Laser-printed panels and other topics

[gstopp at fibermux.com]

     Hi DIY,
     
     Last week I tried a new panel fabrication technique. There were some 
     bumps along the way but it turned out pretty good, so I'll probably be 
     using it from now on. So it's time to share my story:
     
     Up till now all my DIY synthesizer and effects panels were made out of 
     aluminum plate, as follows:
     
     1. Cut plate to size
     2. Get white posterboard, draw the desired panel in 1:1 scale 
     3. Tape posterboard panel to plate, drill pilot holes
     4. Remove posterboard, drill holes out to final sizes 
     5. Orbital sand both sides of plate
     6. Spray paint user side of panel flat black
     7. Apply border and box outlines (white auto pinstriping tape) 
     8. Apply text labels (white rub-on letters)
     9. Spray paint with clear coat
     
     This worked great, and looks very hi-tech. Very evil looking machines 
     that intimidate normal mortals. You know, "wow you must be a mad 
     scientist" yada yada yada.
     
     Drawbacks - cute little waveforms and other graphics are impossible. 
     Okay, not impossible, but I haven't figured out an easy way to do 
     them. Also, you tend to abbreviate a lot since that makes for less 
     work. I mean, yes it's easy to rub the letters on, but if you get too 
     verbose you a) run out of letters faster, and b) each letter takes a 
     finite amount of time and believe me it all adds up.
     
     So a while back I figured that I'd try using a PC to draw panel 
     graphics, with lots of little waveform pictures and huge amounts of 
     text, and laser-print it and glue it to the plate to create a panel. 
     Besides, I figured it was time to try a different look, of white 
     panels with black graphics - kind of a Serge/EML/Oberhiem look.
     
     I bought a package of card stock, which is 8 1/2" X 11". This is the 
     same stuff that business cards are made of. It will feed in a laser 
     printer, barely. Anyway my plan was to print it out, cut it out with 
     scissors, punch holes in it, place it over the panel, mark the holes, 
     drill the panel, glue on the card paper panel, and seal with 
     clearcoat.
     
     For the punching of holes I decided to use brass tubing sharpened with 
     a file. I saw somebody post about this recently, and I remember 
     thinking "Hey that's my idea!". Great minds think alike, I guess... 
     Anyway I did manage to punch the first couple of holes, but found out 
     that the sharpened brass does go dull after a few holes, and the 
     hammer end of the tube starts to deform, throwing off the symmetry of 
     the force to the paper and leaving the hole partially un-punched. So I 
     got the idea to chuck up the brass in my drill press and see how that 
     worked. Great idea! Man I could drill a hundred holes a minute that 
     way, at least until the brass tube fills up with paper "holes" and 
     needs to be emptied. (Two words about drill presses - get one!). Once 
     the holes in the paper were done, I used them to mark out the plate 
     holes for drilling.
     
     For the glue I chose epoxy. Not sure if this is the best, but it was 
     the first thing that came to mind (love that stuff). Anyway I painted 
     the panel with gloss white Krylon, and let it dry. Then I applied a 
     thin coat of 15-minute epoxy to the back of the paper panel, dabbing 
     here and there in strategic spots. I stuck it on the plate and 
     sandwiched it between a couple pieces of plywood and stacked a bunch 
     of heavy stuff on it and let it dry for a day.
     
     The next day I sprayed the panel with clearcoat (Krylon Crystal Clear) 
     enamel. All seemed well until about ten minutes later, when I saw that 
     the paper had swelled up a little and bubbled up in the areas that had 
     no epoxy. Rats. I came up with a quick plan to wait until the clear 
     was dry to the touch, and then do the plywood press thing again. This 
     I did, and waited another day. When I looked at it the next day, it 
     was all flat and dry. Now the only problem was a faint amount of 
     yellowing in spots caused by the epoxy being visible through the 
     paper. Fortunately this has since faded away for some reason.
     
     Now that the panel is completely dry, it doesn't look too bad. It 
     seems to be an off-white in color, rather than a bright white, but 
     with the laser graphics it looks very much like something you'd buy 
     rather than something you'd built. Next time I'll try either a 
     different glue, or some way to apply the epoxy in a thinner coat 
     across the entire back surface of the paper.
     
     BTW this project is the 8-channel DAC driven by the PC parallel port 
     circuit that I built a few months ago. It's on a 4-space rack panel 
     and I'll try to get an image up somewhere when it's done.
     
     Next topic: tube amps! Does anybody know where to get replacements for 
     those old multi-value high-voltage paper electrolytics? Man I went to 
     a half-dozen places this weekend, and I found some, but certainly no 
     direct replacement and maybe a "close enough" or two but I need to 
     measure the power supply voltages because the cap voltages available 
     are not quite the same as the original. I'm looking for some 525 VDC 
     30-20-20-20 quad paper 'lytics for a couple Dynaco Mark III's. 475 VCD 
     is the max apparently. Actually I'd prefer some more modern 'lytics, 
     I'm thinking Spragues or Mallorys.... I'll cruise the catalogs but in 
     the mean time - anybody got any ideers?
     
     Speaking of tube amps, here's another project story - I needed a combo 
     amp for the garage, so I could use it as a monitor amp for projects on 
     the workbench (besides it's good to have a guitar amp lying around 
     anyway). I had an old Magnatone solid-state with two twelves in it, 
     but it had a pretty bad hum and if you were standing on the garage 
     floor in bare feet and touched the input cable ground, you could feel 
     a pretty hefty AC potential course through your body. I could tell by 
     the feel of it, like when I would squeeze harder on the cable jack, 
     that there was plenty of amperage to spare and it would give me all I 
     could take from it if I'd only walk over to a puddle of water. Well 
     needless to say I don't take that kind of crap from lowly electronic 
     stuff so I proceeded to gut the thing after verifying that this 
     behavior was "per design". As I was doing this I started to eyeball an 
     extra old Fender PA head sitting in the corner - it looked like a 
     perfect fit to the top of the speaker case. Sure enough, it was. So I 
     grafted it to the top, and ran a couple speaker wires down to the 
     speakers. Next a little trip to the local guitar junk shop, and two 
     12AX7's and a reverb tank later I had a pretty cool 140 watt combo 
     amp. As soon as I powered it up I tried the ol' finger-on-the-cable 
     hum test to see if it was alive, and I practically got sterilized by 
     the blast. Ha ha, bet the neighbors got a kick outta that. Okay so I'm 
     drifting from synth-related topics - well amplification has its use in 
     synthesis, doesn't it?
     
     Anyway busy week on the workbench, I just wanted to tell someone about 
     it.
     
     - Gene
     gstopp at fibermux.com