The “Vintage” Carlson Ultra Probe is finally done. I’ll try to keep the build log concise and hit some of the major points. There are individual picture links below, or just click on the album link here: Carlson_Ultra_Probe_Album
Goal: There were only a few parameters in mind before building the probe. I wanted a “vintage” looking enclosure and it had to be externally re-chargeable. It was also a good excuse to try a some different construction methods; better to wreck my own stuff than someone else’s.
Enclosure: The enclosure was constructed with various thicknesses of steel from 12ga. – 3/16. I tried my hand with PEM threaded inserts to retain the covers. Those were simple to install; just drill a hole and press them in with an arbor press. Once all the pieces were cut and bent, a hand full of clamps were used to jig the pieces into place and the box was welded.
<Front Panel>
Finish: The copper finish was achieved with SteelFX – CopperFX. It’s easy to apply but difficult to master.
-Patina Application:
1. Grind steel shiny and make sure it is clean. Any impurities on/in the steel will show up after applying the acid.
2. Mist on patina and wait for the color to change; 15-30seconds.
3. Neutralize with water and use compressed air to dry.
4. Clear coat immediately.
It sounds simple, but if your goal is perfectly bright copper, be prepared to regrind your piece multiple times. I had to redo the front panel a few times. The first turned out terrible because I had used masking tape around were the controls would mount; keep the area clean for a good ground connection. Unfortunately, when washing the panel off with water, the adhesive migrated to the front of panel causing really bad black streaking. A streaking pattern is fine as long as it’s even throughout the piece, but when the top is shiny and bottom is marble, it looks terrible. So, after removing the tape and regrinding the metal, I tried again and it turned out better. There are some marble type effects throughout which I was happy enough with, so after the front panel parts were copper coated and dried, clear coat was applied. Clear coat needs to be applied immediately after drying; recommend a 2K clear coat so the parts are sealed and dry within hours.
-Controls: I tried to go for a symmetrical layout of the controls. Originally, all of the controls were supposed to be rotary knobs but, I forgot about the Low/High gain switch as well as the ground wire. The front panel was finished by that point so a toggle switch was added to the center of the box to maintain symmetry and the ground wire connection jack was added to the back.
-Lamps: I was able to get empty miniature bayonet bases for the jewel lamps. 2ma is all that is needed to get reasonable brightness without sacrificing battery life when using high brightness LEDs. The only issue with high brightness LEDs, is that most of them have a very narrow beam pattern; 10-15deg. With such a narrow beam, the LEDs needed to be recessed completely into the bayonet socket so as not to create a dot in the middle of the jewel.
-Decals: The front panel decal was designed around being vinyl cut, so the design was kept very minimalist hoping it was something that could actually be cut. Ultimately, I decided to try stenciling the decal on instead. The stencil system used was from Ikonart. It isn’t compatible with solvent based inks; acrylics only. The original design was used, since I wasn’t sure what kind of detail to expect. It actually turned out well, so I made a more detailed design on the back to test how small I could make the text.
–Decal Steps:
1. Design logo; whatever is black will be where paint is applied. Flip image before printing on their frosted plastic sheet. In order to get better detail, the ink side should be touching the blue stencil sheet.
2. Place sheet on blue stencil and expose under UV light for 30 seconds.
3. Remove stencil and wash with high pressure warm water. The black blocks the UV and remains soft, while the area exposed to the UV gets hard; soft areas washout.
4. Dry stencil and place back under UV for 2 minutes for additional curing.
5. Peel off the plastic backing, stick onto piece, squeegee the paint on, and peel off.
Rear Decal: The finer detail on the back decal turned out better than I thought it would. The A in Carlson and some indicator lines on the power and volume got some drops of water on them when I was cleaning up. 😔 This is not from the stencil. Most of the smaller text turned out. There is some artifacting on the bottom side of some areas. This would be in the direction the squeegee was dragged; maybe too much pressure?
<Enclosure Internals>
-Battery/Regulator/Low Batt: The battery is a 12v/6Ah lithium regulated down to 10v with an LT1963 LDO. Charging is done through the 4 pin front panel connector. The other two pins are for powering the probe from an external source selected with the lightning icon. Low battery detection is accomplished with a fixed 10.8 volt IC supervisor; TPS3847108DBVT.
