and one of the leds of the 3 buttons switches of, leaving 2 lit.I've checked the service manual (https://www.synthxl.com/wp-content/uploads/2020/01/Roland-VA-3-Service-Manual.pdf) for the factory reset procedure, but the keyboard does not seem to respond to (any of) these.I've checked the PSU, that is combined with the Power Amplifier on 1 PCB. The PSU delivers a steady 5V and 12V, and also powers the LCD inverter board, which works. Also, the analogue circuit still works correctly. There is a RCA input (to play along with an external music source) and this input gets amplified and played correctly through the speakers and headphone jack(s).I suspect it must be something with the boot procedure failing, possibly a flash rom or something (system program can be written/updated in flash rom from a floppy), but I cannot figure out how to proceed or what to check / do next. I've inspected all pcb's in the keyboard, detached and reattached all connectors, but to no effect. No visible damage to pcb's or components, no caps blown or leaking as far as I can see (or smell).Also tried to detach components (button pcb, keyboard, floppy drive, D-beam pcb, jack/midi board and booted up to see what happens, but same behaviour at all time: lcd lights up, but it won't boot further, never anything is shown on the lcd. Also checked the lcd contrast pot at the rear of the keyboard, makes no difference varying this.What would be the best way to proceed this analysis?All help greatly appreciated! Thanks.

author: frisc0
author_rank: Regular Contributor
timestamp: August 17, 2021, 10:39:39 pm
content: The behaviour the VA-3 shows is very similar (yellow blank lcd screen) to what Juno-D users report after a failed system update:https://www.keyboardforums.com/threads/roland-juno-d-system-update-1-04-trouble-synth-doesnt-work-after-that.3585/

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 17, 2021, 11:39:36 pm
content: Well, If you have verified the Power lines (+5V, +12V, -12V), I think the next step would be to verify power at the Microcontroller and RAM/ROM/Flash on the MAIN PCB (page 17,19), these will be the basics for booting i'd suspect. If the power all looks good there, then I'd try getting a test disk and system disk, and see if you can get it into the system update mode, or test mode (page 8,9).It might also be worth, if you have the means, to check the clock signal for the ICs is there and functioning.But I suspect like frisc0 says it could be bad software, i've noticed cases of flash going bad seem to be increasing, and maybe if you can reload the system, it might work. You might need to try and find someone with a VA-3 to write you a system disk, as I can't seem to find them online.

author: frisc0
author_rank: Regular Contributor
timestamp: August 18, 2021, 12:44:38 pm
content: Thanks for your reply LateLesley! All voltages look good, so it must be something in the digital area I expect.I also thought about reloading the system to Flash, but the procedure to do so according to the service manual is to hold 3 buttons (piano + one touch + intro) while powering on. This then should display a menu (from static ROM I expect) from which you can choose to save or load an updated system or the test program. However, this first menu doesn't even show, I have never seen any characters or images on the lcd, just blank.Now there is a Flash ROM initialization procedure (holding melody intell pressed while powering on) but this doesn't do anything either where it should display a message.I think the boot software with basic operations (BIOS like) is in static ROM and the system program runs on top of that and is stored in Flash ROM.Since the boot ROM doesn't even come up, maybe it's not a Flash ROM issue, but something around the components and software involved in the boot process. I don't have a scope to check signals, only a multimeter. Are there any suspect components I could check?I can also imagine the system (BIOS) does some checks/diagnostics prior to actual startup to see it receives the right signals from components like the lcd ('is it switched on and working?') and maybe for other components as well and maybe from these checks it halts because a component is failing. You think the PSU should give some signal as well like 'I now can produce a stable 5V..' for example?Btw: I do note the 5V voltage regulator gets very hot (incl the heat dispenser) and also R1 and R11 get very hot (cannot touch with bare finger). Would this be normal?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 18, 2021, 02:29:53 pm
content: Check the reset circuit, XRST on page 22. There is an electrolytic cap there.It is surprising how often the reset signal is the culprit in non boots.

