Vintage Synth Repair

Have you followed the advices from Gordon in Roland jxanalogs group  
concerning transformer and its thermal fuse? What was the result?


Daniel Forro




On Jun 13, 2015, at 10:11 PM, david@... [vintagesynthrepair]  
wrote:


>
>
> I have a Roland JX-8P that works fine except all voices are  
> distorted, not with noise but like the frequency is too high or  
> something.  After some testing, I found that the voltages on the  
> large connector of the PSU were off.
>
> I tested the voltages and this is what I get starting with the blue  
> wire on the large connector
>
> -8, -8, +15, +15, g, g, g, g, g, +9, +5, +5
>
> And the small connector:
> -15, +15, g
>
> Everything is correct there except that the -8's should be -15's.   
> Thinking it was the PSU, I replaced it with a known working one.   
> Same problem.  If I disconnect the large connector from the  
> mainboard, the -8's go back to -15's.
>
> With the connector back on, I get -15V when I first power it on but  
> as soon as it's done with the countdown, the voltage gradually drops  
> to -8 within a couple of seconds.  I disconnected that connector  
> from the mainboard and it stays at -15V consistently.  So, the  
> problem must be something on the mainboard that's causing the  
> voltage to drop.  Also, when it's first done counting down, the  
> sound is normal for a split second and then gradually goes bad.  It  
> almost sounds like a filter sweep.  I am not a technician so I don't  
> know where to go next.  Any ideas?