Looking for EIII CPU Board

[Gul Dukat]

Hi @ll,
my EIII is currently at the repair shop. The technican just called me to tell me that he had figured out that there must be a damage of one of chips on the main board - but he couldn't locate yet which one. Seems that it's going to be expensive :-(
Before I give up I want to start this call where I looking for a working EIII main board. I know it's difficult to get one but maybe there's a forum member who just get a defective EIII to exploit repair parts. If you have a mainboard to spare and for sale please let me know: mam242 AT gmail DOT com.
Because the technican thinks that the main issue might be one of the main cpu's - if you know where to get this chips from please post any hints.

EIII users in Germany: Falls Ihr Euer Mainboard für Testzwecke (nur Messungen zum Vergleichen) für ein paar Tage entbehren könnt, würde ich mich darüber freuen und erkenntlich zeigen! ;-)

Thanks & regards!

[dr.c]

There is NO maine board on an EIII, but boards.

Wich are the symptoms of your machine ?

[Gul Dukat]

The main board is the one where the CPU is located. From top to bottom it's the second one:
- Microcontroller
- CPU (Main)
- ADC
- Output 1-8
- Output 8-16

The symptoms of my EIII:  If you power on the machine you hear the power supply starting, a short flickering of the LEDs and the display just shows black bars (no letters or numbers) and thats it - it remains in that state. There is no access to the harddisc. The technican says that the problem must be on the CPU (board) but couldn't say exactely yet what may be defective there. There are a couple of chips on the CPU board, so it's difficult to find the culprit. The bad thing is to check everything to find the issue which may cause extraordinary charges I have to pay. Therefore I'm looking for a solution to shorten up this effort.

[dvdborn]

Hi Gul,

Did your technician check the voltages from the power supply. Are they within range?

David

[micromoog]

i've no doubts about your technican, but did you check booting by floppy?

i bet you know our austrian synth-freak "frixion" out of the german keyboards forum.
Last theo bloderers bluesynths-meeting in kufstein (austria) he told me, that he has a broken EIII-Rack (which is out of function) for sale, perhaps something for you...

[Gul Dukat]

@dvdborn: the technican said the power supply is ok.

@micromoog: Yes, of course I tried several times booting with floppy (both the system and the service disc) but it's the same issue.
User VDS242 (Christian) who is an old acquaintance of mine just told me that Frixion has an non-working EIII Rack for sale. Thanks for the info, will give it a try to contact him!

[micromoog]

Yes, i know vds242 aka EMULANER CHRIS from keyboardsforum and moogulators synthesizerforum.

[dr.c]

a) - What is the sound of a power supply starting ? I would be very interrested !!!!
b) - A short flickering, or a short lighting, of the LEDS ? This is not at all the same issue!

Have your tech start the EIII with another hard disk connected (flat cable and power supply) even if its not an EIII disk, any SCSI disk will do, don't worry. The best is one of these old Mac Quantum disks.  I ask to do this because even if the CPU board is dead, the hard disk should START, but if the hard disk is dead, the CPU won't start ! At this point (power up), the hard disk is completely autonomous, is should start spinning and run, as long there is +5V and + 12V

Let us know

[Gul Dukat]

Hi Doc C.
thanks for the interesting hints! I will forward to the technican - he is no E-mu guy, but is skilled and knows the old gear very well. However I think you just be familiar with the kinks of the E-mu to locate the problem. Therefore I'm grateful for any relevant info !
1. As far as I can remember the sound of the power supply is turning up - anyway very loud. But I can't say for sure yet because the gear is at the technicans shop and I can't check.
2. It's a short lightning. Time enough to see if there are some LEDs defective. The main display shows then only the LED cells fully filled when you completely turn up the contrast knob.
ThX again and more hints are always welcome!

[dr.c]

Power supply : is it a mechanical noise, or an electric one ?
In other words, can you hear this "noise" if the machine is not plugged anywhere ?

[Gul Dukat]

Hi Doc,
sorry - I'm drawing a blank on that one. Due to the gear is not accessible yet I can't say. But I'll try to find out to get a statement from the technican.
Thanks!

[dr.c]

To your tech :

Put another disk, just any SCSI one, and power. The display will show scanning different ID's. If this is it, its the disk wich is dead.

Something else : there is a circuit, 74HCT240, just change this ugly bastard (you can see I have changed it and out a tulip socket), change it to an 74LS240. Just DO IT, don't worry, and I confirm : 74LS240 (if by mistake, the original integrated circuit is an HCT244, change it to a 74LS244. I can't remember !

See picture. Be carefull, there are wire straps soldered on the pins, on the solder side.

[Gul Dukat]

Hi C!
Now I know why you're called an Emu Doc !!! 
Good hint - I will forward to my technican.
Will keep you updated!
Thanks again - Matt.

[dr.c]

Le t us know. I used to change SYSTEMATICALY this circuit.

[Nikolaus Riehm]

Hello @all,

I'm the technician who's servicing Matt's EIII. The PSU is fine, all voltages are stable and without noticable ripple. The EIII doesn't start up at all and now I've unplugged all cards except the main board to check wether it's an failure of the peripherals (MCU, DACs, ADC) or of the CPU core - and it seems the latter one. Clock and power-on reset generation are working. Actually I pulled out all I/O devices (SCSI, FDC, SCC and the scanner MCU) and will check the internal data/address busses and the CS logic (the PALs and '138 demuxer) today. I'll keep you informed.
Cheers, Niko