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  #1  
Old 05-01-2016, 05:11 PM
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N2IXK N2IXK is offline
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Heathkit GR-900 Build Thread!

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"!

Last edited by N2IXK; 05-14-2016 at 08:49 PM.
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Old 05-01-2016, 08:43 PM
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I had to scrap a 20" heathkit tv a few years back...because the cabinet had gotten RUINED In my old garage. it was SS, with SCR deflection--maybe a HV rect tube--all else modular SS. I kept the tube and chassis, MAYBE the tuner. Know where the chassis is right now. it DID use a large TO-66 audio amp, IIRC. SO--it must have an output transformer. Pretty sure it also had one large vert transistor for the V-out..but will have to look again...

I just KNEW...there would come a time...someone would be needing some part from it...
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Old 05-01-2016, 09:01 PM
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I just looked at an RE magazine from late 1970--my set is there. Looks like a GR_270, 20 inch version. it DOES use a v-out transformer, and a TO-3 transistor mounts on the chassis right above it. is your chassis like this.

Also--the A-out transistor is on the left, above the power tranny, there are a pair of transsitors, but I do NOT think both of them are for audio.
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Old 05-01-2016, 09:42 PM
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Definitely sounds similar to my set. I have a lead on a junker chassis from a local VK member, which I am going to look at in a couple days. If that doesn't work out, I will let you know. Thanks!

I am amazed that within a couple hours of posting, I now have THREE potential sources for these 2 obscure 40+ year old parts lined up! Thought I would be looking for months. The power of the internet....

Last edited by N2IXK; 05-01-2016 at 09:50 PM.
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Old 05-01-2016, 10:00 PM
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After about 15 years on the net...I wonder....just HOW we did it before then. Me, mainly the old "tradin' post" paper--I found a lot of things through that...and of course, word of mouth and the curb...from the beginning.

This tv came from an auction--in about '93, that I did NOT attend...but I ended up with this set form the guy who DID attend. IIRC...it DID work...and had the cabinet not been hopeless...i would still have the complete set. Buty..water and rats do take their toll...
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Old 05-02-2016, 06:34 AM
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Since Heathkit used RCA's SCR sweep I wonder if they also copied the
vert out from one of the early XL's ?? A lot of RCA in them.

The audio should be easy, if they used the high collector voltage
transistor one from a Zenith hybrid should work fine.

73 Zeno
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Old 05-02-2016, 08:02 PM
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Got started on the build by putting together the "Troubleshooter", a simple VOM that Heath included in the kit to aid in testing and repairing the set as needed. Heathkit really went out of their way to make sure that just about anyone could successfully build one of their kits, without any need for specialized tools or test gear. They didn't assume that anyone building a TV kit actually knew anything about electronics, or already owned a multimeter. They didn't even assume you would have access to "exotic" tools like a 1/4" nutdriver, so one was included with the kit, as well as a small open end wrench and the famous red plastic nut starter. As you can see, they even included an Eveready zinc-carbon AA cell, which I was AMAZED to find not only hadn't leaked over the last 40 years, but still read 1.5 volts on my DMM! I didn't install it, though, opting for a modern alkaline AA cell instead. Will keep the included one around for laughs. Haven't seen one of those since I was a kid.

This is a 5 range DC voltmeter and ohmmeter, which also includes a special A-B-C-D-E scale to be used by non technical types to verify that a certain reading is within an acceptable range, such as resistance checks of power supply rails prior to applying power, etc. Function and range selection via a pair of 3 position slide switches. Ranges are 5, 50, or 500 VDC, and R x 1k or R x 10k for the resistance ranges. This meter was only sold as part of their TV kits, not available as a stand-alone kit.

The build itself was obviously pretty simple. The meter, switches, pot, and battery holder get mounted into the case, then the components are wired together point-to point. There are 3 precision resistors for the voltmeter ranges, and a few other resistors and diodes for the ohmmeter and meter overload protection. Construction took a leisurely hour or so, thoroughly enjoying the Heathkit experience again after many years. The meter tests out fine, and was set aside to await installation into the rest of the set.

Next up: The TV build itself gets underway with the Audio module...
Attached Images
File Type: jpg IMG_0520.JPG (119.3 KB, 64 views)
File Type: jpg IMG_0523 (2).JPG (105.7 KB, 84 views)
File Type: jpg IMG_0527 (2).JPG (75.8 KB, 61 views)
File Type: jpg IMG_0528 (2).JPG (85.2 KB, 76 views)
File Type: jpg IMG_0531.JPG (97.4 KB, 88 views)
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Old 05-02-2016, 09:44 PM
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Are you replacing the electrolytics that came with the kit with new ones?

