[sdiy] Vox Continental key noise

[Michael E Caloroso]

Glad you found it.  Had a strong suspicion it was a ground problem.

MC

On 5/2/21, Nathan Trites <nathan at idmclassics.net> wrote:
> got it! The ground wire to one of the resistor networks was literally
> hanging by a thread. Had a coffee and started measuring different ground
> connections, got to this one and it broke free with the lightest tug. Must
> have been from all the movement on the tone board bracket. Photo:
> https://i.imgur.com/zgwqo2b.jpg
>
> As Michael mentioned there is some general mechanical noise that's
> inoffensive in a band setting, comparable to most other switch on an audio
> signal.
>
> Thanks for the encouragement!
>
> Nathan
>
> On Sat, May 1, 2021 at 7:10 PM Adam Inglis (synthDIY)
> <synthdiy at adambaby.com>
> wrote:
>
>>
>>
>> On 2 May 2021, at 1:32 am, Nathan Trites <nathan at idmclassics.net> wrote:
>>
>> Thanks. That’s another thing I wondered about - to what extent do they
>> click/pop under normal conditions.
>>
>>  I know it won’t be perfect but the noise is significantly louder than
>> the
>> tones, sounds just this video but on every key
>> https://youtu.be/NnwJZt3TifI
>>
>>
>>
>> I agree, that low frequency thump heard there is not just key click. And
>> you’re getting that on all keys?
>> At least it looks a bit easier to work on than my old Farfisa!!
>> https://mezzoauto.blogspot.com/2019/05/farfisa-compact.html
>>
>> You seem to have addressed all the things I did in fixing mine - which
>> essentailly got down mainly to replacing 50 year old electrolytics.
>> Obviously, you need to see if the supply voltage is sagging with key
>> presses, it might need some attention…
>>
>> good luck and keep us informed!
>> A
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> I’ll have time to dig in more tomorrow.
>>
>> Nathan
>>
>> On Saturday, May 1, 2021, Michael E Caloroso <mec.forumreader at gmail.com>
>> wrote:
>>
>>> I don't think you can eliminate the noise.  Vox combo organs are cheap
>>> designs, the contact noise is DC transients when the contacts mate.
>>> In an isolated setting you may notice the contact noise, while in a
>>> band setting it will be masked out by all the other instruments.
>>>
>>> Don't expect these to be high fidelity.
>>>
>>> MC
>>>
>>> On 4/30/21, Nathan Trites <nathan at idmclassics.net> wrote:
>>> > Hi all,
>>> >
>>> > I've got a continental v301e here where I'm getting a nasty contact
>>> noise
>>> > on all keys, which varies in level (seemingly due to where the
>>> > waveform
>>> > falls). It's definitely not just dirty bus bars & j wires, which have
>>> been
>>> > cleaned pretty aggressively. Most of the finger connections seem good,
>>> all
>>> > electrolytics replaced, and a few of the (film?) caps replaced for
>>> > being
>>> > open.
>>> >
>>> > With all tone boards in, each bus has an offset of low double digit
>>> > millivolts. With a single tone board in it still occurs with an offset
>>> in
>>> > the single digit mV and it still happens. I've replaced coupling caps
>>> in a
>>> > few and they still have noise.  I can see the spikes on the scope even
>>> > without the preamp board installed. Would such a small offset cause
>>> popping
>>> > like that on the switches?
>>> >
>>> > The continental is a fair bit older than gear I'm used to working on
>>> > so
>>> I'm
>>> > still getting my bearings on the construction and haven't checked this
>>> yet,
>>> > but I suspect the ground from the draw bars or going to the tone
>>> > boards
>>> > needs to be looked at closer.  I do get some very low noise on the
>>> > power
>>> > supply (even with nothing installed) again in the 10s of mV range p-p.
>>> >
>>> > Schematics can be found here:
>>> > http://www.theamericannight.com/voxproject/project.html
>>> >
>>> > Any guidance or advice would be appreciated! If anyone knows of a good
>>> > transistor organ repair forum or list that would be very helpful too.
>>> >
>>> > Thanks,
>>> >
>>> > Nathan
>>> >
>>>
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