Shock Danger Inside DVMark Micro50 Head?

**lawson-stone** · 10-15-2019, 11:15 AM

My DVMark Micro50 head has a problem with the aux. input cutting in and out. I would like to look at it and see if maybe just re-flowing a solder joint would do the trick.

I took the cover off the amp and now I'm wondering if there is anything in here that, like tube amps, stores a lot of current and could shock me! I don't want to damage the amp, and I sure don't want to damage myself.

For those curious, here's the insides:

Shock Danger Inside DVMark Micro50 Head?-img_4672-jpg

Shock Danger Inside DVMark Micro50 Head?-img_4672-jpg

Shock Danger Inside DVMark Micro50 Head?-img_4670-jpg

**Franz 1997** · 10-15-2019, 11:40 AM

There may be stored current in the amp's capacitors, but it should dissipate after a couple of days, and is unlikely to be at high voltage in any event. That said, it can be very tricky to reflow joints on these 'surface mount component' boards, and make sure you don't use a high wattage soldering iron; a 12w iron should do it . Won't it void the warranty though?

Anyway, it should be easy enough to track the aux socket to its mounting board, provide the connections aren't covered in that white gunk. Perhaps try some switch cleaner first, just to eliminate dirty contacts

**Stringswinger** · 10-15-2019, 11:46 AM

I have heard that if you strum a chord while turning an amp off that the dangerous current dissipates from the Caps. Is this true or is it an old guitarists tale?

**jads57** · 10-15-2019, 11:54 AM

I've also heard that if you play "Giant Steps" you can chase your crowd out of the club,lol!

**sgosnell** · 10-15-2019, 12:39 PM

There are generally no dangerous caps in a solid state amp, because there is no need for them. Playing notes while turning off a tube amp has no effect on capacitors that I'm aware of.

**Franz 1997** · 10-15-2019, 12:40 PM

Not if you play I Get A Kick Out Of You..

**Stringswinger** · 10-15-2019, 12:48 PM

Don't give up your day jobs guys....

**Franz 1997** · 10-15-2019, 12:52 PM

Originally Posted by sgosnell

There are generally no dangerous caps in a solid state amp, because there is no need for them. Playing notes while turning off a tube amp has no effect on capacitors that I'm aware of.

Don't want to be pedantic, but not sure that's quite true..maybe not in a small amp like this, but if you short across a high current capacitor at even quite low voltage in a bigger amp, you'll survive but you might burn components, there can be a lot of energy there. If in doubt, there are some dumb experiments on the net with 9v batteries that illustrate this - unless you've shorted out a 12v car battery, in which case you'll know already.

But it won't be an issue here if the caps are allowed to drain for 24 h

I'd say anyone getting involved with amp DIY ought to invest in a multimeter; it can avoid a lot of potential trouble.

**jads57** · 10-15-2019, 01:26 PM

Actually playing in club's is getting rare period. At least if you are over 50!

**rpjazzguitar** · 10-15-2019, 04:24 PM

Originally Posted by lawson-stone

My DVMark Micro50 head has a problem with the aux. input cutting in and out. I would like to look at it and see if maybe just re-flowing a solder joint would do the trick.

If wiggling the jack reproduces the problem -- and you've been using that jack a lot--then a cracked solder joint is reasonably likely.

But, if you've rarely used the jack, have never stressed it, and wiggling doesn't change anything, then you may be dealing with something else. I've had an issue on my Little Jazz with Aux, perhaps having to do with 3 vs 4 conductor cables. If you're using 4 conductor, I'd try a 3 conductor and see if the problem is the same.

**lawson-stone** · 10-15-2019, 04:50 PM

Originally Posted by rpjazzguitar

If wiggling the jack reproduces the problem -- and you've been using that jack a lot--then a cracked solder joint is reasonably likely.

But, if you've rarely used the jack, have never stressed it, and wiggling doesn't change anything, then you may be dealing with something else. I've had an issue on my Little Jazz with Aux, perhaps having to do with 3 vs 4 conductor cables. If you're using 4 conductor, I'd try a 3 conductor and see if the problem is the same.

