[sdiy] Frozen DX7IID

[greg at gzifcak.net]

Thanks for the links.
I'm still pretty lost on this; not sure how to proceed without just
swapping chips out. I don't really want to desolder any more of these than
I have to, the RAM chips were kind of a pain.

> Hi!
>
> You can have a look at the datasheet of the PL version here: page 155
> http://bitsavers.informatik.uni-stuttgart.de/pdf/toshiba/_dataBooks/1982_Toshiba_MOS_Memory.pdf
>
> The first page of the APL datasheet is here:
> http://www.cryptomuseum.com/spy/fs5000/files/TC5564.pdf
>
> The typical standby current definition seems to be the difference on the
> first look, but the maximum standby current seems to be the same...
>
> Ciao
> Peter
>
> http://www.ullrich.at.tt
> ________________________________________
> Von: synth-diy-bounces at dropmix.xs4all.nl
> [synth-diy-bounces at dropmix.xs4all.nl]" im Auftrag von
> "greg at gzifcak.net [greg at gzifcak.net]
> Gesendet: Freitag, 22. August 2014 23:39
> An: MTG
> Cc: synth-diy at dropmix.xs4all.nl
> Betreff: Re: [sdiy] Frozen DX7IID
>
> Thanks for the insight; I hope this isn't the case because I haven't been
> able to find replacements with the exact suffix. If that is what's causing
> it I'll just take them back out and live with a functioning synth with no
> patch memory. I usually program it from scratch anyway, but it would be
> nice to be able to save.
>
>> If it's anything like the vanilla DX7 they require almost exact
>> replacements. There is something funky going on with the memory
>> addressing or the assertion or de-assertion of the control lines but
>> I've never really had the time to examine it. On the regular DX7 I had a
>> bad SRAM and tried quite a few standard types that *should* work but
>> they don't. I had to resort to buying a new one of pretty much the exact
>> type (manufacturer too).
>>
>> Maybe someone knows what Yamaha is doing that makes it so picky. There
>> are so many expansion boards out there (E! et al) that someone obviously
>> knows.
>>
>> GB
>>
>>
>> On 8/21/2014 1:37 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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>>> Synth-diy at dropmix.xs4all.nl
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>>>
>>>
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