Heathkit GR-900 Build Thread!

[N2IXK]

I just scored an UNBUILT Heathkit GR-900 25" color TV kit at the NJARC auction yesterday, and I am going to document the build process here on VK. I have always wanted to assemble a "real" Heathkit TV, after building countless smaller heathkits over the years. I did build one of the mid 80s TV kits for a family friend while I was in high school, but those were simply unassembled Zenith System 3 sets, with all the modules prebuilt, taking away most of the fun.

Anyway, this set was part of a Bell and Howell/DeVry TV Repair training course, and in addition to the 7 (!) standard Heath assembly manuals, there are 5 manuals of "Color TV Experiments" to be performed on various modules and subassemblies during the build, but they require additional parts and an experiment console which didn't come with the set. So I will be building the set in the straightforward manner as the normal Heathkit customer would. This is an early 70s vintage set, which is 100% solid state with the exception of the HV rectifier and CRT. It is built on multiple plug-in PCB modules, which are then plugged into a vertical metal chassis. It was apparently bleeding edge stuff in the day, with a varactor UHF tuner and automatic fine tuning. There are several integrated circuits used, in addition to the dozens of transistors. The tuners, IF, AFT and HV section come preassembled and aligned at the factory, but there is a LOT for the builder to do, unlike their later sets.

Several boxes of this kit had already been opened and dug through, so I started with a COMPLETE inventory to see if everything was still here. On the plus side, the original purchaser apparently received a double shipment on one package, so I have a spare VHF tuner, as well as spares for the IF module and all the parts to build up additional Chroma, 3.58 oscillator, and AGC/Sync modules. Also found was the optional GRA-900-6 ultrasonic remote control kit!

On the downside, I am MISSING the audio and vertical output transformers! I have posted a want ad here on VK, as well as the Yahoo Heathkit list looking for these, and if anyone can help here, PLEASE let me know. It would be a shame for this set to never run because of 2 missing parts. Hopefully, replacements can be located for these, or I am going to end up with a handbuilt electronic doorstop. Another issue is that the NOS RCA 25VABP22 was apparently stored in a damp location that rotted the box away and may have caused a cataract around the edges of an otherwise virgin CRT. Hopefully, it will not be too visible once the CRT gets installed into the mask. A cataract removal or CRT replacement could always be done if the results warrant it.

Anyway I will be getting underway with the build tonight. Because Heath intended even their most complex kits to be buildable without anything more than hand tools and a soldering iron, the first thing that the TV builder needs to assemble is the "Troubleshooter", which is a simple 5 range VOM used for testing the rest of the set as the build progresses. It is then installed inside the set (along with a built-in Bar/Dot generator) to be used for future troubleshooting/adjustments as needed.

Next up--Building the "Troubleshooter"!