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 18, 2021, 04:43:27 pm
content: I no doubt think getting as hot as to not be able to touch is indicative of a fault, sounds like something is drawing too much current. (I take it this is R1/R11 on the power board?). They are series resistors in a power line, paralleled, so I'd expect some heat, but if they are getting toasty fast, and the IC1 regulator is too, i'd say something is faulty. You can narrow that part down relatively easily by disconnecting the FDD, Jack board, and Inverter connectors, and then connect one at a time, and see which one makes IC1 hot. That should identify which one is drawing too much power, and help you know where to concentrate your efforts.Audiorepair makes a good shout too, worth checking the reset signal for the digital side of things, and if IC1 is getting hot quick, and the inverter is causing it, it could just be from the LCD being permanently blank. It may be it's highest state of draw. I do suspect you have a good grip of the bootup process, I'd go for MCU, ROM, RAM, and LCD being the basics needed. But you do have to be aware of other components pulling down the busses (Control, Data, Address) and stopping comms if something is faulty. You might be able to check this with your multimeter, measuring a digital line, if it's hard high or low, it'll read 0V or 5V, if there's comms, you should see it dance around a bit. So any data line with steady readings could be suspect. Though they would all be pretty steady if the reset signal is enforced. So check that the reset is operating correctly before you dig into the data lines n stuff.If the reset is ok, I'd suspect chips in this order : Flash, RAM, MCU, ROM. The reason for this, is Flash does wear out, RAM is sensitive and can fail, Mask ROM tends to be quite hardy, so i'd suspect the MCU being faulty next. I take it you have done the finger test to see if any of these get hot?

author: frisc0
author_rank: Regular Contributor
timestamp: August 18, 2021, 08:07:04 pm
content: Wow, good suggestions both, thanks, I'll try later this evening!Meanwhile, two photo's of the keyboard to get an understanding of how the boards are placed/connected. The photo of the top of the keyboard is to show what happens if connector CN4 is detached; with everything connected at first boot it's intro+fill+variation that light up and after a few seconds (when the lcd changes from white to yellow) intro shuts down and only fill+variation keep being lit. I think this shows there is some logic still working the first seconds, to come to a halt in the process.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 18, 2021, 08:23:22 pm
content: From that position, you could try a warm boot by briefly grounding the CPU reset pin (shorting C71 should do it).There should be 5v across C71 normally.Might show something new.

author: frisc0
author_rank: Regular Contributor
timestamp: August 18, 2021, 10:29:53 pm
content: Interesting stuff: I detached multiple power consumers and checked the heat production on the voltage regulator and resistors R1 and R11. As soon as the jack board is connected, heat rises to untouchable levels. Testing temperature of the components on this board I found that IC6 (NJM2360M, a DC/DC control IC:https://datasheetspdf.com/pdf/455002/NewJapanRadio/NJM2360/1) gets very hot!So I decided to measure the voltage on the pins and found (against analogue ground pin 9 on CN3):pin1: 5Vpin2: nearly 0Vpin3: -12.3Vpin4: (which according to the datasheet should by GND) measures -14.69Vpin5: -13Vpin6: 5Vpin7: 5Vpin8: 5VCan we conclude this IC is broken?It's the only hot component on the board, the big resistor next to it (R39) does not get hot.Also, the IC5 (79L12 negative voltage regulator,https://datasheetspdf.com/pdf/973358/UnisonicTechnologies/79L12/1) does not get hot. On the datasheet I read it has a thermal shutdown protection...?I totally overlooked the -12V which is not produced on the PSU board, but on the jack board.Your advice please

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 19, 2021, 01:07:26 am
content: Actually, it all seems fine. Because it's generating a negative voltage, The IC ground isn't connected to the system ground, otherwise it would short out and destroy it. It's a type of "floating ground circuit"when the IC ground will actually be connected to the negative output voltage, so that all the voltages look positive to the IC with respect to the IC ground pin. But in reality the IC ground is negative, below the actual system ground.This article might explain it better.https://www.electronicspecifier.com/products/power/creating-a-negative-output-voltage-using-a-buck-converterSo I would check the TP8 and make sure you are getting -12V, and check C43,C44,C45,C46 and D6, to see if they get hot, which might indicate a fault. It seems to supply various ICs on the jack board (Page 25, look across from the letters K and M on the left, you'll see various op amp symbols withe the +Vcc and -Vcc supply lines) is ICs 2,9,10,14,and18, and their associated caps could all be suspect, and worth checking for heat, and in the case of the caps, with the power off, shorts.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 19, 2021, 12:46:09 pm
content: The fact that the unit passes audio from the CD inputs to the power amp suggest that both 12v rails are present, and I believe your measurements confirm this.If IC6 is getting really hot, and the 7912 regulator isn't, that would indeed suggest a problem with the circuit around IC6.Since IC6 does appear to be working, or you wouldn't get -12v from the 7912, it kind of points more towards IC6 working too hard.My first suspect would be C46, as this going bad would force poor old IC6 to pump out loads of power to get enough voltage to run the 7912.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 19, 2021, 01:35:21 pm
content: Also, I doubt this issue has anything to do with the non booting issue, as removal of this jack board should remove the boot problem, but you say it doesn't.It's probably just another sign of a piece of equipment growing old, like we all do eventually.Most of the electrolytics will probably not be the same spec they were born with.

