Help Quick! JP-8000 humming! A Lemon?

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Help Quick! JP-8000 humming! A Lemon?

Postby busssy2333 » 10:19, 24 October 2016

I bought a JP-8000 off ebay described as perfect working. Got it, but the ribbon controller didn't work. I did the calibration reset in the service manual, ribbon still didn't work. I also have another JP8K that is broken (screen is all solid light up and no sound whatsoever. This is like my 5th JP8K.

Anyway, so the seller agreed that if I change the ribbon with my broken JP's, and it works, they'll refund the cost of a new ribbon instead of paying shipping to and from me and a full refund. The ribbon from my broken JP works but I'm not sure I want to keep the one I just got off ebay because:

From owning JP8Ks on and off since 2002, I never noticed a humming sound coming from inside the synth where the power plug goes where it says JP-8000 on the panel. I noticed this tonight though on the one I just bought. It's a very slight noise you have to put your ear right next to the synth to hear it. My broken JP8K does this also though (it powers on but all solid digits on screen and can't get any sound or factory reset or anything).

I found this thread: https://www.gearslutz.com/board/electro ... -area.html


someone says
the transformer is buzzing.

there are plates of metal suck to each other inside the transformer which vibrate. over time these plates get loose and vibrate more. eventually they vibrate so much that they loosen the bolts holding it onto the chassis. when this happens you can really hear it, but it's nothing to worry about.

you could try opening it up and tightening the bolts holding in the power transformer. this will probably stop the hum. if not there's other steps you can take to isolate the bolts from the chassis with rubber grommets.


So I just want to confirm if this is something to really worry about or not. The "fix" suggested above seems simple so I'll probably try that. Someone else mentioned it in this thread but got no reply:

http://www.synthzone.com/forum/ubbthrea ... 00_PSU_Hum


So, I'd like to know asap (so I can decide to return or claim ownership of this synth) from other JP8K owners if you can just turn it on and put your ear where the power plugs in, do you hear a buzz?

Also, you know the knobs that click in place at center or zero? I know OSC 2 RANGE knob does this but doesn't on the one I just bought. The replacement pot is only $6 (but a bit of work to install carefully). The knob below OSC 2 RANGE, the one called Fine/Wide, is that supposed to click in place at center also?

The other thing about "Lemon": Other than the ribbon needing to be replaced, the OSC2 knob not clicking in place at center, and the possibility that the humming noise can lead to a serious problem, other than that, the synth is excellent, good condition, all knobs, keys, buttons, sliders etc work perfect is diagnosis test and playing - I hade like 5 JPs before and this one is the nicest, however, the fact that the ribbon went bad (which is quite common but I've never encountered), scares me that other things are going to start breaking and end up with a broken synth. I still have the option to return it with no loss and wait for another to pop up, but it's rare to find a JP in great condition. Even the ones that claim to be perfect usually have some problems. I bought one or two in the past year and after buying them I told the seller it better be "%100 functioning" like they described or don't even mail it because I'll have it sent back, not to be a @%$@, but I want zero defects if advertised as such.

so do you think I should not worry about the ribbon controller being broken and the 1 (or 2) knobs not clicking in place at center point, and just keep this synth and be confident it won't c**p out in a few years? And factor in the the buzzing sound. Or should I return it and wait for one that's described as %100 functioning and have the seller run the diagnosis test mode and check all pots and knobs and keys (and humming sound if that's a potential big problem) before they even bother mailing it to me?
busssy2333
 
Posts: 9
Joined: 22:03, 5 October 2016


Re: Help Quick! JP-8000 humming! A Lemon?

Postby busssy2333 » 03:52, 26 October 2016

My other JP, the OSC 2 fine wide doesn't click in center either but it should. All knobs with a thicker center dash mark (the ring of dashes around the knob) are supposed to click in center. Many on my other broken JP don't work anymore.

The humming is common and shouldn't be a problem. If you google "synthesizer PSU buzzing (or humming)" you'll find info of many synths do this for decades without problems, but some say it could lead to other problems. There are hacks to like re varnish it (glues it all together, and yes I do see the old varnish is on there thick so I wouldn't be too scared to paint some epoxy or varnish on it), but I will just see what happens. Hopefully the worst is it eventually stops working and all I have to do is resolder a new aftermarket one in for ~$15. Some say to jam something in there to stop the vibration but I'm not about to. I don't see any screws that can be tightened which is another suggestion.

I end up keeping this synth after all and happy. The center clicks not working on the two knobs is not the end of the world for me, at least for now, but I'll have the two spare knobs in case I decide to dismantle it and carefully resolder the new ones in. The ribbon being broke, I changed it out but not as worried that means more things will break soon because that's the risk with any JP. The buzzing PSU, I'm not worried of either. Thanks again.
busssy2333
 
Posts: 9
Joined: 22:03, 5 October 2016


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