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Re: Old-timey design from not too long ago

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bitrex <bitrex@de.lete.earthlink.net> wrote:
> On 02/15/2017 10:23 AM, Don Kuenz wrote:
>> Spehro Pefhany <speffSNIP@interlogdotyou.knowwhat> wrote:
>>> On Wed, 15 Feb 2017 08:35:44 -0500, the renowned bitrex
>>> <bitrex@de.lete.earthlink.net> wrote:
>>>
>>>> The Yamaha TX81Z, circa 1986:
>>>>
>>>> http://i254.photobucket.com/albums/hh102/gjm_photo/TX81Z1.jpg
>>>>
>>>> Big transformer, linear regulators, two-sided board, bunch of DIPs.
>>>>
>>>> Looks like the power switch is on the left at the back, and they've
>>>> routed some long piece of metal around the regulator heatsinks all the
>>>> way to the front panel. Anyone know why they'd do that?
>>>
>>> The power switch controls the mains directly- to run traces to the
>>> front would require a lot of space on the board. Or they'd have to run
>>> thick wires insulated to the satisfaction of every safety agency in
>>> the world where they wanted to sell units.
>>>
>>> It's cheaper and better to put all the mains-connected stuff together,
>>> near the power entry and operate the power switch with a button
>>> extender. IIRC my old Tek scope has something similar.
>>>
>>>> The ICs seem scattered all over with not a lot of rhyme or reason to
>>>> their positioning - make room for all the jumpers?
>>>
>>> It's a single-sided paper-based phenolic board- and it looks like
>>> they've laid out an 8-bit microprocessor (maybe a Z80 or 8051
>>> variant?) with external EPROM and RAM.. so yeah there are a lot of
>>> interconnections in the digital part of the circuit and few components
>>> to use as jumpers- looks like it was a massive PITA to lay out.
>>
>> IIRC the innards my Yamaha pf-70 look about the same. Its microprocessor
>> will be noted the next time it's opened.
>
> Historically Roland seemed to prefer Intel-derived processors in its
> products (8051 etc.), Korg and Yamaha liked Motorola/Hitachi, while the
> US manufacturers (E-mu, Oberheim) liked Zilog/MOSTek.

My memory's wrong this time. The pf-70 uses a double sided FR4 PCB. All
components are through hole. (It's several decades old.) It also uses an
HD6303RP MPU.

So the board that looked like the TX81Z was in my bone pile within the
past year. It probably came out of a failed printer or scanner that
was manufactured during the past ten years.

Thank you,

--
Don Kuenz KB7RPU

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Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-15 08:35 -0500
  Re: Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-15 08:43 -0500
  Re: Old-timey design from not too long ago Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-02-15 08:53 -0500
    Re: Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-15 09:30 -0500
    Re: Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-15 09:42 -0500
      Re: Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-15 09:44 -0500
        Re: Old-timey design from not too long ago Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-02-15 19:02 -0500
    Re: Old-timey design from not too long ago Don Kuenz <g@crcomp.net> - 2017-02-15 15:23 +0000
      Re: Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-15 12:07 -0500
        Re: Old-timey design from not too long ago Don Kuenz <g@crcomp.net> - 2017-02-16 20:03 +0000
  Re: Old-timey design from not too long ago Tim Wescott <tim@seemywebsite.com> - 2017-02-15 10:41 -0600
    Re: Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-15 12:00 -0500
      Re: Old-timey design from not too long ago Tim Wescott <seemywebsite@myfooter.really> - 2017-02-15 11:44 -0600
      Re: Old-timey design from not too long ago tabbypurr@gmail.com - 2017-02-15 14:36 -0800
        Re: Old-timey design from not too long ago Tim Wescott <seemywebsite@myfooter.really> - 2017-02-15 17:35 -0600
          Re: Old-timey design from not too long ago tabbypurr@gmail.com - 2017-02-15 23:49 -0800
            Re: Old-timey design from not too long ago Tim Wescott <tim@seemywebsite.com> - 2017-02-16 13:58 -0600
              Re: Old-timey design from not too long ago bitrex <bitrex@de.lete.earthlink.net> - 2017-02-16 23:24 -0500

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