author: frisc0
author_rank: Regular Contributor
timestamp: August 19, 2021, 10:08:53 pm
content: Thanks for explaining LateLesley, learnt something new again!Strange thing is, none of the components get hot on the jack board, only IC6... whereas the big resistor R39 next to it, which is a 1W Oxide Resistor of 0.22 Ohms and I think was designed to dissipate the heat, but it doesn't since it does not get hot. I unsoldered it and measured resistance, which was floating between 0.3 and 0.4 Ohms. Is this an acceptable variance?

author: frisc0
author_rank: Regular Contributor
timestamp: August 19, 2021, 10:12:35 pm
content: Quote from: Audiorepair on August 19, 2021, 12:46:09 pmBy chance I had a replacement for C46 (1000u-25V) lying around, so I changed it, but with no effect whatsoever unfortunately. Thanks for the advice though, it sounds logical...TP8 still measures -12V, so it does still deliver the right voltage(s).

author: frisc0
author_rank: Regular Contributor
timestamp: August 19, 2021, 10:14:18 pm
content: Quote from: Audiorepair on August 19, 2021, 01:35:21 pmThing is, the jack board cannot be removed for a boot-test, since the jackboard passes on the required power for the mainboard. The mainboard itself does not have power lines of its own.

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 20, 2021, 03:18:25 am
content: Yeah, with an ordinary meter 0.3to 0.4Will be close enough. It's hard for meters to read low ohm resistors, you usually have specialised meters for that. It's at the level of measuring the resistance of the meter cables themselves. So the reading you got seems reasonable.It'll also be the reason it doesn't get really hot. As it's a very low resistance, there won't be much voltage drop across it, so it won't actually dissipate that much power. It would need a lot of current to start it heating.As that circuit is producing the right voltage, and it doesn't seem to be disappearing with the power on, I think you can rule out that particular circuit from having a fault. Sometimes some components do run hot.I think you're now into checking the Digital side of things, the power, reset, and data of the digital stuff.

author: frisc0
author_rank: Regular Contributor
timestamp: August 20, 2021, 09:54:17 am
content: It does deliver the right voltages, but I still find it strange this IC6 is heating up that much without a proper heatsink, one would think it's not designed to get this hot. Also, why use such a big resistor designed to handle high temps/amps but it does not heat up at all...But I guess you are right that the failure to boot is not because of this issue (might be something that will be causing trouble later... :| ).Looking at the reset lines: Audiorepair, I guess you mean shorting C76 on the mainboard, on the main CPU, right? The C71 you mention is on the synth board (XPGS4) and has it's own CPU. I think the CPU on the mainboard will be responsible for the boot program, but I'll try both.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 20, 2021, 10:31:12 am
content: Quote from: frisc0 on August 20, 2021, 09:54:17 amOops, yes, my mistake.There are other resets scattered around too, one on the floppy controller pg 20 for instance.It's just worth a go measuring then forcing resets, just in case something happens, maybe characters on the LCD that at least tell you the LCD is working.And short the cap rather than the tiny reset pin, so you don't risk shorting adjacent pins, but I'm sure you've got that already

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 20, 2021, 04:04:43 pm
content: Quote from: frisc0 on August 20, 2021, 09:54:17 amThat may actually be the reason, you pick big resistors so they don't heat up. especially with audio circuits. heat can A) change the resistance, and B) they'll probably be noisier.https://eepower.com/resistor-guide/resistor-fundamentals/resistor-noise/

