View Full Version : Motorola 21CT2B restoration
Electronic M 03-07-2018, 09:19 PM Some time ago I made a deal on one of Motorola's rarest color TV models. After spending more than I paid for the set to ship it here from California (putting my total investment at the going rate for one of these sets) it arrived unscathed.
https://farm5.staticflickr.com/4756/26561338138_51f5ca120a_n.jpg (https://flic.kr/p/Gt8NrQ) https://farm5.staticflickr.com/4723/40432355591_773ee7e0c1_n.jpg (https://flic.kr/p/24ASoFa) https://farm5.staticflickr.com/4663/40432352181_607f20df89_n.jpg (https://flic.kr/p/24ASnEn) https://farm5.staticflickr.com/4748/25560946337_e567942175_n.jpg (https://flic.kr/p/EWJwPk) https://farm5.staticflickr.com/4709/40432343411_3f6106a4f5_n.jpg (https://flic.kr/p/24ASk4a) https://farm5.staticflickr.com/4606/40432336201_5903dcf6b0_n.jpg (https://flic.kr/p/24AShUR)
Radio63, the member here I bought this set from believes he may have purchased it from the original owners (CRT was already necked at the time) in the Fort Worth area. Which would make me the third owner, and make this the second early color originally from the region that I've purchased.
It arrived safely late Thursday the 24th. Over the course of that weekend, I managed to change nearly all the capacitors. I decided not to restuff the paper caps since most were tubular ceramics. Even if I restuffed other paper shells it would not look right, plus the chassis was a bit cramped around some caps. Most of the peaking coils were defective too. I've replaced most with close approximations, but need to order better ones for some places (that will be on my next bulk parts order).
https://farm5.staticflickr.com/4713/39758910184_bceea27c4e_n.jpg (https://flic.kr/p/23zmNPs) https://farm5.staticflickr.com/4770/25598161097_3e4a0eab6d_n.jpg (https://flic.kr/p/F12gt8) https://farm5.staticflickr.com/4756/39758901354_7f72241dc3_n.jpg (https://flic.kr/p/23zmLcd) https://farm5.staticflickr.com/4656/40425548112_1f7cdb17b6_n.jpg (https://flic.kr/p/24Agv3Q) https://farm5.staticflickr.com/4700/25598107897_b9109b7658_n.jpg (https://flic.kr/p/F11ZDT) https://farm5.staticflickr.com/4603/40665648121_99e1883b1c_n.jpg (https://flic.kr/p/24Xu5qa) https://farm5.staticflickr.com/4672/40469126771_397fd1b61b_n.jpg (https://flic.kr/p/24E7Rt2) https://farm5.staticflickr.com/4695/40665552761_aa5597f7c2_n.jpg (https://flic.kr/p/24XtA52)
More chassis pics can be found here: https://www.flickr.com/photos/137849736@N08/albums/72157688118463260/with/40425548112/
Electronic M 03-07-2018, 09:49 PM I decided to replace the 21AXP22 CRT with a 21FJP22 I had until I can source a 21AXP22 (I could really use a couple of those)...I've done this procedure before on a CTC-4. The Motorola proved both easier and harder than a 4 in its own ways. I was able to get the stock mounts to just barely reach and hold the FBP in, but the yoke mount that is part of the CRT mounts was too high relative to the neck for the yoke to mount properly...So I had to get creative. I struck out on junk box hardware for the mod, and the right size of threaded rod to replace the top ones was not stocked so I came up with extenders made from coupling nuts an eyelet and a hook. I had to Dremel down the shafts, but they worked.:thmbsp: I also notched some rubber grommets to use as ~1/4" spacers between the grounded yoke mount and the HV suction cup....In the process of doing that the Dremel managed to catch the rubber and ride it up on to the thumbnail holding it. :yikes: It went clean through the nail and into the flesh enough for it to eventually bleed some (burned it shut partially as it cut/ground) and scare the sud outa me. I did get the mount done though. The nice part was that instead of molding the HV wire into the plastic shroud Moto routed it under the shroud and to a metal clip. I was able to unsolder and save the clip and add a suction cup to the end of the HV lead which saves me from having to jury-rig a plug for the HV lead connector like on my CTC-4. I can reverse this CRT swap and go back to a 21AXP22 with the original unmodified hardware anytime almost as fast as one could change a CRT in this model.
