Tag Archives: problem

Repairing an E-MU Emax having a key always on

I’m about to sell my Emax since I don’t use it very much, and it takes up a lot space. It did have one problem though, that I hadn’t looked into at all. The problem is that as soon as the Emax had loaded a disc, the E4 note was always on. I suspected it had something to do with the that particular key, and hoped that maybe some cleaning with alcohol would do the trick.

I turned the Emax upside down and opened the bottom lid. I must say it’s very easy to open, less than ten screws and then you have access to almost everything. The key error was easily spotted as soon as I got the lid off. The spring wasn’t in position, so I simply put it back, did a little cleaning of the Emax, and put the lid back on. Worked perfectly.

This is the spring that needed to be put back in place. After doing that, that note wasn't always on anymore. A very easy fix.
This is the spring that needed to be put back in place. After doing that, that note wasn’t always on anymore. A very easy fix.

So, if you ever hear about an Emax with an always-on-key, it’s probably a very easy five minute fix.

Some other stuff worth commenting regarding my Emax.

  1.  It has the revision 3 CPU board, I’ve read that this is the easiest one to upgrade to SCSI.
  2. The Emax was probably factory upgraded to SE, all the SE markings are separate stickers as you can see on some photos. The serial number of the Emax is fairly low, so this is one more evidence that this is an upgraded non-SE.

Oberheim DPX-1 CPU problem?

In early March this year I bought an Oberheim DPX-1 on eBay. This example had the latest OS and the rare 8 output expander plus a brand new PSU! Unfortunately it was probably dropped on the ground on the journey from the US to Sweden. I was refunded but got to keep it since the buyer wasn’t interested in paying the shipping back to the US.

This night I opened the DPX up to try and find any clue of what was wrong. Not being an electronics expert, I tried usual of way of troubleshooting, namely removing part by part and see if anything made a difference.

The error could simply be described as the DPX not booting. When it’s powered on it immediately shows a strange character in the LCD display and then lits the MIDI CHANNEL, DATA DUMP and ERROR leds. See the video below day I shot when it arrived.

What I did tonight was:

  1. I started to remove the floppy cables and power cables. No difference, Same error.
  2. I removed the cable to the expansion board. No difference, same error.
  3. I removed the OS chips and doing that on a working unit would most probably generate an error. But no difference, same error.
  4. I removed the CPU, and without the CPU it’s certainly guaranteed that nothing should work, but no difference, same error.

However, removing the CPU, the most important part in a digital instrument, and not getting any other error points to the fact that the CPU might be the problem. I also remember that when I looked at DPX the last time when it arrived broken, the CPU had popped out. What I also noticed now was that one pin of the 64 pins were missing.

CPU is missing pin 1, also known as 'D4'. The CPU will certainly not run at all without this according to a forum member with lot's of 68k experience.
CPU is missing pin 1, also known as ‘D4’. The CPU will certainly not run at all without this according to a forum member with lot’s of 68k experience.

The CPU is a Motorola MC68000P10, a version of the in the 80’s widely used 68k family. I looked it up in the data sheet, and the pin is number pin number 1, named ‘D4’. I asked in the 99musik forum, and someone replied that the CPU most definitely can’t start without D4.

I took a look at some photos taken when the DPX arrived, and in those photos the pin is actually there. However, it could have been very loose then, just waiting to fall off. I’ve looked for the pin in the DPX, but I guess it’s like looking for a pin in a haystack.

I found a Chinese seller on eBay that sells  Motorola MC68000P10s for $8 including shipping to Sweden, I’ll order one of these within the next days and hope that it’ll bring the DPX-1 back to life again. To be continued…

Boss DR-110 arrived

I just received the Boss DR-110, a.k.a electronic toy. Very good packaging, condition looked as on the eBay pictures. Serial number 400300. However, when I started playing with it I noticed that only the HAND CLAP had any volume. The other sounds were there, but very quiet.

I posted on the 99musik forum. I shortly got an answer from a guy that never had used a DR-110, but had taken a look at the schematics. He suspected the balance knob, according to the schematics all voices are wired through the balance knob except for the hand clap that goes directly to the amplifier.



The DR-110 has four knobs, from left to right:
As you can see, the BALANCE soldering doesn’t factory

I opened the DR, and guess what, the soldering on the balance knob didn’t look at all like the other ones. Note that the schematics are seen from the top, my photo is from the bottom, that’s why the knobs don’t make sense at the first look.

I’ll have to fix this, to be continued…

Oberheim DPX-1 arrived all dented

I just got the DPX-1 I ordered from eBay, unfortunately in a non working state. The front panel is dented, so someone has probably dropped it during transport. I contacted the seller who had just refurbished it and replaced the PSU. He wasn’t very happy to hear the news and offered me a refund.

If I want my $100 custom fees back I had to send it back. However, the transport to the US cost $150. So I decided to keep it and maybe try to repair it someday. Or use it for parts. Now I’ll have to find another one, they’re not too common.

By the way, I opened the DPX-1 and saw that the CPU was loose. Someone must have dropped it really hard. I put the CPU back in its socket, but the DPX-1 still wouldn’t start.