Today I finally got schooled on how to use the laser in the model shop. 

As mentioned in a previous post, I drew up the graticule for my Tektronix 519 as a DWG for this laser intro.

The basic workflow is:

1. make a DWG, using colors to represent different laser attributes (power, speed)
2. Power up the laser, and use bed Z control and spacer stick to focus
3. open the file in AutoCAD Trueview(?)
4. Print to laser driver, which opens up driver app
5. load the medium
6. assign colors to laser attributes
7. drag the print file onto the print area
8. a few other things
9. hit go

We used 1/8″ clear cast acrylic.  I don’t remember what the cutting power was, but the engraving setting was power of 8, speed of 1.  Keeping the power the same & halving the speed would result in a deeper cut.

We made two, just for kicks, and they turned out pretty well

With the paper removed

Compared to the one from my 551

Closeup

the 551 graticule stacked on top of the freshly cut 519.  Just different enough to be annoying.

Here it is, installed

Not bad for my first attempt.  I’m going to build a solid black aperture plate next.

I purchased and subsequently scanned the manual for the Waveforms 510-B Oscillator.  I’ve uploaded it up BAMA, and included it here as well.
Wavefrorms type 510 oscillator

Enjoy!

‘Boat Anchor’ is an affectionate term used to refer to old tube gear, primarily radios and test equipment.

This guy has a great site dedicated to his collection & adventures in restoration.  I didn’t see any Tektronix gear, but hey, no one’s perfect.

Speaking of boat anchors, I stumbled across this site that attempts to humorously quantify the relative beauty of these old relics:
BABE (boat anchor beauty evaluation)

My 519 is generally in immaculate condition, however it’s missing it’s original bezel.  It came with what appears to be a standard 500 series bezel, and some aluminum knurled knobs keeping it loosely attached.

I think there were two versions of the original bezel assembly, one with a camera attachment, one without.  Tim Koeth’s appears to have a the camera attachment (chronicled here), while the one I saw at Skycraft did not.  Check out this shot of his collection – he just may have me out oscilloscope’d.  Here’s the shot of the one at Skycraft:

What’s interesting about this one is that the entries for serial, sensitivity, and risetime appear to be blank.  A few things to note about the 519 and it’s CRT:

• There is no vertical amplifier.  The signal is passed directly to the distributed vertical deflection plates.
• The CRT & shield are typically paired, in part to help protect the CRT.
• The vertical sensitivity and risetime is individually characterized for each CRT at the factory, and is marked on the shield and faceplate.  They’re typically on the order of 10v per cm and 350ps, respectively.
• The sensitivity and risetime are marked on the backlit faceplate such that it’s incorporated into photographs, like this
• Because of the extreme speeds that this device operates on, the usable area of the CRT is comparatively tiny; 6cm x 2cm.  Compare that with other scopes of the time, which had an active areas of 10cm x 4cm, or 10cm x 6cm.

A little more on that last point.  In order to capture extremely fast events in real time,  you have to sweep the beam across the screen very quickly.  The quicker the beam scans across the screen, the less time the beam spends at any given point, and thus the less energy is imparted onto the phosphor.  To get enough energy on to the phosphor to make it glow visibly at these speeds requires tremendous accelerating voltages; 24,000 volts(!) in the case of this scope.  The trouble is, the more energy an electron beam has, the harder it is to move it around.  This is why the 519 ended up being a 100 lb beast, with sweep generator is driven by a forced-air cooled RF transmitter tube, a relatively dreadful vertical sensitivity, and a minuscule viewable area.   Another thing to keep in mind is that while repetitive signals keep sweeping across the CRT face, continuously refreshing the image, this was made to capture single shot events on camera (such as nuclear events), so the beam had to be bright enough to register on film on a single pass lasting less than 50 billionths of a second.

Back to my scope.  Here’s what it looks like with the bezel removed

For kicks, I tried installing the graticule from my 551.

That’s not just parallax.  The graticule illumination lamps and the notches on the plexi sheet don’t line up.

Remember, this was bespoke machine, only loosely based on the 500 series standards of the time.

Upon closer examination of the CRT shield, I noticed mine is sadly lacking the sticker that proclaims the sensitivity and risetime.

Other examples chronicled have a second sticker above this one with hand marked sensitivity & risetime.  I really don’t have the courage to pull the CRT from it’s shield to hunt for any other markings.

I went ahead and drew up a graticule that should fit:

This’ll make it’s way to the laser next week when I’m back in town. Stay tuned!

On my way home from InfoComm, I had a chance to visit what I would highly recommend as a pilgrimage to any geek,  Skycraft Surplus.

I didn’t snap too many photos, since I thought it seemed rude, but here’s a few:

Would you believe a Tektronix 519 was staring me down as I walked in the door?

Sadly, not for sale (on second thought, maybe that’s for the best).  Serial # 000729.

