View Full Version : Heathkit GR-900 Build Thread!


N2IXK
05-01-2016, 06:11 PM
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! :banana:

On the downside, I am MISSING the audio and vertical output transformers!:cry: 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"! :D

rca2000
05-01-2016, 09:43 PM
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...

rca2000
05-01-2016, 10:01 PM
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.

N2IXK
05-01-2016, 10:42 PM
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....:thmbsp:

rca2000
05-01-2016, 11:00 PM
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...

zeno
05-02-2016, 07:34 AM
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:smoke:

N2IXK
05-02-2016, 09:02 PM
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...

Findm-Keepm
05-02-2016, 10:44 PM
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.....


Cheers,

N2IXK
05-02-2016, 11:06 PM
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.

jr_tech
05-03-2016, 12:26 AM
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

N2IXK
05-05-2016, 08:32 PM
Back to the build! First off, a big thanks to Tim for supplying replacement audio and vertical output transformers for this set! :thmbsp:

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.

N2IXK
05-05-2016, 08:35 PM
More pics:

old_coot88
05-05-2016, 11:58 PM
Never having built a kit myself, just luuuv seeing this one go together.:yes: Built a few projects from the schematics Heath used to put in their catalogs, though. They all worked, too.

MIPS
05-06-2016, 12:17 AM
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? :thumbsdn:

N2IXK
05-06-2016, 06:47 AM
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? :thumbsdn:

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.

Ed in Tx
05-06-2016, 08:54 AM
Back in the mid-'70s a friend (and still good friends today) built one of these. Never could get it aligned quite right. At the time we had a Heathkit store down on Ross Ave. in downtown Dallas. He hauled it there and they aligned it. Knockout excellent picture!

I got a lot of my initial experience building Heathkits and Knight kits for myself and friends. One of my first, a Heathkit tube clock radio from about 1963, I still have.

dtvmcdonald
05-06-2016, 11:22 AM
What Heathkit list? I'd love to go there.

WANTED: unbuilt or built, alive or dead, Heathkit GR-180 TV

WANTED: Alive, very alive only, correct picture tube for above.

N2IXK
05-06-2016, 11:37 AM
What Heathkit list? I'd love to go there.


https://groups.yahoo.com/neo/groups/heathkit/info

N2IXK
05-08-2016, 02:40 PM
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
05-11-2016, 08:05 PM
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/Heathkit_TV/conversations/messages

N2IXK
05-11-2016, 09:28 PM
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. :thmbsp:

wkand
05-12-2016, 12:38 PM
Never having built a kit myself, just luuuv seeing this one go together.:yes: Built a few projects from the schematics Heath used to put in their catalogs, though. They all worked, too.

Wow! I never saw the schematics in the catalogs... I only got into Heathkit in the 1970's and '80's however. Were these schematic laced catalogs earlier than that?

Kevin Kuehn
05-12-2016, 01:31 PM
Looks like a fun project. Impressive that they used G10 epoxy circuit boards.

If I ever find an un-built Heathkit TV I'd have to build it too. :thmbsp:

zenith2134
05-12-2016, 08:22 PM
Wow what a thread! I would be so excited to be embarking on this project. I know where there is an unbuilt color Heathkit locally but the guy is insisting on keeping it in original box. Not sure which set it is but, he claims to have acquired it in the early eighties.
The parts stock seems to be of nice quality on yours. Probably a good move to perform a leakage test on the original capacitors.
Say, if (heaven forbid!) one of the ICs were bad, would a replacement be procurable on its own, outside of a whole kit?
Not too many people left today who could say they actually built their own TV set!

WISCOJIM
05-12-2016, 08:29 PM
I know where there is an unbuilt color Heathkit locally but the guy is insisting on keeping it in original box.

More likely "boxes".

I know where 3 unbuilt color TV kits are right now. I don't expect they're going anywhere soon.

.

zenith2134
05-12-2016, 08:37 PM
Yep. I suppose I can see the desire in keeping the "boxes" sealed but I offered this fellow good money in cash and he wouldn't even hear it!
Plenty of old sets out there still...it is amazing really

old_coot88
05-12-2016, 08:44 PM
Wow! I never saw the schematics in the catalogs... I only got into Heathkit in the 1970's and '80's however. Were these schematic laced catalogs earlier than that?
This was the late '50s.

Electronic M
05-12-2016, 09:44 PM
Wish I could find a unbuilt tube Heathkit TV. That would be a fun project.

WISCOJIM
05-13-2016, 12:49 AM
Wish I could find a unbuilt tube Heathkit TV. That would be a fun project.They're still around, sometimes right under your nose. Got my latest one at the ETF convention this year when the rest of you guys were off to lunch! My van was packed to the roof on the return trip. This one included the multimeter and tube tester kits with it.

