RCA CTC-90 questions - Videokarma.org TV - Video

Whirled One · #1 04-10-2010, 06:11 PM

Hi all!

Some of you may remember me as an active member in the past (Hello everyone!). Long story short, I suddenly ended up with a lot of other things taking up my time-- I bought a house last summer (and, I gotta tell you, it seemed to take *forever* to get everything packed up and moved!), then I had all of the things that start taking up your time when you own a house, etc., etc. Some other things have been happing in real life too that just have ended up taking time away from other stuff. It's going to take a while to catch up with some of the posts here from the last several months!

In my area, the spring-cleanup "bulk trash" days have started up again for the season, and I've got a few interesting curbside finds which I'll post about in another thread.

For now, I've got a quick question about an RCA CTC-90 console (built in January 1978) that I picked up today. It wasn't a curbside find, however. It was the same price as a curbside find, though (Free). It actually came from a local "junk store." Typically with large 'unpopular' items like this, they'll try to get a modest sum for them in case someone happens to be interested (they originally marked this set at $20, which seemed a bit high for this store), but if they don't move within a couple weeks they typically just give them away or toss 'em to clear the space for 'fresh' items-- they really keep the stock moving there. I don't normally care much for solid-state color console TVs, but I was kinda looking for a low-value-but-reasonably-fun 70's TV for a particular spot in my house, and this set (a) appeared to be working quite nicely, and (b) had a bit of character to it with its ultrasonic remote control and varactor tuner with big green lighted channel numbers on its tuning drum. I guess I just felt sorry for this unwanted waif.

Here's my question. I can't figure out how to skip/unskip channels on the tuning drum, or how to change out the plastic channel number tabs (with the channel numbers printed on them). If all else fails, I'm sure that I can do both of those things if I remove the tuner from the cabinet, but there must be a more "preferred/customer friendly" way to do this. I noticed that the front control bezel can be easily removed by 'popping' it out of the front, and doing so reveals the fine tuning trimmers for the 12 VHF channels and the geared tuning controls for the 6 UHF channels that can be preset. However, I can't find access to some sort of "channel skip" tabs on the drum for unused channels.
There's got to be some secret for this without having to remove the tuner entirely. I don't see anything on the back of the tuner (like on many Zenith TVs) either.

On another note, I'd like to add a composite video input to this set. Anyone happen to know where the video detector (or more suitable place) is on this chassis? I might have a CTC-90 schematic in an old service manual in storage though. By the way, does anyone have any ideas for making substitute channel number tabs for these sorts of TV sets? Of course, the original tabs that came with the TV are missing. I figure I could print some out on a laser printer with transparency film using a similar font to the original numbers, but does anyone have a better idea?

Thanks!

Findm-Keepm · #2 04-10-2010, 07:26 PM

I've got some RCA Service literature and Goldenrods for the CTC9X chassis - gimme til Monday noonish to get to it and I'll see what I can scan for you. I've got three and a half binders of stuff starting with CTC72 and endinng with CTC108, so I probably have exactly what you need.

Most sets came with a complete set - often you'll find the paper envelope stapled/ziptied inside the set with the remaining inserts. If not they are available from Moyers or others.

Cheers,

Whirled One · #3 04-11-2010, 06:10 PM

Quote:

Originally Posted by Findm-Keepm

I've got some RCA Service literature and Goldenrods for the CTC9X chassis - gimme til Monday noonish to get to it and I'll see what I can scan for you. I've got three and a half binders of stuff starting with CTC72 and endinng with CTC108, so I probably have exactly what you need.

Most sets came with a complete set - often you'll find the paper envelope stapled/ziptied inside the set with the remaining inserts. If not they are available from Moyers or others.

Cheers,

Thanks Findm-Keepm! I checked the RCA books I had in storage, and I don't have anything that "modern". I also don't happen to have the SAMS folder around either. Thanks for the suggestion of contacting Moyers for a set of replacement channel numbers-- I didn't even consider that they might have something as pedestrian as that.

In case anyone's curious, attached are a couple of quickie pics of the set. Notice that there's no manual tuning knob at all (not even hidden behind a panel)-- just a pushbutton to actuate the motorized tuning.

Geoff Bourquin · #4 04-11-2010, 06:21 PM

I think there was a tab on the numbers that either made it skip or not skip by hitting a switch as the drum rotated; change the number tab to make it skip. If my manuals were not packed away in neverfindthemland I'd look it up. Hopefully Findm has the right manual

Findm-Keepm · #5 04-11-2010, 09:00 PM

Quote:

Originally Posted by Whirled One

Thanks Findm-Keepm! I checked the RCA books I had in storage, and I don't have anything that "modern". I also don't happen to have the SAMS folder around either. Thanks for the suggestion of contacting Moyers for a set of replacement channel numbers-- I didn't even consider that they might have something as pedestrian as that.

What's the model number? The RCA literature puts the TMA/Tuners in appendices with reference only to the model number .... I'm gonna need that.

I may know of a source locally for the inserts if Moyer's doesn't have them. I'll get the RCA part number for them when I look up the tuner info.

Cheers,

Whirled One · #6 04-11-2010, 10:40 PM

The set's model number is GB 728 SR. Thanks!

I can't find a "KRK"-type model number on the tuner (either the actual tuner module, or the drum selector unit), though perhaps RCA stopped using that style of marking by this time. The tuner itself has several numbers on it which are probably part numbers. The PC board on the selector drum switch is marked PW4000A, which sounds like a module name.