https://farm5.staticflickr.com/4657/40623513162_3d463e28a0_n.jpg (https://flic.kr/p/24TL8am) https://farm5.staticflickr.com/4697/40623504652_46a3930c10_n.jpg (https://flic.kr/p/24TL5CC) https://farm5.staticflickr.com/4751/40623517922_45a248b6a7_n.jpg (https://flic.kr/p/24TL9zq) https://farm5.staticflickr.com/4783/38855429220_525d18b8e7_n.jpg (https://flic.kr/p/22cweps) https://farm5.staticflickr.com/4704/40665641701_35e103f5b3_n.jpg (https://flic.kr/p/24Xu3vt) https://farm5.staticflickr.com/4789/26794369248_827f13b4b8_n.jpg (https://flic.kr/p/GPJ9tA) //Todo Tom: quit stareing at yer thumb and take a picture of the new crt in it's mounts!
Hot was weak, so I swapped it. I gave it a powerup on the bench and got good H drive so I gave it a power-up in the cabinet. First try heaters light, but otherwise dead (learned of power rect. socket/wiring intermittents). Second try sound with horizontal lines video modulation in lines, screechy Horizontal whine, and occasional pops accompanied by brief vertical stage operation. Third try raster...Horizontal adjusted for sync (which stopped the screech) vertical running at 120Hz shrunken/non-linear intelligible video...This is about where I stopped yesterday. I went over the vert stage resistors. Some were changed to values not in the Motorola issues schematic on the ETF...Others appeared original but different value. Getting resistors in tolerance did not fix vertical issues. I wish I had a copy of sam's 371 for this set to cross-reference.
The occasional loud pops seem to be arcing from one of the screen pots...It only did it once for me on the bench.:scratch2:
https://farm5.staticflickr.com/4648/40665638581_338083f921_n.jpg (https://flic.kr/p/24Xu2zF) https://farm5.staticflickr.com/4658/26794336898_1de17a15ef_n.jpg (https://flic.kr/p/GPHYRQ)
I'm probably going try decade box engineering the vertical RC time constants soon if making it match Moto's service lit don't fix it.
There are plenty of interesting observations about the construction, design, and repair work I'd like to make, but it is getting late, so I'll make them another day.
dieseljeep 03-09-2018, 06:23 PM When doing a job like that, always have a tube of Super Glue handy!
It was originally intended for that. For minor injuries, I use it all the time. :thmbsp:
Tom9589 03-09-2018, 07:18 PM My wife is from Kingsport, TN, home of Tennessee Eastman. Eastman came out with one of the first cyanoacrylate glues, called Eastman 910, in the late 60s. It was pulled from the market when they discovered that doctors were using it to "glue" incisions on people. I managed to snag a tube and it was absolutely amazing at gluing things back together. No, I didn't use it on any wounds, but 30 years later a similar product was used on some major surgery I had. Worked great.
dieseljeep 03-10-2018, 10:16 AM My wife is from Kingsport, TN, home of Tennessee Eastman. Eastman came out with one of the first cyanoacrylate glues, called Eastman 910, in the late 60s. It was pulled from the market when they discovered that doctors were using it to "glue" incisions on people. I managed to snag a tube and it was absolutely amazing at gluing things back together. No, I didn't use it on any wounds, but 30 years later a similar product was used on some major surgery I had. Worked great.
I had read or understood that the product was developed as a temporary means of mending injuries in battle during the Vietnam War.
radio63 03-11-2018, 10:42 PM Tom, I'm very happy to see the progress you've made on this set! After so many years of being dormant, it's great to see it lit up and slowly coming back to life. Will be following along as you move forward.
reeferman 03-12-2018, 11:41 PM Good to see this thread got back on the original topic.
dieseljeep 03-13-2018, 10:37 AM Good to see this thread got back on the original topic.
I tried to enter a new, more relevant entry to this topic regarding the tricky color circuit used in the Motorola set, but my new playfull kitten jumped on the keyboard and erased it.
