Category: Equipment

New MkIII benchtop degasser

So I’ve finally managed to get some bits together and assemble the new smaller degasser.

I used the fire extinguisher from the MkI degasser, which I cut shorter. Sadly it’d been out in the rain, as well as having been used for degassing previously.
Even sanding it heavily obviously didn’t remove all the traces. I used a nice zinc primer on the inside which seemed to take, but once I went over it with white enamel it refused to bond where the resins had previously splashed.
Next time I’ll fork out for some Hammerite. I’m not even sure this enamel will survive cleaning any spatter off the inside later.

Found that Poundland is doing rather large tubes of two-part epoxy! Handy stuff to have around. Especially for £6 cheaper than Araldite. It does reek of fish before it sets though.
The 99p Shop nearby provided a cheap frying pan which got cut up into the lid surround. Fitted so tightly there was no need for a retaining pipe-clip strap.

I brazed a load spreader to the UTA manifold, and glued it on. The nossle holder of the extinguishers base perfectly holds the up-to-air filter so it’s a ready-made support. Without it I’d be worried about the lever-handled ball-valve dislodged the manifold after only a few uses.

Made a proper handle from some curved extruded aluminium and some bolts. Again, glued onto 10mm polycarbonate cut to size. I’m unsure if it’ll need internal lighting yet. The white inside reflects a lot of ambient light and it’s not as deep. Will see.

So I now have a nice small degasser for using on the workbench! Both controls are nice easy to use lever-handled ball valves. I should be able to leave the pump running to the catchpot and simply switch the two valves for fast control.
It should make the degassing of the resins prior to pouring them far simpler. And if one is sealed under a static vacuum, the other chamber can be used under pumped vacuum.

One thing to note is that it looks messy because the Poundland 131 epoxy is thinner and slower-setting than Araldite. But if it works, it works, and it seems just as strong when set.

As another improvement to the system I also mounted up the MkII chamber, pump and catchpot to a plank of wood. It reduces the footprint a bit but mostly stops them from moving around in use and flexing the pipes which can result in leaks or manifolds breaking.

Will try to get a short demo video up on youtube.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Bampf.

The little Unimat 3 circular saw just made a *bampf* noise and stopped. The fuses are still good, and the breakers haven’t tripped.

I think the motor just blew.

This is troublesome.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

A nice change

Casting has gone splendidly. Best yet even. I will be stunned if the resulting casts are anything but ideal.
Three-stage degass, apparently good pigment mixing, no spills, minimal mess.
Did make an excess mix though. Fortunately had spare moulds on hand. Odd that sometime’s it’s just under but sometimes way over. Better check my notes.

Used large jam-jars for mixing. Can handle larger amounts and can withstand cleaning with acetone afterwards, as well as letting me view the mixing.
Will have to look out for some with wider mouths though, and rounder bottom corners with no overhangs.

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Used a reinforcing spring and some araldite to try and repair the broken wing strut. Will see if that holds.

Salvaged some nice long bits of steel from a wrecked cabin bed.

Also must email Receipt #44. They did not collect their item at the LF meet just gone as they said they would.

Time for a shower.

Tomorrow will correct some masters and get new moulds for them cast. Then either do artwork or design the new display stands I have in mind. Glad I have lots of masking tape.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Camera diagnostics, part 1

Always knew getting the service manual would be a good move.

Dug out the old JVC GR-S707’s. They’re a pair of SVHS-C semi-professional camcorders I picked up off ebay years back. One worked fine, only needing a new microphone muff. This came with me all the way to the USA to do some filming at a convention, and damn near broke my spine in the process.
The other was acquired a couple of years after that and turned out to be actually broken, as opposed to a little temperamental in high humidity. I set it aside as a parts camera, or something to try and fix later. It now may be “later”.

I still haven’t tested the capture rig, but will be in the next few days. I was actually looking for a lens this evening when I dug out the spares/repair cam. I had a couple of ideas though, and tried them out quickly.

