Wednesday, October 7, 2009

Continuing on the Bi-N-Tic Filter

All of the parts are stuffed, except for the socketed ICs that haven't been inserted yet. Here's how it looks:

That blob in the upper right corner is where the VCO's expo converter is; it consists of an integrated matched pair with a tempco in contact with the top of the package. Here's a close-up:

The white stuff is heat sink compound, which should improve the thermal contact between the IC and the tempco. The board silkscreen calls for an LM394 here, but the kit came with a SSM2210, which caused me a bit of confusion until I went back and looked at the Bridechamber writeup for this module -- it specifically mentions this substitution, as having been done for improved tracking.

This gap-toothed socket is where the 4024 counter will go:

That's pin 9 that is broken off, which is the counter's bit 3 (8's) output. I am going to add a switch that will allow that line to be switched to either bit 3 or 4 (16's), which will alter the scanning pattern of the capacitor banks and should produce interesting results, I think. I'll bend that pin of the IC out so it doesn't go into the socket, and tack a lead wire directly to it to route to the switch. The return from the switch will come back to the un-contacted pad, to be routed to the cap switching muxes. Here's the underside, showing the as-yet unsoldered pin 9 pad:

Next step is the panel wiring. I'll solder in MTA-100 headers for some of it, but there are some places where there won't be enough room for the connectors.

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