Troubleshooting Jupiter 4 Voice card.

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Jakobz
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Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Sat Apr 24, 2021 8:41 am

Hi there
At the moment im trying to troubleshoot on a Jupiter 4, with 1 silent voice. Since i have 3 working voice cards, i think it should be possible to locate the issue. But i was wondering if anyone could offer some advice on how to proceed, since it is quite hard to do any measuring when the cards are mounted on the main PCB. Im thinking maybe making some sort of extension socket/cable so i can have the card connected outside the synth. But i would love to hear how people usually approach this.
:)

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Yekuku » Sat Apr 24, 2021 9:16 am

HI , you need a voice card extension to troubleshoot properly, I think there was a post somewhere from Mr. Allgood ( oakley modular) explaining what is needed.
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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Sun Apr 25, 2021 8:38 am

Thank you for your input, i will try to find that post :D

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Sun May 02, 2021 8:32 pm

Unfortunately i have not been able to find the post mentioned :( Does anyone know the kind of connectors used on the Voice card is called. I have not been able to find them anywhere.

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Yekuku » Mon May 03, 2021 8:36 am

Hi Jakob,
here is the voice card:
Image
It uses 4 X 9 pin connectors to connect to the mainboard.
I have not done this yet, but theoretically you need a large stripboard
Image
Angled 9pin connectors like this
ImageAngled 9pin sockets like this
Image
I am planning on building such an extension card later in the summer, if you are not in a hurry, maybe i can provide more help .

Edit : here is another thought , instead of building an extension card it could be possible to extend the card using male to female dupont wires:
Image
Let us know how it goes!
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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Mon May 03, 2021 3:47 pm

Hey Yekuku :) That was kind of what i had in mind actually, only with wires, nice touch with the stripboard. But the pins used on the Jupiter 4 are pretty wide (almost 2mm) så the usual pins and sockets, at least what i have been able to find, will not fit and neither will dupont wire :?

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Yekuku » Mon May 03, 2021 5:41 pm

Hi Jacob,
is it possible to measure exactly :
1) pin width ( pin diameter)
2) pitch ( the distance between 2 pins)
I am confident that Mouser has what you want, but you need to know the upper specs in order to find the right part.
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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Tue May 04, 2021 9:41 pm

The pins are : width 2mm , height 6mm and spacing between 0,5-0,8mm.
I linked to a photo.
Image
https://www.dropbox.com/s/lz891bqkeiml6 ... 9.png?dl=0
I will see if i can find something at mouser.
Meanwhile it turns out, the voice is not completetly quite after all. The Noise generator seems to work allright. I suppose this would rule out parts of the circuit.

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Yekuku » Wed May 05, 2021 1:37 pm

Well , I was not expecting these type of pins..... :facepalm:
I have never seen this type of connector, it will be quite difficult to find one.
I need some time to research about it .
BUT you might not need the extension after all, since noise is working the problem should rely on the VCO core or the exponential converter, so it wont be hard to find it. I hope the problem is not the ua726 which is insanely expensive.
By swapping components on the faulty card and a working one you can find the faulty component.
Have you identified which card has the problem?
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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Wed May 05, 2021 5:10 pm

Yes, i did some card swapping and have isolated the bad one.

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Yekuku » Wed May 05, 2021 6:09 pm

Well I had another facepalm by looking the VCO schematics, it is a strange design, but thankfully the manual is quite informative.
Since there is no extension ,my approach would be to attach wires (with parrot clips) to all critical points , so that you can take measurements while the unit is powered on.
First we need to know if there is any oscillation on the faulty card, you say it is silent but maybe it is oscillating low in Hertz. (below 20hz) Low Hz oscillation could be due to faulty IC1 4558 (voltage adder) or IC2 ua726 exponential converter.
If there is no oscillation , I would attach a wire on test point CP34 and check if there is pulsing.
If no , check /replace the 555 timer along with IC4 4069 & IC5 TL082.
If yes , check/replace IC6 4024 & IC7 4052
I would suspect the 40xx CMOS first, then the opamps (4458 & 082) and lastly the ua726.
Hopefully later in the weekend I will be able to search for the connectors.
If you have any news , let us know. Good luck !
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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Thu May 06, 2021 6:54 pm

Thank you, this is great stuff. I will look into it, and report back :D

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Tue May 18, 2021 9:23 pm

So i had a chance to do some probing around. Im having a hard time to grasp exacly what is going on in this circuit but as far is i can tell, i may have a bad IC7, as you suggested. I see no oscillating on CP 36. I think i have one lying around somewhere, so i will try to replace it when i get the chance and report back :)

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Re: Troubleshooting Jupiter 4 Voice card.

Post by Yekuku » Tue May 18, 2021 10:17 pm

Since you have no vco output, CP36 is expected to be sillent, better check CP34 for pulses to rule out the 555.
If there is pulsing, probably the fault could be in IC7 or IC6.
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Re: Troubleshooting Jupiter 4 Voice card.

Post by Jakobz » Wed May 19, 2021 10:02 pm

Since you have no vco output, CP36 is expected to be sillent, better check CP34 for pulses to rule out the 555.
If there is pulsing, probably the fault could be in IC7 or IC6.
Forgot to mention, i already confirmed oscillation on Cp 34 And comparing output from IC6 with the working modules it seems to be OK. I will try and replace IC7 later tonight :shock:

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