I didn't know it didn't get entered. :scratch2:
Electronic M 03-15-2018, 11:27 AM Good to see this thread got back on the original topic.
It does make one worry about VK when a resto topic for an early color set that only 9 examples of are known to remain goes straight into a discussion of stupor glue... I've never had good luck gluing my wounds, so I save the stuff for certain resto tasks such as fixing the occasional terminal strip wafer snapping in two.
I was able to make all the vertical stage resistors match the schematic from the ETF. http://www.earlytelevision.org/pdf/motorola_ts905_manual.pdf
Several were marked different values from the schematic, and some of the different ones were clearly replacements that were tacked in ages ago. Changing the resistors did not solve or change the problem...Scoping revealed it is closer to running at 3X correct frequency than the 2X I assumed earlier.
I could not find my RC decade box, but jumping capacitors and resistors in did not help/change much.
Voltage checks indicate there are major issues in the output...The grid of V15 should be -14V to -2.8 it seems to only be adjustable from -3V to 0V...The plate voltage is low and the cathode is high indicating excessive current flow in the output tube (big shocker given the grid voltage lol). The linearity control seems to be ineffective.
I really wish I had sam's 371 right now...I've got every sam's folder from 101-580 EXCEPT for 371 (which contains the folder for this set)...Just my luck. I'd really like to cross reference the sam's lit.
Presently I'm stalled on this project...Not by the set but by the flu. I've been running 102 fevers on and off all week and have been feeling generally miserable. No basement bench time for me for now.
dieseljeep 03-15-2018, 07:40 PM It does make one worry about VK when a resto topic for an early color set that only 9 examples of are known to remain goes straight into a discussion of stupor glue... I've never had good luck gluing my wounds, so I save the stuff for certain resto tasks such as fixing the occasional terminal strip wafer snapping in two.
I was able to make all the vertical stage resistors match the schematic from the ETF. http://www.earlytelevision.org/pdf/motorola_ts905_manual.pdf
Several were marked different values from the schematic, and some of the different ones were clearly replacements that were tacked in ages ago. Changing the resistors did not solve or change the problem...Scoping revealed it is closer to running at 3X correct frequency than the 2X I assumed earlier.
I could not find my RC decade box, but jumping capacitors and resistors in did not help/change much.
Voltage checks indicate there are major issues in the output...The grid of V15 should be -14V to -2.8 it seems to only be adjustable from -3V to 0V...The plate voltage is low and the cathode is high indicating excessive current flow in the output tube (big shocker given the grid voltage lol). The linearity control seems to be ineffective.
I really wish I had sam's 371 right now...I've got every sam's folder from 101-580 EXCEPT for 371 (which contains the folder for this set)...Just my luck. I'd really like to cross reference the sam's lit.
Presently I'm stalled on this project...Not by the set but by the flu. I've been running 102 fevers on and off all week and have been feeling generally miserable. No basement bench time for me for now.
That was the wrong poster to pay attention to.
Electronic M 03-24-2018, 10:31 PM Some progress; I got the vertical working right. The 4700pF cap on the vert osc trans had drifted in value a good bit...However, the real issue appears to be tin whiskers in the hold pot. I was briefly able to get the freq right while rotating the control, hitting it with cleaner while running and working the pot cleared the whisker.
https://farm1.staticflickr.com/799/27127453598_e5794b59b9_n.jpg (https://flic.kr/p/HkahRd) https://farm1.staticflickr.com/799/39189059280_dcb4d515c1_n.jpg (https://flic.kr/p/22H1aZS)
Thanks to referman for supplying the sam's. I was able to confirm from cross-reference that one of the 'wrong value replacement' resistors were correct value in the sam's revision.
I was able to get off freq chroma osc noise in the video so the chroma section has life...I need to check the chroma stage tubes. This set has an interesting chroma section...It has the diode demodulator circuit of a porta-color, but with a crystal chroma reference osc like most other sets.
