Roland SH-101 won't turn on!

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Roland SH-101 won't turn on!

Postby camjon2 » Tue Aug 18, 2009 5:26 pm

Hi everyone,

First time posting on the boards so hopefully I can outline my problem accurately! :)

I've got a Roland SH-101 which has been fine for the last year or so until it refused to turn on! The power light flashes in sync with the lfo light for about 5 seconds then goes out accompanied by a burning smell!

I opened the synth up and checked some of the values for the power supply. There is 9V from the battery side when the synth isn't turned on but is 3v when turned on. The value at the diode (d1) is 0.35V when the synth is turned off and 3.5v when turned on. From searching the 'net this should be 21V unregulated? If so this makes me think that the transformer (T1) isn't working properly? There is also one heck of a burning smell after the synth is on for about 15 seconds.

The transformer is stamped Sumida 1140 E2N1 but I've done a search to no avail for this transformer. Is there any replacement transformers that I can use and if so what spec should it be?

Any help would be much appreciated as I love the sound of this synth and want to get it working again as soon as possible!

Regards,

Jonathan
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Re: Roland SH-101 won't turn on!

Postby rhino » Wed Aug 19, 2009 3:25 am

could be thaT C1 or C8 (both connected to the transformer) could be shorted
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Re: Roland SH-101 won't turn on!

Postby Maschinengeist » Wed Aug 19, 2009 5:45 am

Sounds (or smell) like a frying transformer.

First, for you post, the diodes is way too low. Procede to a test when the synth is off and test them red probe to anode and black to cathose. You should get ÒL on your mu;timeter. That's ok, After, inverse the probes and you should read between 0,5 - 0,8, ANY OTHER READING INDICATE THAT THE DIODE IS DEFECTIVE.

Also, chech the filter caps in the power section. Chances are they are dead or about to,

Am I suggesting to work more than what seems obvious on the PS? Yes. A SYNTH THAT AGE OFTEN NEED TO BE TOTALLY REVISED, ESPECIALLY THE POWER SUPPLY SECTION.

hope that helps
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Re: Roland SH-101 won't turn on!

Postby sam » Wed Aug 19, 2009 10:46 am

I am slowly recapping all my synths...It's very important and you will have a synth that should last another 20 plus years.

I recapped 2 of my MS 20's last month...One had corrosion on one cap ....(power supply)

THIS IS VERY GOOD ADVICE FOLKS...

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Re: Roland SH-101 won't turn on!

Postby Mooger5 » Wed Aug 19, 2009 2:31 pm

If you can´t find a replacement, take the defective transformer to your local coil winder for a rewind.

Also check the protection diode D8. Look for burn marks on the pcb near the diode. I replaced mine with 1N4007, very common and it works.

Good luck.
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Re: Roland SH-101 won't turn on!

Postby camjon2 » Sun Aug 23, 2009 12:34 pm

Hi all,

Thanks very much for the replies! As this is my first time working on a synth all your help is much appreciated! :D

I've just opened the SH-101 up and have now found what would appear to be the problem..the protection diode-D8 is completely dead along with burn marks on the pcb as Mooger5 suggested.

My question is what would have caused the diode to burn out? Does it's function as a protection diode mean there is, or potentially is, a fault with another component further along the circuit? Or if I just replace the component as Mooger5 suggested everything else should be ok?

I will certainly be recapping the synth once I've got over this problem as you have all suggested! :D

Many thanks for the help! :D
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Re: Roland SH-101 won't turn on!

Postby Operatron » Mon Aug 24, 2009 1:28 am

my (2nd hand) 3 day old DX7 went through the same problem about a month and half ago :( , and because the technician ( preety much the only on in auckland) is mega busy my synth still sitting there ........ :shock:
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Re: Roland SH-101 won't turn on!

Postby Mooger5 » Mon Aug 24, 2009 5:35 pm

camjon2 wrote:Hi all,

Thanks very much for the replies! As this is my first time working on a synth all your help is much appreciated! :D

I've just opened the SH-101 up and have now found what would appear to be the problem..the protection diode-D8 is completely dead along with burn marks on the pcb as Mooger5 suggested.

My question is what would have caused the diode to burn out? Does it's function as a protection diode mean there is, or potentially is, a fault with another component further along the circuit? Or if I just replace the component as Mooger5 suggested everything else should be ok?