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 20, 2021, 07:55:16 pm
content: Quote from: frisc0 on August 20, 2021, 09:54:17 amI really don't think also that IC6 should be getting hot, it is only powering a few op-amps.IC6 is run from the 5v supply.If it is drawing excess current, this may be putting ripple on the 5v supply, which could cause all sorts of mayhem with the computer stuff.If there is a way to easily disable the 5v supply to the IC6 circuit to rule it out as a culprit, then I would try that, you don't need the audio to test the boot.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 20, 2021, 08:04:01 pm
content: But it could also be the case that the 5v supply is crippled, in that the extra current IC6 needs is the straw on the camels back that makes the whole system fall over.

author: frisc0
author_rank: Regular Contributor
timestamp: August 22, 2021, 10:39:27 pm
content: Like the analysis...C49 can easily be removed from the board, as well as R39. That should do the trick to shut down IC6, right? And in the process I could replace C49 right away.Added some photo's of the 'suspect area' that might help. Still find it strange they fitted this big a resistor for R39 even with the legs protected without it ever getting hot...

author: frisc0
author_rank: Regular Contributor
timestamp: August 22, 2021, 10:44:17 pm
content: Also added a photo of C88 on the back of the mainboard which looks melted; it seems to be a bridge between analogue and digital ground; not sure this could harm? Could replace it with a normal ceramic cap...Also added a photo of the PSU for reference.

author: frisc0
author_rank: Regular Contributor
timestamp: August 23, 2021, 08:30:33 am
content: Quote from: LateLesley on August 20, 2021, 04:04:43 pmMakes sense in an audio circuit, again learned something new, thanks

author: frisc0
author_rank: Regular Contributor
timestamp: August 23, 2021, 10:18:30 pm
content: Okay, quick update: removed C49 and R39 which leaves IC6 without power, but no boot...Also replaced C88 (low hopes) and replaced C49 with a fresh cap with higher specs (100u 63V) and resoldered R39 again, still no boot...Then I measured voltage over C70 (around -9.7V) and C69 (expected +12V but found 100mV varying). So I replaced C69 for a fresh cap again 63V, but to no effect. I expect this missing +12V is the issue here, but where in the chain could this go wrong? Or is the low voltage measured on this C69 cap correct?

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 24, 2021, 03:54:06 am
content: can't for the life f me find C69 on the diagram for the jack board (I'm assuming this is on the jack board?) C72 should have 12V on it. The -9.7V on C70 sounds sus too. It might be a bad ground, or bad measurement. According to the diagram C70 is to do with a circuit for the pedal input.It might be worth naming which board you are talking about, as a few of them have the same component numbers, confusing things.So maybe just preface them MAIN, JACK, PSU/AMP, CONTROL, XPGS4 etc. so we know which board you are referring to. But C69 on the jack board is a mystery.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 24, 2021, 07:05:53 am
content: It took me a while to find C69 and C70.They are on page 17, upper right around CN9.The Nomenclature is a bit messed up on this PDF. What is marked as +12v and -12v on page 17 is actually +Vcc and -Vcc.The raw 12v from the power supply on the jack board is called 12v on page 29, then it becomes VA, then it is turned into Vcc using a transistor circuit Q1 on page 25.-Vcc comes from the negative switching circuit and 7912.The voltages on C69 and C70 are marked 12v and -12v but are actually +Vcc and -Vcc.What a mess.

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 24, 2021, 09:21:56 am
content: Ah! so they were on the main board. That's kinda what I suspected, when I couldn't find C69 on the jack board. I did find a C70 on the jack board too though, making me think I was just missing the cap somewhere. Seeing C69 and C70 in the main board, it makes more sense.So yeah, they should have +12V and -12V on them. One thing I will say @frisc0, is just check the ground connections between the boards are intact, sometimes they can pass grounds via the chassis, and if you have the boards out, it can disconnect these. SO make sure they are intact, and that you have the meter connected to a good ground before measuring voltages.A floating ground could mess up all sorts of stuff.And if you aren't getting voltage in the right place. just start from the source, and measure components/connections along the path, till you find where it's getting lost. Sometimes tracks on boards can be cracked, or blown out. You've already seen that damaged cap C88, so maybe check for any other damaged caps connected to the chassis, from other boards. But since voltage is being lost somewhere, that is a definite thing to investigate. It could explain the IC6 heating too, if voltage is being dropped somewhere, might be something shorted on the main board. I'd measure the voltage on the connector with the main board disconnected, then try again with it reconnected, and if it drops dramatically, something on the main board is pulling those power lines down.Thanks @Audiorepair for pointing me in the right direction of those caps. :-)

