Yamaha DX7 Powers up, not much else

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loopy reed
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Yamaha DX7 Powers up, not much else

Post by loopy reed » Fri Mar 23, 2018 5:09 pm

Hi everyone! Brand new here, have already done a bit of digging on different topics and this seems like a really great, helpful forum.

I bought a DX7 on the real cheap recently, knowing that it had issues with not doing much else other than powering up. The guy I bought it from was aware of the issue and sold it as is, full disclosure, so I kinda knew what I was getting into.

Here's what happens when I turn it on:

Image

I get this screen and that's it. Nothing else happens for as long as I leave it on. There is no hesitation when powering up and it turns off as soon as I flip the switch.

The guy I bought it from didn't seem to know much about it either. He mentioned that part of the power board was supposed to be putting out +12v, but was only around +2 or +3. I'm not sure what he meant, how to measure that, or if that's completely accurate.

Considering how old it is, I went ahead and replaced the small battery for the memory, figuring that couldn't hurt. I didn't expect the new battery to solve the problem, and I was right about that.

I also purchased a replacement power supply board, just to be safe, because they seem to be hard to find.

Does anyone have any advice for what would be my next step? I'd really like to get this thing working. Although I'm not much of a keys guy, I enjoy projects, and I like having synths around for writing and recording.

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rhino
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Re: Yamaha DX7 Powers up, not much else

Post by rhino » Fri Mar 23, 2018 11:37 pm

Welcome to the board!

do any of the buttons make changes?

Yamaha used alot of Tantalium capacitors in their synths back then. They get old and short out causing problems. This may be what's pulling down the +12v line. NOTE: if so, the bad caps may not even be on the power supply board. Maybe time to take it to a Tech.
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loopy reed
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Re: Yamaha DX7 Powers up, not much else

Post by loopy reed » Sat Mar 24, 2018 3:37 am

rhino wrote:Welcome to the board!

do any of the buttons make changes?

Yamaha used alot of Tantalium capacitors in their synths back then. They get old and short out causing problems. This may be what's pulling down the +12v line. NOTE: if so, the bad caps may not even be on the power supply board. Maybe time to take it to a Tech.
Hey thanks!

Nope, none of the buttons do anything, unfortunately. It just sits there on that screen.

I'm not afraid of digging in and testing the capacitors. I'm just glad you didn't say "transformer." I remember seeing a lot of what looked like tantalum caps on the main board, so I'll start there, unless you can point me in a different direction first.

I just really want to avoid taking it to a tech. I wanna keep cost down as much as possible, should I decide to get rid of it. I always like to trade up whenever possible.

Do you know how to check the voltage? Mainly, where I would be looking for a place to attach the leads on my multimeter? I just want to make sure that's what's going on.

Thanks for checking out my post!

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rhino
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Roland JX-10
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Ensoniq SQ-80
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Location: kentucky hills

Re: Yamaha DX7 Powers up, not much else

Post by rhino » Sun Mar 25, 2018 2:36 am

A good capacitor meter is $$$. They use a series of pulses to tell if the cap is shorted or not. Using a ohm meter on the cap will not give a accurate reading because of all the other componets in the circuit. Carefuly unsolder one side (lead) of a Tantallium cap (one at a time) and see if change or not. If not, resolder that cap and move to the next one.

best of luck
When the wise man points to the stars, the fool looks at the finger.
- Confucius

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