Misc Electronic Questions

[KeepItSimpleStupid]

Is U17 an open collector inverter fed with a +12 V supply? Logic family/chip #?

Where does that signal go to the right (source of the FET)?

So far, I think it's just to ease the interfacing to a CMOS logic family, but can't tell yet.

This sure looks like a complicated beast and/or definitely high power.

The CV-8 supply here https://www.vesco-usa.com/ves-prints.html was my little baby. Quite a beast to fix. 70 Amp 3 phase input power. 15 kV at 1A shunt regulated (tube) output power.

It's basically a very high power electron beam. Think 30 KW of an electron beam sweeping in a raster pattern over a 1" diameter area or so. It was basically a work horse. Later, we had 3, with 2 operating.

We got a similar system (different manufacturer) at an auction that had three guns. All of the wires were either cut or removed when it was delivered. All they had to do was unplug a couple of "hidden connectors" and unbolt 3 High voltage cables. They chose to just cut them. It was just me to put humpty dumpty back together again. First problem - They put the wrong power source in. 100 A 3 phase 208 three wire instead of 4 wire.

 

[Billy Mayo]

Here is more pictures

 

[KeepItSimpleStupid]

Looks like it's used primarily because of the logic family used in the 4073 and the FET may actually be faster switching than a bipolar transistor.

PS: Pretty nice pics BTW.

 

[Billy Mayo]

so the FET just speeds up the switching from the output of the 555 timer?

The 555 Timer Is TTL , and the FET converts TTL to CMOS ? likes a level shifter?

 

[KeepItSimpleStupid]

More like the latter. A "to CMOS" level shifter. But the timer isn't really TTL, but close enough.

 

[Billy Mayo]

the timer isn't really TTL, but close enough.

Some 555 timers are transistor based , and other 555 timers are CMOS

 

[KeepItSimpleStupid]

True. TTL has specific characteristics like a 5 V supply. TTL compatible means logic levels are compatible usually, so we have 3.3 V CPU's that have 5 V tolerant inputs if current limited by a series resistor.

 

[Billy Mayo]

For adjusting very small trim pots most of my jobs use this Miniature Potentiometer-Trimmer Adjustment Tool : 8608
Click here:
https://www.amazon.com/Miniature-Po...d=1366000428&sr=8-1&keywords=pot+trimmer+tool

GC Electronics Miniature Potentiometer-Trimmer Adjustment Tool Specifications: Material: Nylon Shaft: 1/4" (6.3 mm) dia. 4-15/16" (12.5 cm) long Ends: .085" (2.2 mm) wide steel tip; .085" (2.2 mm) wide steel tip, recessed .040" Total Length

I'm guessing the flat head width is .085

I'm trying to find a Trimmer like this but that is "magnetic" tip

Do you know who makes one that has a magnetic flat head as small as .085 so I can trim pots?

Why I can't it magnetic flat head is because it keep slipping out of groove and I'm using those Blue color multi-turn trim pots which i hate

They are called Alignment Tools , but they are for TV trim pots, the problem is that the flat head is not magnetic
click here:
https://www.amazon.com/Waldom-Alignment-Tool-Kit-Anti-Static/dp/B000PDO3G4/ref=pd_sbs_indust_2

 

[KeepItSimpleStupid]

I used on that was essentially a regular screwdriver with a cup on the end. You could probably make one from a Whia screwdriver. Glue or silver solder a brass piece on the end.

**broken link removed**

I have some of the tools. I might be able to check how well they fit a trimmer if I can find a trimmer.

Once you made it, you could coat with Plasticoat.

 

[Billy Mayo]

a regular screwdriver with a cup on the end

What u mean by a cup? what can i use as a cup?

What wide size is those Trimmers? the flat head size is ? its very very small

Why use plasticoat?

I'm trying to make the trimmer screwdriver magnetic , some screwdrivers flat heads are magnetic

 

[Billy Mayo]

My manager said that the Logic FET in that circuit just sinks the voltage to Zero volts

The 555 timer gets triggered by a comparator op amp
The 555 timer sends out a pulse train for 20 seconds to the FET
The FET than sinks the voltage to zero volts

 

[Billy Mayo]

Do you think this milliohm meter is good enough?

I use to use a milliohm meter a lot at my last job to track down shorts, it would measure 0.00036 resistance, 0.0046

Do you think this one is as good as the big ones?

My Fluke 87 meter now, I use the REL button , I put my probes together and than Zero them out using the REL button
The problem is , is that I can' measure lower than 0.2 ohms on a Fluke 87 meter

I would need to by a milliohm meter to troubleshoot SHORTs better

 

[Billy Mayo]

Milliohm meter click here:
https://www.amazon.com/Vici-Vc480c-...qid=1366072588&sr=8-4&keywords=milliohm+meter

Vici Vc480c+ 3 1/2 Accuracy + 4 Wire Test Multimeter Digital Milli-ohm Meter

 

[KeepItSimpleStupid]

I had a one of these at home: https://www.digikey.com/product-detail/en/3299W-1-102LF/3299W-102LF-ND/1088136

and a Whia 20/2,0x50 screwdriver. The blade fits perfectly. It actually extends a tiny bit on each side.

So, get some tubing like this: **broken link removed** Line the entire length of the screwdriver 50mm. In reality, you would want the blade recessed.

Glue (Epoxy) the tubing in place. Then take a piece of heat shrink and cover the entire OD. You now have a nearly insulated trimpot screwdriver

The screw on the pot is brass. Unless you can defy physics, it won't magnetize.

Plasticoat or heat shrink fixes the Oops factor.

 

[Billy Mayo]

So If i spray plasticoat on the flat head part of this trigger it will stick better to the brass trim pot?
https://www.amazon.com/Miniature-Po...d=1366000428&sr=8-1&keywords=pot+trimmer+tool

 

[KeepItSimpleStupid]

Probably not. I'd bet the biggest issue is that the blade doesn't properly fit the trim pot head AND the plastic doesn't hold up.

The OOps factor is if you drop an uninsilated tool, you could have unintended consequences. Insulating part of the screwdriver makes a lot of sense.

I've used both the plastic and the metal tool.

 

[Billy Mayo]

So what can I do to the flat head tip to make it connect and stick better to the brass or steel trim pot?

 

[KeepItSimpleStupid]

The screwdriver has to fit the head of the trimmer better and the tolerances of the shroud has to be better.

BTW, I was thinking PlastiDIp: https://www.plastidip.com/home_solutions/Plasti_Dip

I do think it will work, but it won't be $2.98

There was a tool I had that I lost which also would have worked. It was all metal though. It was less than 1/4" diameter and had a push rod down the tube. You would push the plunger down and then contact the screw. The blades would spread gripping the screw. To release, push plunger.

Similar to this, **broken link removed** but way thinner.

This **broken link removed** is what I had.

 

[KeepItSimpleStupid]

Millohm-meter: This http://cappels.org/dproj/dlmom/dlmom.html guy I like.

The only issue with the one you pointed out is the need for 4 leads. Force can probably be anywhere along the trace and then the sense leads can be used to track down the short. At least I think it would work.

 

[Billy Mayo]

The one at my last job , you could use the 2 probes , you didn't have to use all 4

It would measure 0.0036ohms or 0.00036 ohms with using only 2 probes out of 4

Because most DVM meter will read 0.2 ohms