.

rca2000
05-13-2016, 01:00 AM
Did not see it..or perhaps I too would have bid.. But I got enough from the ETF this time... INCLUDING the BW set in my avatar...certainly NOT disappointed !!

N2IXK
05-14-2016, 09:41 PM
All of the ICs in this set were (or went on to be) industry standard stuff of the day. Mostly Motorola and RCA linear ICs, most of which were second sourced by other vendors, and were available from ECG, SK, or NTE at least at one point. Same types of chips that started showing up in other manufacturer's sets of this era.

This kit had already been unpacked and partially gone through, and I received it in 2 large boxes, 4 smaller boxes (one for the remote control option), and of course the CRT carton. One of the smaller boxes was apparently a duplicate shipment. Not sure if the training classes shipped the whole kit at once, or in multiple shipments to each student.

Anyway, the build continues on board by board. My best friend and her daughter were over last weekend (Daughter needed help with replacing a fuel pump on her car that we had diagnosed as bad a few weeks earlier), and she was asking about all the boxes of parts down in my basement shop. I told her that I was putting together a DIY TV kit, and she was intrigued with the idea of building your own TV. Showed her a few of the modules I had been working on, and she was so interested in it that I gave her a few quick lessons on soldering, and turned her loose on the Chroma board (which was one of the ones I had a spare for from the duplicate shipment). She did an AMAZING job putting it together, and wants to drop by again to do some more on the set, before I finish it all. :thmbsp: By the end of putting the board together, she was already starting to learn the resistor color code, too...:)

The Chroma, 3.58 MHz oscillator, and AGC/Sync modules all went together that afternoon. Here's some pics of the finished board, plus a shot of my soldering student in action....:smoke:

Up next, Vertical Oscillator, Horizontal Oscillator, and Pincushion modules....

N2IXK
05-17-2016, 09:13 PM
The last 3 of the plugin modules are completed and ready to go. Construction is much the same as the previous ones. Here we have the Vertical Oscillator, Horizontal Oscillator, and Pincushion modules. I have been replacing the electrolytics with modern equivalents as I go along.

I have tested a random sample (maybe 25-30) of the resistors during the build, and have found the values within tolerance (some just barely). Solderability of the boards remained very good through 40 years of storage, and almost all of the components have been perfectly usable right out of the box, as well. Some of the diodes which had silver plated leads had a bit of tarnish on them, but it wiped right off. The CTS brand trimpots were the only major soldering problem, with the wiper terminals refusing to take solder until I heavily wirebrushed the terminal (removing whatever the plating was and exposing the brass underneath). Not sure what the plating is, but it develops a thin brownish/purple tarnish that solder flux does nothing to. The end terminals of the pots are just fine, having what appears to be a tin/lead coating.

The final pic here are all 9 of the modules completed so far. Next up is the convergence panel....

N2IXK
05-22-2016, 12:58 PM
The convergence panel is the largest PCB so far. It houses the usual array of wirewound pots and coils used for the dynamic convergence adjustments. It is mounted on a small subchassis, along with the UHF tuning presets and several secondary/service controls. It uses 6 silicon diodes rather than the traditional selenium convergence diode assembly found in most commercial sets of this era.

The UHF preset tuning assembly is similar in concept to the preset tuning panels that became common a decade later in early VCRs. It consists of a carbon film resistive divider, with 12 separate adjustable sliders to set the varactor tuning voltage for the desired UHF channels.

Most of the wiring comes in the form of prefabricated harnesses which are soldered to the various points on the subchassis. The 3 convergence magnet assemblies that go around the CRT neck are attached to one of these harnesses, and the other harnesses have connectors that will get plugged into the rest of the chassis at final assembly.

The convergence panel completes the first of the assembly manuals. Before moving on to the next manual in order, I am going to go through the assembly of the optional remote control, which has its own manual, separate from the ones for the set itself. The next post will deal with the assembly of the remote control transmitter...

N2IXK
05-24-2016, 09:37 PM
Got started on the GRA-900-6 remote control, by building the handheld transmitter unit.

Unlike the Zenith type mechanical transmitter using ultrasonic chimes, the Heathkit design is electronic, consisting of a very simple 1-transistor Hartley oscillator, driving a small ultrasonic transducer. 8 separate ultrasonic frequencies can be generated by pressing each end of one of 4 rocker style buttons. Functions include on/off (which can also select one of 3 audio levels), UHF/VHF select, channel up/down, color up/down, and tint red/green. Each function button contact switches one of 8 precision (2%) silver mica caps into a single transistor oscillator circuit. The circuit is powered by a standard 9V battery.

