[sdiy] Andromeda A6 repair?

[Roman Sowa]

I've got strong feeling it is bad flash chip. This would explain why it 
does not pass the splash screen at first. And when you say it fails on 
verifying write, it may be because it encounters the same bad byte/block 
that caused initial fail.
If the bootloader is in the same flash chip, and hopefully in good part 
of it (it works as you say), I think you could just copy the content of 
entire chip to brand new part, then replace, and then try to load new OS 
with bootloader.

Roman

W dniu 2015-01-13 o 19:40, Barry Klein pisze:
> An update and feeble cry for help on the Andromeda repair...
> I checked with a scope most of the I/O, supplies, and crystal oscillators - ok.
> I replaced the CPU of the main board with a new part.
> The unit now will sometimes be "willing" to go into the (press 7) bootloader page or (press 2) front panel test page.
> With a press 7 I can upload the latest OS - it loaded successfully the last time I tried (once).  It then says to hit "store" and it writes to flash.
> Here it hangs on Verify block 14.
> It will also hang on the test of the slow ram - NVRAM.
> I have ordered a replacement part from China...
> I am a bit confused though about the memory management.
> There is a Flash, NV SRAM, and two "high speed" SRAM chips.
> Would an issue with the NV SRAM chip be responsible for a hang on the write to flash?
> Anyone know if really there is a separate bootloader sysx file?  There is a discussion on a forum about this (which wasn't answered).
> I guess not to worry for me if I can manage to get a successful sysx file dump over.(?)  It is the then write to flash that chokes.
> Should I shotgun this and also replace the SRAM chips while I'm at it?
> I'm wondering why it is so flakey to get it to go into the various soft button test modes - takes many tries and then it will do it for some time repetitively on demand.
> Something not quite kosher is the flash chip select.  3.3V part with 4V /CS.  Has a series "current limiting" resistor.
> As a last resort I may "sprinkle" some ceramic caps near VDD pins.  They used a lot of .01uF's and maybe .1's would be better.
>
> Barry
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