I'd be a bit wary building such a rare treasure with 40-year old caps.....


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  #9  
Old 05-02-2016, 10:06 PM
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Quote:
Originally Posted by Findm-Keepm View Post
Are you replacing the electrolytics that came with the kit with new ones?

I'd be a bit wary building such a rare treasure with 40-year old caps.....
I am going to carefully reform the 2 multisection cans on a power supply, and see if they drop down to acceptable leakage current values.

The smaller low voltage ones will be tested for capacitance and ESR, and replaced if warranted.
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Old 05-02-2016, 11:26 PM
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Quote:
Eveready zinc-carbon AA cell, which I was AMAZED to find not only hadn't leaked over the last 40 years, but still read 1.5 volts on my DMM! I didn't install it, though, opting for a modern alkaline AA cell instead.
About 5 years ago, I replaced the original carbon zinc Ray-O-Vac battery that had been in my V-7a VTVM for over 50 years with a new Duracell. Recently the meter was observed to be somewhat erratic... turns out, the Duracell had leaked extensively, causing some damage to the circuit board. The old Ray-O-Vac is *still* leak free, but is down to 1.43 Volts.

jr
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  #11  
Old 05-05-2016, 07:32 PM
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Back to the build! First off, a big thanks to Tim for supplying replacement audio and vertical output transformers for this set!

Got started on the first PCB assembly, the Sound module. This module implements essentially the entire audio section, with the exception of the chassis mounted power output stage. It contains 2 transistors, one IC, and a ceramic 4.5 MHz IF filter.

Most of the modules in this set use tubular contacts on the PC boards, which mate with pins mounted on the chassis. Construction begins with the installation of these contacts, which insert into 2 rows of square holes along the top and bottom edges of the board. A plastic alignment jig that resembles a lego block is placed over each row of contacts, the contact tabs are bent over to contact the foil pads on the board, and the tabs are soldered down to the board. Once the soldering is complete, the alignment jig is removed, leaving a properly spaced, straight row of contacts. The kit provided a long length of 3/16" diameter black PVC tubing, which is cut into short lengths and slipped over the contacts to provide protection against shorting adjacent pins. The provided tubing was pretty sticky and in poor condition from plasticizer breakdown, so I substituted some red heatshrink.

The board is then stuffed in stages, starting with a jumper wire, followed by the resistors, IC and transistor sockets, capacitors, inductors, and the IF filter and coil. Finally a short 2 -pin cable is attached, and the semiconductors are installed in their sockets, completing the module.

Next up: The Luminance module.
Attached Images
File Type: jpg All Parts.jpg (115.0 KB, 68 views)
File Type: jpg Tool.jpg (87.3 KB, 43 views)
File Type: jpg Pin Install.jpg (61.2 KB, 55 views)
File Type: jpg Pins bent.jpg (95.2 KB, 65 views)
File Type: jpg Pins installed.jpg (115.8 KB, 65 views)
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  #12  
Old 05-05-2016, 07:35 PM
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N2IXK N2IXK is offline
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More pics:
Attached Images
File Type: jpg Resistors.jpg (112.8 KB, 39 views)
File Type: jpg Sockets.jpg (111.6 KB, 29 views)
File Type: jpg Caps and Coil.jpg (106.0 KB, 36 views)
File Type: jpg Mylars.jpg (114.1 KB, 32 views)
File Type: jpg Sound board.jpg (109.3 KB, 88 views)
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  #13  
Old 05-05-2016, 10:58 PM
old_coot88 old_coot88 is offline
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Never having built a kit myself, just luuuv seeing this one go together. Built a few projects from the schematics Heath used to put in their catalogs, though. They all worked, too.
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Old 05-05-2016, 11:17 PM
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I still think there's a bunch of miswired freaks out there wishing death upon you because god forbid you assembled a heathkit set.
What's the point of owning the kit if you don't want to assemble it?
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  #15  
Old 05-06-2016, 05:47 AM
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N2IXK N2IXK is offline
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Originally Posted by MIPS View Post
I still think there's a bunch of miswired freaks out there wishing death upon you because god forbid you assembled a heathkit set.
What's the point of owning the kit if you don't want to assemble it?
There was at least one person on the Heathkit list who couldn't understand how building the set was more rewarding than flipping it for $ on eBay.
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