Construction was pretty straightforward, with only 2 age-related issues. The 16 small brass rivets used for the board mounted switch contacts were pretty heavily tarnished and needed a good cleaning in order to be soldered onto the board and make reliable contact with the rocker leaf switches.

The other problem was that the provided foam tape had completely dissolved into sticky goo that was all over the bare PCB. Luckily it cleaned up well with IPA, leaving the board unharmed. The foam tape was replaced with a modern equivalent weatherstripping tape, and is used to cushion the battery and ultrasonic transducer inside the 2-part plastic housing.

For some reason, the remote transmitter and receiver PC boards are phenolic based, rather than the nicer epoxy glass ones in the rest of the set.

After finishing the remote transmitter, I installed a battery to see if it worked. I tried plugging the TV receiver microphone into a scope (it has an RCA plug cable attached) to see the signal, but saw nothing at all. A quick look at the receiver schematic shows that the microphone needs a 200V or so bias voltage which the receiver provides. I connected my scope probe right across the transmitter output leads, and got nice strong sinusoidal signals right at the transducer, with a different frequency for each button pressed, so the transmitter seems to be functional.

Up next, the remote receiver and the first hints of trouble ahead?

N2IXK
05-26-2016, 11:10 PM
Next up on the bench was the remote receiver unit that goes inside the TV itself. The receiver consists of an ultrasonic microphone, a wideband preamplifier, and 8 separate LC tuned circuits driving 8 relays which then drive the control motors and other set functions. The board is phenolic like the transmitter board was, and the transistors are actually soldered to the board, rather than being socketed as in the rest of the set.

The board built up quite quickly, having a lot of repetitive wiring for the 8 control channels. The finished board then gets installed into a metal frame/shield which holds the remote receiver power transformer and a stepping relay used for the power and volume functions. The unit also includes a small signal strength meter used for tuning the 8 channels for best operation.

I decided to test the remote control subsystem on the bench before moving on with the build, and I am glad I did. I began by finding the appropriate pins on the molex power connector and connecting the primary of the transformer to 120 V power. Power supply rails came up OK, and I was able to tune 6 of the 8 adjustable coils (using the built in meter) to get all functions except channel down and tint green operating. The channel down function seemed completely "deaf", with no signal indication on the meter at all, and the tint green function showed a strong signal when the transmitter button was pushed, but no click could be heard from the corresponding relay. :scratch2:

A couple quick checks showed an open coil winding on the tint green relay. The relays used here are SPDT contact, 12VDC coils, with a DC resistance of ~1k ohm. Was glad to see that they were nothing exotic that couldn't be replaced, but a close examination of the open relay showed the coil wire broken right at the base pin where it entered the inside of the relay. Luckily, it was the outside end of the winding, so I was able to carefully unwind a single turn and reconnect the wire to the pin, which restored proper operation of the tint green function.

The channel down issue was more of a puzzler. a check with a scope at the output of the preamp circuit showed that a proper signal WAS being received through the microphone, ruling out a dead transmitter channel. A quick check showed all the proper components installed, and injecting a small DC signal into the relay coil drive transistor's base showed that the transistor WAS capable of turning the relay on and off. That left only the LC tuned circuit for the affected channel. The 680 pF silver mica capacitor was tested, and found to be OK, which left just the tunable coil. An identical coil (Heath p/n 40-842) is used in the power/volume channel, and preliminary DC resistance checks between the 2 showed similar result (40.8 ohms vs 41 ohms), with the "bad" coil showing the slightly lower value. Shorted turn maybe?

I swapped the coil from the power channel into the channel down position, and sure enough, it now worked fine. :yes: A comparison of the 2 coils using the ringing test function of a VA62 showed a clear difference between the 2, confirming the diagnosis of a shorted turn. Now what to do about it?

The parts chassis I got from Tim didn't have the remote option, so a donor coil wasn't easily available. The coils are typical adjustable types, wound on a fiber form, but the high inductance needed due to the relatively low frequency requires a ferrite "pot core" over the outside of the winding, as well as the adjustable ferrite slug inside. The pot core would need to be removed to examine the coil more closely, and attempt a repair. The pot core was held onto the coil form with a blob of epoxy adhesive that was quite resistant to scraping or picking at it, and I didn't want to risk damaging the core or the coil form by mechanical methods of removal. I placed the coil inside a small jar, with a few mL of dichloromethane (just enough to submerge the epoxy) overnight, and by the next day, the epoxy literally fell off freeing the pot core. The cause of the problem was easily found, a small "ding" in the side of the winding, which exposed bare copper on a couple wires and caused a shorted turn. It must have been that way from the factory, as the area was completely protected under the ferrite shell. Careful separation of the wires and a drop of insulating varnish restored the coil to proper function. The pot core was glued back on, the coil was installed into the receiver, and now all 8 functions were working!

