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Infamous Power Switch Question

Infamous Power Switch Question

2011-12-07 by Jim Atwood

Hello everyone,

I recently purchased a red Roland SH-101 and upon receiving it, everything work fantastic.  Then after a couple of days with it powered off, I turned it on and instantly it was all over the place with regards to tuning.  I read up on the internet that it could be a power switch problem.  I massaged the power switch without turning it off and sure enough tuning was being manipulated by the power switch movement.

As a result I clean the power switch from the outside and then turned it on about 100 times with the power cord detached.  This did seem to toughen up the switch a bit and when I moved it, the switch no longer affected the tuning, however, the SH-101 will not pop back into it's original setting.  It's still out of tune.

Sooo, does this mean that when the power switch kicks the Roland SH-101 out of tune, that you have to open the unit and make adjustments to re-tune the Sh-101 again?  OR, should the SH-101 have kicked back into tune automatically?

It looks like I'll have to tune the SH-101 again and this would make sense given the power switch messed things up.  If I stabilized the power switch then it should be ok until I order a replacement.  Otherwise, I may have a different problem.

I can't tell from comments here if the power switch fixes the tuning when working properly or it you have to tune the SH-101 all over again each time the power switch messes with the tuning.

Thanks for any insight!

Jim

Re: Infamous Power Switch Question

2011-12-07 by Jim Atwood

By the way, I found a place that sells replacement power switches for the Roland Sh-101.  Anyone know about this place?  Are there alternatives?

http://www.technologytransplant.com/product_info.php?cPath=30_29_4&products_id=78

Thanks!

Jim

Re: [vintagesynthrepair] Re: Infamous Power Switch Question

2011-12-07 by John Henson

Hi Jim,
TT is pretty well the only alternative for power switches for the SH101.
The replacement switch only has 6 pins whereas the original had 8, but don't panic!
It will fit perfectly and work fine.
Almost every SH101 through here has needed a power switch replacement, and yours will never be right until it is replaced.
Regards,
John.

www.retroactivesynth.com
Show quoted textHide quoted text

By the way, I found a place that sells replacement power switches for the Roland Sh-101. Anyone know about this place? Are there alternatives?

http://www.technologytransplant.com/product_info.php?cPath=30_29_4&products_id=78

Thanks!

Jim

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Re: Infamous Power Switch Question

2011-12-07 by Jim Atwood

Thanks John for the great info.  

I just ordered a couple of SH-101 power switches from TT, one for immediate use and another as backup.  TT seems like the only place around where I can immediately get a replacement part from Japan here.  Hopefully this will fix my problem and I'll be on my way playing music with the SH-101 again.

Thanks again.  Very much appreciated.

Jim

Re: [vintagesynthrepair] Re: Infamous Power Switch Question

2011-12-07 by PeWe

Hello John !

Just read your post below and visited your website,- bookmarked.

I see you´re servicing Moog and Oberheim and after reading about the Minimoog D,- I wonder whether you´re able to provide contact wafers for the
Minimoog D oscillator waveform- and octave switches as well as a master volume pot which is scratchy here because someone might have used contact spray in the past.

please let me know and thx in advance

best

PeWe



Am 07.12.2011 12:32, schrieb John Henson:
Show quoted textHide quoted text

Hi Jim,
TT is pretty well the only alternative for power switches for the SH101.
The replacement switch only has 6 pins whereas the original had 8, but don't panic!
It will fit perfectly and work fine.
Almost every SH101 through here has needed a power switch replacement, and yours will never be right until it is replaced.
Regards,
John.

www.retroactivesynth.com



Re: [vintagesynthrepair] Re: Infamous Power Switch Question

2011-12-07 by John Henson

Hi Pewe,
I am in the middle of a Mini-D restore right now.
I don't stock the wafers, I believe RS components carry an equivalent switch but they are shockingly expensive.
The switch contacts are silver plated and thus tarnish over time.
They can be cleaned with silver polish and cotton buds, but it is fiddly and time consuming.
De-Oxit can be very helpful if only a few contacts are iffy
Isopropanol can also help, or some combination of all 3 options.
The Octave switches use only half the switch, so it is possible to bridge across to the unused contacts to improve reliability (after cleaning of course).
Instructions, photographs and more detail used to be available on-line (Google is your friend).
If the Volume pot is the original Allen-Bradley type, then it is sealed, and you can't get contact spray in there.
Just take it out, dismantle, clean (using Isopropanol and/or De-Oxit) and rebuild, and assuming it's not worn out, you should be good for another 20 years. It's a lot easier to remove than a wafer switch.
Hope this is of some help,

John.
Show quoted textHide quoted text

Hello John !

Just read your post below and visited your website,- bookmarked.

