Vox mini 3 amp

[Broadsword]

Hello midibob,

I was hoping I'd hear something from you (as you're the expert with these), so thank you very much for getting back to me, and for the information! That's a shame about the diagrams. I'm gonna do some testing over the weekend, I shall report back.

Cheers,
Broadsword

[midibob]

I've not seen the later version before and it's totally different. The audio o/p chip is now a TPA3130 (IC3) which if you believe the Data sheet is more or less bombproof!
It could be that the regulator has failed? IC8 is one, 50BC0W and there may be another where the PSU connects but I can't read the number?
I'm pretty sure there won't be any diagrams on the web of this model (as the earlier version) so you will probably have to trace the circuit out. You could confirm whether any any power is getting to the audio chip.

[Broadsword]

Hello everyone,

I have a Vox Mini 3 G2 (second generation) guitar amp. It was used with the wrong power adapter and as a result, it no longer turns on.

Unfortunately, with these little amps there is no simple and easily changeable fuse. I've opened it up to take a look at the main board etc., and there doesn't appear to be any burn marks etc. Obviously, one or more components must have failed, as it will not turn back on.

I've tested for voltage, there is 12V DC present at the main board when the amp's 12V adapter is plugged in, I've also tested the power button (black button by the red LED), and this measured 10.6V DC.

This was one of the few forums where I could actually find some information regarding repairs to Vox Mini 3 guitar amps. I would really appreciate some help as to what the problem might be? I've attached some photos.

Best regards,

Broadsword

[midibob]

Re: Vox mini 3 amp

You're welcome, glad you managed to get it sorted.

[vidji]

Re: Vox mini 3 amp

Hi midibob, the amp is running smooth again... I've made it myself a little bit easy and ordered a little PAM8403 amp board, which is also 3W and piggybacked it onto the circuit board using your input for connecting. This was very straightforward and easy to do.
Thanks again for all the information which made this possible.
Cheers, Yvan

[midibob]

Re: Vox mini 3 amp

I think it was just a .bmp file which any graphics package will open ie Paint or even Word.
Glad the info has been useful.

[Kingjerry]

Re: Vox mini 3 amp

I have the same blown output and have read and downloaded all diagrams etc
The Midibob schematic just shows up as a windows file that i have not been able to open...yet!
Of course im also just learning how to repair electronics and it will be a good challenge for me.
Thx so much for all the work you have put in over the years helping everyone with this blown output problem midibob!
Hopefully someone more knowlegeable than i will be able to pick up the ball and help me get this thing fixed!!
Thx again

[midibob]

Re: Vox mini 3 amp

Hi Adalberto,

All the info is in this thread. It's very simple as the design is basically the same as the IC spec sheet.

Good luck
Bob

[adalbruto]

Re: Vox mini 3 amp

Hi midibob! What a great job! My name is Adalberto, I'm from Argentina and I have the same problem with this amp!!! I'd like to know if there's any chance to get your daughterboard schematic and/or pcb to replicate it, just one time, just for my brother's amp.

I forgot to attach my email address since I'm fresh new on this forum
adalbertoledesma@gmail.com, any information will help. Thanks!

[adalbruto]

Re: Vox mini 3 amp

Hi midibob! What a great job! My name is Adalberto, I'm from Argentina and I have the same problem with this amp!!! I'd like to know if there's any chance to get your daughterboard schematic and/or pcb to replicate it, just one time, just for my brother's amp.

[vidji]

Re: Vox mini 3 amp

No indeed, I will not use SMD as I havent got the tools for it nor the capability of making PCB's, and as it is just a one of to repair our VOX amp. I think a breadboard wil do the trick, it will be somewhat larger but there is enough space.
I've found back in the thread you used 0,85ohm 10uf caps (SMD), the ones I've got on the order list is a 0,68ohm 10uF cap so it will be ok I guess...
Thanks a lot for all the documentation on this topic.
Cheers.
Yvan

[midibob]

Re: Vox mini 3 amp

No, they all went I'm afraid.

The low ESR cap was necessary otherwise there was internal feedback. I did document this way back in the thread. The type you need is shown in the installation instructions. I can't remember the exact one off the top of my head but if you're doing it on breadboard you won't be using SMD components anyway.

[vidji]

Re: Vox mini 3 amp

Hi Bob, was just hoping you might had one still lying around ;-) I going to try one myself thanks to your information post, but as I do not have the possibility to create PCB's I will try to build it on a breadboard. Should not be that complex I think, but not as compact as yours.
What is the reason you went for a low ESR and how low should it be? I'll search Digi-Key for components this afternoon I think as it is a rainy day...
Have a nice day,
Yvan

[midibob]

Re: Vox mini 3 amp

Hi Yvan, as the post above says I won't be making anymore.

Happy Easter to you too.
Bob

[vidji]

Re: Vox mini 3 amp

Hi midibob, I'm wondering iff you still have one off your daughterboards, I've read you stopped producing, but just checking if perhaps you've made a new batch? I think you've made already a lot off people happy with it, so I was just hoping...
Have a nice Easter Sunday
Yvan

[midibob]

Re: Vox mini 3 amp

Hi, I'm afraid I don't make them anymore. I posted all the build details a little way back in this thread so people could make their own.

Cheers
Bob

[Tomasrueda]

Re: Vox mini 3 amp

Hi Midibob, I need to order one of your daughterbaords. Are they still available?
can't see pm, can u send me an email
tomasmauriciorueda@gmail.com

[midibob]

Re: Vox mini 3 amp

Have you checked the resistor is ok? The only other thing would be the diodes.

[Muhamedqira1]

Re: Vox mini 3 amp

Thank you for the reply.
I have attached top and bottom pics of the small board. Also attached a pic of the main board as well.
Thanks again

[midibob]

Re: Vox mini 3 amp

Hi, not looked at these for a long time so I can't remember what was on the small board? I'm thinking there was just a diode to prevent reverse voltage being applied but I don't have a unit easily accesible to check. Post a pic then it should be easy to see what might be wrong.