Hopefully, the 2 bad components in the receiver aren't an indication of component problems in the rest of the set, or there may be a LOT of troubleshooting ahead. :sigh:

Up next, work begins on the heart of the build--the main chassis!

wkand
05-27-2016, 01:09 AM
Wow. Amazing journey you are on. Thanks for the details and great pics...

N2IXK
06-01-2016, 09:31 PM
Onto the 3rd volume of the assembly manuals, the Main Chassis.

The first couple bench sessions involved in the chassis construction were strictly mechanical work. LOTS of parts to be installed onto the vertical metal chassis pan. Terminal strips, power transistor sockets, filter caps, various transformers, module connectors, pots, switches, shields, and 3 factory wired sub-assemblies for IF, AFT, and High Voltage. The nut starter and 1/4" nutdriver got a real workout! :D

The chassis takes up a fair amount of space on the bench, and needs to be repositioned as assembly progresses to different areas. The heavy power transformer is one of the first parts that get installed, and it allows the chassis to be stood up in a vertical position when needed.

Assembly was pretty uneventful until it came to the HV assembly. Despite coming to me still in it's sealed box, it needed a little bit of rework to repair a broken terminal strip, a wire that never received any solder at the factory, replacement of a large electrolytic cap, and cleaning the leached sticky plasticizer from the 2nd anode cap (which I may end up replacing entirely at final assembly). The workmanship on the factory wired parts of this set was not very good at all, with a few spots of burned or melted insulation, somewhat haphazard lead dress, and a few random solder splashes which were found and removed. Probably equivalent to most assembly line wiring jobs of the day, I guess. :thumbsdn: The 3CU3 HV rectifier tube (Sylvania branded, FWIW) was rattling around loose inside the cage, free from the socket but still firmly connected to the flyback lead. Luckily it was unbroken, as were the flyback and other parts inside the cage. The tube was tested and reinstalled. Finally the reworked HV unit was bolted into place, completing chassis mechanical assembly.

I did make a minor upgrade to the set, using modern "Sil-Pad" rubber type thermal pads on all the power transistors rather than the plain mica washers and clear silicone grease that Heath provided. I replaced the thermal pads on the sweep SCRs of the HV assembly, as well. The 2 multisection twist lock caps were thoroughly reformed on a power supply and tested before installation. All the other smaller electrolytics were replaced as a precaution.

Next up--chassis wiring begins!

N2IXK
06-05-2016, 08:28 PM
The chassis wiring gets installed in 3 stages, starting with routing and connecting the leads from 3 transformers (power, vertical output, and CRT filament) previously installed on the chassis, and running various individual wires between different points as instructed. These are individually cut to length from bulk wire, stripped, routed, and connected.

The second stage of chassis wiring involves the installation of prefabricated wiring harnesses and multiple Molex type connectors used to connect to components mounted off-chassis. The CRT socket harness is also installed at this point.

Finally, all the chassis mounted electronic components (resistors, caps, diodes, etc.) are put into place and soldered. All together, the chassis wiring was completed in 4 bench sessions, totaling around 9 hours. Easily the most demanding work of the project so far.

The pictures attached here are from the early stages of chassis wiring. More to come...

zenithfan1
06-05-2016, 08:39 PM
Very neat work, beautiful job so far. I can't wait to see it finished!

N2IXK
06-06-2016, 10:11 PM
Thanks!

Here are some pics of phase 2 of chassis wiring, the installation of several prefabricated wiring harnesses and connectors.

I added a few black nylon zip ties to tie the harnesses together for improved support and a neater appearance. I also trimmed a few leads from the harnesses that were longer than they needed to be. Most wires were just perfect as provided, and the prestripped wiring goes in much faster than the short individual wires done previously.

Up next, completing the underside of the chassis with a LOT of components....

andy
06-07-2016, 02:17 AM
Is there any chance you could post larger pictures? I can't see much detail in those tiny pictures.

Kamakiri
06-07-2016, 08:57 AM
This is truly impressive. I'm following this thread with great anticipation :)

N2IXK
06-07-2016, 09:08 PM
Thanks!

I have kept the images small because of the sheer number being posted, as I don't want to overrun my storage quota here at VK. If anyone wants to see the full resolution copy of any of these pics, just send me a PM.

The installation of chassis components went pretty smoothly, with the only solderability issues being a few of the diode leads, which needed a good cleaning to remove the silver plating tarnish. The components form the final "layer" of the chassis wiring, and complete the work on the backside of the chassis.

N2IXK
06-07-2016, 09:10 PM
More pics attached.

Next up: Finishing the chassis topside wiring, and module installation.

Phil Nelson
06-07-2016, 09:17 PM
This is truly impressive. I'm following this thread with great anticipation :)Yes, the suspense is building! Let's hope the remainder of the project goes smoothly.

