VOGONS


First post, by Salient

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I recently bought an SC-55 for very little money and I decided to try to do with it what I did to my MT-32.

Basically what I did is took an existing 'low profile' power supply of 12 Volts, added an 7809 voltage regulator and connected it internally to the 9V plug. Then I drilled and cut a hole in the casing to make room for the mains connector. Then I connected that to the power supply, glued the plastic holder for the power supply on top of the 3 chips of the sc-55 mainboard and voila, an sc-55 like an sc-88. 😀

Photo's (clickable for bigger versions):
SC-55_open1_resize.jpg SC-55_open2_resize.jpg

SC55_PSU_1_resize.jpg SC55_PSU_2_resize.jpg

SC55_PSU_3_resize.jpg SC55_PSU_4_resize.jpg

SC55_PSU_5_resize.jpg SC55_PSU_6_resize.jpg

SC55_PSU_7_resize.jpg

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Reply 1 of 15, by HunterZ

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xs4all.nl is blocked at work, can't see the pics 🙁 Sounds cool though, someone should do the same with an MT-32 - there's a good amount of space inside of its case I think.

Reply 2 of 15, by Salient

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Actually I have done this with my MT-32 as well long before. 😀
Indeed on the left side in the casing there is plenty of space.

Here is the pic (clickable):
MT32_psu_resize.jpg

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Reply 4 of 15, by Salient

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With the SC-55 I hear no difference at all with the internal or external psu.
With the MT-32 only when I set my amplifier at near maximum I hear a vague 50hz noise which I believe wasn't there with the external power supply. However in normal use I never notice it.

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Reply 5 of 15, by keropi

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that is a very nice idea, might do that to a CM-32L I have... 😀
nice job!

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Reply 6 of 15, by Salient

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keropi wrote:

that is a very nice idea, might do that to a CM-32L I have... 😀
nice job!

Was thinking about that myself also, but I doubt there is enough space in the CM32L.
Will open my MU80 soon too to find out if I can do the same with that thing also. 😀

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Reply 7 of 15, by Salient

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A little update on the power supply (thanks to mace):

Added 2 capacitors to smoothen the regulator's output.

SC55_PSU_8_resize.jpg

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Reply 9 of 15, by Salient

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h-a-l-9000 wrote:

You really shouldn't put the output wires so close to the live ones.

It's just a short distance and the device doesn't draw a lot of current. Why would it be bad to have them next to eachother?

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Reply 11 of 15, by Salient

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h-a-l-9000 wrote:

If the isolation fails you get electrocuted.

I'm counting on the isolation not to fail 😀

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Reply 13 of 15, by HunterZ

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Shouldn't be a big risk if the enclosure is kept sealed since there are no moving parts inside :p I was thinking you were going to say it might cause EMI issues.

Reply 14 of 15, by h-a-l-9000

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The glue or isolation can melt (who says the power supply can't partially fail and produce a lot of heat?) and then you have moving parts. There are possibly sharp edges that cut in the isolation over time. Keeping the wires and voltage regulator away from the live side is only a small effort but decreases hazard a lot.

Oh, and from the EMI side: The live side of a switching power supply produces lots of interference, you'd like to put it as far away from analog audio stuff as possible.

1+1=10

Reply 15 of 15, by Salient

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I hear no interference at all, even with my amp. wide open. at least not more than with the original external power supply.

But maybe you are right about the danger of melting. Although it's unlikely to happen I will take some actions to make sure the live wires will not be able to touch the output wires in case of overheating.

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