[sdiy] Vox Continental key noise

Nathan Trites nathan at idmclassics.net
Sun May 2 23:52:30 CEST 2021


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
>
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> 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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