DX7 IID won't power on

This section is for all variants of the Yamaha DX series. DX1/DX100/DX11/DX21/DX27/DX27S/DX5/ DX7/DX7IID/DX7IIFD/DX7S/DX9/TX81Z/TX7

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Miks
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Re: DX7 IID won't power on

Unread post by Miks »

djazz75 wrote: Sun Oct 14, 2018 3:54 pm My dx7 is alive ! The fault came from capacitor C23 C24. Thank you Miks, you were right :)

Thank you all !
WOW - that's great! ((i)) (Y)
I'm so glad you brought your synth 'back to life' again. :D

Did you replace more than these two capacitors (as I suggested)?
parametric wrote:@Miks - another triumph! - you KEEP being right about these things LONG may it continue . . . .
Thanks para - I LOVE it when things like this happen... 8)


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),
WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
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Re: DX7 IID won't power on

Unread post by djazz75 »

Thank you Miks :)

no I only replaced C23 and C24. but I bought the others and when I have a little time I'll do it !


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Miks
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Re: DX7 IID won't power on

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djazz75 wrote: Sun Oct 14, 2018 5:08 pmThank you Miks :)
You're welcome! :D
no I only replaced C23 and C24. but I bought the others and when I have a little time I'll do it !
That's fine - it absolutely makes sense to replace them all whilst you have the synth open. I think after replacing all caps on the PSU your DX7 will be good for another few years to come. (Y)


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),
WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
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rawl747
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Re: DX7 IID won't power on

Unread post by rawl747 »

Glad that you were able to fix this yourself. It amazes me that most of these DX7 synths from the 80's are still functioning with their original capacitors. The build quality of these vintage Japanese synths is to be commended. Today, a PC power supply is lucky to last 5 years if that!


DX7 (MKI) w/ E! Card & S80 Keyboard synths
WX7 & MDT (Morrison Digital Trumpet) MIDI windcontrollers, TEC MIDI Breath & Bite controller
VL70m synth module w/ Patchman Turbo
Tx81Z, FB-01, RX-5, Roland XV-5080, Emu Emulator E6400 Classic - (this last thanks to James M.)
Win 10 Pro 64 bit with Focusrite Scarlett 18i20 & MOTU MIDI Express XT, Cubase Pro 10, Halion 6, NI - Kontakt 6, Komplete 12, IKMultimedia SampleTank 4, 3 & 2.5XL, East West Symphonic Orch., Kirk Hunter Diamond SO, AAS Suite, BiaB 2019, Emulator X v2 & v3, Wusik Suite, Vienna Ensemble Pro v7
Assorted acoustic brass & woodwind instruments & numerous guitars both acoustic & electric
Harmonicas - oh and a 100+ years old full upright piano...

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JonathanW
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Re: DX7 IID won't power on

Unread post by JonathanW »

Great stuff - the caps in my II FD were Nichicon so Yamaha didn’t skimp on quality. I have replaced them all though .. with Nichicon!

To further assist others with a “dead” unit, I too discovered in my case it was an open circuit wire wound power resistor R3 and a shorted C24 cap.

Jonathan


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parametric
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Re: DX7 IID won't power on

Unread post by parametric »

Nice info there Jonathan, and a great result!

Thanks for coming back to us with that info (Y)

parametric


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rik
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Re: DX7 IID won't power on

Unread post by rik »

Had the same problem last year, opened it up and problem tracked down to power supply. Finally got time to look at it again recently. Removed all the 9 electrolytics and replaced them, at about $10 cost. Couldn't find Nichicons in most of the values I needed, so they are Panasonic except for the 1uF. This did the trick, seems that it was the two 2200 uF ones that have failed. It really helped having this forum to give me the idea, and also being able to find the service manuals online which show the component layout.

Thanks to everyone who shared here, and Miks in particular for his insightful recommendations.

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Saul
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Re: DX7 IID won't power on

Unread post by Saul »

Hi richard, welcome to the forums :)

Great to hear you have managed to fix your DX7IID and that the forum was of some help with this. Also thanks for the info on the components too :)


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Miks
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Re: DX7 IID won't power on

Unread post by Miks »

rik wrote:Thanks to everyone who shared here
Hi Richard - glad you've got it working again and reporting the outcome here! (Y)
...and Miks in particular for his insightful recommendations.
You're welcome - and thanks for the kudos :wink:


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),
WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
rubarb
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Location.: USA

Re: DX7 IID won't power on

Unread post by rubarb »

I just wanted to thank everyone on this thread. So helpful. I have a DX7iid that wouldn't power up, replaced all the electrolytic caps on the power supply, still nothing. Starting measuring resistors, R3 (1.8ohm 3W) seemed off. Desoldered it to measure and it was dead. Replaced it and viola! All up and running.

I do have a question -
I'm getting a good +5VDC
But on the +12 and -12 I'm getting +11.84 and -11.76

Any tips on getting these two up to spec? Or are those ok numbers?

Thanks so much!


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Miks
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Re: DX7 IID won't power on

Unread post by Miks »

rubarb wrote: Thu Sep 17, 2020 3:34 am I do have a question -
I'm getting a good +5VDC
But on the +12 and -12 I'm getting +11.84 and -11.76

Any tips on getting these two up to spec? Or are those ok numbers?
With the trimming potentiometer VR1 on the PSU's pcb you can adjust the output voltages of the PSU - but only all at once! You should measure the +5V DC and adjust it carefully as close as you can get it to 5V, using the trim pot. The values of the +12V and -12V should now be within their specs. Those values you have measured are absolutely OK! The +5V DC is for the 'digital section' of the synth (CPU, Memory etc.), the +12V and -12V are supplying the 'analog section' (Op-amps etc.)


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),
WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
rubarb
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Location.: USA

Re: DX7 IID won't power on

Unread post by rubarb »

Thanks Miks. I thought that something might be affecting the +12 and -12 to measure slightly under but if you say the difference is ok, then great!
Happy I got it working. Thanks again for your insights on this forum.


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Miks
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Re: DX7 IID won't power on

Unread post by Miks »

You're welcome! :D


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),
WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
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