[sdiy] Frozen DX7IID

[greg at gzifcak.net]

I do see that in the service manual, what's the best way to test for a
failure?

Thanks,
Greg

>    This might be a bad address decoder. I think it was an 'HC138, I'll
> have to look. --Crow
>
> On 8/21/2014 3:37 PM, greg at gzifcak.net wrote:
>> Hello,
>>
>> I just replaced the RAM in my DX7II. I swapped the existing Toshiba
>> TC5564PL-15 chips for TC5564APL-15 since this is all I could find
>> available. I searched for info on the meaning of the suffix but couldn't
>> find anything.
>>
>> Anyway, I did not try powering it on before I did the repair, but it
>> worked fine (aside from the RAM) when I last used it about a month ago
>> or
>> so.
>>
>> When I powered it on after replacing the RAM chips, all lights came on
>> and
>> the screen is blank except for the top row, which is showing solid bars.
>> It is making no sound and no panel controls have any effect.
>>
>> I probed around with my scope and the sub-CPU and main CPU are both
>> receiving clock and show approximately 5v on the power pins.
>>
>> Any ideas what else to check or should I hunt for replacement CPUs?
>>
>> Thanks in advance,
>> Greg
>>
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>
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