I was thinking that this must be one of the most complicated kits ever offered to consumers. Color TVs have an awful lot of parts & pieces.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

N2IXK
06-07-2016, 09:29 PM
I was wondering about the "most complicated kit" title. This is certainly the most complicated Heathkit I have had the fun of putting together, with the second being a "Hero Jr." robot.. I think the later GR-2000 and GR-2001 sets with the on screen display beat this one by a bit, with the addition of several digital boards for the advanced features.

The other contenders for the complexity prize would possibly be the Heath/Thomas electronic organs, or possibly the H1 Analog Computer:

http://www.technikum29.de/en/computer/analog

N2IXK
06-08-2016, 09:46 PM
The chassis assembly is completed with a handful of electrical connections on the top side of the chassis, to the IF module and power supply filter choke.

The 9 previously completed PCB modules are then installed into their proper locations, and the chassis set aside for final assembly with the rest of the set. These pics are of the top side of the completed chassis, with all modules installed.

Up next, assembling the VHF/UHF tuner cluster and control panel...

zenithfan1
06-08-2016, 11:52 PM
:rockon:Wow!

Electronic M
06-09-2016, 07:12 PM
Interesting that it uses a HV rect tube.

Ed in Tx
06-09-2016, 07:29 PM
Probably has to do with the year it was first available-1969. I don't think there was a reliable solid-state substitute yet.

In 1974 I went to work for Varo Inc. and among the things they manufactured were solid-state high voltage rectifiers and triplers for TVs. By then they were reliable and common.

N2IXK
06-09-2016, 08:21 PM
Varo pretty much owned the market on those things, didn't they? I think they were the first to produce them. I agree the 1969 introduction of this model would have been just a bit early for SS. I assume the GR2000 series sets used a solid state HV rect or tripler?

I have an ECG solid state replacement here which I think would work in this set should the 3CU3 ever give problems.

N2IXK
06-12-2016, 11:28 PM
Onto the next assembly manual, covering the assembly of the Tuner cluster/Control panel. The manual is divided into 2 sections, and the builder follows the half with or without the remote control option as applicable.

Work starts out as more mechanical assembly. The VHF and UHF tuners come preassembled, and are mounted into a metal subchassis. The tuner drive motor and gearbox get attached, along with numerous terminal strips and a large oil filled capacitor (4 uF, 370V) used for reversing the tuner drive motor. The supplied capacitor was a Sprague "Chlorinol" capacitor, which was a trademark for polychlorinated biphenyl, or PCB. :thumbsdn: Although the cap looked pristine with no signs of leakage, I replaced it with a modern non-PCB cap to remove the environmental hazard. The new cap fits the original mounting perfectly and looks original to the set. The original cap is safely stored away for the next hazmat collection day.

All the pots get attached to a bracket, which is then mated to the front subpanel and the tuner chassis, completing the mechanical assembly. Because I am installing the remote option, drive motors get installed onto the back side of the color and tint pots to allow remote operation. The UHF and VHF channel indicator dials are backlighted by incandescent lamps, and driven via a small timing belt drive. The VHF fine tuning is driven with a ballchain drive system. 4 pushbutton switches are installed for power, channel up/down, and UHF/VHF select.

The wiring is almost completely prefabricated harnesses, which are quite long and make for a real pain on the bench. The unit ends up with quite a wad of wiring attached.

The final part of the assembly is the stuffing of a small PC board which they call the "UHF" board, but what it really handles is the switching between UHF and VHF tuners, and driving the appropriate dial backlight for the selected band. The board is connected to the chassis via a 15 pin Molex connector which supports the entire board. While Heath sent a 15 pin Molex connector which I dutifully installed, It wasn't until trying to plug the board in that I discovered that the WRONG GENDER of connector shell was supplied! Luckily, I had a proper connector shell, as well as the pin extraction tool to remove the contacts from the supplied shell, and reinsert them into the proper one. The board survived the desoldering and resoldering just fine, and the tuner cluster was completed in 3 bench sessions totaling around 5 hours.

N2IXK
06-12-2016, 11:30 PM
More pics.

Up next--Installing the CRT and bringing all the parts together for final assembly!

N2IXK
06-13-2016, 08:36 PM
Onto book #4, covering assembly of the CRT, mask, and chassis frame.