Thanks. I do think it's a solder issue. I use the aux input all the time. I don't get to play with others much, so using backing tracks, drum machines, iRealPro, etc. are my lifeline. I don't have a specific memory, but I have no doubt that jack has been jerked a time or two. I can push the plug to one side and it makes contact and works. It's almost like the internal spring contacts are pushing too hard.

I'll try a different kind of plug to see what happens. Would be nice if that solved the problem. I hope so, because it looks like the main board is really, really, hard to get out of there to look at the connectors. It would be nice if just a different plug would work.

Here's a clip of what's going on seen from the inside while I gently move the plug side to side on the outside:

**sgosnell** · 10-15-2019, 05:01 PM

I'm not sure that's a solder joint problem. I think the jack may need to be replaced. Those are mostly plastic, and rather flimsy, and won't take much pressure on the plug. Replacing the jack isn't going to be easy, if you can even find a new one. Good luck with the project.

**lawson-stone** · 10-15-2019, 05:11 PM

Originally Posted by sgosnell

I'm not sure that's a solder joint problem. I think the jack may need to be replaced. Those are mostly plastic, and rather flimsy, and won't take much pressure on the plug. Replacing the jack isn't going to be easy, if you can even find a new one. Good luck with the project.

I can feel my enthusiasm for DVMark products dropping sharply. I'm not about to try replacing the jack. So I will just use the amp with no aux input capability, which is disappointing since that's why I chose it over one of the Quilter mini-heads.

**rpjazzguitar** · 10-15-2019, 05:40 PM

I'd suggest emailing that video to DV Mark and asking them for help.

I can't see in the video whether you're rocking the solder joint when you do that. Or if, somehow, the tip of the male jack is separating from the section of the female which is supposed to touch it. If it's the latter, you might be able to bend it in to make better contact.

But, usually, when the jack is soldered into the board (which I hate, and I'm sorry to see, since I own the Little Jazz), the problem is that the solder joint gets cracked.

I've had this problem on a bunch of different devices over the years, most recently a JC55. The hard part is exposing the solder joint without breaking something by accident while you work on it.

**lawson-stone** · 10-15-2019, 05:46 PM

Originally Posted by rpjazzguitar

I'd suggest emailing that video to DV Mark and asking them for help.

I can't see in the video whether you're rocking the solder joint when you do that. Or if, somehow, the tip of the male jack is separating from the section of the female which is supposed to touch it. If it's the latter, you might be able to bend it in to make better contact.

But, usually, when the jack is soldered into the board (which I hate, and I'm sorry to see, since I own the Little Jazz), the problem is that the solder joint gets cracked.

I've had this problem on a bunch of different devices over the years, most recently a JC55. The hard part is exposing the solder joint without breaking something by accident while you work on it.

Thanks. I will ponder the options.

**rpjazzguitar** · 10-15-2019, 07:13 PM

Originally Posted by lawson-stone

Thanks. I will ponder the options.

Good luck with it. Please let us know what happens.

**DonEsteban** · 10-17-2019, 02:08 PM

Originally Posted by Stringswinger

I have heard that if you strum a chord while turning an amp off that the dangerous current dissipates from the Caps. Is this true or is it an old guitarists tale?

It's true, and valid for analog power amps (the DV Mark is one of those), any kind of signal does the trick...

**DonEsteban** · 10-17-2019, 02:15 PM

The 3.5 mini jack is far from being a reliable connector. Unfortunately it's the standard for headphones since the "Walkman" times.

Best would be to replace the socket, but DON'T try to solder on a SMD PCB* with a standard solder iron. You'll ruin it. You need a technician who has a hot air solder unit and experience using it.

It's not really hard to do but everything being so tiny, you need the right tool for the job, big magnifying glass or goggles too BTW... and a reeeeaaaallly calm hand...

Good luck!

*
SMD Surface Mounted device
PCB Printed Circuit Board