Tag Archives: solder

Roland MKS-80

Replacing the backlight of a Roland MKS-80 rev 5

Today I changed the backlight on a Roland MKS-80 rev 5. If the backlight is very weak, the electro-luminescent foil it’s probably worn out. They simply have a limited lifetime. When this happens you have three choices;

  1. Ignore the problem and use a flashlight
  2. Replace the whole LCD
  3. Replace the foil

I think the missing backlight is really annoying and makes the synth harder to use, so not doing anything was not an option.

Replacing the LCD would probably not be too hard, it has standard dimensions of 80×36 mm and are cheap. If you’re lucky a new LCD would just work, but in the worst case there could be compatibility problems. I’m not saying there will be problems since I haven’t tried it, but there’s an obvious risk. For example, changing the LCD on an EII to modern LCD also required changing a chip, otherwise the LCD just displayed strange characters.

I went for the third option, namely just replacing the foil. There are some companies providing replacement foils cut to the right size in various colors. However, I thought I’d give Roland a try since they seem to have a lot of old stuff left in stock. So I emailed Roland Scandinavia asking for a foil for a Roland MKS-80 rev 5. Since they didn’t know exactly what part was, they emailed me the service manual for me to look up the part number.

After browsing the manual I finally found what I suspected was the correct part, namely “15029181 EL-101 (electro luminescence)”. Roland said it’d be around €20 and recommended me to visit my local Roland retailer to order it, so I did…

Replacing the foil is quite straight ahead. Most of the work is getting to the LCD. To do this you of course have to remove the lid, and then the front panel. Then you have to undo three screws and three standoffs so you can fold the two voice boards upwards to finally reach the CPU-board at the bottom which the LCD is connected to in three places. Two of the connectors are snapped in place, so use a small, flat screwdriver to fold the latches away. Then you finally remove the four screws holding the LCD in place, remove the LCD and heat up your soldering iron.

I used desoldering wick to remove the old solder. Then it’s just a matter of sliding the old foil out of the LCD. The “new” one I got from Roland is probably NOS, because it looked exactly the same as the original one. I slid it into the LCD and soldered it’s two legs to the circuit board. I actually cut away about two mm of each leg since they were a bit too long. I powered the MKS-80 up, and the backlight was really bright – success! However, it seems that I should have placed it a little more to the right.

Then it was just a matter of reassembling the MKS-80. However, this was not as easy as disassembling it. The tricky part is the front panel that has three rectangular holes for the OMNI, POLY, MONO leds. The leds have to go straight in their holes, otherwise the front panel won’t sit where it should. There’s also a similar led for MIDI MESSAGE to the right which makes it even more trickier… Do not try to force the front panel, just take it easy and align the leds, and do try not to get too annoyed.

I put the MKS-80 back in the rack and fired up my DAW to realise that the MKS-80 sounds great and the backlight is strong – but – the MIDI MESSAGE led doesn’t work… I will replace it some other time.

E-MU Emulator II

E-MU Emulator II LCD screen change

One thing that sooner of later will die on your EII, if hasn’t already, is the backlight of the lcd display.  There are basically two things that can go wrong: The backlight itself or its transformer.

The backlight The original EII display don’t use leds for the backlight as modern displays do, but another kind of lamp. These can be replaced, but I’ve understood that it’s quite a lot of work, and it’ll definitively die on you again.

The transformer transforms 5V to a much higher that supplies the backlight with power. These kind of transformers often emit a high pitched frequency which can be quite annoying.  Since my transformer didn’t sound at all, I thoguht that this might be the faulty component, and not the backlight itself. The transformer used on the EII is the NEC NEL-D32-46.

The solution is to replace the whole lcd display with a newer one that has led-backlight and remove the transformer. On my EII I suspect someone has been doing some kind of operation on the display before, since the display wasn’t physically connected to the display.

Parts

EII OEM displays can be bought on eBay for a lot of money, and they will die sooner or later. There are also other modern “EII/SP1200 replacement lcd displays” available, but they are way overpriced.

Probably any standard modern 16×2 lcd display will work, but be careful when you look for one that it has the correct dimensions, 84×44 mm. Most 16×2 displays that you find are 80×36 mm, and they a) won’t fit in the standard mounts b) require a new flat cable to be soldered to the upper board. Take my advice and get one in the correct dimensions! There are some lcd displays avaible that don’t have backlight, you don’t want one of those. The lcds with backlight are usually 13.5 mm deep, the ones without 9mm.

I found a suitable lcd display manifactured by “Midas” on the UK eBay for around $30 including shipping to Sweden. They can be found much cheaper on Farnell and RS Components, but they require that you purchase stuff for a minimum amount.  I chose the model with blue background and white characters.  You’ll also need a new hex-inverter chip and two short wires for the power.

  • Midas MC21605A6WD-BNMLW 16×2 lcd display 84×44 mm with backlight, I bought it from here
  • Hex inverter Texas Instruments SN74LS04N (this was strangely enough in a zipper bag included with my EII when I bought it…)
  • A pair of 5 inch red and black wires

Replacing the display

Start by opening the EII and remove the upper board that the display is mounted on. More details on that in the E-MU Emulator II slider pot A replacement post.

First thing was to remove the transformer. I cut the melt glue and then used a solder sucker and some heat to remove it. I then soldered the red and black wire to get 5V and ground from the same place as the transformer did.

Next thing, and probably the most time consuming one, was to desolder the 14 pin flat cable from the old display. First I removed the four nuts so that the display was loose from the board. I then had to use plenty of heat and soldering wick. Because of the heat, the insulation on the flat cable took a hit and split itself, but that was actually not a problem, I see no risk in short circuits.

Next step was to solder the 5V and ground wires to the new display, 5V goes to hole 15 and ground to hole 16. The flat cable’s 14 pins goes to hole 1-14. I then reattached it with the nuts and nylon spacers to the board, it was 100% perfect fit!

Just for fun,  I booted the EII to see if my desoldering action had caused any damaged, but it didn’t! I did see the garbled text in the new lcd that I’ve read about in forums when you don’t have the correct hex inverter.

I turned the EII off and located IC25 on the right lower board, it’s near where the floppy cable connects. Make sure you work the right board and not the left, because there’s an IC25 on the left as well with the same physical dimensions! I removed the original RCA H 506 and replaced it with the SN74LS04N and booted. It worked, and it looked great!

Conclusion

I really recommend doing this switch, the display is very easy to read and also has a good display angle. The hardest part is desoldering the flat cable, other than that the swap is straight forward. Make sure you get a display in the correct dimensions as well, 84×44 mm, and double check that it features backlight.

Boss DR-110, Drum machine

Boss DR-110 temporarily repaired

Even doctors may need help sometimes… A few months ago, I got my Boss DR-110 that I bought on eBay on which only the HAND CLAP worked. All other sounds were there, but at a very low volume. With the help from the 99musik forum the BALANCE potentiometer became the primary suspect.

A few weeks ago I ordered a new 20KΩ linear potentiometer even thought the dimensions weren’t right, just to verify that the pot actually was the problem.

When looking at the PCB it was quite obvious that someone had try to repair/replace the pot before. It was quite badly done, one of the trace leading to wiper connection on the pot was loose.  I desoldered it and soldered a three lead cable that I inserted through the hole where the pot is supposed to be. I had to scrape the trace where the wiper had been and solder directly to it.

At first I forgot two bridge the earth that normally is though the body of the pot, but since I have no pot but three leads instead, I soldered a new lead to bridge the earth. Then the doctor was alive again! Now I only have to find a fitting potentiometer…