Who wouldn’t want one of these?!?

Isles and isles of hardware, fasteners, fittings, switches, passive & active components.  Drawers full of any little bolt, nut, washer, or standoff you can imagine, in a variety of materials.

I need one of these for my Meth Lab.

Don’t forget to look up

Somehow, I walked out of here spending less than $50, probably because none of these would fit in my carry-on.

Need wire?

This is about a third of their stock.  I ended up picking up a few 50′ coils of some nice silicone jacketed hook-up wire, great for patch-cords.

And finally, I snapped a few close-ups of the 519’s bezel, since mine doesn’t have one, and I’m attempting to recreate it

More on that effort in another post.

The idea of designing a programmable, high voltage power supply came to me after hobbling together all of the gak that I needed for reforming old electrolytic capacitors.  There are a few good examples circuits out there for home-built reformers,  but none of them were exactly what I was looking for.  I’m into sure how digital or programmable I want this to be, but my thought was that if there was at least some logging capabilities, I could easily plot curves of the process and maybe tease out some interesting trends.

Without thinking too much, I’m going to spitball a list of possible features:

• 0 – 600v DC
• 10-20mA max, with current limiting.  20mA is probably a lot for reforming, but maybe this would also see use as a general lab supply
• Current & voltage meters
• Logging current, voltage setting, and voltage across terminals, with timestamps (rtc needed?)
• Discharge resistor (variable ?)
• Ability to set a maximum voltage setting, and automatic incrementing of voltage when current drops below a threshold
• Voltage regulation?  This probably won’t have the effect I’ll usually want when reforming (i.e. I wouldn’t want the supply chase to match a target level),  so perhaps it wants to be disable-able,  if that’s even possible.

Some questions:

• Form factor – rack mount gear is cool,  but often impractical 
• UI – keypad entry? Menus? 
• Meters?  Ideally analog, if possible, with switchable ranges.
  
• Tube or solid state?

Research:

Heathkit PS-3 Power supply schematic – I feel like there may actually be one of these up at the “upstate home for wayward oscilloscopes” (aka, Mom’s basement)  as a side note, I also have an unbuilt Heathkit PS-4 waiting for a nice rainy day (or my retirement) </brag>

This guy built a beast of a high voltage power supply

Repair log of a Heathkit IP-17
Antiqueradios thread on a Heathkit IP-17 repair

Side note – I’m trying to sort out the difference between blog posts, pages(or posts) about actual projects, and pages(or posts) about specific pieces of equipment, so there will likely be some organizational turmoil over the coming months.

To be continued….

OK, so sometimes I search craigslist for:
Oscilloscope
Tektronix
Heathkit

Well this weekend I got lucky, and found someone selling some unbuilt heathkits for a great price.  He also had a few Archer 5V power supply kits for sale, which I’d never seen before, appeared complete, and were reasonably priced.  I bought two, here’s the one that I’m going to build.

In it’s original box:

Unboxing:

Well, it’s clear how the manual was folded in the box.

The enclosure and (stick-on) front panel was in flawless shape.

The circuit board showed some signs of age.  One or two pads lifted a little while soldering, but nothing tragic.

Components neatly packed within the chassis

Box-O-Parts

The Build

The screw heads were proud of the surface, which would have compromised the front panel application.

And then I remembered I had a drill press and a countersink bit.

The manual suggests soldering the transformer and rectifier together on the bench based on a rough drawing, but given the rigidity of the wire and the tight dimensions, it seemed a better plan was to at least tack-solder the two together while temporarily in situ.

Transformer & rectifier permanently mounted.

All other elements mounted.

 Testing

Brought it up on the variac with no troubles.  I was able to trim the voltage to 5.46V, and it held across a wide range of line voltages, without a load.

I was unable to calibrate the unit to 5.0V with the stock parts, so first I re-installed the circuit board with the bottom screws in the top holes, so it was easier to access.

Then I soldered in some jumpers in place of R2 and hooked up a decade box.

Then I soldered in some jumpers in place of R2 and hooked up a decade box.  1.8k would have put 5.0v directly in the middle of the trimpot range, but I didn’t have any so I got away with 2k.  I was able calibrate it to 5.0v, and so far it’s been performing without trouble.

You’ll notice that there are actually 4 terminals on this supply.  That’s because this is a ‘sensing power supply’, which allows it to compensate for losses in the wires from the power supply to the load.  The two sense lines can be of a much lower gauge then the supply wires, since they’re not passing any appreciable current.  They sense the voltage at the load, and are part of the regulation feedback circuit.  The regulator’s target is 5v at the load so if it’s gotta output 6.3v to overcome 1.3v of drop, then it happily obliges.

In addition to being fused both at the line side and low voltage side, it also has short circuit protection.

Oh, and here’s the schematic.

I think this is going to be a nice supply for LED tape experimentation.