[sdiy] Need help about how to service an amp

cheater cheater cheater00social at gmail.com
Sun Apr 4 02:13:21 CEST 2021


yeah if that's the case you can sometimes just put a jack in and out
like 20 times and it could be good. just don't use a good jack

On Sun, Apr 4, 2021 at 12:43 AM Jean-Pierre Desrochers
<jpdesroc at oricom.ca> wrote:
>
> Jean,
>
>
>
> Here is the link for the good schematic and PCB layout:
>
> https://www.audioservicemanuals.com/p/peavey/peavey-kb/1335254-peavey-kb-100-12-89-schematic
>
> There are KB100 schematics showing on Google which actually are
> KBA100 schematics so not the one you need..
>
>
>
> I've been working on music instruments for many years..
>
> Here is a list of what you could do:
>
> Since it's powering up that means there are no shorts caused by shorted power transistors (Q101, Q105).
>
> Many times this ‘no sound problem’ on both the output speaker and headphone jack
>
> Is caused by jacks connected between the preamp section
> and the power amp section.
>
> These jacks have normally closed contacts that carry
> the signal through them when there are no plug connected in them.
> These contacts get dirty when these jacks are not used
> and cut the signal completely from reaching the final output stage..
>
> In  the case of the KB100 there are 2 jacks to check for:
>
> Front Pre-EQ patch jack
>
> Rear PWR AMP IN jack
>
> You can first feed the PWR AMP IN jack with some audio source
> and check if there is sound at the speaker. If so the internal contact is dirty and
> need to be cleaned.
> Do the same test on the EQ patch jack at the front.
>
>
>
> JP
>
>
>
>
>
> De : Synth-diy [mailto:synth-diy-bounces at synth-diy.org] De la part de Jean Bender via Synth-diy
> Envoyé : 3 avril 2021 14:52
> À : SDIY List
> Objet : [sdiy] Need help about how to service an amp
>
>
>
> Hi list !
>
>
>
> A friend gave me a Peavey KB100, not working, i mean it's powering up but no sound, even in the headphone output.
>
>
>
> Well, i realise in don't know from where to start when you have to service an amp. Is there a specific way to work once you have check all the basics (fuses, power supply, and visual check up around caps and chips) ?
>
>
>
> Do i need, for example to simulate the speaker impedance if i disconnect it from the board for troubleshooting the circuit ?
>
>
>
> So this thread is more to have tips, readings about this kind of thing, since i don't feel really comfortable working on it from scratch knowledge !
>
>
>
> Thanks per advance
>
> J.
>
> --
>
> Jean Bender
>
> Hak Lofi Record
>
>
>
>
>
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