By the way, I think Geoff is right on-- upon closer inspection, I see that the channel number tabs are very thick and have a "finger" that sticks out to cause the drum to stop. The 'skipped' channel positions have blank opaque tabs instead which do not have the "finger." I removed the selector assembly from behind the front panel to get a better look, and indeed it looks like this might the only way to change out the tabs. There's a small plastic panel that looks like it should slide out to gain access from the front (I noticed this when I pulled off the bezel cover to find the channel tuning trimmers), but it appears to be glued in place. Either that, or it's just *really* stuck. Otherwise, it doesn't make sense-- it'd be very strange if RCA made this task essentially impossible to be performed by the customer.

Findm-Keepm · #7 04-12-2010, 12:10 PM

While I don't have the exact manual (1978 C-8 or 9), the RCA literature for other models (1977 C5, it supplement, and some 1978 material) reveals the following:

Your set has the VTCA-1 Tuner control assembly - channel land/skip is controlled by the inserts. It seems if it has a number or letter, the tuner will land on that channel, if a signal is found. Blank inserts will always be skipped, as they have shorter tails. The insert kit part number is 141501 ( channel 2 - letter H) Fine tuning is achieved by removing the front bezel (as you discovered).

From the RCA Goldenrod:

For symptoms where the motor starts, but stops on each detent, a defective Q5 holding tranistor (141330) on PW400E or it's pulsing circuit is a good possibility. Also, if motor will start, but stops at each detent, even when a blank tap is inserted, suspect a shorted S4001A (leaf switch assembly).

I do have the Sams (1710, folder 2) and it yields pretty much the same info. Lemme know if you need anything further.

Cheers,

Jeffhs · #8 04-12-2010, 09:21 PM

Without a manual channel selector knob anywhere on the set, how did one change channels if the remote got lost, broken, the motor drive went bad, or the remote's batteries went dead?

Seems like a very poor way to design a TV power tuning system; after all, most TVs with power tuning and remote had a manual channel selector on the back of the set, to be used in case anything went wrong with the drive system or the remote hand unit itself.

Findm-Keepm · #9 04-13-2010, 06:00 PM

Quote:

Originally Posted by Jeffhs

Without a manual channel selector knob anywhere on the set, how did one change channels if the remote got lost, broken, the motor drive went bad, or the remote's batteries went dead?

Seems like a very poor way to design a TV power tuning system; after all, most TVs with power tuning and remote had a manual channel selector on the back of the set, to be used in case anything went wrong with the drive system or the remote hand unit itself.

The front of the set has the requisite controls - channel and volume up/down, which also control the power. See the second photo above.

If the motor drive went bad, neither remote or front controls would do much good. It's a varactor design, so manual means are exactly what RCA was "designing out" of the set. It's the precursor of todays sets with no manual means other than tactile buttons on the set and remote.

Cheers,

Whirled One · #10 04-13-2010, 07:37 PM

Thanks Findm! At least now I've got the part number for the inserts. I'll see if Moyer has it. The tabs are thick and heavy enough (and have a rather critical shape) that making your own set wouldn't be all that simple.

By the way, it doesn't appear to matter whether there's a signal or not on the selected channels. The channel selector only goes in one direction, but the drum rotates *very* quickly, and does not pause or hesitate at all on 'skipped' channels.

As Findm says, the up/down volume buttons also control the power. If the set is off, pressing "volume up" (on either the remote or the front panel) switches the set on. Turning down the volume past the 'zero' point switches the set off. As such, it functions much like a 'digital' version of the traditional combined off-on-volume analog control knob. Incidently, the power/volume controls on this set appear to be fully solid-state-- I don't hear any motors or relays when operating the up/down volume buttons.

Yamamaya42 · #11 08-07-2019, 06:51 PM

had it for years!

https://imgur.com/Aj3i3mb

been in my storage shed forever.

never knew what the hell it was.
got it with a dead CRT, and then tossed the tube from my dad's failed TV build attempt into it (heath kit ) so it hardly has 2 years on it.
it then came up with vert problems and was stuck in storage even since.
Is this thing even worth any effort?

Yamamaya42 · #12 08-08-2019, 08:01 AM

BTW, Not that it matters much after all this time, ( this is an old thread ) but, the CTC-90 is 100% solid state, so should it not be under “Solid State CRT Televisions” ?

Electronic M · #13 08-08-2019, 08:38 AM

Quote:

Originally Posted by Yamamaya42

BTW, Not that it matters much after all this time, ( this is an old thread ) but, the CTC-90 is 100% solid state, so should it not be under “Solid State CRT Televisions” ?

Going back a few years...IIRC when I joined there was no solid state forum section (and a number of others didn't exist) if this thread predates the split then it started in the right place...us members have written a ton of stuff over the years to the point no one can blame the mods for not wanting to go back and split out all the content in to new categories it better fits.

A friend of mine really likes these modular XL100s. As such I've had to work on one before. They are nice sets when working right.

Yarehobbyso$ · #14 08-13-2019, 10:20 AM

I realize this is an old thread, but here is a part number for the channel inserts in case someone ever needs; 1449368-502. I included a photo link to one of my sets.
The blanks had no side tab.
When we delivered one of these sets to someone with a UHF antenna, we'd use a small pocket screwdriver to gently release a blank, and insert one of our local UHF #'s, then put the blank in the owners manual packet (just in case this set ever got traded in and the next person needed a different line up!). Dan

Yamamaya42 · #15 11-25-2019, 09:44 PM

heh

no one has really said if this TV is worth putting any effort into yet or not :p

I really don't want to work on if I don't have to, but I have a near new 25vxxx22 just sitting around itching to be used.
and the chances of ever finding something to put it in that is tube tech ctc-68 or the like are very small