I began the process by building a temporary "T" extension (3/4" plywood and 2x4 legs) onto my workbench to provide enough room to work on the assembled set. Most of the projects I tackle in my shop are a good bit smaller than this beast! :yikes:

First up, I decided to actually test the CRT to make sure it was still electrically good. The CRT carton was pretty well destroyed by moisture, and the tube itself has a nasty cataract extending 3-4 inches in toward the center in a few spots. Assuming the set makes a good picture, a cataract removal or (preferably) a CRT replacement can be pursued later. The supplied tube is an RCA 25VABP22, but the manual refers to a 25VADP22. Comparing datasheets shows the tubes are pretty much identical, with the later VADP having a "Temperature Compensated" (Invar?) shadow mask for improved purity. I seem to remember that most of the 25V-series tubes were fairly interchangeable, with minor differences like black matrix, rare earth, mounting ears, etc.

Firing up the tester, the tube was a bit slow to warm up after sleeping all these years, but after a few minutes warmup the guns balanced perfectly, with emission and life test readings consistent with a NOS tube. :smoke:

Assembly begins by placing the plastic CRT mask face down on supports (4 blocks of 2x4), and lining the inside of the mask surface (where the edges of the CRT faceplate rest) with aluminum foil tape as an electrostatic drain. The provided roll of 3M foil tape was still perfectly usable after 4 decades in storage. The foil is carefully overlapped in the corners, and folded over to make contact with the CRT mounting hardware.

The CRT is then placed into the mask opening, making sure that the anode contact faces the top edge of the mask.

The CRT clamps and straps are prepared by adding adhesive felt pads (also amazingly viable despite age) and rubber cushions at the points where the clamps bear against the glass. the clamps are carefully drawn down tight in several stages until they bottom against the mask, then the strap screws are tightened to clamp the tube into place.

A long length of bare solid wire and a coil spring are installed as a grounding contact for the outside dag coating, and the degaussing coil is wrapped around the tube in a very carefully specified pattern (to assure even magnetic field over the mask area), and anchored in place with cable ties.

Next up--final chassis assembly and moving toward "First Light"....

zenithfan1
06-13-2016, 09:09 PM
I can't wait to see this up and running! Great job!

MRX37
06-14-2016, 11:11 AM
Very interesting thread!

Though, sorry but that remote is ugly as sin! Even for an old ultrasonic remote that thing is just ugly!

Josef
06-14-2016, 02:53 PM
Great work no question. It's always a pleasure to build a device with your own hands. I built a few custom devices at work and know how much time it takes because I had to drill every hole and crimp every connector by hand. Did you clean the pcbs with spiritus after soldering and count the hourīs it takes? Greetings and good luck!

N2IXK
06-14-2016, 10:43 PM
Yes, the remote is pretty fugly. The "thousand island dressing" color scheme doesn't help...:scratch2:

I did clean the modules with flux remover after soldering. I haven't been keeping all that close a count of hours, but 40-45 hours to this point is my best guesstimate, not including the time inventorying the parts, ordering replacements, and related activities.


After installing the CRT into the mask, the 4 sides of the chassis frame/magnetic shield are attached to the mask and bolted together forming a rigid box structure. The dag ground from the CRT assembly is grounded to this frame. The deflection yoke is installed into the "flowerpot" style holder, and installed onto the CRT neck. The completed chassis is hung on its hinges, and the degaussing leads and CRT anode wire are connected, before closing the chassis. I elected to replace the somewhat stiff and degraded anode cap with a nice silicone rubber one salvaged from a discarded BPC set.

After the chassis is installed, the entire framework and tube was thoroughly degaussed (using a real coil, not the dinky external one provided with the kit), and the convergence magnets/coils and blue lateral/purity magnets were installed, along with the CRT socket. The convergence board, tuner cluster, and "Troubleshooter" meter are hung on screws in the framework for the initial test/adjustment procedures, and all the interconnecting cables plugged in.

This completes the assembly of the set! Up next, using the "Troubleshooter" to check for problems, and power gets applied for the first time....

Boobtubeman
06-15-2016, 01:05 AM
Light that sukka!!! :D

SR

N2IXK
06-16-2016, 09:05 PM
Testing begins with a series of testing flowcharts, where the builder uses the provided VOM to make a series of resistance tests to verify that no major shorts or miswiring exists. Tests were made using both the "Troubleshooter" VOM and a DMM (Fluke 87). As Heath gave no specific resistance values, just which area (A-E) the troubleshooter needle should indicate for each test, I noted the actual resistance reading taken with the DMM in my build notes.

You test the AC line circuitry first, checking for continuity and shorts to chassis ground. Then the various main power supply rails are checked for resistance to ground, to rule out shorts or reversed polarity components that might cause damage at powerup. About a dozen tests all together, and all passed with flying colors. :thmbsp:

At this point, you preset the brightness, brightness limiter, drive, screen and kine bias controls as specified, and unplug the CRT socket. The set gets connected to 120 vac, and the switch is thrown.....


