Roland SH2 - Schematic and original PCB populated component does not match

[FreqFarm]

So the latest puzzle in the adventure that restoring this SH2 has turned into is a mis-matched cap. You have probably guessed by the colour of the caps in the photos that I am at the re-capping stage of the process.

According to the schematic the C7 cap should be BiPolar or NP as Roland like to call them on the schematic, but they have also added a + leg for that cap too. Roland I love you, but you are killing me.

However I have what looks to me like a polarised cap populated on the PCB, and also there is no NP marking on the PCB which all the other BiPolar caps have.


So do I stick with what was populated and replace that cap with a polarised cap or do I follow the schematic and go with a BP?










C7 is circled

 

[Yash]

I wouldn't recap those types of caps. For old synths, I'd focus on the Electrolytics in the PSU, and perhaps some Tantalums that I'd replace with non-Tantalums as some of those go bad.

Did anyone work on this synth before you?

 

[Khron]

Maybe hedge your bets and replace that with a series pair of back-to-back 6.8u's? Wouldn't be surprised if 3.3u non-polar electrolytics might be more tricky to find nowadays... That cap shouldn't see much (reverse) DC in the first place, but hard to tell.

 

[FreqFarm]

I wouldn't recap those types of caps. For old synths, I'd focus on the Electrolytics in the PSU, and perhaps some Tantalums that I'd replace with non-Tantalums as some of those go bad.

Did anyone work on this synth before you?

interesting. I was under the impression it was just a matter of time before those caps go bad, they are 45 years or more old.

>Electrolytics in the PSU
I did those first,

>Did anyone work on this synth before you?
doesn't look like it.

 

[FreqFarm]

Maybe hedge your bets and replace that with a series pair of back-to-back 6.8u's? Wouldn't be surprised if 3.3u non-polar electrolytics might be more tricky to find nowadays... That cap shouldn't see much (reverse) DC in the first place, but hard to tell.

the 3.3u bi-poloar caps I have to hand, as I used the schematic as a guide to order the parts.

 

[zamproject]

According to the schematic the C7 cap should be BiPolar or NP as Roland like to call them on the schematic, but they have also added a + leg for that cap too. Roland I love you, but you are killing me.

The C7 -NP- mark on the schemo seem a later correction ? Design transcription error, or mismatch sch/pcb are not unusual, especially at a time when drawing were hand made. Maybe you can find a date print and a mention -valid for n°.....- and compare with your SH2.
If you have the NP in hand, just use this one.

I wouldn't recap those types of caps

For what reason ??? vintage sound .....?
With the few Roland from this era I get on the bench (Jno 60 and Jupi8 ) I definitely recommand to recap... they can leak electrolyte all around.

As a side note, There is a great mod around KCV hold, it consist of floating the Q3-C3-IC2 net, to minimise tune drift with long note.
Get this idea some time ago trying to help someone having issue with a drift of about 1/2 tone in half a minute, after that the SH2 drift 1 semitone in 15 min !

 

[FreqFarm]

The C7 -NP- mark on the schemo seem a later correction ? Design transcription error, or mismatch sch/pcb are not unusual, especially at a time when drawing were hand made. Maybe you can find a date print and a mention -valid for n°.....- and compare with your SH2.
If you have the NP in hand, just use this one.


For what reason ??? vintage sound .....?
With the few Roland from this era I get on the bench (Jno 60 and Jupi8 ) I definitely recommand to recap... they can leak electrolyte all around.

As a side note, There is a great mod around KCV hold, it consist of floating the Q3-C3-IC2 net, to minimise tune drift with long note.
Get this idea some time ago trying to help someone having issue with a drift of about 1/2 tone in half a minute, after that the SH2 drift 1 semitone in 15 min !

Oh for real! The schematics are littered with crossed out values and corrections

Thinking about it, it's probably more likely the PCB silkscreen is correct as it would have been done after the schematic and would likely have gone through one or more revisions and error checking rounds.

The serial indicates it was made July-1979 the service manual is dated Oct 15, 1979 but there are no dates on the schematics in the service manual so it's anyone's guess if they tweaked the schematics on that date or they are exact copies of the unmolested originals (mistakes and all).


That's interesting re the mod! Current plan is to do a restoration style service including recapping, then work out why the osciliators are not working and fix any issues there. Once everything else is checked and confirmed to be working 100% as new the following mods are going to be done:
1) SH2-M midi kit from CHD Elektrosevis
2) Add osc sync

I was thinking about 3d printing a little enclosure for the MIDI IN/THRU and osc sync switch and attach it to the back using neodynium magnets so the synth is kept original and can be revetered to 100% stock condition easily.
Would adding a couple of midi sockets to the original case by making holes devalue the synth? or am I overthinking it here?

 

[Yash]

With the few Roland from this era I get on the bench (Jno 60 and Jupi8 ) I definitely recommand to recap... they can leak electrolyte all around.

In which sections of their circuits did you find leaks?

 

[zamproject]

In which sections of their circuits did you find leaks?

It was long time ago...but IIRC, at least I had to clean a great mess on the J60 at the pcb under pidchbend, on the left side of the keyboard, chorus board ?

 

[FreqFarm]

I have a friend with an SH2 and he has confirmed that there is a BP cap populated on his synth at that position (same PCB revision).

So a NP has gone in there and this SH2 is now officially recapped

So for fun, what do you guys think happened?
a) someone at Roland messed up when populating the PCB
b) it was a later revision that was implemented after my SH2 had already been built

 

[FreqFarm]

It was long time ago...but IIRC, at least I had to clean a great mess on the J60 at the pcb under pidchbend, on the left side of the keyboard, chorus board ?

this is the chorus board from the Juno 60 for reference