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Old 5th February 2015
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M.Retra's Avatar

Troubleshooting an Alesis A6 Andromeda - No Boot

Hello folks! For those A6 gurus out there, I need some help. I am troubleshooting a "somewhat lifeless" A6. I say somewhat because the unit powers up but does not display a splash screen.

So far, I have obtained a lot of information regarding the operation of several IC's, ports, pins, and interfaces inside the A6. As I have experience in board-level analysis, and tools and test equipment to allow for repairs and troubleshooting.

The person that I purchased it from said that it worked well a month or two before the sale. So I am holding onto hope.

Most things seem to be in order, hardware wise. The power supply seems OK; all voltages seem good, not only at the PSU terminals, but all around the boards at various points as well. Crystal oscillators are all oscillating at their respective frequencies. The 87C52 is sending out pulse trains on the read pin and the LCD cable pins, which lends me to believe the 87C52 and the Front Panel Left PCB should be OK. But the fact that absolutely nothing is displayed on the screen is the weird part. At this time, I cannot confirm if the LCD is 100% functional as I don't have a spare.

As far as I can tell the Front Panel Left PCB EPROM chip should be programmed correctly. How can I confirm this? Well, with experience in programming 87/89C51 micros myself, it's either all or nothing. If the device is not programmed correctly internally, or did not receive the proper program from an EPROM IC, then it's not going to work, period. So if the EPROM IC is removed, and the unit started up, no pulse-trains occur on the LCD cable. However, upon reinsertion of the EPROM and subsequent power up, then the pulse trains are back. That, to me, confirms the programming of the EPROM to be OK.

Other than that, I found some easy fixes such as two, bulged and leaking capacitors on the main output. Yay for easy fixes!

Alas, I need to ask a couple of basic questions and confirm a few things:

1. The stupid question: what is the sequence of events that occurs when a normal Andy is powered up? Since I have no experience in the Andy, I don't know what to expect. So if the screen is indeed dead, then perhaps it would display something if it could. Know what I mean? I've searched for videos on YouTube, but nothing showing what I need. Is there any sort of confirmation button I need to press, like "OK to proceed," or does it simply show the splash screen, light up the LEDs, and change the display to EDIT (or something), and allow keys to be pressed and make sound?

2. Per the Service Manual, the 87C52 processor handles the LCD. So does that mean all of the graphics are handled by the 87C52 too? If so, then in theory, shouldn't the 87C52 processor be able to display something without being connected to the Main Board? This really isn't possible since the main ribbon cable provides power.

3. The observed pulse-trains on the Coldfire processor, as well as the various flash IC's, are a little "iffy." I'm trying to look for periodic pulse-trains that would confirm communication between devices. Right now, it's a toss up. I don't suspect a possible bad Coldfire "Host" CPU, but I do suspect a possible flash or programming issue. Therefore, how likely is this to occur? Have any of you with trouble Andy's had the flash IC replaced and/or reprogrammed?

4. The Service Manual states the SRAM IC's could be problematic. Those may be easy to replace as they don't have programmed data on them. But how many Andies out there had their SRAM chips replaced? If many users report that their SRAM chips have been replaced, then it would become a strong consideration to swap them out.

5. From what I can gather from the Service Manual, "ECN's" (Engineering Change Notices) have occurred over the years to update the boards, replace components, etc. Think of these like factory TSB's for your car. However, what ECN's are out there? What was involved?

As you can see, I'm getting pretty deep in repair of the fragile monster known as the Andromeda. I thank you all in advance for any information you can provide. And I believe that every thread should have a resolution and closure, so I will keep working on this thing and not give up!

If I truly exhaust all my skills and abilities, I will take it to a repair shop and give them the dossier of what I've done up to that point!