Vintage Synth Repair

Introducing DC voltage of the wrong polarity to electronics can cause a lot of damage.





________________________________
From: Miguel Mendoza <miguel@...>
To: vintagesynthrepair@yahoogroups.com
Sent: Thu, 11 March, 2010 17:18:45
Subject: Re: [vintagesynthrepair] Roland SH 101 power adaptor problem

  
I just checked the psu and it's a regulated psu. I think 
that I never connected it in the wrong way into the SH, it hapened with other 
machines. Anyway, I though that swaping the polarity couldn't produce 
damages, is this common in other instruments?
 
Thank.
 
Miguel.


From: Philip 
Sent: Thursday, March 11, 2010 4:38 PM
To: vintagesynthrepair@ yahoogroups. com 
Subject: Re: [vintagesynthrepair ] Roland SH 101 power adaptor 
problem
  
There's your problem right there, if you've plugged it in the wrong way 
round it will almost certainly damage internal components.

The 101 is pretty sensitive to wrong psu's. It also needs a 
regulated supply and so It specifies a Roland PSA adaptor. Most cheap 
adaptors are un-regulated.

Phil.


________________________________
 From: Miguel Mendoza <miguel@filminteract ive.es>
To: vintagesynthrepair@ yahoogroups. com
Sent: Thu, 11 March, 2010 
15:20:38
Subject: Re: 
[vintagesynthrepair ] Roland SH 101 power adaptor 
problem

  
Hi Scott, thanks a lot for your answer. The polarity of 
the external power supply can be swaped changing the position of the tip. 
Sometimes I have plugged it in the wrong way and the result is that the unit 
doesn't work. Anyway, I'll check that.
 
Thanks!
 
Kind regards.
 
Miguel.
 


From: Scott S. 
Sent: Thursday, March 11, 2010 4:13 PM
To: vintagesynthrepair@ 
yahoogroups. com 
Subject: Re: [vintagesynthrepair ] Roland SH 101 power adaptor 
problem
  
Miguel, what type of power supplies are you using? I think the SH-101 is 
positive ground, unlike most other external power supplies. That probably is not 
your problem, but thought I would mention it here for reference. Roland could 
have put in diodes to protect it, or possibly a zener to correct the 
polarity?

Out of tune could just mean that it needs 
calibrating.

thx-shs


On Wed, Mar 3, 2010 at 2:17 PM, Miguel Mendoza <miguel@filminteract 
ive.es> wrote:

  
>Hello group, I'm having a problem with my Roland SH 
>  101:
> 
>When I turn it on, it takes some time to start 
>  working. After this, the synth is completly out of tune.
>After some time, the external power supply is getting 
>  very hot and I turn it off.
> 
>I tried with several external power adaptors with the 
>  same result.
> 
>I think that it could be a problem with the internal 
>  voltage regulator or a conderser but I would like to know if any of you 
>  know anything about this problem or have any idea of what it could 
>  be.
> 
>Thanks a lot in advance.
> 
>Regards.
> 
>Miguel.