No bang....:yes:

The gentle crackling sound of HV supply coming alive! :banana:

No smoke or bad smells...:yes:


Back to the testing charts, where measurements are made of cathode, G1 and G2 voltages, and a couple power supply rails. All well within the specs...:D

An occasional snap/crackle was noted from inside the HV cage and traced to a bit of cardboard packing material that was trapped under the edge of the HV rectifier tube socket. :sigh:

The set is then powered down, and the CRT socket connected. Ready for "first light" tomorrow night, when my chroma board helper and her mom are dropping by for dinner and to watch this thing come to life. The suspense is killing me...:eek:

Not much in the way of pics for this post. I hope some screen shots will be taken tomorrow night....:smoke:

N2IXK
06-18-2016, 09:59 PM
Power applied.

Heaters start warming up, and....

It Lives!!!

First light: June 17, 2016.

After a couple minutes of snapping pictures and sniffing for smoke, I flipped on the built in dot generator and got pretty much what I expected. Could have been cover art for a 60's psychedelic band. Convergence just about as far out as it is possible to be in every direction. Horrible purity, and overall reddish cast with blurry retrace lines, but it makes an image! My visitors seemed puzzled why I was as happy as I was with what we saw. Had to explain the large amount of adjustment and tweaking that needs to be done to a set of this vintage to get everything just right. And that having a picture even this good means that 90% or more of the set is already working properly.

A quick purity setup, static convergence setup and greyscale adjustment produced a nice stable black and white image. A few tweaks of the 3.58 osc and burst phase got a reasonable color image, and tweaking the AGC got it fairly viewable in about 20 minutes.

Today I went through and finessed things in a bit better, and got things as good as the "non instrument" alignment procedure is going to, I think. I plan to follow the full alignment procedure detailed in the final volume of the manual set, and at least verifying that the IF and chroma circuits are lined up. Several coils and traps are left unadjusted when using the simplified procedures, and I think I can squeeze a bit better image out of this thing with a real instrument alignment. Both the color and tint controls have a very limited range of action, right around the center of travel. Color level particularly touchy to set to get reasonable skintones without over or saturation.

It's been a month and a half since I started this journey, and had a great time doing it! Will begin looking for a suitable NOS replacement tube and designing some kind of cabinet for this beast. Any leads or ideas gratefully accepted...

N2IXK
06-18-2016, 10:00 PM
Couple more pics...

zenithfan1
06-18-2016, 10:41 PM
That thing looks awesome! Almost like a brand new set:thmbsp::smoke:

N2IXK
06-25-2016, 08:56 PM
Over the last week or so, I have managed to track down a potential source for a replacement tube, and should have it in the next few days. New tube is a 25VCZP22, which appears to be a tension banded successor to the bonded faceplate VAB/VAD types. Hoping it fits the mask on my set OK. Datasheet comparison looks promising.

Spent an hour or so setting up the UHF tuning presets. To use all 12 presets, I selected all the now defunct local UHF stations I can remember, and added a handful of others. 14 and 83 just to cover the entire band for testing purposes, 37 just in case I want to listen for aliens, and channel 62 to tune in the occasional Blonder/Tongue modulator broadcast of "UHF". :D Dialed all channels in using a VA62. All the channel number stickers were in great shape, and applied to the UHF channel display wheel.

Varactor UHF tuner works VERY nicely, good stable reception on all channels. Did any commercial sets have varactor UHF tuning in 1969?

Am pondering how best to add a composite AV input to this set. Video amplitude out of the detector measures about 2Vpp, but proper polarity. Applying a proper level video signal from the VA62 right into the video cable to the IF module gives a GREAT picture. I need to design a video amplifier with a gain of ~2, preferably to operate from the single ended 30V power supply available in the set. Shouldn't be too big a deal using a modern video opamp. Line level audio input will probably be done by just rewiring the provided "HiFi out" line level audio output jack to be a line level input to the top end of the volume pot.

The set has an unused position between 2 and 13 on the VHF tuning dial (where UHF would be on a non varactor setup) which displays "H" (for Heathkit I guess:scratch2:) on both UHF and VHF tuning dials. I am contemplating rigging up a switch/relay to automatically select the AV input in this tuner position, so as not to have to add a separate line/RF switch.

Dynamic convergence has drifted a tiny bit in the last week or so (maybe 8 hours run time). Nudged it back, but obviously going to be redone again at CRT swap.

Contemplating a cabinet design to be a winter project. Thinking wooden front and bottom, with transparent top, sides, and back.

msimendi
07-01-2016, 03:34 PM
I've wanted to ad a composite video input to my GR-900 also. I found a circuit from an Early Television Foundation presentation from some years back. I built it but it wasn't flat out to 4.5 MHz so I abandoned the idea.