EdKozk2 03-25-2018, 01:13 AM It's looking good Tom.:yes:
Ed
old_tv_nut 03-25-2018, 03:32 PM Nice progress!
kvflyer 03-26-2018, 01:04 PM Tin Whiskers... Hmmm, I have an Admiral 26R12 that I restored. It was working well on the bench and then all of a sudden, I heard a snap and lost vertical linearity. It took a long time to figure out (didn't check the obvious) that the vertical linearity pot had tin whiskers. I removed the pot, cleaned and brushed it and all was good. What a relief that was!
Nice job.
Steve D. 03-26-2018, 03:25 PM 1958 Motorola color tv ad.
-Steve D.
Electronic M 03-26-2018, 09:17 PM 1958 Motorola color tv ad.
-Steve D.
Very cool!
Electronic M 07-07-2018, 03:23 PM Getting back into it again. Thanks to Dave, I now have a good 21AXP22 in it. My brief glass conversion proved to be easily reversible...The most time-consuming part was patching a hole in the CRT shrowd that appears to have been chewed by mice...I filled that with clear silicone caulk and it is hard to tell it ever had a hole (at least from the outside).
I decided to swap the rectifier tube socket contacts in the 5U4 sockets. They were making poor contact (sometimes the set would power up and not have B+ until one was wiggled) and the heater contacts were getting heat discolored so I swapped the 4 unused contacts on each socket with the 4 used ones and tightened the new ones so they make good contact...It used to be I could barely see the 5U4 heaters glow now they glow properly.
Got the new AXP installed yesterday, and finally got to the yoke issues. The yoke cover and the sides had rotted. Approximately 1/4 of the side of the yoke was gone, the bottom half of the side was just hanging by the wires that pass through it. I got a ~2-3 quart plastic paint container from ACE hardware. Below the top ~1/2" of the container the diameter was too small to go around the yoke properly and the yoke sides had to be taller than 1/2" so I sliced strips from the side of the bucket with 'teeth' coming out the bottom of the strips, wrapped the strips around and melted the two strips together to fuse them into a ring that enclosed the remains of the old sides of the yoke. I then bent the teeth under and slipped them into gaps between the windings and structure and glued them in place. I trimmed the new sides to match the height best as I could tell it from the warped remnants, then added the ring the lid snaps to and heat fused it in and cut two notches*.
I cut a center hole for the neck out of the old lid then enlarged it at top and bottom to match the original. By then I had ground out the rivets that joined the metal parts of the old cover. *The cover contains two levers that protrude from the side of the yoke below the lid (thus the two notches). Those two levers move two pieces of, presumably, steel in and out of a plastic slide track that rides between the yoke windings and CRT neck as some sort of adjustment. I painted the lid and new sides Lincoln touch up paint black and assembled. The result while not perfect is a heck of a lot better than exposed yoke terminal strip and uninstalled adjustment levers. Up close you can tell it is a repair but at least it is a decent looking/working one.
https://farm2.staticflickr.com/1802/29379760718_cab999752d_n.jpg (https://flic.kr/p/LLbXhA) https://farm2.staticflickr.com/1801/42531689414_363cd1853e_n.jpg (https://flic.kr/p/27No2tU) https://farm2.staticflickr.com/1764/42346036425_ed60ab1b71_n.jpg (https://flic.kr/p/27vYvji) https://farm2.staticflickr.com/1807/42531679014_8ac2c379eb_n.jpg (https://flic.kr/p/27NnYoA) https://farm2.staticflickr.com/1766/42346030485_5e08bd726f_n.jpg (https://flic.kr/p/27vYtxT) https://farm1.staticflickr.com/914/43201103432_0941b817ba_n.jpg (https://flic.kr/p/28PwWWU) https://farm2.staticflickr.com/1806/43201099912_148b4309f0_n.jpg (https://flic.kr/p/28PwVUd) https://farm1.staticflickr.com/843/43201096462_092f7417be_n.jpg (https://flic.kr/p/28PwUSJ) https://farm1.staticflickr.com/847/41440261180_ddaf13285e_n.jpg (https://flic.kr/p/268WaTJ)
While I was at it last night I also repaired a contact in the yoke. There is a box above it that contains an adjuster and a terminal for a device mounted on the blue lateral that is in series with one of the horizontal yoke leads. The terminal that device plugs into broke on me early in the resto and I was using an alligator clip to get by.The contact was basically the same as a fat pin tube socket heater contact so I robbed one from a junk socket and soldered it in on top of the original contact. The yoke is now good. I was able to do a quick roughing in of the purity adjustment last night.