author: frisc0
author_rank: Regular Contributor
timestamp: August 24, 2021, 08:34:04 pm
content: Thanks guys and sorry to leave you searching without naming the PCB...Good tips again with tracing the missing 12V..., I did some tracing already, but the schematics are rather err... schematic, so I need some time to trace things down. Good tip on the ground, I did have the boards unscrewed from the chassis indeed, so I'll take that into account!

author: frisc0
author_rank: Regular Contributor
timestamp: August 26, 2021, 09:59:13 pm
content: I'm an idiot. I measured voltages on C69 and C70 on the mainboard via the top of the caps, don't know what one actually measures then? I know now that it's not the actual voltage over the cap... :|I checked the flatcable from the jackboard to the mainboard, the -12V is a solid -12V (okay, -11.96V), but the +12V is somewhere around +8.7V. Tracing the +12V towards the PSU I see the +12V from the external adapter dropping a volt or so on the PSU already and on the jackboard again. Without the mainboard attached it reads +9.4V. Would this be normal? Probably not something that causes the boot issue since the 12V lines aren't used in the digital circuit I think?So it's probably now up to checking the reset lines as audiorepair suggests (and still trying to find why IC6 on JB and IC1/R1/R11 heat up that much...).

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 26, 2021, 10:29:38 pm
content: I would suspect that the +12V should be near to it, 8.7V sounds way too low.2 options.1) The external adapter is faulty, and not able to supply the load of the Keyboard.or2) Something on the +12V line is drawing way too much power, and pulling it down.It might just be worth testing the adapter, as these do fail. Load it up and see if it can maintain the load. (Car bulbs can be good for load testing it.) See if the voltage drops down when it's loaded.If it checks out fine, then its off to trace everything running off the +12V.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 26, 2021, 10:59:52 pm
content: Quote from: frisc0 on August 26, 2021, 09:59:13 pmWell actually they are.pg17 top left.They use op-amps run from +12v -12v supplies to drive the bender and mod signals etc to the CPU.Should one of these 12v supplies fail, the op-amps would go full DC and try to input +12v or -12v to the CPU.They have diodes in place to prevent anything going above 5v, but still, they are mixing 12v and 5v circuitry.I would make sure you fix all the obvious 12v problems first, and then tackle the boot issue if that doesn't fix it.

author: frisc0
author_rank: Regular Contributor
timestamp: August 28, 2021, 11:33:54 pm
content: Quote from: LateLesley on August 26, 2021, 10:29:38 pmFollowed your suggestion and checked the 12V adapter with a car bulb. Could only find a 21W bulb and put the trusty multimeter in between, which measured a steady 1.75A without drops. The adapter is a 2A adapter and seems to be able to deliver that.So tracing the 12V is next then. Any clues as to where to begin, what would be the suspect components? I'll start with disconnecting everything from the PSU and start measuring there, then moving 'up' to the jackboard and mainboard next. And I guess it's only the (unregulated) +12V that's suspect and not the (regulated) -12V?

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 29, 2021, 03:43:51 am
content: OK, IC47 on the main board and surrounding caps (page 17, C-5 grid reference) IC26/27 + caps (Page 18 N-11/12)IC10 +caps on the D Beam board (Page 26, D-28) and D215 (D-22)IC2 on the LCD Control board (Page 24, G-28)I think thats it. Maybe check Zener D1 on the jack PCB (page 25, E-26) and Q1 (M-15)

