[Coco] WTB Orchestra 90 cartridge

RETRO Innovations go4retro at go4retro.com
Mon Aug 1 03:40:17 EDT 2016

On 7/31/2016 11:50 PM, Zippster wrote:
>> * The r2r ladder.  I assume the original resistor networks were 1/8W
>>    or 1/4W Did you go with 1/4W or 1/8W on the surface mount
>>    replacements?  Or, did you go with something smaller?
> Bourns isolated resistor arrays.  Rated  .16 W per resistor, so somewhere in-between.
I tried to find a calculator that would show the power ratings required 
for a R2R ladder fed by 8 5V/8mA TTL outputs, to no avail. That'd be my 
only concern, as don't the CPLD output drive quite a bit of current?  I 
can't tell whether one can safely assume that since the impedence of the 
R2R is 10K, that the most current output would be 3V3/10K = .33mA and 
thus 1mW of output.  That seems low to me...
>> I hate to open my sealed cart up, or I could probably answer part of the second question.  Anyone have hires pics of an open cart?
> There’s a pic in the folder here, but not very high resolution.
> <https://drive.google.com/open?id=0B1sgl615FlGnLWk1akpheXhCcWs <https://drive.google.com/open?id=0B1sgl615FlGnLWk1akpheXhCcWs>>
:-)  There's also a youtube video of some guy cleaning one, but it's got 
360px resolution so it was no help...


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