Hopefully in the coming week I'll have it working right.
WISCOJIM 07-07-2018, 06:12 PM And here I thought you'd be using some 45rpm records and black electrical tape. I ran into that on a set once...
.
wkand 07-07-2018, 06:30 PM WOW!!! Great job. Using the Ace paint buckets, did you have any issue getting the Lincoln (paint brand?) paint to stick and stay stuck to the plastic?
Electronic M 07-07-2018, 11:27 PM And here I thought you'd be using some 45rpm records and black electrical tape. I ran into that on a set once...
.
:lmao: :lmao: :lmao: Yeah, I 'could' have done that, but why?...Most of ~99% the 45's I keep are good listening.
About 10 years ago I did something similar on a Zenith that was the 3rd tube TV set I owned...I sliced up the plastic top to a cheap dead VCR and made a really lousy yoke cover stand in...It even had electrical tape...I need to redo that one of these days if I haven't yet.
WOW!!! Great job. Using the Ace paint buckets, did you have any issue getting the Lincoln (paint brand?) paint to stick and stay stuck to the plastic?
Thanks.
It was actually Duplicolor paint; the stuff I use on my 78 Lincoln Mark V...It stuck okay with the caveat that I cut the center hole, painted it then later widened it at the top and bottom...When I widened it the ~1/32" along the cut peeled. It touched up fine though.
Electronic M 08-03-2018, 11:23 AM About three weeks ago I tested the tubes in the color circuits...Nearly all were weak and or shorted so I replaced nearly every color stage tube (took a good bit of searching to find the oddball types it uses, but I had them in stock). That got me the rainbow of off-frequency chroma osc. I soon found the osc. slug was both stuck and cracked...Ugh! I pulled the osc. coil and after some debate began the nerve-wracking process of gently compressing/crushing the coil form by a fraction of it's diameter just above the coil where the slug was stuck...With great finesse I was able to crack the old slug up enough for it to drop out of the form in pieces yet keep the form usable and not damage the coil. A tiny bit of the top of the form chipped off, but it is inconsequential.
I took a larger slug (I plan to hunt up the estimated correct size soon) that was handy and adjusted it for color sync. I have color bars now, the tint does not really get them the right color, but I've got them! :banana:
https://farm1.staticflickr.com/940/42921843595_864e65c020_n.jpg (https://flic.kr/p/28oREJ8)DSCN9658 (https://flic.kr/p/28oREJ8) by Tom Carlson (https://www.flickr.com/photos/137849736@N08/), on Flickr
Between a vacation and other projects, it has sat since then. I need to try either direct video injection or do an alignment...That pastel pic is with color maxed and fine tuning set for max color level.
Electronic M 03-30-2020, 11:12 PM With a lot more bench time than I've had in a while due to covid19 lockdowns I finally got back to this.
So far I have replaced some off tolerance resistors in the IF and color stages and managed to coax a decent color picture out of it.... however it don't want to stay good. The color osc is drifty and looses lock occasionally....more frustrating is the tendency of the osc to jump between being locked on the correct phase of color burst and the inverse phase...I can sometimes get it to jump between the two by adjusting horizontal hold... Which is not wonderfully stable either.
old_tv_nut 03-31-2020, 01:10 PM Nice progress. I think I would worry about the horizontal sync first - could be messing up the burst gate.
Charlie 03-31-2020, 03:12 PM .... however it don't want to stay good. The color osc is drifty and looses lock occasionally....more frustrating is the tendency of the osc to jump between being locked on the correct phase of color burst and the inverse phase...I can sometimes get it to jump between the two by adjusting horizontal hold... Which is not wonderfully stable either.
Perhaps infected with covid-19? Make sure you're wearing a mask when you power it up! :D
Electronic M 03-31-2020, 03:44 PM Perhaps infected with covid-19? Make sure you're wearing a mask when you power it up! :D
Lol...It's been under quarantine for a year so it's more likely to have polio or mumps... Pretty sure it hasn't been vaccinated.
