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 ICs seem scattered all over with not a lot of rhyme or reason to their positioning - make room for all the jumpers?
Old-timey design from not too long ago
Started by ●February 15, 2017
Reply by ●February 15, 20172017-02-15
On 02/15/2017 08:35 AM, bitrex 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?A horror of having any chance of mains voltage appearing on the front panel, maybe? Other manufacturers of the era seem to have had no problem using a power switch that switches the main directly - so long as it's on the back...
Reply by ●February 15, 20172017-02-15
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. --sp -- Best regards, Spehro Pefhany
Reply by ●February 15, 20172017-02-15
On 02/15/2017 08:53 AM, Spehro Pefhany wrote:> 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. > > --sp >Oops, yeah, I meant single-sided...;-) That fashion of "paper-based phenolic" board seemed very common in "prosumer" equipment from Japan in the 1980s, right up until around 1990 when it seems everyone made the jump to double-sided FR4.
Reply by ●February 15, 20172017-02-15
On 02/15/2017 08:53 AM, Spehro Pefhany wrote:> 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. > > --sp >The service manual shows it using the somewhat obscure (to me) "63803X" uP, plus an "XB 186002" 64kbit ROM chip, and a "TC5544PL" 8kbit RAM chip, to scan the front panel and MIDI and drive the 4 op FM chip (YM2414.) Here's the underside if you're curious: http://imgur.com/a/wc1nC
Reply by ●February 15, 20172017-02-15
On 02/15/2017 09:42 AM, bitrex wrote:> On 02/15/2017 08:53 AM, Spehro Pefhany wrote: > >> 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. >> >> --sp >> > > The service manual shows it using the somewhat obscure (to me) "63803X" > uP, plus an "XB 186002" 64kbit ROM chip, and a "TC5544PL" 8kbit RAM > chip, to scan the front panel and MIDI and drive the 4 op FM chip (YM2414.)Oops, it's "63B03." I guess it's a 6809 variant. Hi tek!
Reply by ●February 15, 20172017-02-15
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
Reply by ●February 15, 20172017-02-15
On Wed, 15 Feb 2017 08:35:44 -0500, bitrex 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 ICs seem scattered all over with not a lot of rhyme or reason to > their positioning - make room for all the jumpers?One sided board. The long bar looks plastic. -- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com
Reply by ●February 15, 20172017-02-15
On 02/15/2017 11:41 AM, Tim Wescott wrote:> On Wed, 15 Feb 2017 08:35:44 -0500, bitrex 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 ICs seem scattered all over with not a lot of rhyme or reason to >> their positioning - make room for all the jumpers? > > One sided board. > > The long bar looks plastic. >Yep. As Spehro said, the routing does look like quite a PITA: http://imgur.com/a/wc1nC Wonder if they used some early "tool assist" to help with that, or if it was all done by brain...
Reply by ●February 15, 20172017-02-15
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.
