EEVblog #677 - Mailbag

[Rutger]

Ah, I want to get my Time Circuit clock working again for that, thanks for the reminder.

The BTTF clock sounds cool, but I don't think we will be able to read the digits from that distance an analog clock would better.

[womai]

I did a short search and it seems the 4260A is more like 1966 vintage, not from the 80s.

http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1966-09.pdf

IMHO that fits the overall design of the unit, just looks the way they did it in the 60s.

[EEVblog]

I did a short search and it seems the 4260A is more like 1966 vintage, not from the 80s.
http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1966-09.pdf
IMHO that fits the overall design of the unit, just looks the way they did it in the 60s.

Yeah, that feels right to me. I was going by the date in the manual. The 80's is when they must have archived it.

[arekm]

For Cree LEDs it's better to use copper plates (+ small isolation) instead of typical pcb and "power pegs".

Example, noctigons, sinkpads, maxtoch:

http://budgetlightforum.com/node/21547

http://budgetlightforum.com/node/33488

[TEMProducts]

Hello everyone! A few responses here...

Those power pegs are an interesting idea, I have never been a fan of multiple vias on a PCB installed underneath a chip in an attempt to promote heat flow. One thing though, with the power peg installed in the hole how do I solder the chip to the board/peg?

The pegs do not press fit. This would cause stress in the FR4. They slip-fit in a 2.5MM via.

Simply add a dab of flux, tack in place, allow to cool, and paste/reflow as usual. Action of capillarity holds the peg in place when the solder is molten.

I will try to make a video soon.

I really like the Power Pegs, I will definitely have them in mind the next time I am considering though hole TO220s or similar with a standing heat-sink.

As I understand you screw the heat-sink into the peg after everything has been soldered. But since they are tiny, how much momentum can you use on the screw? How do you prevent the screw from shaking loose (Loctite?)?

1.0 inch pounds of torque MAX. Use a clutch driver, or screw by hand.

http://tem-products.com/TCAP-4325-TR_Datasheet.pdf

As long as the screw is fully engaged in the Peg, the screw will actually break before the thread strips. 0-80 screws are delicate!

PowerPeg is made of copper, so friction is enough to hold the screw in place when fully tightened. I have never seen one come loose (and I have used them in every way imaginable  ). However loctite can be used, and does not effect the thermal interface.

Additional screws from PCB to heatsink are recommended to relieve mechanical stress from the thermal connector. PowerPeg is tough, but not invincible!

Those thermal pegs are quite nice, but one thing concerns me about them: Can the solder joints withstand the mechanical stress created by those pegs? Imagine you have 6-10 transistors on a board, all connected to the same heatsink, each with its own powerpeg. The heatsink will certainly have a different thermal expansion coefficient than FR4 - something will have to give.

The effects of thermal expansion of copper are negligible over short distances. For example: with a temperature change of 100C the length of the peg will change 0.000068 inches.

PowerPeg is precision machined to have matched thickness allowing many pegs to be attached to a single heatsink.

these Thermal Connectors are nice
but they are overpriced. $1.4 each ?? too expensive.

In the past two years we have made only one batch of 1200 pegs. The small quantity is the reason for the high price.

These pegs were (partially) hand made. They are precision  machined from copper alloy and plated with nickel, then 24 kt gold.

The next batch will be larger. I forsee the price under $0.80.

[JuiceKing]

The HP 4260A is an amazingly compact and convenient analog bridge. Direction lights tell you which way to crank and it automatically finds D and Q. I believe it was the first product from the YHP group and they poured a lot of passion into it. Check out the HP Journal article that came out when it was launched.


Sent from my iPad using Tapatalk HD

[simingx]

The HP 4260A is an amazingly compact and convenient analog bridge. Direction lights tell you which way to crank and it automatically finds D and Q. I believe it was the first product from the YHP group and they poured a lot of passion into it. Check out the HP Journal article that came out when it was launched.


Sent from my iPad using Tapatalk HD

Linked for your convenience

www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1966-09.pdf

The HP Journals make very good reading... the theory of operation is described in much detail, rather than nowadays where it is just given a cursory description, as everything is done in software

[TheWelly888]

Dave - I work on blood pressure monitors as part of my job in the local hospital so I would like to point out that they do not use "vacuum pumps" as you described it, they are actually compressors to inflate the cuff, the air is then released slowly ( at a set rate of about 5 - 10 mmHg per second ) through a slow release valve.

I'm looking forward to the teardowns of the gear.

[TEMProducts]

This video shows how PowerPeg thermal connectors integrate easily with typical PCB assembly techniques.

Simply tack the peg in place, stencil, and re-flow as usual. Capillary action holds the peg in place while the solder is molten.

[EvilGeniusSkis]

Dave, in the previous mailbag (or the one before) you received an cool EEVBlog clock. Can you please hang the clock on the opposite wall of the web cam (above the small desk), so the world can see the local time and live action.

Ah, I want to get my Time Circuit clock working again for that, thanks for the reminder.

I'm surprised no one has sent you the chips yet.

[TEMProducts]

Anyone who was interested in the The PowerPeg thermal management system, it is entered in the 2015 Hackaday contest.

Theres tons of interesting information on the project page.

https://hackaday.io/project/6874