Yesterday one of my habbits specifically tuning to cartoon Network for test signal with saturated color bit me in the butt...the amazing world of gumball was on and with the chroma osc phase sync issue the orange character and the blue character were taking turns being each others color... Glad I had the sound muted or it would have been a confusing episode.:D
dieseljeep 03-31-2020, 07:16 PM About three weeks ago I tested the tubes in the color circuits...Nearly all were weak and or shorted so I replaced nearly every color stage tube (took a good bit of searching to find the oddball types it uses, but I had them in stock). That got me the rainbow of off-frequency chroma osc. I soon found the osc. slug was both stuck and cracked...Ugh! I pulled the osc. coil and after some debate began the nerve-wracking process of gently compressing/crushing the coil form by a fraction of it's diameter just above the coil where the slug was stuck...With great finesse I was able to crack the old slug up enough for it to drop out of the form in pieces yet keep the form usable and not damage the coil. A tiny bit of the top of the form chipped off, but it is inconsequential.
I took a larger slug (I plan to hunt up the estimated correct size soon) that was handy and adjusted it for color sync. I have color bars now, the tint does not really get them the right color, but I've got them! :banana:
https://farm1.staticflickr.com/940/42921843595_864e65c020_n.jpg (https://flic.kr/p/28oREJ8)DSCN9658 (https://flic.kr/p/28oREJ8) by Tom Carlson (https://www.flickr.com/photos/137849736@N08/), on Flickr
Between a vacation and other projects, it has sat since then. I need to try either direct video injection or do an alignment...That pastel pic is with color maxed and fine tuning set for max color level.
Good thing you bought the 6BV8 tubes that time. It's not a common type.
oldtvman 04-08-2020, 03:41 PM Here in the midwest, we predominately saw RCA and then Zenith sets. I never had a chance to see a Motorola color until mid 60's. Old people liked them because they had a really smooth picture (no detail)
JohnCT 04-08-2020, 04:15 PM Nice progress. I think I would worry about the horizontal sync first - could be messing up the burst gate.
Yep. Saw a lot of odd color issues accompanied with a secondary complaint of a twitchy horiz hold control.
John
Electronic M 04-08-2020, 05:18 PM Horizontal hold behavior is intermittent. Sometimes it won't sync worth a damn sometimes okay but control lock range is limited sometimes I can get close to the 30 degrees lock in range Sam's suggests is correct. The hold pot has a VERY broad effect on the frequency compared to other sets (heck it will pull it so far the osc will die on a good portion of one end of the range). Trying the Sam's H osc adjustment procedure that involves grounding the H AFC, putting a .1uf between the H osc coil and ground, locking with the hold, removing the cap, locking with the coil (can't do it it isn't very close to frequency), removing the AFC short and calling it done. All the resistors in the horizontal are good the paper caps have been changed and the 680pF mica was changed... I'm not sure what could be changing the coil lock point.
After doing the sams horizontal osc proceedure I got the horizontal lock good but color lock was barely present/not stable for more than a minute. The picture often has bad ringing on high contrast so I have started my first video IF alignment with my B&K 415..the first 2 injection points went well the adjustment on the first was almost spot on, the second needed touch up but was cooperative, the third that goes through the tuner is not close and getting it there is proving difficult...I may have to dig for a 6BC8 for the tuner. Sam's calls out a 6BC8 but a 6BK7 is what is in there... I'll probably have to dig as there are no BC8 in my boxed/labeled tubes so it will be a bunch of digging into my bins of loose pulls.
I when I have more time I'm going to have to rant about how Motorola and Sam's think you should deal with removing the H output tube during alignment... they musta been bribed by ohmite.
oldtvman 04-10-2020, 07:31 AM When I had my shop sometimes I used to compare factory service manuals with photofacts. Sometimes they were right on and other times there were errors in the Sams version. I guess sometimes you had to take it for what it's worth, keep in mind a lot of time there were service bulletins that came out after both versions were released, and those had some very good info on them
Electronic M 04-10-2020, 10:39 AM When I had my shop sometimes I used to compare factory service manuals with photofacts. Sometimes they were right on and other times there were errors in the Sams version. I guess sometimes you had to take it for what it's worth, keep in mind a lot of time there were service bulletins that came out after both versions were released, and those had some very good info on them
I've had Sam's errors mess me up good enough on other sets to double check other literature when available.