author: frisc0
author_rank: Regular Contributor
timestamp: August 29, 2021, 10:19:45 pm
content: Quote from: LateLesley on August 29, 2021, 03:43:51 amThanks LateLesley for these tips!Checked the LCD control board, the negative voltages (incl the -21V on TP1) are good, the +12V is too low, around +8.7V. The LCD control board is powered via the mainboard, which in turn is powered via the jackboard.I checked on the jackboard, zener diode D1, there is 4.08V over it, where specs say it the zener voltage should be 5.1V if I understand correctly. Unsoldered it and measured with the ohm meter. It measures 25Mohm in the 'right' direction, O.L. the other way around. Would this diode be faulty?How is it used in this circuit, as a voltage regulator?The adapter delivers 12.3V without load. On the PSU the 12V line is 11.5V, when only the jackboard is also connected the voltage drops to 10.8V. This 0.7 drop is the magic 0.7 silicon number... coincidence?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 29, 2021, 10:35:12 pm
content: Quote from: frisc0 on August 29, 2021, 10:19:45 pmThere is little point pondering why a zener circuit may not be producing what you think it should, after you have explicitly stated that the +12v supply is too low at around 8v.THAT is your problem.Get the 12v supply working first, and forget everything else for now.

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 30, 2021, 02:38:06 am
content: Yeah something's drawing too much. IF you ran a car bulb at 1.75A without a power drop, and then it's dropping lots on the keyboard, something is pulling WAY too much power.I went back to the circuit diagrams, And started looking at the PSU setup.So here's what I'd like you to check if possible.First, on the Power & Amp board, with the power off, Check the resistance across R1 and R2. For R1 you should see around 1.1 ohms. It's a 2.2 ohm resistor but in parallel with R11 which is the same. R2 I think should be 10 ohms??If that checks out, power it up with the jack board connected, And measure the voltages in these few places.Across D2Across the power switch. (Just eliminates a faulty switch)Across R1Across R2Across C14Across C3On the jack boardAcross C117 (near IC19 i think, going by the schematic)Across C77 (Should be near IC11)Across C72Across C56The reason for this is to find out where the voltage is dropping a lot, and figure out which circiut is drawing too much power, to narrow down where the fault is.Nice to knows are if IC1 on the Power board (should be a 3 pin regulator on a heatsink TO-220), and IC19 on the jack board (another 3 pin regulator) are getting warm quick at all.That hot IC6 could be in question too. But get those measurements back, and well see if we can start narrowing it down.Audiorepair is right, we do need the 12V stable, but that might be hard if something is sucking enough current to draw it down in voltage. These measurements, especially across R1 and R2, might help narrow it down, while checking everything is healthy on the power and amp board.

author: frisc0
author_rank: Regular Contributor
timestamp: August 30, 2021, 10:39:12 pm
content: First of all I must say a big thank you for spending so much time helping me out here, I have all the confidence these efforts will pay offHere are my measurements:Adapter without load: 12.3VAdapter with 21W car bulb: 1.75A and 11.7VR1, unsoldered: 2.3 ohmsR11, unsoldered: 2.3 ohmsR2, in circuit: 10 ohmsWith jackboard NOT connected:Across D2: 0.76VAcross the power switch: 11.27VAcross R1: 5.5mVAcross R11: 5.5mVAcross R2: 0mVAcross C12: 11.46VAcross C13: 11.46VAcross C14: 11.46VAcross C3: 4.95VWith jackboard connected:Across D2: 0.76VAcross the power switch: 11.27VAcross R1: 244mVAcross R11: 244mVAcross R2: 0.48VAcross C12: 10.82VAcross C13: 11.33VAcross C14: 11.05VAcross C3: 4.95VOn the jackboard:Across C117: 9.71V (near IC19 i think, going by the schematic)Across C77: 5.01V (Should be near IC11)Across C72: 10.82VAcross C56: 9.72VDoes this point into some direction?Again many thanks in advance for your help and analysis!!!

author: Audiorepair
author_rank: Frequent Contributor
timestamp: August 30, 2021, 10:47:01 pm
content: Short the power switch, if it has volts across it it is not a working switch.

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 31, 2021, 12:50:07 am
content: OK, not really. As AudioRepair mentioned, when I said measure across the switch, I meant between the two connections, not between switch n ground. But I managed to figure out it's probably OK.I went through the circuit, and it doesn't seem too horrendous what you are measuring. It seems it has been designed like that.As far as I can work out, there's 200mA on IC1 in the Power.Amp Board, and about 48mA on the jack board, and the voltages seem consistent with that. It seems VCC on the jack board will drop down to 9V (I simulated part of the circuit around Q1, cos the 1V drop concerned me, but it seems right)So I suppose the next step would be to connect main, Then give me the voltages over R1, R2 , C12, C14, and C72 C56 on the jack board. Lets see if that increases the power consumption a lot. ( Thats why I get you to measure across R1 and R2, I can work out the currents on those power lines from there. )Also, I'm not ruling out your 12V adapter, the way it's dropping voltage, it could be weak, though the bulb test seems to discount that a little. I wonder if you have another 12V adapter with enough current to try??

