2445b shelf vents for bottom air intakes - should I?


Keith
 

Hi Leo and others,

Thanks for chiming in;

re: U800, Yes, definitely had that discussion in my head. I've heard it both ways on the U800 chip - sink and no sink. I know they get fairly warm, or at least mine does, because I checked it several years ago. At the time it seemed like a good candidate for a little heat sink, but I'm only guessing. I reckon I should relax and trust Tek on the airflow design.

re: "holes could make it worse". Yeah, I have some experience loading racks and racks of hot gear in a variety of settings and so I'm quite familiar with what you describe. (i.e. "chimney effect") Although I didn't build such a problem into my setup, I think I may just let the 2445b cooling ride as is for now while I work on replacing the nasty burned up RIFA caps and cleaning up the mess I know it left inside. That's a "for sure" problem.

In any case, after today I have a lot more things to fix on my bench now. The 2445b stink bomb, and replacing that oil-filled cap that gave up the ghost in my Sola constant voltage transformer today. Then about ten other real work projects that need my attention.

Oh well, that's why I have a fancy new electronics bench! :-)

Keith


satbeginner
 

Depending on the devices placed below the shelf holding the 2445, it even might be worse to have holes.

The holes in the bottom of the scope are there to let in air at ambient temperature, so if there is another warm device below it, the 2445 might suck in warmer air than expected, so the holes in the shelf could have an adverse effect.

That's why in telecom technology rack mount devices must be designed to have front to back cooling only, and not bottom upward cooling, to avoid one big chimney.

Just my 2 cents,

Leo


Michael W. Lynch
 

RIFA Caps

--
Michael Lynch
Dardanelle, AR


Tom Gardner
 

When my delayed action smoke generator fired, it destroyed a series
resistor, a 1cm diameter patch of prepreg, and deposited pots of
carbon on the PCB and the exhaust fan.

At the very least you should inspect the area to see if you need to
remove a carbon deposit. Replacing all the RIFAs and the Al
electrolytic isn't difficult, but replace one at a time since there is
a discrepancy on some 24x5x.

On 14/07/2021, Keith <coolblueglow@gmail.com> wrote:
Thanks Jose,

Yes, that's the one I was worrying about. I'm going to cut the holes and add
a small fan too.

Curiously, I just put the 2445b up on the finished shelf and fired it up.
(no holes yet)

A few minutes after I fired it up, she made a terrible sound and magic smoke
came out.

I believe it was simply the Line RF filter module failing, which I've heard
others describe here on the forum. Apparently, it gives this rather
magnificent and stinky display of failure - and the scope keeps on working,
though without (I presume) RF filtering on the AC line in.

Just a good reminder that these devices are not getting any younger, and
neither am I!

Cheers

Keith
coolblueglow






Alex
 

As long as the scope has its 4 bottom legs intact and the bottom of the scope is separated by that amount from the shelf I'd say its enough. I use my 2465B sitting on top of my 2247A and the exhaust air from the 2465B does not seem to be restricted in the least. Its not like you are going to have a huge amount of airflow at those spots anyhow. I would think the design of those four bottom legs took into account that the scope could be ran while sitting flat on them on a solid surface. I am usually at 27-29 deg C ambient, unless I run the AC, but your mileage may vary.

Furthermore very knowledgeable persons extremely familiar with Tek designs have mentioned in this forum and others many many times that U800 as it is factory mounted is NOT heat sensitive as long as you have a normal airflow inside the scope, and certainly no huge dust accumulation. That is the reason why Tek never installed the planned heatsink after they ran some operational tests and found out it was not needed. I for one just left U800 alone and it works just fine.


Keith
 

Thanks Jose,

Yes, that's the one I was worrying about. I'm going to cut the holes and add a small fan too.

Curiously, I just put the 2445b up on the finished shelf and fired it up. (no holes yet)

A few minutes after I fired it up, she made a terrible sound and magic smoke came out.

I believe it was simply the Line RF filter module failing, which I've heard others describe here on the forum. Apparently, it gives this rather magnificent and stinky display of failure - and the scope keeps on working, though without (I presume) RF filtering on the AC line in.

Just a good reminder that these devices are not getting any younger, and neither am I!

Cheers

Keith
coolblueglow


Jose Luu
 

Hi Keith

The failure prone U800 IC is underneath, I remember that its failure is heat related.
Make sure it is well taken care of.
I did put a small 20mm fan inside the case to blow some air on it.

Best
José


Keith
 

Hi guys and gals,

So, laying out a new shelf for my 2445b (and my 465b) on my revised electronics bench. For my scopes I have gone with a tilted shelf with 18 degrees tilt, because that's what my big brother did. (Thanks Mike! :-) While moving my 2445b around, I was reminded that the 2445b has air intake holes on the bottom side. I did some searching of past threads here about those holes. From searching these posts, and from common sense, I understand the bottom vents should not be blocked by sitting the bottom of the unit "flat down" on the shelf surface.

So, got that...don't block bottom vents. However, that got me to wondering...should I go one step further and open up more generous vent openings on my shelf? I mean several circular holes aligned with the scope bottom vent pattern - holes that would service the unit with relatively unrestricted airflow up through the bottom.

Normally, I wouldn't mind doing the modest amount of work required to cut four or five holes in my shelf...but these days I'm not looking for extra work. as the COVid disability aftermath makes every little cutting task an adventure. However, I perceive from reading various posts and comments that the cooling in the 2445b is about at the limit for a single muffin fan.

Has anyone else taken this precaution? Am I worrying about nothing? I really like my 2445b and hate to see her run hot just because I was lazy. I appreciate the great advice here on this group, and thanks in advance.

Keith
coolblueglow