Hello..my first TV

[Donj]

Well, Fired it up after a day attempting to restore continuity in the 12 prong plug attaching the low voltage supply to the main chassis. The prongs, as well as the mating receptacles are coated with a grey substance, almost looks like it is plated on. Problem is it appears to be a damn good insulator. Got it scuffed off the prongs, however, the receptacles are pretty much inaccessible to all bit the finest dental pick. Hard to scrape with the Bakelite casing allowing such a tiny access hole. Got the set fired up by constantly fidgeting with the plug until all circuits came to life. I think I'll try putting my smallest drill bit in the Dremel to abrade the contacts from within.
Anyhow the set finally came to life with an incredibly bright raster so all the HV must be functioning properly. Cannot go any further till I remedy the multiple bad connections. Had it on for about 10 minutes and in that short time had to readjust the plug about 4 times to restore operation.

[JohnCT]

Originally Posted by Donj

The prongs, as well as the mating receptacles are coated with a grey substance, almost looks like it is plated on. Problem is it appears to be a damn good insulator.

I wonder if that coating wasn't some sort of contact lubricant that decided to morph into something else after a few decades.

Before running a drill into the contacts, I'd experiment and see if the coating can't be dissolved with a cleaner first.

John

[old_coot88]

I would certainly try contact cleaner first, like Deoxit or similar.

[Donj]

OK, finally got the problem taken care of. No amount of deoxit,alcohol,acetone, brake cleaner, oxalic acid or just plain water would touch it. Not wanting to overdo things with the Dremel tool, I found a diamond Dremel abrasive wheel that I managed to cut into a strip the width of the plug pins. In and out of the socket holes a few times seems to have removed the deposit to the point of reliable contact.
Once powered up I found that the speaker was dead. Took a look at the connector pins on the leads that plugged into the speaker and found the same thing. Cleaned them up with abrasive and now have a working speaker. Leading to the next question...
I presently have no input source for the set .. Wifey tossed the vcr a while back and I have to order a modulator for the dvd player..
Should I not be hearing something from the speaker even with no signal input?
Static, a hiss, something? All I hear is a slight hum controlled with the volume and a short static click when I change between channels.

[old_tv_nut]

Originally Posted by Donj

...
Should I not be hearing something from the speaker even with no signal input?
Static, a hiss, something? All I hear is a slight hum controlled with the volume and a short static click when I change between channels.

You posted a pic with a blank raster (no "snow"). I'm guessing without any RF noise getting through, your audio may be quiet also.

Is this chassis one of those where the "contrast" control is really an IF gain control?

[Donj]

Just did a bit more reading and found this.." A potentiometer (contrast) control, permits this voltage to be changed on v2, v3, and v4 so as to vary the gain of the video i-f amplifier"

[old_tv_nut]

Originally Posted by Donj

I'm not thinking so..... OOPS. Just did a bit more reading and found this.." A potentiometer (contrast) control, permits this voltage to be changed on v2, v3, and v4 so as to vary thegain of the video 1-f amplifier"

So, I presume you're going to turn it and see (or hear) what happens

[Donj]

Turned on the beast and was greeted with an inch wide horizontal bar????? Maybe all my contact cleaning wasn't sufficient. I think I'm going to bed.

[Donj]

OK, Depression has passed ... After removing chassis and putting it on the stand I found absolutely nothing that I felt might have caused this minor setback. Hooked all back up and same horizontal bar across the screen. Messed with the 12 pin plug with no positive results. Then I noticed that one of the two LV rectifiers (5R4) on the PS chassis was glowing very dimly filament-wise. Removed it and reamed out the socket, bright filament and a full screen raster!!
Spent the day on the remaining sockets just to avoid further poor connection scenarios down the road.