author: frisc0
author_rank: Regular Contributor
timestamp: August 31, 2021, 09:57:17 am
content: Quote from: Audiorepair on August 30, 2021, 10:47:01 pmWhat I did was unplug the power switch from the PSU board and measure the voltage between the pins that the switch would short when connected. I thought that was wat LateLesley meant and I think she confirmed that.This evening I'll connect the main board and report my measurements. I must say that with only the jack board connected to the PSU, IC6 on the JB already gets hot (although not as hot as with the MB connected as well).Meanwhile I asked around for another 12V 2A+ adapter, unfortunately I don't have any of these (I do have laptop adapters but they are 15-20V which I think will be too much for this keyboard?).To be continued...

author: LateLesley
author_rank: Frequent Contributor
timestamp: August 31, 2021, 11:11:12 am
content: Actually, AudioRepair was right, I was wanting you to confirm, with the power on, IE the switch closed, that there was no voltage across it. It's a quick check for a bad switch. You weren't meant to disconnect the switch, I wanted to know if there was any voltage across it while it was in place and on. Sorry!!As for other adapters, yeah, laptop ones will be too high a voltage.I look forward to the next test results. That hot IC6 is annoying me, but since you're getting the right output voltage, and the current consumption isn't too nuts (I think - though maybe thats why there was 200mA running through IC1 on the power board, maybe there is something wrong on the -12V somewhere - maybe check the op-amp ICs for any hot ones??).Maybe just do the finger test on IC 2,7,9,10,14,18 on the jack board, before adding the main board, to see if any of them are getting hot. In fact, baybe just check IC11 too, and any transistors you see, like Q1,Q10,Q11. I'm beginning to think that the hot IC6 might be telling us something else is wrong.

author: frisc0
author_rank: Regular Contributor
timestamp: August 31, 2021, 08:04:54 pm
content: Quote from: LateLesley on August 31, 2021, 11:11:12 amAh... makes senseThere is 2.4mV across the switch, should be 0V I guess...does that indicate a fault?

author: frisc0
author_rank: Regular Contributor
timestamp: August 31, 2021, 08:44:34 pm
content: Quote from: LateLesley on August 31, 2021, 12:50:07 amOk, with the main board connected, here are the voltages:PSUAcross powerswitch: 4.8mV (hmm...?)R1: 0.68VR11: 0.68VR2: 0.62VC12: 10.42VC13: 11.12VC14: 10.35VJBC72: 10.43VC56: 9.20VC117: 9.20VC77: 5.01VWith the main board connected IC6 is getting hotter and also IC1 on the PSU gets warm incl the heatsink and also R1 and R11 warm up (with only the JB connected there is hardly any heat on the PSU components). Apart from IC6, no other components on JB or MB get hot.

author: LateLesley
author_rank: Frequent Contributor
timestamp: September 01, 2021, 02:03:56 am
content: OK....A couple of mV across the switch isn't too bad. Switch contacts do have resistance, and will drop something, if it was 0.5V, we'd start looking at it. 5mV, not so much.Right - 0.68V across R1 = 618mA being drawn on the 5V rail - I actually don't think that is too unreasonable.And you still have about 9V on the +12V line - again something I'd seen as an acceptable drop considering the circuit.Time to add the LCD board, and see what changes.IC6 would get hotter, more current drawn on the -12V by adding the main board. I am wondering if there is a fault, or it was designed to run hot.

author: frisc0
author_rank: Regular Contributor
timestamp: September 01, 2021, 09:17:58 pm
content: Quote from: LateLesley on September 01, 2021, 02:03:56 amOk, with the LCD board connected, here are the voltages:PSUR1: 0.77VR11: 0.77VR2: 0.66VC12: 10.32VC13: 11.06VC14: 10.22VJBC72: 10.32VC56: 9.05VC117: 9.04VC77: 5.01VAnd with the inverter board also connected:PSUR1: 1.31V (hot)R11: 1.31V (hot)R2: 0.66VC12: 10.04VC13: 10.81VC14: 9.39VJBC72: 10.04VC56: 8.78VC117: 8.78VC77: 5.01VSo, maybe everything normal after all? That would be back to square one and looking at a digital issue...I'm mentally preparing for a 'case lost'...I'll see if I can get my hands on another power adapter with higher specs, to rule it out.Update: I found a 12V 3A power supply from and old Asus EEEpc, but, unfortunately, same results as with the other adapter...

