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Re: Old-timey design from not too long ago

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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.

One of these days, real soon now, a half dozen of its biggest 'lytic
caps will get replaced. ... hmmmm ... hold up ...

.. goes out to look at the brand name on the replacement 'lytics in
the parts drawer ... Lelon ... out of Twaiwan?!?! ... the land of the
capacitor plague?!?! [1] No fricken way!

My beloved pf-70 was this close ][ to getting pathogenic transplants.
It's time to throw out those Lelons and replace them with Fujitsu,
Nichicon, Oscon, Rubycon, Samxon, or UCC. What other brands does the
group find trustworthy?

1. https://en.wikipedia.org/wiki/Capacitor_plague

Thank you,

--
Don Kuenz KB7RPU

The key to the mystery of a great artist: that for reasons unknown to
him or to anyone else, he will give away his energies and his life just
to make sure that one note follows another inevitably. ... The composer,
by doing this, leaves us at the finish with the feeling that something
is right in the world, that something checks throughout, something that
follows its own laws consistently, something we can trust, that will
never let us down. - Leonard Bernstein

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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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