Vox mini 3 amp

[rholden49]

Re: Vox mini 3 amp

Hi Russell,

I've not come across that before. My only thoughts would be to try and trace the inputs through to where they join up with the input from the aux connector and work backwards from there.

I can't remember if the aux volume is controlled by the master volume or not?

Bob

ok thanks will try to go backwards. the aux in has no volume control at all on the vox 3. you are expected to control it from the device you plug in. at least thats how it works on this one which of course is broken in some way.
could you pass on any flashes of inspiration you may have as you go thru your daily life -thanks russell holden

[Hayabusa]

Re: Vox mini 3 amp

Hi Midibob
I too am a victim of the same problem, any chance of getting one of your daughter boards sent to Sydney 2162? About to start learning guitar and this little amp would be perfect for me.

Cheers simon
Simell at optusnet.com.au

[midibob]

Re: Vox mini 3 amp

PM sent.

[HVACGUY01]

Re: Vox mini 3 amp

Bob,
Do you have any of those daughter boards available for the VOX MINI 3 guitar amplifier ? I love that little amp and would be sincerely grateful if it was up and running again. I had sent you a p.m. yesterday about it as well.
Thank you for your time.

Jay

[midibob]

Re: Vox mini 3 amp

PM sent

[peter.uttley]

Re: Vox mini 3 amp

I'm sure you'll find many tutorials on Youtube. I can't recommend any specific ones as I've never needed to look.
I've sent you a PM with my mail address. If you reply I'll send you the instruction sheet so you can see what's involved.

Midibob

Hi there ... I would be interested in a Daughter board for the vox mini 3 my email is peter.uttley@virginmedia.com what would be the cost including postage to Brittany France






regards Peter

[midibob]

Re: Vox mini 3 amp

Mail sent.

[tonedeaf]

Re: Vox mini 3 amp

Thanks to the contributors on this thread. Your suggestions have helped me out.

Just wanted to add my experience on these amps as the solution was different even with the same symptoms.

I just bought a job lot of amps including two mini 3's listed with the headphones OK but no speaker problem. I had anticipated finding the problem to be the power amps same as everyone else but when tested, I found resistance of 130K on both cables and on both amps so I looked elsewhere.
The headphone socket must have some means of cutting the speaker signal so I used electrical cleaner and worked it in and out using a headphone jack.
Bingo! One worked but the other not.
Took out the board and noticed that there seemed to be solder shorting two of the pins on the headphone socket. De-soldered and re-soldered. Now working.
These amps came to me direct from Korg as I think customer returns.

[midibob]

Re: Vox mini 3 amp

That was lucky and it just goes to show that it's not always the chips that fail.
The headphone jack is connected to the input of the PA not the output as you would normally expect, so it always pays to check the resistance of the speaker output wires to confirm whether the PA chip has blown.

Thanks for contributing as it might help someone else out.

[tonedeaf]

Re: Vox mini 3 amp

Okay, final update, honest.

I thought I'd fixed the problem but it came back, here's the permanent solution.
The key to understanding was knowing that the h/phone output is before the power amp stage. Thanks to MidiBob and others.

Symptom - sound can be heard via the headphone socket but nothing from the speaker.

Tests

1. Speaker tests ok using another source (speaker disconnected from mini 3 & hot wired onto another device).
2. With speaker disconnected & all power removed, measure resistance of each speaker cable to ground. Showed around 130K on both cables. This indicates that the power amp is still ok. If it had blown then you would expect to get very different values with one of them being very low.

Solution
I had some success spraying cleaner into the h/phone socket and working it in with a jack. However, after a few hours and re-testing, the problem returned. I guessed that the issue was mechanical inside the socket with some of the tangs/plates not contacting properly. I suspect that the cleaner was forming a temporary bridge and closing the circuit but stopped being as effective when fully dried out.
To fully correct this;
1. remove all the knobs and the 10mm nuts securing the pots to the faceplate.
2. unscrew rear panel and push to one side.
3. unscrew control panel and lift out. Separate faceplate from underlying board by unscrewing the 3 screws on the underside.
4. Carefully use a fine flat blade screwdriver to release the FOUR plastic tangs on the h/phone socket cover from it's base. If they keep springing back in, hold open and slip a piece of paper underneath to keep them open. If you are a bit heavy handed and push the clips out too far, don't worry about it as they'll probably go back in but if not the entire cover is held down by the faceplate.
5. Use pliers to ease the cover up and off. With the cover removed you will find that the tallest upright connector is making only a weak push against the shorter tang next to it. It's the lack of a strong push that means the connection is not re-made when removing a jack from the socket. Test that this is the case by firing up the amp and pushing these together - you should hear a noise but make certain that your volume controls are not set to zero.
6. bend the connectors slightly to form a more solid connection. Re-assemble everything.

Sorted!

[dotkokott]

Re: Vox mini 3 amp

midibob are you still selling/shipping your daughter boards? Awesome to hear you created a solution.

In case there is still one available, would love to hear from you!

I live in Germany, btw.

[midibob]

Re: Vox mini 3 amp

PM sent.

[JayC]

Re: Vox mini 3 amp

minibob, I'm in the US and looking at the cost of shipping/purchase of one of your daughter boards for the mini3. I have the equipment to do SMD other than a preheater so a through-hole solder would be no sweat.

Thanks in advance,
-Jay

[midibob]

Re: Vox mini 3 amp

PM sent.

[plucky_00_]

Re: Vox mini 3 amp

Hi midibob

I'm from Chile, what would be the price + shipping for the daughter board?. Do I need any special tool other than soldering iron for doing the job?

thanks
Patrick

[midibob]

Re: Vox mini 3 amp

Hi Patrick,
PM sent.

[jondoe]

Re: Vox mini 3 amp

midibob, can I be cheeky and ask the part number used for the IC? I see mouser has two;

TPA2039D1YFFR

and

TPA2039D1YFFT

I think the only difference is THD.

Thanks.

J

[midibob]

Re: Vox mini 3 amp

Hi, I can't remember now what samples I originally got back from Texas. I thought it was the TPA2034 but don't recall what letters there were after it? As I never used it in the end I never ordered any.

[jondoe]

Re: Vox mini 3 amp

I think the TPA2034 is rated at 2.75w, the TPA2039 is 3.2w, I suppose the TPA2034 is a better fit power consumption wise so I should go for that.

I've got the old one off the board cleanly, now to find a replacement at reasonable cost!

[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.