How about injecting it right after the diode and before the final IF stage? Haven't tried that yet as it is in a sealed can.

andy
07-01-2016, 04:20 PM
Over the last week or so, I have managed to track down a potential source for a replacement tube, and should have it in the next few days. New tube is a 25VCZP22, which appears to be a tension banded successor to the bonded faceplate VAB/VAD types. Hoping it fits the mask on my set OK. Datasheet comparison looks promising..

Why don't you just fix the cataract on the original CRT? It's not that hard to do, and will save wasting the NOS CRT that came with the kit.

N2IXK
07-01-2016, 09:55 PM
I have serious doubts about the safety of tubes that have undergone the standard cat removal procedure. The whole purpose of that resin was to effectively form a glass/resin/glass laminated panel, similar to automotive safety glass. Without the resin layer, it is just an unprotected CRT behind a second sheet of non-safety glass (the reinstalled faceplate). At least the older sets actually used a laminated glass safety panel in front of the unprotected CRT. The faceplates on laminated tubes are just tinted or frosted glass, which would only add to the shrapnel from an implosion if not bonded with the resin.

Obviously CRT rebuilders must have had a way to remove and rebond these faceplates properly when rebuilding tubes, as the resin would never have stood up to oven bakeout. Does anyone know how this was done? It isn't addressed in the excellent film made of HawkEye's rebuilding process over on the ETF site. I imagine that it takes some special setup (like vacuum impregnation) to ensure no trapped air bubbles in the resin. Clear 2 part urethane casting resin is available from several suppliers, and would probably be a good substitute for the PVA that was originally used, if a way was available to get a void-free fill.

The 25VCZP22 that I found locally turns out to have issues with the red gun, so probably won't be used. The ETF has a pair of NOS 25VABs available for $75 each, so if one of them is cat-free I will likely purchase one of those. They are in the process of checking them for me. The VCZ would have actually been a nicer tube, being a tension banded type with no cataract worries at all. Bummer about the red gun...

N2IXK
07-24-2016, 05:57 PM
The new tube arrived yesterday, and looks like a beauty. A Sylvania "AA" grade, all new "Chromatrix" tube. Completely cataract-free, and with a date code of "2013" which I am guessing is a code of some kind, not a 3 year old tube. Box looks a good deal older than that. :D Even got the warranty registration card (should send it in for a laugh!):yes: Thanks to Steve at the ETF, and a friend of mine who was able to bring the tube from Ohio back to NJ for me, saving $$$ on shipping

Tube tests perfectly on the CR-31A, and will be installed after I return from a week's vacation.

jr_tech
07-24-2016, 07:18 PM
I have serious doubts about the safety of tubes that have undergone the standard cat removal procedure. The whole purpose of that resin was to effectively form a glass/resin/glass laminated panel, similar to automotive safety glass. Without the resin layer, it is just an unprotected CRT behind a second sheet of non-safety glass (the reinstalled faceplate). At least the older sets actually used a laminated glass safety panel in front of the unprotected CRT. The faceplates on laminated tubes are just tinted or frosted glass, which would only add to the shrapnel from an implosion if not bonded with the resin.

Obviously CRT rebuilders must have had a way to remove and rebond these faceplates properly when rebuilding tubes, as the resin would never have stood up to oven bakeout. Does anyone know how this was done? It isn't addressed in the excellent film made of HawkEye's rebuilding process over on the ETF site. I imagine that it takes some special setup (like vacuum impregnation) to ensure no trapped air bubbles in the resin. Clear 2 part urethane casting resin is available from several suppliers, and would probably be a good substitute for the PVA that was originally used, if a way was available to get a void-free fill.


In this post, I described a process that I have observed:

http://www.videokarma.org/showpost.php?p=2993611&postcount=2

jr

N2IXK
07-24-2016, 09:42 PM
Interesting. Thanks for posting that. The PPG number you posted appears to be an automotive paint, not a bonding resin. I have used various products from Forsch Polymer Corp. over the years, and they have a few resin systems that seem like they would work well for this application, with low uncured viscosity and good transparency when cured.

May have to give it a try on a dud tube at some point to see if the cataract problem can be solved without compromising future safety.

jr_tech
07-25-2016, 03:55 PM
Interesting. Thanks for posting that. The PPG number you posted appears to be an automotive paint, not a bonding resin.

I tried to dredge another number out of the old memory cells, but I keep comming back to PPG 5252. Dead cells? Two numbers associated with this task had a nice rhythm, like 5252 and 1418 for the UL crt implosion test document. Wonder if the 5252 number got recycled to another product after the process was retired. :scratch2:

The resin that was used was heated (85 C ?) in small batches and the mek-p catalyst was added and mixed in just before the pour was made. When cured, the resin had a rubbery consistency.

Good luck with your experiments,
jr