The Multi Amp aka Dynalo Mk2

[HemiSam]

I've been thinking about some logical setup to help my aging eyes with the finer work.  Was thinking perhaps a jewelers type setup or something but have not investigated anything seriously yet.  

HS

[congo5]

yes looking too, mostly use harbor freight visor but want better

seems that you have to spend hundreds to get past the junk.

on a side note:

if you solder the 680R parallel with the lettering ....It just does not work!

gotta love hot air

[Pars]

This is what I have used for several years. I think the DA10 is the insert that I have. Focal distance is a bit close at 4".

http://www.doneganoptical.com/products/optivisor

[kevin gilmore]

That is what I use.

but planning on a microscope with a had video camera

not sure how well that is going to work

[Arthrimus]

On 1/31/2017 at 11:05 AM, Skooby said:

Thanks Kerry, for the clarification and providing us the board design.

Any advice on the best way to solder the TI 7A4700?  That thing's tiny, I ruined one board doing this already.  I'm thinking melt some solder first on the pins and then put the chip on.  I got a rework air gun, not sure it's the best way though. 

I haven't started building my board yet, but the pitch on the regulator appears to be about the same as tsop40 and some qfp packages I'm used to soldering/desoldering. I'd recommend positioning the regulator on the board and holding it in place with tweezers. Flood the area with no clean flux, then with a fine chisel tip try to tack down one corner of the regulator, then move to the opposite corner, adjust the positioning if necessary then tack that corner down. Reflux the chip and load your tip with solder then drag it accross the remaining sides of the chip until you have all contacts soldered. If you have any bridges, then reflux the chip, clean your iron and drag it across any side of the chip that has bridges. Repeat as necessary until you've cleared all shorts, reapplying flux as needed. 

I personally only like to use hot air for removing large packages and reworking BGA packages. I really don't think it's any good for soldering projects like these. A reflow oven would be much better for this, but my personal preference is always hand soldering if possible.

EDIT: Now that I look at the regulator a little better, hot air might actually be the way to go. I didn't realize that there was actually a pad on the underside of the chip. Solder paste and hot air is probably the best bet for this one.

8 hours ago, HemiSam said:

Good stuff, congo.  I like the look of the Hakko micro handpiece / pencil.  Might have to spoil myself with one of those.

HS

[whisper] Ditch Hakko... buy Metcal...[/whisper]

Edited February 6, 2017 by Arthrimus

[Kerry]

You really need to solder the large center pad or you could have thermal issues.  I don't think there's a way to do that with an iron.

Edited February 6, 2017 by Kerry

[HemiSam]

Something tells me that is going to leave a mark, Arthrimus....on my wallet.

Cheers for the recommendation.

HS

[Arthrimus]

No doubt, but it's the apex of soldering. You can actually pick up retired factory production line Metcal systems for dirt cheap on ebay, that's how I got my soldering station and deslodering gun. 

[Torpedo]

7 hours ago, kevin gilmore said:

That is what I use.

but planning on a microscope with a had video camera

not sure how well that is going to work

Surgical microscopes are awesome. A bit expensive though 

[kevin gilmore]

actually i have a surgical microscope i use at work. problem is its old enough that it has no center tube for the camera

[wink]

2 minutes ago, kevin gilmore said:

actually i have a surgical microscope i use at work. problem is its old enough that it has superannuation benefits

FTFY

[Torpedo]

1 hour ago, kevin gilmore said:

actually i have a surgical microscope i use at work. problem is its old enough that it has no center tube for the camera

Wouldn't it accept an intermediate piece between the oculars mount and the objective/zoom body to act as a "side-path" to a camera? Some of our oldest Zeiss microscopes could be by-passed in such way. Depending on the brand and quality it'd be cheaper to get a new one, there are several good-enough quality brands including a camera and even flat monitor for a few thousands.

[kevin gilmore]

i have a nikon microscope that is setup that way. For some reason i have a hard time using it due to diameter restricted optics. And i'm not going to spend $35k for it.

[joehpj]

Chinese made surgical microscope are cheaper ($25K) and quality are average. 

Surgical loupes are better for this job I believe. Zeiss and Pentax make nice loupes at reasonable prices. ($2K)

Edited February 6, 2017 by joehpj

[luvdunhill]

You really need to solder the large center pad or you could have thermal issues.  I don't think there's a way to do that with an iron.

If you have plated through vias it's possible to use solder paste then heat from the bottom with a iron. It's not the best option though.

[Torpedo]

4 hours ago, kevin gilmore said:

i have a nikon microscope that is setup that way. For some reason i have a hard time using it due to diameter restricted optics. And i'm not going to spend $35k for it.

No need to spend that much, you have much much cheaper alternatives like this. They're not the ultimate optical quality you need to perform an estapedotomy, but they offer great depth of field, little chromatic aberration and sharper image than any magnifying glasses. If you want much better quality, they've got this Leica model (we have one of those at our clinics) which I'm sure is not that expensive compared to 35 or 25K bucks. On the cheap side of things, yet with very good quality (we have one of these too) the Optomic is rather decent, I would operate an ear with it, so probably I could do a few things else. You'd need to ask them how to mount a video camera on it though.

[Kerry]

3 hours ago, luvdunhill said:

If you have plated through vias it's possible to use solder paste then heat from the bottom with a iron. It's not the best option though.

 

They do have plated through vias.  I've found that a hot air gun does the trick very nicely.

[Skooby]

Finally gave up on getting the QFN regulators on the board (even with Amtech flux).  Getting shorts probably due too much solder.  Ordered these instead:

http://www.ebay.com/itm/TPS7A4700-Ultralow-noise-4-VRMS-low-dropout-linear-regulators-3-5PIN-1-4V-20-5V-/252348749037

Any chance that we can have gerber files for these boards (positive and negative regulators) for the group buy?  I would like to practice some more but not on the dynalo mini board and ruin more.  

 

[johnwmclean]

whoops..

Edited February 13, 2017 by johnwmclean

[johnwmclean]

On 24/12/2016 at 5:24 PM, nopants said:

Using the AMB stuff we can just leave the underside of the PSU section unpopulated

 

On 25/12/2016 at 1:19 AM, Kerry said:

Looks about right.

Can I get clarification, I’m using AMBs off-board regs (set to 20v), what other parts (obviously beside the regs themselves) are to left unpopulated?

[JoaMat]

4 hours ago, johnwmclean said:

Can I get clarification, I’m using AMBs off-board regs (set to 20v), what other parts (obviously beside the regs themselves) are to left unpopulated?

Positive:  10uF, 1uF, 4x10uF and 5x0ohm resistors for voltage setting.
Negative: 10uF, 1uF, 4x10uF and 89ohms, AOT, 1M43, 10nF.

[Kerry]

^ this

[johnwmclean]

Thankyou Joamat and Kerry that's great info.

In regards to biasing the mini dynalo I assume it mirrors same procedure as the through hole version. I noticed Kerry you had soldered the servos to that first board (V1.3 back in the thread) prior to bringing it up, from what I understood the servos need to be removed when biasing, hence my confusion. 

[congo5]

8 hours ago, johnwmclean said:

servos need to be removed

or put the 0 ohms resistors on after, they connect pin 6 to the center of the 49.9k's

I took them off for biasing

Edited February 15, 2017 by congo5

[johnwmclean]

Thanks congo5.