Well I did.
Typically Fridays are my “lab” days. My only day out of the week when I have the entire day to myself to work on my projects and just bury myself in my own little world of evil genius-ness. Some days I get more accomplished than others, but typically I don’t walk away feeling completely frustrated like I did at the end of the day yesterday. Everything I did wound up in the shit-can. I guess I can look at all of it as a learning experience however. I learned a lot about what NOT to do… let me expand..
To Glow or Not to Glow?
For my Vector Amp project I had decided to not waste money building an actual tube amplifier due to the cost of building an amp that had sufficiently cool-looking tubes. I decided I’d just get some cool looking large tubes and hook up the heaters to get that cheery tube glow without dropping bank on huge transformers to build an actual circuit. So I bought myself a KT-88 power tube and a matching socket from Parts Express. This is a cool looking tube. There are cooler and larger ones out there, but the KT-88 runs about 25 to 30 bucks, so it was in my price range for experimentation.
I’d had an idea to build a small polished wooden box with a copper plate on top holding a glowing vacuum tube. I thought it might be a cool little desk accessory for those who dig vacuum tubes and steampunk stuff.. nothing too complex, just a cool little amusement. I figured this was a great chance to try out my construction ideas for the vector amp on a smaller scale before pulling the trigger. I just needed a few things from the Depot and Radio Crack. A 1-1/8″ hole saw, some wood, and a transformer. Most of the other things I had.
So Friday morning I hopped on my trusty steed (my bicycle) and rode up into new town to make my weekly sojourn to Home Depot. It’s a nice leisurely 2 or so mile ride, and it makes for a nice start to the day.
I picked up some brass nuts and bolts, a hole saw, and a small piece of 1/2″ Oak for the base. Across US-1 from Home Depot is the local Radio Shack, so I popped over there to buy a transformer to power my tube. The guy behind the counter looked at me like I was speaking swahili when I asked for a center-tapped transformer. He then led me to the phone chargers. No, I explained.. a bare transformer. OH he says, I have to go in back to find those.
After about 10 minutes he returned carrying a cardboard box with about 20 transformers dumped in it. He apologized for the state of the stock system and helped me dig for the one I was looking for. After a bit we located the 12V (6-0-6) transformer. I needed 1.6 amps, but they only had 1.2 and 3 amp versions.. I opted for the smaller one just because I didn’t think it would matter terribly since I wasn’t trying to actually make something to spec.
Back on my bike, I pedaled my way home. I walked in the door at 5 minutes to noon.. what timing! Noon in Key West is a pivotal time in the day.. time for a bloody mary.
Drink in hand I made my way back to the lab (a workbench in the corner of the bedroom) and began to put my evil plan into play.
Fail number One.
The tube wouldn’t glow. It got warm, so I knew the heater was working, but it certainly wasn’t glowing like I know tubes do. I had a couple small tubes lying around, and they glowed fine when I hooked them up to the transformer. Dejected, I decided that my transformer pumping out 1.2 amps wasn’t sufficient to fire up a tube that needed 1.6 amps. OK. Fine. I decided to move on to constructing my base.
Fail Number Two.
The hole saw I’d bought had a different size shank mounting hole than the shank I had. Sigh. Enter the memory that the set of hole saws I had was bought at Lowes in Orlando, and were a different brand than the one I just bought at Home Depot, despite being the same color. Since the closest Lowes to Key West is at the very least much farther than I’m willing to travel on my bike, I decided I’d just buy a new shank and get it over with next time I was at Home Depot (Which as it turns out was much sooner than I expected).
I decided to just build the wood part of the base and deal with the rest of the stuff later. Except when I started trying to decide on the size of it all, I realized that if I needed a new, more powerful transformer, it was likely to be larger than the one I had in my grubby little hands. God DAMNIT!
Back to the trusty steed for another delightful 1-hour round trip to Home Depot and Radio Shack. Except this time I mixed myself a vodka tonic and stuffed that puppy in the drink-holder on the handlebars. That made the trip less tiresome. Luckily the weather was absolutely delightful, but then it usually is here.
Fail Number Three.
Back at home after the second trip to new town, I pulled out my newly-acquired, amped-up transformer and hooked the tube to it. Nothing. I could see the bottom of the heater filament glowing, but nothing impressive at all. All my plans for the vector amp began dissolving in front of my eyes at this point. I posited that tubes must need to be in a full-on circuit and under load to really put off a nice rosy glow, and that just hooking the heaters up didn’t cut it at all. Fuck Fuck Fuck.
I put all that failure behind me and decided to go back to working on the base now that I had the proper hole-saw shank. I got out my 3/16″ sheet of copper plate that I had lying around and scribed out a 3″ square for my top plate. Now last time I had to cut this stuff I had a radial-arm saw and a metal saw blade. I left all that stuff back up in Orlando though, so I decided to try my hand at cutting it with a jig-saw.
I clamped a piece of wood to the sheet for a straight-edge and began cutting. After about 20 minutes I had gotten through about 4 inches. This was going to take all day! Then I remembered something. I had taken shop class back in High School and I remembered something about using oil to help while cutting metal.. Hmm. Enter a can of WD-40. Woah! I zipped through the rest of the 12″ of that plate in about 5 minutes.. definitely faster!
All in all it was a pretty straight cut.. which actually surprised me. It wasn’t nearly as nice as the cuts I’d gotten with my radial arm saw, but beggars can’t be choosers I suppose, and with a decent amount of file-work, the edge could be made to be nice.
On to the drill press!
Springing back after successfully cutting through the copper sheet, I decided to go for the gusto and drill my tube-socket hole. I wanted a ring of 1/4″ holes around the socket hole to allow air to flow up through the base and help keep the tube cool. In addition to being functional, this looks really cool in all the home made tube amps I’ve seen out there. So I scribed out my lines, and used a punch to dimple the surface where the holes would go.
Fail Number Four.
I clamped the metal down on a scrap of wood and started drilling. Right away I knew I was in for a long, tedious, and possibly ruinous process. I used a ton of wd-40 to lube it up while cutting and still it took the better part of 20 minutes to get through the plate. I was using a 1-1/8″ bi-metal hole saw, and it worked.. to a point. The hole turned out being about 1-1/4″ due to the wobbling of the tall saw. Definitely NOT aerospace quality construction, but at least it worked.. the hole was round and straight. Unfortunately however, the increased diameter of the hole meant my tube socket plowed right through the hole instead of butting up to the underside. Sigh. Back to the drawing board.
This was most definitely not a process I want to repeat, and I have decided that for future projects I am buying sheet metal hole punches for making holes. Screw trying to get through sheet metal with a hole saw. The noise and vibration alone are enough to turn me off of the technique, but combine those with the inaccuracy of the hole size, and it’s a deal killer. Hole punches only work up to about 10 guage metal however, so I won’t be able to use the 3/16″ plate I have, but I can get 1/8″ copper sheet readily (if not cheaply) on the internet.
So in Closing Let Me Just Say This…
There was some drinking going on after this day to be sure. One step forward and two steps back seems to be the lesson learned. I’m not giving up though. I guess I’m going to have to break down and actually build that tube amp for the Vector Amp project after all. Hey, it’s only money right?