> From: Mark <casiotone1331@...>
> Subject: [vintagesynthrepair] Re: Yamaha DX21 will not power up
> To: vintagesynthrepair@yahoogroups.com
> Date: Sunday, August 1, 2010, 8:46 PM
> Yeah, the fuse was the first thing I
> looked at. I'm now starting to think it may be a bad diode
> or resistor or something. Could the transformers be the
> culprit? If so I can't find them anywhere on the net. They
> are marked TM205 and 3021A.
>
> --- In vintagesynthrepair@yahoogroups.com,
> "Quazimodo" <noddyspuncture@...> wrote:
> >
> > You checked the main (mains) fuse - either on the
> machine or in the plug...!?
> >
> >
> >
> > --- In vintagesynthrepair@yahoogroups.com,
> "Mark" <casiotone1331@> wrote:
> > >
> > > OK, I just plugged in the supply on my workbench
> and tested the pins. I also checked and tested all of the
> traces and found no cold joints or cracks in the PCB. Just
> to be safe I reflowed all of the joints and cleaned up the
> board to no avail. Anyway, these are the voltages I should
> be getting, and what I AM getting. There is literally NO
> power leaving the PSU.
> > >
> > > Pin 1+2 should be 5V, I get 0V
> > > Pin 2+3 are ground
> > > Pin 5 is 0V
> > > Pin 6 should be +15V, I get 0V
> > >
> > > What should I do next? I'm not too used to
> working on power supplies, so any direction is a good
> direction.
> > >
> > > Thanks!
> > > Mark
> > >
> > > --- In vintagesynthrepair@yahoogroups.com,
> Alan Probandt <alan_probandt@> wrote:
> > > >
> > > > I would assume that it is a problem in the
> power supply. I suggest getting a cheap used PC power
> supply and bypassing the DX21 supply just for
> testing. I got a recent Dell supply from
> one of their mini DeskTops for $5. It's only 15"x5"x2"
> in size. It puts out +5, + and - 12V, +3.3v
> regulated. For a PC supply it's unusual in that it
> works without any minimum load. Usually PC power
> supplies need about 0.5 amp load on their +5V line in order
> to operate correctly.
> > > >
> > > > There is a DX100/DX27
> schematic floating around and possibly here in the files
> section. It shouldn't be that much different from the
> DX21.
> > > >
> > > > --- On Sat, 7/31/10, Doug
> <dougslocum@> wrote:
> > > >
> > > > > From: Doug <dougslocum@>
> > > > > Subject: [vintagesynthrepair] Re:
> Yamaha DX21 will not power up
> > > > > To: vintagesynthrepair@yahoogroups.com
> > > > > Date: Saturday, July 31, 2010, 6:42 AM
> > > > > Mark,
> > > > >
> > > > > Rhetoric: Troubleshooting anything
> without seeing it is
> > > > > always difficult, at best. :-)
> > > > >
> > > > > That said, I'm not familiar with the
> DX21 specifically, but
> > > > > I would be looking for voltage
> measurements and values from
> > > > > a oScope to determine if it is acually
> the power supply that
> > > > > is at fault here.
> > > > >
> > > > > I wouldn't be too quick to judge the
> power supply, just
> > > > > because it's the easier thing to
> troubleshoot.
> > > > >
> > > > > Doug
> > > > >
> > > > > --- In vintagesynthrepair@yahoogroups.com,
> > > > > "Mark" <casiotone1331@> wrote:
> > > > > >
> > > > > > I recently scored a non-working
> DX21 on the cheap, and
> > > > > it will not power up. No lights,
> response, or life
> > > > > whatsoever is in this machine. I don't
> even hear the audible
> > > > > "click" when I turn the machine on. I
> tested the power cord,
> > > > > the switch, the fuse, and replaced most
> of the capacitors on
> > > > > the main PSU board, and it still is
> doing the same thing.
> > > > > >
> > > > > > What worries me is that a previous
> owner replaced the
> > > > > big black cap in C5 with a 100uf 50V
> capacitor, and I know
> > > > > that it is MUCH too low of a voltage to
> be there. I'm not
> > > > > even sure if the capacitor is even the
> right value... I'm
> > > > > used to seeing things like 2200uf and
> such in power supplies
> > > > > like this one. If anyone could point me
> to the proper
> > > > > replacement, that would be great.
> > > > > >
> > > > > > Anyway, before I start to go nuts
> tearing this thing
> > > > > apart, I was wondering if anyone here
> could possibly help me
> > > > > out, I had great success bringing a
> dead TX81Z back to life
> > > > > thanks to the collective minds on this
> group. Where should I
> > > > > start? Many thanks!
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > ------------------------------------
> > > > >
> > > > > Yahoo! Groups Links
> > > > >
> > > > >
> > > > > vintagesynthrepair-fullfeatured@yahoogroups.com
> > > > >
> > > > >
> > > > >
> > > >
> > >
> >
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
> vintagesynthrepair-fullfeatured@yahoogroups.com
>
>
>
