jupiter 8 power supply

[pucho812]

schematics, page 28 of the service manual is the power supply
http://www.synthfool.com/docs/Roland/Roland_Jupiter8/

my buddy has one on his bench, he is not much the tech. He can iron well and recap no problem.  He recently recapped the PSU because he felt like it. I worked for a minute then  lost 5VDC.  A cursory glance has me with, recap was done well, and I measure 9VDC after the rectifiers  but half a volt at the output of the 7805.  I measure around 1.6V at the input to the 7805.  He already replaced the regulator and the 2sd844Y because he was just shotgunning parts before I got there. I didn't get into it  further but wanted to bounce ideas here. 

 

[JohnRoberts]

Look for a reversed polarity electrolytic on PS output...especially if he recapped it.

JR

 

[scott2000]

my buddy has one on his bench, he is not much the tech. He can iron well and recap no problem.  He recently recapped the PSU because he felt like it.

He felt like it because it wasn't working before or it worked before he felt like it?

 

[CJ]

after you are done with that dinosaur i have a DX-7 that needs work! 

 

[pucho812]

He felt like it because it wasn't working before or it worked before he felt like it?

It worked before he felt it needed a recap. Then it worked about a minute after the recap.  Then when it died he asked me for assistance

 

[pucho812]

after you are done with that dinosaur i have a DX-7 that needs work! 

Oh yeah I know a guy. I am too. It's with other things?
You still in sf I will be there at the end of the week.

 

[pucho812]

After a lengthy Back and forth my buddy swears it didn't work prior to recapping and only ran a minute after. More clues.  Lol I'll see the supply soon can really do a look and see what is up.

 

[JohnRoberts]

if there is a reversed cap it may reveal itself with a mess....

JR

 

[scott2000]

After a lengthy Back and forth my buddy swears it didn't work prior to recapping and only ran a minute after. More clues.

Puchlock Holmes is on the case.... 8)

 

[pucho812]

Puchlock Holmes is on the case.... 8)

I rather not, I got enough of my own to take care of. Lol.

 

[zamproject]

Hello

He already replaced the regulator and the 2sd844Y because he was just shotgunning parts before I got there.

Meaning he disassemble the BIG heat sink (JP8 get damn hot...) for access to change them
Be sure electric insulator still there after replacement.
Just another idea...

best
Zam

 

[pucho812]

Hello

Meaning he disassemble the BIG heat sink (JP8 get damn hot...) for access to change them
Be sure electric insulator still there after replacement.
Just another idea...

best
Zam

Yes it is there.

 

[Tubetec]

Never worked on a Jupiter 8 ,but I have done lots of other Roland stuff .
I often found bad solder joints on the psu's in Roland , purely thermal fatigue , close to the filter caps and Regulators , some of them were hard to spot ,and in opperation were intermitant . Reflow all the joints on the psu board.

 

[pucho812]

detective pucho discovered a transistor in backwards.  It is on the 5 V line  so there ya go.  supposedly it was not touched but I believe it when my sh*t turns purple and smells like rainbow sherbet.  ;D

So o.k. replaced tr3 which was backwards. But as suspected no change.  I get about 10VDC right off the rectifiers. I get  10VDC going into the 2sd844. I measure 1V at pin 24 and half a vol a pin 23. Which is way off.  all solder points were reflowed and aside from the aforementioned backwards transistor,  all caps are not shorted, all resistors are o.k., all diodes are o.k out of circuit but measure open while in circuit,  this is opposite what happens with a working unit.  the tr1 and tr2 transistors are working so I am stumped.

 

[filipposamore]

Sorry to revive this thread but did you have any luck ? i found myself in the exact same situation.

detective pucho discovered a transistor in backwards.  It is on the 5 V line  so there ya go.  supposedly it was not touched but I believe it when my sh*t turns purple and smells like rainbow sherbet.  ;D

So o.k. replaced tr3 which was backwards. But as suspected no change.  I get about 10VDC right off the rectifiers. I get  10VDC going into the 2sd844. I measure 1V at pin 24 and half a vol a pin 23. Which is way off.  all solder points were reflowed and aside from the aforementioned backwards transistor,  all caps are not shorted, all resistors are o.k., all diodes are o.k out of circuit but measure open while in circuit,  this is opposite what happens with a working unit.  the tr1 and tr2 transistors are working so I am stumped.

 

[radardoug]

Are you getting the feed from the +15v supply,which makes the whole 5v regulator start up?

 

[filipposamore]

Are you getting the feed from the +15v supply,which makes the whole 5v regulator start up?

I get the +15 V till R7, on the +5V side of R7 I have only 1V