[sdiy] Roland JX-3p vca - noise

[Travis Thatcher]

I'd be interested in a jack part number here in the states too.
Syntaur has them for like $7 but if there's a more modern, cheaper
replacement that'd work for me.

I ended up working till late last night so I didn't have a chance to
crack open my synth (which i'll do tonight) but assuming the muting
transistors have gone south, would it be un-wise to replace the
2sc2878 with a regular 2n3904? Any other drop in replacements that'd
work if not?

Also, would it be really harmful to just bypass the muting circuit
altogether? Assuming I kept the volume on my mixer low on power
on/off?

On Thu, Feb 28, 2013 at 9:04 AM, Tom Bugs <admin at bugbrand.co.uk> wrote:
> If anyone has a part number for the output sockets, please share.
> Could be that I've experienced similar(ish) problems.
> I did get a new socket that may be suitable from Rapid, but haven't taken
> the time to check it yet..
>
> And wanting to do some of Florian's mods..
>
> Ta, Tom
>
>
> On 27/02/2013 19:39, Tom Wiltshire wrote:
>>
>> If you're going to desolder the jack anyway, put a new one on. Don't mess
>> around with the old one. It's 25 years old and it probably needs replacing.
>> Once that's done, you've got a reliable connection you can trust for the
>> next 20 years and if crackles still show up, you know it isn't from there.
>> If you put the old one back, you'll never be sure ("well, it sorta *looked*
>> ok…").
>>
>> I'm not one for recapping every electrolytic in the synth just cos, but I
>> do reckon that most old gear needs a new filter cutoff pot and jack socket
>> for starters. They get wrecked. It's the bare minimum. At least on the JX3P
>> you don't have to worry about the cutoff pot!
>>
>> 2 cents,
>> T.
>>
>>
>> On 27 Feb 2013, at 19:16, Travis Thatcher <recompas at gmail.com> wrote:
>>
>>> Thanks Tony - I'll look into the output mute transistors when I take
>>> the synth apart tonight to check everything else out.  Its been a bit
>>> of a mess of weird problems since I got it this summer (used to have
>>> one  years ago) but its close to fully functional now.  What exactly
>>> is the purpose of the muting transistors? Just to make sure the signal
>>> goes to ground if there's no actual synth signal coming through - kind
>>> of like a gate?
>>>
>>> As for the outputs - the right output barely works at all. I'm going
>>> to desolder the jack and test the mechanics of it off board. Same with
>>> the headphones and looking at the schematic the two signals seem
>>> isolated.  The audio connector could very well be corroded so I'll
>>> definitely give that a good check.
>>>
>>> Thanks!
>>>
>>> On Wed, Feb 27, 2013 at 2:28 AM, Oakley Sound <oakleylist at btinternet.com>
>>> wrote:
>>>>
>>>> It's probably a poor connection somewhere since it goes away when you
>>>> change
>>>> the volume levels. But if not, one other place to look is the output
>>>> mute
>>>> circuit. TR7 and TR8 being the mute transistors. These can go bad and
>>>> produce some odd distortion effects.
>>>>
>>>> Virtually every JP-6, which has a similar circuit to the JX-3P, I have
>>>> seen
>>>> has poorly output mute transistors. But that tends to manifest itself as
>>>> an
>>>> overdriven sort of sound when you have the VCA level and volume up. I
>>>> sometimes see a comment about the JP-6 having some sort of deliberate
>>>> overdrive capability but it's usually just a bad output mute circuit.
>>>> Take
>>>> the mute circuit out and it's as clean as a whistle.
>>>>
>>>> Since the output of the JX-3P is stereo - does it crackle identically on
>>>> both sides? If so the problem is possibly before or in the chorus unit.
>>>>
>>>> Tony
>>>>
>>>> http://takla-makan.bandcamp.com/
>>>> http://www.oakleysound.com
>>>>
>>>>
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>>>
>>>
>>>
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