Old Nut.. messed with the contrast control as per your suggestion, with no real noticeable video or audio effects...screen darkens up as contrast is increased, that's about all.
I was running the tuner through its paces and I found one position almost between chs 8&10 where I actually got some real off-air audio. Fine tuning had a major effect on volume of the noise. No real effect on the raster however. As I said, the contrast control really did not have an effect either.
I suppose that I should pull the tuner and give the switches a major going over in case they are suffering from this Gawd awful problem that every other connection point in this set seems to have.
Has anyone else ever seen a set suffering from this malady?

[Donj]

Some progress has been made.. With a VCR connected, my first thought was that I was getting no input signal response. However, I did detect an audio output with the set's volume set at max. Very low, but there. Since there was audio I started to look for video by playing with the various controls and finally found it somewhat. It seem as though with the brightness and contrast both set to minimum there is a viewable signal. Not great, but viewable.
Since it is there, what do you think I should be doing next?
I am going to check over components in the audio section, but don't expect to find much and as far as the video goes it seems as though every thing is way too bright. There is nothing I can adjust to obtain a black.
Now that I have an input source I will attempt to record a test pattern.
Can I test voltages with the CRT disconnected? It is still fastened within the cabinet and I really do not have room for it on the bench.
Also wondering if this is more likely component or alignment issues.

[truetone36]

I'm glad to see you're making progress. Just be warned, when you've finished getting this set going you'll be looking for another, and then another, lol. My journey down the path started with a '59 Admiral console and now I've got TV's stashed all over the place. Welcome to the Dark Side, my friend.....

[Donj]

Truetone, you may be correct. Repairing radios and jukeboxes has become almost second nature to me... but this tv thing has shown me that the grasp I have on electronics is a tenuous one and the challenges posed by this beast, as frustrating as they might be, have so far been ones that I ended up figuring out. A lot more satisfying than repairing a radio!
I am now at a point that seems beyond me... Pic is good but audio is nonexistant..in the normal sense anyways. VCR output on ch3, yet the only way I can get audio out of the set is to tune it to ch 2 and adjust the fine tuning until it pops in. No image just audio. If I set the VCR output on ch4, I have to set the tv on ch 3 and again adjust the fine tuning until it pops in. Its like the audio is a channel below the video. I'm hoping this is a symptom of something that may be beyond my understanding but not you guys'.

[Electronic M]

Edit: it is good practice in my book to change off tolerance resistors and all paper caps before touching alignment.

I forget if this is an intercarrier sound set or not.....regardless if you know which end of the ch2 fine tuning is closest to ch3 you can " walk " the audio IF alignment by ear. The process is fine tune the audio then detune the fine tuning in the direction you want the audio to move but keep faint audio present then peak the audio IF to be loud at that fine tuning position, then detune the fine tuning further in the direction you want to move the audio and repeat till you moved it where you want it...some will claim that this is harresy on split sound IF sets but I've done it successfully on both split and intercarrier sound TVs.
YMMV.

[Notimetolooz]

Originally Posted by Donj

Can I test voltages with the CRT disconnected? It is still fastened within the cabinet and I really do not have room for it on the bench.

You need the connections to the yoke. You can remove it from the CRT neck.
If there is a ion trap that will have to be removed first, but mark the position so that you can put it back on later in the same spot and orientation. Make sure that HV anode lead is well insulated by putting the end into a glass bottle or the like. There is very little current flow to the connections at the CRT base socket except for the filament. BTW, it this set has series string filament connection you will have to substitute something for the CRT filament.
You should check the voltages on the CRT socket anyway, it may indicate something.
EDIT: Just looked up the dats on the CRT, it doesn't use an ion trap, but it does use a focus coil. What I said about the ion trap applies to the focus coil. You will have to have the focus coil connected as well as the yoke.

[Donj]

Back to work. As per advice I'm measuring all that is measurable on this set. All coils ohm out as per the schematic. Resistors as well with some exceptions. These are pretty much all the 1 watt resistors, and seem to have a molded sort of body. They are all measuring extremely low. Below is an example. Shows as 47K on the schematic and that's what the colour code says... Measures out at 561 ohms. I'm used to seeing old resistors measuring high, but this set's seem to be doing just the opposite. Just the molded body ones.
Anybody seen this?