I will certainly be recapping the synth once I've got over this problem as you have all suggested! :D

Many thanks for the help! :D


YW. I think it was in a Yahoo group someone posted that hint, along with pictures. The way I see it, and someone please correct if I´m wrong, that diode is there to prevent damage by a wall-wart with reversed polarity. It has to be + at the sleeve and - at the tip. Otherwise the diode will shunt the DC to ground. With correct polarity in the rails, the diode won´t conduct but I suspect it might put it under stress. A diode in series looks more common, but probably they didn´t use that approach because of the loss of 0.6V at the diode. Might be a waste of power when using batteries, IDK. Again, if this isn´t correct, someone please enlighten us.
So, if the diode is conducting both ways, I suspect it was due to stress over time in normal conditions, or a wrong wall-wart was used. I bought my SH-101 from a friend who probably either had reversed the polarities by accident or used one of the Boss wall-warts that outputs AC. The 1N4007 I used is probably overkill for what it is, but it´s easy to find at any electronics store. I say it works, but I´m referring to the diode line of defense only. If you´re lucky, that´s all you have to do to make the synth power up. After replacing the diode the unit powered on but I found the CPU was damaged. I got a new chip from Vintage Planet and the synth now works like new.
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Re: Roland SH-101 won't turn on!

Postby hageir » Mon Aug 24, 2009 6:56 pm

(I didn't want to start a new thread)

My red SH-101 has it's Hold stuck on but I plugged a jack into the Hold socket and it went away!
What could that be?

A "stuck" socket?
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Re: Roland SH-101 won't turn on!

Postby Mooger5 » Mon Aug 24, 2009 7:41 pm

hageir wrote:(I didn't want to start a new thread)

My red SH-101 has it's Hold stuck on but I plugged a jack into the Hold socket and it went away!
What could that be?

A "stuck" socket?


Probably. Have you tried inserting a mono cable and shunt the other end to see if the LED lights up again? Try inserting/removing the plug a few times to either mechanically fix it or to clean the contacts. If it stays the same, (IMHO) the connector must be broken.
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Re: Roland SH-101 won't turn on!

Postby hageir » Mon Aug 24, 2009 10:20 pm

Mooger5 wrote:
hageir wrote:(I didn't want to start a new thread)

My red SH-101 has it's Hold stuck on but I plugged a jack into the Hold socket and it went away!
What could that be?

A "stuck" socket?


Probably. Have you tried inserting a mono cable and shunt the other end to see if the LED lights up again? Try inserting/removing the plug a few times to either mechanically fix it or to clean the contacts. If it stays the same, (IMHO) the connector must be broken.


Alright!
Thanks,

I'll check it out when I get back home :)
I just tried it because I took it apart and cleaned the buttons and that didn't do anything,
so I just decided to stick my headphone jack into the hold socket (because, currently it's the only big jack that I have :) haha) and then finally the Hold light went off..

It's something simple,
I'll figure it out,
if I don't, I'll chime in again!

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Re: Roland SH-101 won't turn on!

Postby camjon2 » Thu Sep 10, 2009 2:59 pm

Just a quick update..finally managed to get down to my local RS components yesterday and picked up all the parts required. Replaced the protection diode (D8) with the 1N4007 as suggested by Mooger5 and the synth is working perfectly now! :D

Many thanks to everyone for their help and it just shows me how much I missed the sound of this synth. In the meantime I'm away to recap the power section just to be on the safe side! :D

Regards,

Jonathan
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Re: Roland SH-101 won't turn on!

Postby Mooger5 » Fri Sep 11, 2009 12:08 am

Congrats! :) Glad I could help.

About recapping the power section, and not meaning to disrespect, but you know the saying: "If it´s not broken..."
If you so wish to do that, IIRC in the jackboard there´s a big cap across the DC connector´s terminals that you might want to replace. By any means don´t desolder the DC connector. The part is tricky. Don´t melt the solder there [-X
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Re: Roland SH-101 won't turn on!

Postby billbigrig » Wed Feb 28, 2018 9:26 pm

I have 3 101s, one won't work. The resistor R-8 burns when power is supplied. The schematic says 1 ohm, photos show a jumper. I have replaced TR1 TR2, checked the diodes, capacitors, in the power section. The transformer shows continuity, how do I check for a bad transformer? If not the transformer, what's the next met likely thing to short out? Where can one get a transformer?
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