I see you´re servicing Moog and Oberheim and after reading about the Minimoog D,- I wonder whether you´re able to provide contact wafers for the
Minimoog D oscillator waveform- and octave switches as well as a master volume pot which is scratchy here because someone might have used contact spray in the past.

please let me know and thx in advance

best

PeWe



Am 07.12.2011 12:32, schrieb John Henson:

Hi Jim,
TT is pretty well the only alternative for power switches for the SH101.
The replacement switch only has 6 pins whereas the original had 8, but don't panic!
It will fit perfectly and work fine.
Almost every SH101 through here has needed a power switch replacement, and yours will never be right until it is replaced.
Regards,
John.

www.retroactivesynth.com



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Checked by AVG - www.avg.com
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Re: [vintagesynthrepair] Re: Infamous Power Switch Question

2011-12-07 by PeWe


Hi John !

>>>

Am 07.12.2011 15:29, schrieb John Henson:
Show quoted textHide quoted text

Hi Pewe,
I am in the middle of a Mini-D restore right now.


Ha,- I hope it´s fun !
Now, after reading everything in your blog, I wonder if you´ll come up w/ a report of this restoration too.
My Mini plays fine, I´m 1st owner and it´s my last one out of 3 I owned, but it needs some work near future not to lose it´s functionality.

I don't stock the wafers, I believe RS components carry an equivalent switch but they are shockingly expensive.


Well, I didn´t expect ´em to be cheap at all ... at least not a complete switch.

The switch contacts are silver plated and thus tarnish over time.
They can be cleaned with silver polish and cotton buds, but it is fiddly and time consuming.
De-Oxit can be very helpful if only a few contacts are iffy
Isopropanol can also help, or some combination of all 3 options.


Thx for advice, I didn´t know they can be cleaned up to now.

The Octave switches use only half the switch, so it is possible to bridge across to the unused contacts to improve reliability (after cleaning of course).
Instructions, photographs and more detail used to be available on-line (Google is your friend).


:-)

I have these instructions but thought about it might be easier to replace than doing the bridging job.

If the Volume pot is the original Allen-Bradley type, then it is sealed, and you can't get contact spray in there.


Ah, good to know !
If I move the pot back ´n forth a dozen of times or more,- the scratching goes away,- but it comes back.
I expect it to be the original pot because as 1st owner, I´m never became aware it was replaced in the past.

Just take it out, dismantle, clean (using Isopropanol and/or De-Oxit) and rebuild, and assuming it's not worn out, you should be good for another 20 years. It's a lot easier to remove than a wafer switch.


O.k., I see I have to go the hard and tie consuming route now ...

Hope this is of some help,


Yes, it is,- thank you !


John.


PeWe

Re: Infamous Power Switch Question

2011-12-07 by Quazimodo

Hi John,

Would you happen to have the RS part number for that switch please?

One of my Mini's has a waveform switch where the shaft came away from the rotator inside. I have tried tightening it up but a new pot would be the answer really.

Thanks,
TOM


--- In vintagesynthrepair@yahoogroups.com, John Henson <synthnerd@...> wrote:
Show quoted textHide quoted text
>
> > I don't stock the wafers, I believe RS components carry an equivalent 
> switch but they are shockingly expensive.
>

[vintagesynthrepair] Re: Infamous Power Switch Question

2011-12-09 by John Henson

Hi Jim and list,
I did originally answer the question that was asked, and I stand by that answer.
If twiddling the power switch changes the pitch, then the switch is faulty and needs replacing.
That being said, there can be a myriad of other possible faults lurking under the obvious surface.
The SH101, being made entirely of plastic, being nearly 30 years old and using a Wallwart power supply leaves it prone to a huge number of other possible problems.
Missing screws are common, usually on the voice board, but if putting one back in tidied things up, I would be looking for cracks in the relevant circuit board (why was the screw missing in the first place unless a fall ripped it out).
Check for dry joints around the Tuning pot, or if not that, the integrity of the tune pot itself, could it be broken?
The SH101 looks like a simple device at first glance, but it is full of traps for the unwary, what you may think is wrong at first glance may have no bearing on the actual fault(s).
The service manual calibration by the switch on and Transpose and Load keypresses will give you a very good idea of the state of play with your synth, I normally solder permanent test points to the CV out and ground points on the socket panel as I expect I will see them again one day, and it will save time now and probably later.
Also there are errors in the calibration section, the worst offender being to calibrate the bender offset. telling you to trim VR3 when what is actually meant is the trimmer on the bender board itself.
Regards,
John.


I just ordered a couple of SH-101 power switches from TT, one for immediate use and another as backup. TT seems like the only place around where I can immediately get a replacement part from Japan here. Hopefully this will fix my problem and I'll be on my way playing music with the SH-101 again.

Thanks again. Very much appreciated.

Jim

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