Heathkit GR-900 Build Thread!

[N2IXK]

The GR-900 build continues..

Next up, the luminance module. This module incorporates the standard luminance circuitry found in any color set, in addition to the dot generator circuitry used for the convergence setup. The dot pulse generator circuitry incorporates a relaxation oscillator based on an NE-2 neon lamp, followed by some wave shaping circuitry.

Testing a sample of the original electrolytics showed that most of them were acceptable, but a few showed borderline high ESR, even after reforming for a few hours at or near rated voltage. I decided to replace all the small electrolytics as cheap insurance against problems. The 2 large twistlocks for the main chassis seemed to reform perfectly well, and will be used. Replacing the electrolytics on the smaller modules allowed me to get radial lead types where needed, rather than the rather ugly vertical mounting of axial caps that the board layout originally called for.

Next up--the Video Output board.

[msimendi]

I have the same TV. Is this the cabinet you have? I got mine from a guy at work who built it as part of a correspondence course. It had sat not working for many years. I fixed it (blown rectifier diode) and it is my daily driver. It has the original electrolytics. Its had other problems - it would not color sync and also there was a problem with dirty pots, but it's been working pretty good lately. Also I had to replace that main circuit breaker with a fuse as that was shot.

There is a yahoo group on Heathkit TVs but they don't seem to be active lately.

https://groups.yahoo.com/neo/groups/...tions/messages

[N2IXK]

My kit came with no cabinet, which I understand was somewhat common with the home training courses. Apparently, many veterans enrolled in these courses, which were paid for by the GI Bill. The government would pay for the training course, the test gear, and the TV kit, but not a piece of furniture with no educational value. Lots of these sets ended up in built-in installations. Not sure exactly what I will end up doing with the set when finished with it, but I am considering a homebrew clear acrylic/polycarbonate cabinet to show off the guts.

Anyway, some progress has been made in the last week, beginning with the Video Output module. This board contains the RGB decoder IC, the 3 CRT cathode driver stages, and the 3 drive controls.

So far with this build, there have been very few issues with solderability of components. One of the exceptions was the 3 section drive potentiometer on this board. The wiper terminal of each section had acquired a thin layer of a dark tarnish that thoroughly resisted the action of soldering flux. A quick cleaning with a tiny wire wheel in a Dremel tool cleaned them right up, though.

Next up, the Chroma, 3.58 Oscillator, and AGC/Sync modules, along with a guest builder who helped out last weekend.