Resurecting a dead E-MU Morpheus - Page 1
Forum section: electronics / repair

author: foxxb
author_rank: Newbie
timestamp: November 24, 2021, 08:07:16 am
content: Hi Guys,I got a dead E-MU Morpheus (digital rack mount synthesizer) and I'm trying to bring it back to life. It had a bad PSU but I bought a new one (those are still available on e-bay). Now I can turn the power on but it still doesn't workI have also installed a new CR2330 battery with no effect. The LCD screens backlight turns on but there is nothing displayed (sometimes black boxes appear instead).The failure mode is:1. Without a battery on board - blank screen, all red LEDs are lit for couple of seconds and dim afterwards. After another 5 seconds some LED stay on but it doesn't respond to any key. Screen still blank.2. With a battery installed - all LEDs except ENTER are off just after power up. Screen is blank.3. When trying to boot in Diagnostic mode (either MASTER+Cursor Right or both Cursor keys) all LEDs are off right away. Screen is still blank.I have checked the output voltage on PSU and it seems kinda right: +5V, +12V and -10V. I have also checked the voltage in some random places on the board and looks like that there is power distributed.I have taken out all the ROM chips and cleaned them properly before re-installing. I also removed all the connector strips and cleaned them as well. I have exchanged all the capacitors on the main board and checked it with another display module (HD44780 based). Still dead as a dodoAny ideas what else could be checked? I haven't found a service manual and I'm pretty sure it doesn't exist (at least online). Any suggestions on how to proceed would be highly appreciated. I have multimeter and oscilloscope in terms of measurement gear.FoxxB.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 24, 2021, 10:20:50 pm
content: Was this once in your possession working, or did you acquire a faulty unit somehow?Reason for asking, do you know if this LCD is the right one?

author: foxxb
author_rank: Newbie
timestamp: November 25, 2021, 09:54:59 am
content: Quote from: Audiorepair on November 24, 2021, 10:20:50 pmI acquired a non tested unit that turned out to be faulty. The original LCD display is a module based on hd44780 and I have found a similar unit in my supplies. I have checked the connection and prepared a strip connector. Still nothing is displayed.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 25, 2021, 11:58:21 am
content: Ah, OK.I used to change these displays in synth and FX modules occasionally, and sometimes the headers on the currently available replacements were not the same pinouts of the original, though they would physically fit the cable. Was wondering if someone had fitted a replacement before you got it.Also, sometimes the contrast voltage requirements were different, so you had to come up with a bodge to see anything as well.

author: foxxb
author_rank: Newbie
timestamp: November 26, 2021, 10:24:41 am
content: I made a connector myself based on the original module. I have added a pot to check the contrast voltage and apparently there is nothing displayed.Is there a way to check if there is any data going into the display?

author: picburner
author_rank: Frequent Contributor
timestamp: November 26, 2021, 12:13:23 pm
content: In another forum a user had the same problem as you. He solved it by cleaning the oxidized contacts of the rom chip. Since I noticed that your instrument's chassis has oxidation it might be the case too.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 26, 2021, 02:56:14 pm
content: Quote from: foxxb on November 26, 2021, 10:24:41 amThat may be a bit difficult if the data pins share a common databus with the rest of the system.The only pin that may be unique to the display is the Enable pin.If you have a storage scope you may be able to catch this toggling at bootup, when the uP initialises the display.I'm not an expert on LCD's, I have messed around getting them to say "bollocks" using a PIC, so I know you have to send a few bits of code on bootup to set it up for the machine and mode it's intended for.After that, no data is sent unless the display needs to change its message.

author: foxxb
author_rank: Newbie
timestamp: November 29, 2021, 02:42:21 pm
content: I have started with complete disassembly and cleaning all the contacts. I have also removed all the removable RAM chips and cleaned them but with no effect.Regarding the display I can see on oscilloscope that there is some signal on "E" connection on the bootup. There is also a different behaviour with and without a battery installed. Still no clear message is being displayed but I will continue checking that path as currently I out of other ideas...

author: cdev
author_rank: Super Contributor
timestamp: November 29, 2021, 03:32:05 pm
content: I used to fix a lot of old synths by simply following a logical process, looking for obvious lowhanging fruit, (obvious problems) and giving up when the problem was caused by unobtanium old parts.We had service manuals for the most popular models but often the parts were next to impossible to find. But by following the logical approach more than 80% could be fixed. Like much electronics.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 29, 2021, 09:44:50 pm
content: It may be that with the battery disconnected, the unit is trying to display "low battery voltage", which it wouldn't do with a good battery, hence the different behaviour, as I think you may suspect.But then it seems to boot into a hung state regardless.But it does also seem to be trying to initialise the display if there are signals on the E line.I would still be looking carefully around the display, perhaps some lines are swapped around somehow, or maybe shorted together.Good luck.

author: foxxb
author_rank: Newbie
timestamp: December 01, 2021, 12:29:13 pm
content: Quote from: Audiorepair on November 29, 2021, 09:44:50 pmThanks! I will look around the display as I have no other idea anyway

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 01, 2021, 08:13:47 pm
content: How sure are you that the display you found in the unit is the original that shipped from the factory?