Need help to revive Rotovibe!!!

[bjornf2]

Hello
I grabbed the wrong power supply and put 9v AC into my Rotovibe. Ordinarily I don't believe this should cause a problem with most devices, but something happened to my Rotovibe. No lights, no effects, no sound, no smoke, no visible problems.

Does anyone have schematic or link to one for the ch63052 rev d ??
Any typical component to replace for this type of problem? There is probably just no power getting in. I am handy with the solder iron.

Thanks
bjornf2

[Bloodbath]

Here is a thread with the only Rotovibe schematic that I know to exist.

http://music-electronics-forum.com/t10157/

There is a diode and what looks like to be a chip at the power supply input. Check there first.

[bjornf2]

Temp Fixed-It

I managed to temp fix my Rotovibe!
First, the only available schematic is not the same as my circuit at all, unfortunately.
The power, battery or external plug, feed into a MPSA18 which is an NPN transistor. The 9v feeds the collector with a 2.1K ohm resistor between collector and base. Very little power was getting to the emiter, so I simply pulled the transistor and shorted accross. Works.
Now I just have to buy a new transistor.
Bjornf2

[oreolong]

Thanks it worked for me

I bought a rotovibe some 6 or 7 years ago always bought cheap universal adjustablle dc chargers from walmart the kind with 3 tips on one plug and i learned my lesson not long after when i reversed the polarity i kept the pedal since then i dunlop emailed saying they would charge 65 bucks to fix it but i followed the advice here and desoldered the transistor and shorted the base collector and emitter points and it works!!!!!!!! after all these years im quite proud of myself a long lost pedal is back in business !!!!!!

[Phostenix]

Now, make us proud & replace that bad transistor so that the pedal is protected against the next oops and all you have to fix is that transistor again.

[oreolong]

oh yeh

I found a replacement matching transistor in a bunch of components i had and replaced it thanks again guys i am currently learning about electronics radio and audio as a hobby and would like some reccomendations on where to get schematics for simple guitar pedals

[Phostenix]

I would suggest going through R.G.'s website:
New Page 1

[Phostenix]

Check out the DIYstompboxes.com froum, too:
DIYstompboxes.com - Index

[bob1]

rotovibe fix

Fixed a dead JD-4s Rotovibe today.
by replacing the MPS18 transistor in the Q7 position.
it lights up and works great.

I have another one JD-4s but it has the REV D pcb board.
did the same fix as above , but it is not powering up*
any suggestions?
Please feel free...
Thanks,
B

[Bassbuddy]

So there are quite a few of these pedals that suffer the same defect.
If this happens so often isn't it wise to build a protection diode in the power supply connection?

[Steve Conner]

The transistor is the protection. It sacrifices itself to save the rest of the pedal, and it's a 10 cent part that takes a few minutes to replace.

[bob1]

Which transistor in the rotovibes rev d

Steve
is there a different transistor I should be looking at
In the rev d version of the rotovibe?
I have replaced the mpa18 but nothing??
Any ideas??

[Bassbuddy]

The diode would also save the transistor. And you don't have even a few minutes and the right tools just before a gig starts, nor the transistor at hand. And not everyone has the skills to replace the transistor. When you're repairing anyway, why not put in a diode?

Bb

[Steve Conner]

If it's a series diode, it takes 0.7 volt off the supply voltage, which the designer might not want. In particular, if the diode is also in circuit when the unit is running off the battery, then battery life will appear to be shorter.

A Schottky would solve this, but might break the budget for a mass-produced unit, where they care about the difference between a 5 cent diode and a 50 cent one.

If it's a shunt diode, it might burn out your power supply or fail short.

[Enzo]

WHat is even cheaper than a diode is paying attention to what we plug into the power jack. When was the last time you shook salt on your breakfast cereal instead of sugar?