Vox mini 3 amp

[bharley]

Re: Vox mini 3 amp

Hi Midibob
I saw this thread, and thought you might have a suggestion for me. I have a Mini3 2G, which I love for portable practice. In my music room my main setup is a deluxe reverb with a Digitech pedal for distortion and effects. But I have a gig coming up with really limited space; last year in this venue, I used my Mini3 and plugged the headphone out into the line input of an amp that was sitting around, and mostly it worked well. I love the simple dial-in of effects, mostly I use a couple of the amp models, flanger, chorus, and reverb. And I have not found any simple, compact multi-function stompbox with similar functions.

So this year I was thinking to get another mini-3, and take it out of the cabinet - leave the speaker behind and mount it in a much smaller box - and make a tiny multi-effects table-top controller out of it. I'd bring my blues junior and have a much better setup in less space.

So my question is, rather than use the headphone out (which seems like too high a level, and wrong impedance) into the guitar amp input, is there somewhere on the mini3 board where you'd suggest getting a lower-level signal that is post-effects? Maybe it doesn't really exist, if all the effects are done at line level anyway - I know I can always turn the gain down on the guitar amp, and keep the mini3 volume down as well. Or maybe there's a way to add a resistive circuit from the headphone out, to limit the output level and match the impedance? Just a 100k pot perhaps?

I would probably set it up with its own 1/4" phone jack to use a standard patch cord to the guitar amp. And if i'm not using it directly, I'd probably need to leave the headphone jack filled to disconnect the speaker properly and not damage the output channel (most power amps break if you run them with no load attached). In case I ever want to put it back in its original form.... So you seem like a good person to ask for recommendations on this, thanks in advance. (Anyone else with ideas welcome too!) Post or PM would be great!

[midibob]

Re: Vox mini 3 amp

PM sent.

[Studiomaster1]

Re: Vox mini 3 amp

Hi Midibob,

I've just joined this excellent forum because I have the same problem with a Vox mini 3. Headphone output fine but no main power amp output to speaker.

Thank you for all your work on this problem it helps so much not to be starting from scratch.

I don'd suppose you have any of the daughter boards still available do you?
If you do I would love to buy one from you to solve this problem.

I do have a lot of experience with electronics including smd work so I should be able to fit it without too much difficulty.

Please could you let me know if you have any and if so how I could buy one from you.

Kind regards

Brian Hillary

brian.hillary3@gmail.com

[midibob]

Re: Vox mini 3 amp

PM sent.

[steveh99]

Re: Vox mini 3 amp

Hi, I've just joined this the hope midibob can help, I've got a Vox mini 3 amp and its fault is the one mentioned several times in the thread- lights on, no sound from speaker. Are you still doing the kits? I'd be massively grateful if you were able to help!

best wishes

Steve

[midibob]

Re: Vox mini 3 amp

Glad to hear it all went well.

[BlueBert]

Re: Vox mini 3 amp

Yippee! Twenty Minutes work and my amp switched on as normal. Cant thankyou enough for the daughterboard and the instructions. You are a hero.

[midibob]

Re: Vox mini 3 amp

PM's sent to BlueBert and Larsc88.
Happy New Year.

Bob

[larsc888]

Re: Vox mini 3 amp

Hi Midibob, would like to know if you still had those daughterboards available since my Mini3 just died after my father in law sang karaoke through it. =)

[BlueBert]

Re: Vox mini 3 amp

Hi there
New to this forum joined through a search for vox mini3 speaker not working but headphone fine. Happened just after I put a looper pedal thru the mic input. Just Died. Anyway Im hoping Midibob still has one of your daughterboards available, as for sure I'm not up to soldering these microscopic parts.

[midibob]

Re: Vox mini 3 amp

Hi, I need to make up a new batch which will take a couple of days. I'll PM you in the meantime.

Bob

[Slaminsammy]

Re: Vox mini 3 amp

Hey midibob, I too need one of them repair boards for my Vox MINI 3. Are they still available?

[gmoshe27]

Re: Vox mini 3 amp

I found myself in the same situation, my headphone jack works, but the speaker doesn't engage when I disconnect the headphones. I found the issue to be similar to what Tonedef identified, which is that the headphone jack has a weak internal connection to ground. I took the casing of, played with the jack a bit and got it to a point where the speaker and the headphones work... kind of. Now my issue is that the headphone jack is a bit loose internally so the headphone connection isn't very solid. I have to play with it to get audio in both left and right channels.

I dug around digikey looking for a replacement part, but I didn't see anything that would work. Does anyone know what this part might be?

[jondoe]

Re: Vox mini 3 amp

I need to borrow something to measure the original chips dimensions, my old wooden ruler won't cut it!

I've singled out three other alternative chips that have the same pin out, the last one is also a Ti, didn't see that one when I searched before

SA58672
IS31AP2010B
LM4670 (LM4670ITLX/NOPB)

[midibob]

Re: Vox mini 3 amp

Have a look at the thread I found with my original question to TI. It makes you wonder if anyone knows to be honest.

https://e2e.ti.com/support/audio/f/6...identification

Glad you got it sorted though. I know it was a real pain when I attempted it.

[jondoe]

Re: Vox mini 3 amp

Well it looks like the TPA2039 is noticeably smaller than the original chip in all dimensions, so the one fitted to the Vox Mini 3 G1 is perhaps not a Ti IC? The BGA foot print is therefore a little smaller, however, it is just about OK to use.

I heated the back side of the chip location for a short period then flipped it over and placed the new chip on the tinned pads, with a little hot air it nudged itself into place and all was good on the first pass.

Happy to report the amp is working fine, I didn't hear it working originally so I can't comment on how loud it is other than it sounds about right for a 3 watt practice amp.

It would be nice to know what the actual IC as I suspect a better fitting IC would make the job more likely to work first time.

Thanks again for this thread

[jondoe]

Re: Vox mini 3 amp

If I prep the board, use plenty of flux and let the balls on the supplied chip find their location it should be OK, it's only 9 balls after all, it could be worse! I have a fairly high power magnifying glass so I can at least look at the outside edge and I can also check for shorts before powering up.

I have ten tries to get it right

[midibob]

Re: Vox mini 3 amp

Without a microscope it's impossible to tell if all the balls have melted to the pads and even then it's tricky especially the middle one.

[jondoe]

Re: Vox mini 3 amp

If it's just the one you want go to the Texas site and ask for a sample. I think they gave me three and they came back very quick. Getting the new ones on is a challenge unless you have the right gear which I suspect you may have.
I wish you luck with that.

I did start to go through the sample process but they wanted me to fill in some extra forms and explain what my business was, why I wanted them, etc. I gave up at that point

Mouser/Digikey worked out very expensive with shipping, thankfully I found a seller on Aliexpress so I've bought 10 at half the price of 3! I went for the 3.2Watt version in the end.

There's a square section of solder under the chip on the reverse side of the board (for heat sinking I guess?), I pre-heated it with a soldering iron for a moment then flipped it over and used my cheap hot air station to finish it off, that seemed to work well and all the pads survived, nothing was scorched or melted.

Fitting might be a bit harder, times like this I wish I had a scope. I'll probably add some more solder to the pad underneath to give it a bit more meat to soak heat into during operation.

Thanks for sharing your experience midibob, I'm grateful

[midibob]

Re: Vox mini 3 amp

If it's just the one you want go to the Texas site and ask for a sample. I think they gave me three and they came back very quick. Getting the new ones on is a challenge unless you have the right gear which I suspect you may have.
I wish you luck with that.