The system current draw with nothing plugged into the front panel and all controls at zero, is 33.5ma; the amplifier board is 22.5ma, Lo Battery Board 25ua, Power Lamp 2ma, difference must be from the regulator. The system current draw with probe connected and all controls at zero is 37ma. At moderate volume picking up noise with green LED illuminated the current draw is around 45ma.
-Board Mounting: The controls were in the way for amplifier board holes, so a copper interface plate was made with brass threaded inserts soldered to the copper. The board is fastened to the copper plate with 3/4″ length threaded standoffs which are used to hold the copper cover.
<Probe> The struggle was real when assembling the probe. The first hurdle was getting the solder to take to both the brass insert and the aluminum cap. I wanted the brass insert completely soldered before attaching the board. I used a 250watt American Beauty soldering iron so heat wasn’t a problem. After trying different surface prepping techniques I ultimately got some aluminum flux. The surface was sanded while being coated in flux and then I was able to get a decent fillet all the way around. With the brass insert now soldered, the cap was thoroughly cleaned and then the board was attached.
The second hurdle was attaching the wires. It’s obvious that the probe shell was not designed to be used with larger coax or power wires. Not Mr. Carlson’s fault, but I already ordered the RG400 and connector so they were going to be used. The outside shield had to be removed leaving the inside shield. The only braided shielded cable I had for power that would fit was a 4 pin, 24awg, M12 sensor cable; Automation Direct. I was able to get everything in there, but if another probe is made, I’m definitely going to have to get smaller cable.
<Testing> At the time of this post, not much testing has been done. I heard audio play from a cable, and picked up a radio station in demodulation mode with the probe laying on the basement concrete. Success I guess? He wasn’t kidding about the volume. The speaker is loud enough at indicator line 1; 94dB speaker. The entire coax is crazy “microphonic” for lack of a better term. I can flick the any part of the coax and hear it. Maybe a smaller coax would be less susceptible? Overall I’m happy with the build and need to do more testing to see if it is actually working right and I didn’t goof something up.
Looks incredible Lea! That is some extremely nice work you have done there.
@ LEA: Wow, wow, wow !!! Well, … all I can say is that, at this point your build is beyond stunning and this can only be achieved when a device built becomes: “A Pure Labor Of Love! and I can tell you’re loving it to bits 🤩
Because of the bigger enclosure and the speaker size the audio sound (I imagine) would be really good with a proper amount of “base” which is always desirable. Well done. Tnx. for sharing.
PS: I haven’t had time to do my build yet but is in the pipeline this year for sure (perhaps soon). 😋
WoW, it’s gorgeous. It must have taken you some time, but perfection does not come easy. Well done.
Woodb180
What a very nice build and thank you for sharing.
I see a lot of nice work you did in this project. 😍
Larry – N7LUF
Thanks to everyone for the kind words. Yes, it is definitely a labor of love…32lbs of love. It did take a lot of time and wasn’t cheap, but I should have something that is durable and repairable.
The audio does sound pretty good and is painful at indicator line 2-3, which surprised me for such a low power chip. With a 32lbs enclosure on rubber feet, there are no audio vibrations. Hopefully this weekend I can play around and get a feel for it.
That looks so amazing. Quality work.
…<Testing> … The entire coax is crazy “microphonic” for lack of a better term. I can flick the any part of the coax and hear it. Maybe a smaller coax would be less susceptible? …
Not sure if you mean the probe tip coax or the cable from probe to amp (tether) or both.
I find the probe tip coax on mine is microphonic too. Whenever it taps something when I am probing I get noise through to the amp. Also get that noise if I flick that probe coax anywhere along its length. I am using RG402 for the probe tip which is slightly thinner than RG400.
For the coax that tethers the probe to the amp I am using RG316 which is quite thin. I have mine bundled into braided sleeving with the other tether cable. I do not get any microphonic issue flicking that tether.
@plurn Yes, both the probe tip and and connection cable to the box. I might try covering the cable in nylon or something similar. The probe is definitely very sensitive and I’m sure there will be some fine tuning on my part until I’m happy with everything, or I’ll just make another probe with smaller coax.