Yamaha DX 7 mk2 noisy distortion/hum

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Yamaha DX 7 mk2 noisy distortion/hum

Unread post by OOS » Mon Sep 23, 2019 4:56 pm

Hi all



As i describe on the title i get a constant noise/hum and no sound on the synth at all while patch names are there. Any ideas ?

Some people told me that its a PSU problem, i opened it up and after inspecting the PSU i found a blown orange colour cap on C 10 position can anybody tell me the specs of these caps ?

Hope this is the issue since previous owner told me that in all of a sudden that they synth stoped working.
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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by parametric » Mon Sep 23, 2019 5:04 pm

THAT sounds to be the likely cause, OOS . . . .

I'm sure that <Miks> will be along shortly and I'm sure he can telly you what that Cap is.

Due to the age of the DX7, it is probably wise to replace ALL the Caps in the PSU . . . .

(I'm sure the others are getting ready to fail . . . ) :roll:

You will probably need to do a factory reset AFTER you have done this to get the DX7 back working again . . . .

It would be a good idea to check the state of the battery too - and replace, if it is reading LOW . . . . :doh:

ATB

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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by OOS » Mon Sep 23, 2019 5:09 pm

Thanks for the instant reply hope this is the issue i will wait for Miks to get a reply about the specs of these caps too.
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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by Miks » Mon Sep 23, 2019 9:32 pm

Japp guys - here I am :mrgreen:

Those capacitors C4, C5, C9 & C10 are all the same type: 2200 pF / 250V (they're no electrolytic caps) - hope it helps :wink:

Edit: some examples of caps which should fit...

reichelt.de/keramik-kondensator-2-2-nf-0-v-20-85-c-mur-de1e3kx222mn-p247574.html?&trstct=pol_95
reichelt.de/keramik-kondensator-2-2-nf-500-v-20-85-c-hita-hb2h222k-l5-p246890.html?&trstct=pol_11
reichelt.de/keramik-kondensator-2-2-nf-0-v-20-85-c-hita-ke4a222m-l0-p246909.html?&trstct=pol_29

it-tronics.de/Kerko-radial-2-2nF-440V-AC-RM10-d11x5mm-K1Y222MQ47FACKA-2200pF.html
it-tronics.de/Kerko-radial-2-2nF-440V-AC-RM7-5-d8x4mm-ERO610RJ4220MCRA-2200pF.html
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: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by OOS » Tue Sep 24, 2019 1:05 pm

Hey Miks

Thanks for the reply as always, and now straight to the electronics store to get them and replace them all, best Panos.
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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by OOS » Thu Sep 26, 2019 10:46 am

Btw what about thepolarity of the caps ? i mean do they need to be soldered in a specific way ?
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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by Miks » Thu Sep 26, 2019 11:25 am

OOS wrote:
Thu Sep 26, 2019 10:46 am
Btw what about thepolarity of the caps ? i mean do they need to be soldered in a specific way ?
No, those caps have no polarity - you can solder them in either way.
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
Greece
OOS
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Member
Posts: 51
Joined: Mon May 01, 2017 10:25 pm

Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by OOS » Thu Sep 26, 2019 10:00 pm

Thanks Miks for all as always, i will update the post with any news if needed.
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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by Miks » Thu Sep 26, 2019 10:30 pm

OOS wrote:
Thu Sep 26, 2019 10:00 pm
Thanks Miks for all as always, i will update the post with any news if needed.
You're welcome! Yes, please let us know how you go on. 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
Greece
OOS
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Member
Posts: 51
Joined: Mon May 01, 2017 10:25 pm

Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by OOS » Wed Oct 09, 2019 10:13 am

Service update (apart from the extremely help from the expert here Miks). I replaced the ceramic cap resulting in almost no progress, and i say "almost" since that when i soldered the cap i got exactly the same result, quite extreme hum and no sound, but when i decided to desolder and solder the cap the other way, i got less hum and a faint sound that sound distant enough. i am certain that the problem lies on the PSU definitely, but if the caps have certain polarity i dont know which ones to replace and in which way. The one that i replaces had blown up leaving a small black area around the PCB, but others seem to be OK (definitely are not, they are near their end of life).
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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by OOS » Wed Oct 09, 2019 10:45 am

A detail is that i replaced the cap with one for 500 V and not 250 V like Miks suggested, if that plays a role since they told me from the store that its OK to do it this way.
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Re: Yamaha DX 7 mk2 noisy distortion/hum

Unread post by Miks » Wed Oct 09, 2019 11:04 am

OOS wrote:
Wed Oct 09, 2019 10:45 am
A detail is that i replaced the cap with one for 500 V and not 250 V like Miks suggested, if that plays a role since they told me from the store that its OK to do it this way.
Yes, that's ok.
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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