Dx7iid question/help

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Seanlyons80
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Joined: Sun Sep 08, 2019 1:41 pm

Dx7iid question/help

Unread post by Seanlyons80 » Sun Sep 08, 2019 2:07 pm

Hi received this keyboard and it has no power. I looked at the power supply board and found what appears to be residue or scorching.
Is the board done for and could there be other issues to be concerned about in order to get it working properly?

Please see attached photos.
Thanks
Attachments
E7FC71DD-EDDD-4F9A-8F14-8E1C9A52CF21.jpeg
134325F8-B63D-4EC8-9FE9-DD8CADFCB3F3.jpeg
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Miks
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Re: Dx7iid question/help

Unread post by Miks » Sun Sep 08, 2019 3:54 pm

Hi Seanlyons80,

welcome to the forum (Y)

I can't see any 'abnormal' kind of residue or scorching. That 'yellowish goo' around some of the electrolytic capacitors foot is a kind of glue, applied by the manufacturer. Obviously to fasten components to the pcb not to wiggle lose during transportation...

To find out on what issue your psu suffers please have a good reading here:

viewtopic.php?f=35&t=11766

Let us know what you'll find...
My (key related) gear (in alphabetical order):
Ferrofish: B4000+
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500,
TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), DataBlade32 (1x),
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rawl747
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Re: Dx7iid question/help

Unread post by rawl747 » Sun Sep 08, 2019 6:00 pm

Your picture does not show anything excessive to my eyes. The transformer does generate a fair amount of heat and for a unit that is from the mid 1980's, some discoloration from that transformer's heat is to be expected. The area in question is on the underside of that transformer.

Power supplies are actually pretty simple for a tech with moderate experience to troubleshoot. I always start with measuring the DC voltages on the output. If some are OK and others not then it is often a fault specific to the section providing the missing or aberrant DC voltage rather than a failure of the step down transformer if one is present.

Often in units this old, the electrolytic capacitors (round cylindrical "cans" with plastic labels covering the sides) fail first. They start leaking (not the yellow glue) their electrolyte often out of the bottom end near the PC board or the top starts bulging. These are both signs of pending or complete failure. Many folks replace all the larger electrolytic caps in a unit this old just as preventative maintenance since a catastrophic failure of some of these caps may also damage or destroy other connected components.

Troubleshooting this will require some "tech" tools and some experience. If you lack either or both of these, you need to find a reliable technician in your area.

Best of luck,
Rawl
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