I double checked the Sam's video IF alignment against the Motorola manual on the ETF and the video alignment was the same....
Rant time: both Motorola and Sam's (who appear to have copied Motorolas proceedure only renaming the coils to match their numbering) say to pull the horizontal output and to properly load the B+ to connect a 2K ohm 100W(!) Resistor across the B+...so I soldered 4 NOS 50s ohmite 500 ohm power resistors (with rheostat sliders not connected due to paper insulator) in series and set those in a jar...10min in I noticed the paper was smoking profusely so I pulled the plug about 10 seconds later the rigid assemblage of resistors desoldered themselves and collapsed to the bottom of the jar I was keeping them in for safety... Since I had more of those resistors I ended up using 16 in series-parallel to increase the wattage and make a 2K ohm resistor that needs an hour to char the paper... I have to wonder what Motorola was thinking specifying a 100W dummy load resistor...I don't think I have ever seen a TV that used a 100W resistor and I can't imagine the average repair shop would just have one laying around.
The video IF response on the first 2 injection points was dead on, the 3rd I was able to get close.
Electronic M 04-10-2020, 11:07 AM The third uses the tuner slug to get the 47.25 marker at %50 of the slope. The max it would go was in the %40-47 range. Bandwidth centering and flatness of the main curve were to spec... granted even with the tuner osc disabled the curve would change from channel to channel...most were an amplitude shift but a couple changed the shape...some showed the dip above the 47.25 trap and some didn't...
I finished the video IF alignment 2 nights ago. I think I did okay the picture and sound have not gotten worse (not much better either) and yesterday morning my by eye adjustment of the chroma osc would hold lock for about an hour if I let faces be a bit greenish and 10-30 min if I had the osc on the edge of it's lock where faces looked normal...
All and all I feel like I did well for my first attempt at doing a Video IF alignment on a TV.
Electronic M 04-10-2020, 11:22 AM Then in search of a stable chroma sync point where correct tint wasn't past the end of control travel I went and and messed up the chroma!
Last night I tried to do the chroma AFC adjustment procedure in Sam's and skip the chroma bandpass buuut Sam's instructs to touch up an adjustment from the bandpass so after starting the chroma AFC (which has totally detuned the osc, and possibly cracked a slug) I went back and started bandpass last night...the chroma bandpass proceedures first step was inject on pin 2 of the bandpass amp and went well, but the next step has me stuck. The injection point and circuit for the step I'm stuck on is nutty. They want me to build some goofy hand-wound ferrite transformer resistor isolation/matching network...I obviously don't have the Motorola core part specified on hand and I don't intend to look for it, but I did try to approximate the circuit....
I can get a signal from the generator through but it is so weak the markers on low are stupid wide and tall, there's a good bit of noise on the curve thanks to cranking up the scopes sensitivity, and the first 2 adjusters don't seem to affect the curve....
This Motorola is becoming a time vampire...I put a day into it and it barely improves...I just want to get this thing done, out of the basement and move on to other things...
Tom9589 04-10-2020, 11:30 AM Out of curiosity... What's the HV regulator on this set? A shunt regulator or a Victoreen regulator.
Electronic M 04-10-2020, 11:47 AM Out of curiosity... What's the HV regulator on this set? A shunt regulator or a Victoreen regulator.
A normal 6BK4. This chassis was introduced in 1957 IIRC so it makes sense that Motorola would use the proven 6BK4.
Electronic M 04-10-2020, 03:39 PM I think I figured out the weird chroma bandpass curve...the half done AFC adjustment had detuned coils necessary to get the bandpass curve....I was able to reset 2 of the 3 slugs I adjusted for the AFC adjustment and get the chroma osc running off frequency and the bandpass amp curve suddenly existed and had some reasonable resemblance to what it should be... only problem is the 3rd AFC slug that cracked on me...I suspect the bandpass can't be done till the slug is fixed and the chroma osc is adjusted on (or atleast much closer to) frequency.
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