author: LateLesley
author_rank: Frequent Contributor
timestamp: September 02, 2021, 05:13:54 am
content: ok, I think we might need to look at the inverter board, as it seems to add a significant jump. It's going from ~700mA on R1/R11 to 1191mA, thats about a 500mA jump.Ok scratch that, it seem normal, according the datasheet.https://datasheet.octopart.com/CXA-M10A-L-TDK-datasheet-10491771.pdfSeems it can draw 0.6A - 1.0A which then fits in line with your figures.I think all the power seems to be operating as intended, given the circuit.I think we are into a digital issue, maybe just verify the supply voltages to all the digital ICs on the main board, and check them all for hot spots??

author: frisc0
author_rank: Regular Contributor
timestamp: September 02, 2021, 10:07:26 pm
content: Back in the digital domain...Supply voltages are good, ~5VNothing gets hot on the MB/XP boardChecked several reset lines, all ~5VShorted these reset lines to GND and watched the LCD for action:MB CPU: system reboots, LCD goes gray and after 3 seconds goes yellow/orange, without anything on the LCD (same behaviour as when turning on the device)XP CPU: system reboots, sameLCD ctrl: system reboots, sameFDC: no actionIt does not seem to be forced in reset, something else is halting the boot process. I wonder if I can do some additional measurements to trace down the issue or whether this goes into ROM/Flash failing, which would be end of story...

author: frisc0
author_rank: Regular Contributor
timestamp: September 19, 2021, 07:13:06 pm
content: I noticed the adapter cable easily disconnects/connects and I can imagine that that might cause issues if this would happen during a memory write action. Would there be a possibility to 'reset' / 'reflash' the flash memory on this board? And then not via the key-combi mentioned in the manual since it does not respond to that, but maybe on the IC itself, by applying the right voltages to the right pins?

author: LateLesley
author_rank: Frequent Contributor
timestamp: September 20, 2021, 12:38:26 pm
content: I think this might have to be the way you go. You probably need an EPROM programmer.From the manual, I think this is the flash chip (IC20 on the Main Board, Listed on page 6 of the manual) -https://datasheetspdf.com/pdf-file/62817/SharpElectrionicComponents/LH28F160S5T-L70A/1You could probably get a programmer like the TL866II, and program it using that.http://www.autoelectric.cn/en/tl866_main.htmlYou will need an adapter though, a TSOP 56.Ouch! I just looked up the adapter and it was $130!!!...OK, there's a couple of other programmers, which seem to come with the TSOP56 adapter, for cheaper.https://www.aliexpress.com/item/32812908596.html?spm=a2g0o.productlist.0.0.15591808vDCcPp&algo_pvid=3369ab48-2d96-4f97-bb5a-8a20dc909118&algo_exp_id=3369ab48-2d96-4f97-bb5a-8a20dc909118-39&pdp_ext_f=%7B%22sku_id%22%3A%2264559555259%22%7DAnd actually the other one isn't cheaper with the adapters. it's cheapest option seems to be the T56 + 12 adapters, which has the tsop56https://www.aliexpress.com/item/32812908596.html?spm=a2g0o.productlist.0.0.15591808vDCcPp&algo_pvid=3369ab48-2d96-4f97-bb5a-8a20dc909118&algo_exp_id=3369ab48-2d96-4f97-bb5a-8a20dc909118-39&pdp_ext_f=%7B%22sku_id%22%3A%2264559555259%22%It's gettin kinda pricey. Sorry.I wonder if it would be worth just getting a new flash chip, chucking it in, and seeing if it would be ready to program then? I mean flash chips do fail, so maybe having a fresh one in, it might just fire up ready to program? it might be the cheaper option.https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=lh28f160+tsop&_sacat=0&LH_TitleDesc=0&_odkw=LH28F160&_osacat=0I'm just spit-balling now, cos i'm at the limits of my knowledge. Maybe other peeps can pitch in and help.