The viewfinder displays a heavily distorted and rolling image when filming or on playback. The spares kit included all the proprietary cables, so I tried hooking it up to the capture card. Same result there, only in colour. Very heavy blue distortion.
Noticed however the viewfinder and AV output share the same connector type. May mean I can fit one or the other with a colour viewfinder from a different camera at some point. I think I have an even more elderly camcorder with a colour tube.
Found a tape to test in camera. Noticeably worse playback than on dedicated playback unit.
So here’s the interesting bit: PLAYBACK on the damaged camera works fine. However recording is badly affected.

A/V board eliminated. Viewfinder eliminated. Playback eliminated.

Now, from the diagrams it APPEARS that the viewfinder connects to the CPU board. Probably since on-screen info can be included on the video and the viewfinder separately, so that’s done there.

Pain the bum is a lot of these block diagrams had sections in green, and they were scanned in black and white for the PDF, so large portions are near-illegible grey smears.

Still, that both outputs from the CPU board are effected, including the portions that should be different for each output, says it’s either the CPU board itself, or the CPU board’s trying to fit the on-screen data to corrupted video. And since I can’t see how the CPU could corrupt the video feed as well, we move further down the line.

The overall wiring block diagram has the CPU connect to the THD (no explanation of abbreviations included for PCBs). Schematic diagrams show this to be motor and sensor control for the optics themselves as well as pass-through for video and character data, to the Video board.
The video board seems to have tonnes of lovely little trim-pots, any of which might have gotten out of whack. Two are named “Sync level” and “1H Delayed sig level”, both of which sound to me like they could be the cause of this odd issue. It does seem to be some sort of timing issue, afterall (and maybe more, if the blue tint isn’t an associated effect).

That said, the grip on the camera has always been.. sticky. As in coated with something. It could be something leaked down inside the camera through the zoom controls and onto the PCBs under it, altering component values.

In any case, opening it up and giving it a clean-out would seem in it’s best interests.

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Ah, forgot I also bought an original non-PDF copy of the service manual. PCB diagrams are still in greyscale, but in much more detail. Schematics are detailed in colour. Indications of binder-holes though suggest either isn’t (wholly) original itself, or JVC actually sent out service manuals that were photocopied from an original.

Mind you, nice that it even goes into detailing the functions of the pins of each IC used, including part numbers. If I should ever need to make a new CPU board for one of these, it’s nice to know it’s only cost me $300 in processor chips alone. :P

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Power, lathes, wings

Reprap prototype PSU is done and ready for the stepper controllers to arrive now. All boxed up nicely. If memory serves, it didn’t have a fan when it was in the fax machine, so should be fine in the enclosure. At worse I might have to drill it some extra air holes.
Mains lamp, some (vintage) terminal posts, switch and IEC C14 socket.

Even took the engraver to the front panel to mark out the various terminals and added a couple of ferrite beads to the lines to be on the safe side, and used some cable wrap to keep the wires tidy.

Today I also finally removed the piston and cam off the old compressor pump, and filed down a pully to fit. I’ve hooked this up to the 3rd party headstock from the Black and Decker extruded aluminium wood lathe I found last year. It’s meant to be run by a type of drill they no longer make, so the compressor motor should be easily powerful enough. Currently getting a head speed of about 3200rpm, so it’s currently about twice as fast as it needs to be. Will see about swapping the headstock pully for something larger (I have one, but getting the old one off will be a pain).
It’s not urgent, but it’s sitting around and there’s a friend who should be able to use it once it’s basically working.
Also made a control box for it, currently a simple latching safety power switch (see background of first image) from a broken garden shredder and an old RS project box. If I find a spare suitably rated rheostat I may add a limited speed controller.

Also the sewing for the set of “Navi” wings was mostly done today, but one of the blue plastic rods snapped while trying to flex it into it’s “pocket”.
After some considerable swearing and therapeutic angle-grinder time (see above compressor pump), I will tomorrow attempt to construct a coupler out of clear perspex rod and use it to join the two broken ends, as the stress on them will likely be more than any other repair would take. this may mean purposefully breaking and repairing the opposite wing to match.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]