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  #31  
Old 05-14-2016, 08:41 PM
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N2IXK N2IXK is offline
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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. 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....

Up next, Vertical Oscillator, Horizontal Oscillator, and Pincushion modules....
Attached Images
File Type: jpg Soldering.jpg (53.9 KB, 76 views)
File Type: jpg Chroma.jpg (107.0 KB, 45 views)
File Type: jpg 3.58 Osc.jpg (106.4 KB, 40 views)
File Type: jpg AGC Sync.jpg (110.5 KB, 53 views)

Last edited by N2IXK; 05-14-2016 at 08:46 PM.
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  #32  
Old 05-17-2016, 08:13 PM
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N2IXK N2IXK is offline
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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....
Attached Images
File Type: jpg Vert Osc.jpg (109.9 KB, 32 views)
File Type: jpg Horz Osc.jpg (97.5 KB, 32 views)
File Type: jpg Pincushion.jpg (69.5 KB, 39 views)
File Type: jpg All Boards.jpg (107.8 KB, 60 views)
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  #33  
Old 05-22-2016, 11:58 AM
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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...
Attached Images
File Type: jpg Conv Board.jpg (64.8 KB, 48 views)
File Type: jpg Conv Panel.jpg (51.8 KB, 44 views)
File Type: jpg Conv Wiring.jpg (60.4 KB, 46 views)
File Type: jpg UHF Presets.jpg (64.7 KB, 50 views)
File Type: jpg Pots.jpg (57.9 KB, 51 views)
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  #34  
Old 05-24-2016, 08:37 PM
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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?
Attached Images
File Type: jpg Xmtr2.jpg (81.2 KB, 47 views)
File Type: jpg In Case.jpg (71.6 KB, 39 views)
File Type: jpg Finished.jpg (69.7 KB, 46 views)
File Type: jpg Grille.jpg (76.8 KB, 34 views)
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  #35  
Old 05-26-2016, 10:10 PM
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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.

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. 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.

Up next, work begins on the heart of the build--the main chassis!
Attached Images
File Type: jpg Rcvr parts.jpg (92.2 KB, 33 views)
File Type: jpg board partial.jpg (102.4 KB, 29 views)
File Type: jpg Full board.jpg (95.2 KB, 45 views)
File Type: jpg Preamp.jpg (89.2 KB, 33 views)
File Type: jpg Rcvr complete.jpg (81.4 KB, 48 views)
File Type: jpg Meter.jpg (83.3 KB, 38 views)

Last edited by N2IXK; 05-26-2016 at 10:14 PM.
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  #36  
Old 05-27-2016, 12:09 AM
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wkand wkand is offline
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Wow. Amazing journey you are on. Thanks for the details and great pics...
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  #37  
Old 06-01-2016, 08:31 PM
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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!

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. 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!
Attached Images
File Type: jpg Bare Chassis.jpg (71.9 KB, 49 views)
File Type: jpg Chassis 2.jpg (76.8 KB, 40 views)
File Type: jpg Chassis mechanical.jpg (75.3 KB, 64 views)
File Type: jpg Broken Strip.jpg (56.7 KB, 49 views)
File Type: jpg Strip repair.jpg (51.4 KB, 40 views)
File Type: jpg Unsoldered.jpg (66.8 KB, 43 views)

Last edited by N2IXK; 06-05-2016 at 08:36 PM.
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  #38  
Old 06-05-2016, 07:28 PM
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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...
Attached Images
File Type: jpg Xfmr.jpg (79.8 KB, 46 views)
File Type: jpg Wiring 1.jpg (75.3 KB, 42 views)
File Type: jpg wiring 2.jpg (63.1 KB, 30 views)
File Type: jpg Wiring 3.jpg (67.7 KB, 32 views)
File Type: jpg wiring 4.jpg (79.8 KB, 42 views)
File Type: jpg G2 Pots.jpg (74.8 KB, 47 views)
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  #39  
Old 06-05-2016, 07:39 PM
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Very neat work, beautiful job so far. I can't wait to see it finished!
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  #40  
Old 06-06-2016, 09:11 PM
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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....
Attached Images
File Type: jpg Harness 1.jpg (90.1 KB, 37 views)
File Type: jpg Harness 2.jpg (84.7 KB, 32 views)
File Type: jpg Harness 3.jpg (88.9 KB, 51 views)
File Type: jpg Harness 4.jpg (96.0 KB, 38 views)
File Type: jpg Harness 5.jpg (85.1 KB, 44 views)
File Type: jpg Harness 6.jpg (97.9 KB, 55 views)
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  #41  
Old 06-07-2016, 01:17 AM
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...

Last edited by andy; 11-20-2021 at 03:11 PM.
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  #42  
Old 06-07-2016, 07:57 AM
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This is truly impressive. I'm following this thread with great anticipation
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  #43  
Old 06-07-2016, 08:08 PM
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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.
Attached Images
File Type: jpg Comp 1.jpg (124.2 KB, 37 views)
File Type: jpg Comp 2.jpg (131.7 KB, 36 views)
File Type: jpg Comp 3.jpg (137.0 KB, 46 views)
File Type: jpg Comp 4.jpg (119.4 KB, 41 views)
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  #44  
Old 06-07-2016, 08:10 PM
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More pics attached.

Next up: Finishing the chassis topside wiring, and module installation.
Attached Images
File Type: jpg Comp 5.jpg (124.8 KB, 31 views)
File Type: jpg Comp 6.jpg (123.8 KB, 38 views)
File Type: jpg Comp 7.jpg (120.1 KB, 37 views)
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  #45  
Old 06-07-2016, 08:17 PM
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Phil Nelson Phil Nelson is offline
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Quote:
Originally Posted by Kamakiri View Post
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.

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