Vintage Synth Repair

Yes I am in the Crawley area.

 

Also yes unregulated power supplies do have higher than spec voltages OFF
LOAD!  Bear in mind that almost all keyboards of repute have a voltage
regulator the other side of the power in socket.  The max voltage you can
apply to the majority of these regulators is 36V.  Consequently a few volts
higher shouldn't matter.

 

Having said the foregoing I would add that it is always best to use the
manufacturer's recommended option.

 

Regards

Brian G3OYU

 

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of robwilljy
Sent: 25 February 2010 9:20 PM
To: vintagesynthrepair@yahoogroups.com
Subject: [vintagesynthrepair] Re: Yamaha TG33 power supply

 

  



Royce and Brian...you are obviously profesionals that know a lot better than
me about all this but I always warn folk about the dangers of using
unregulated power supplies into (especially) low power kit as the actual
measured voltage can be much higher than specified.

Also the obvious problem (my son fried a Roland keyboard by putting in a
Yamaha power supply) of the wrong polarity power supply. Its amazing that
Roland and Yamaha took the opposite paths with polarity, while using
identical plugs!

And...almost too ambarassed to mention this, but it does happen!...putting
an AC adapter into a DC device...again the manufacturers often use the same
type of plug. 

Nice to get your info Brian...I Googled your details and will add you to my
"little black book" for keyboard repairs..yes? Crawley UK area?

--- In vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> , "Brian" <brian@...> wrote:
>
> Hi Royce
> 
> 
> 
> No problem. I have access to the entire Yamaha on-line database, plus I
> carry a 3 CD set of schematics. I am a professional engineer repairing, to
> component level, electronic keyboards and guitar amps. Similarly I have
> access to the Kawai, Fender and Marshall databases. Regrettably many of
the
> other manufacturers don't treat me as well!!
> 
> 
> 
> Your power supply schematic was lifted direct from Yamaha hence the
> excellent scan.
> 
> 
> 
> Yes I would say that 12V should be OK, but as previously suggested I would
> check on the temperature of the various regulator components to ensure
that
> things are not over-heating.
> 
> 
> 
> As an example of this my local church has a Yamaha P80. The power unit
> supplied gave a lot of trouble and I repaired it on several occasions.
Then
> the inevitable happened I setup the unit for the pianist one Sunday
morning
> only find that the power unit had failed. I rushed back to the workshop
and
> picked up a selection of spare power supplies and plugged in a Kawai unit
> that gave out 20V, whereas the Yamaha unit only gave 12V. Two years on and
> all is still fine!
> 
> 
> 
> Regards
> 
> Brian G3OYU
> 
> 
> 
> From: vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> 
> [mailto:vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> ] On Behalf Of Royce
> Sent: 25 February 2010 9:38 AM
> To: vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> 
> Subject: [vintagesynthrepair] Re: Yamaha TG33 power supply
> 
> 
> 
> 
> 
> Thanks Brian.
> What a great scan. I wish I could get my ccts to scan that well.
> 
> Looks like there is a 5V reg for the digital and the full voltage is sent
to
> power some OpAmps 
> As well there is a split off regulated with a 9.1V 1A zenner but most of
the
> load is passed through a transistor. I assume it is on a heat sink.
> 
> Did I miss anything?
> 
> So 12V should be OK.
> 
> Thanks again
> Royce
> 
> --- In vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> 
> <mailto:vintagesynthrepair%40yahoogroups.com> , "Brian" <brian@> wrote:
> >
> > I can offer you a copy of the whole cct, however you should be OK with
12V
> > but you may want to check the operating temperatures of the regulator
> ccts.
> > 
> > 
> > 
> > If the Yahoo system removes the attachment contact me off list.
> > 
> > 
> > 
> > Regards
> > 
> > Brian G3OYU
> >
>