Motorola 19k3 chassis ts-101 help needed
 

I don't get any pic or sound , the mix Osc was not lighting , found a .2 ohm choke was open m jumped it with a wire , still nothing , tried sign generator , ripples / rf interference on screen on 6ah6 and 12au7 , 3rd if there is same but might not be as strong , 2nd if nothing , checked resistors , open coils etc , nothing found , here is a list



V7 video 6ah6 pin 1 is 18 volts , should be 1 volt
V5 third if 6cb6 pin 2 is .850 volts should be 1.4
V4 second if 6cb6 pin 1 is -227 should be -.5
V3 first if 6cb6 pin 1 is -.377 should be -1
V2 mix Osc 12at7 pin 2 is -1.5 should be -3.6
V1 rf 6cb6 pin one is -4.00 should be -3.2# pin 2 is 1 should be .5

SAMs online
http://www.earlytelevision.org/pdf/m...sams_122-5.pdf

Mike

Mike, sorry I don't have an answer to your problem. But I couldn't help but notice something weird is happening to the clarity of these schematics during the process of Steve posting them on the ETF website. It appears as if they're getting thrown way out of focus. I've seen it happen in the past and I thought we had figured it out, but now here it is again with this Motorola schematic. :scratch2:

Kevin they printed out clear , only thing I can think of is they got compressed somewhere along the line , that would impact the clarity

If I knew how I'd bypass the tuner and if section and feed right into the video , audio I think you just feed into the volume taps, the outer ignoring the center if I'm not mistaken

This article has some info about directly injecting video and audio in a vintage TV:

https://antiqueradio.org/A-V_AdapterForVintageTVs.htm

The TV used in that article was a different (Admiral) set, but you may be able to adapt the principles for your TV.

Regards,

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

Mike,

If by chance you have a B&K analyst you can feed video direct into the video amp, you just need to get the polarity correct. Sometimes I've been able to directly inject component video into the video amp, too. Just depends on the TV circuit whether or not the signal needs inverting. Or maybe you want to permanently use component inputs? In that case Phil's article is of great help.

The B&K analyst can be a godsend in these situations. Not only can it inject video, but IF and several channels of RF too. Knowing if your If chain is good before going after the tuner is essential. You won't realize you fixed a bad stage if there is another bad one between it and your output unless you use signal injection.

In that article the schematic shows inject video to pin 4 , so the plus goes there and the ground to the chassis ground ?

Yes. But I'm not sure if your set uses the same tube type and pin out?

The video circuit is similar , the brightness goes to a different pin ?

Not sure what you're asking. I was referring to the video amp circuit using a different tube type.

10lp4 in the admiral schematic , my Motorola uses 19ap4 .
If you look at the admiral video section and the Motorola looks similar.
I put up a link to the SAMs for the moto , that link to article shows a part of the admiral schematic .

The difference is the Admiral has a dc coupled video circuit, therefore they applied the brightness bias to the CRT grid. Notice the lack of coupling caps from the video amp plate to the CRT cathode. On your Moto you have a .1uf cap coupling the video to the CRT cathode, which allows the brightness bias to be applied to the same point.

So you don't think it will work injection the signal on the moto ?

I think it will work just fine. But you'll need to connect to pin 1 of your 6AH6(video amp), not pin 4 as in Phil's Admiral example.

Yes I figured that it was pin 1 because that's where the connection from the IF section comes to the video tube just like the admiral , it uses pin 4 for the sane connection.
It is interesting to note that pin 1 is the spot where the voltages are the most crazy , should be 1 volt and I have 18 volts .

That doesn't sound right. You better double check the other pin voltages on that 6AH6. If you do inject video into pin 1 you might want to go through a .1uf cap.

The other pin voltages are correct , I can try another tube but that's probably not the problem .
Btw the pin reads 0 if the tubes pulled .

I looked at Riders and they say -.5V. on pin 1. Sams shows with their dotted lines and x's an optional circuit for the cathode(contrast control)circuit. Do you have the simple pot in series with the cathode to ground, or do you have the version with all the extra's?

Make sure that 1M resistor from grid to ground hasn't drifted way up in value.

I will recheck that 1m resistor , as far as the contrast circuit I will have to check it , I thought those x marks were from a former person who marked them on the schematic while working on a set I didn't realize it was an alternate circuit , What the alternate circuit is I'm unsure.

Tube may have grid emission.

jr

It didn't show on the tester so will try another tube but how could this tube knock out the audio too ?

All I was able to do was put a new tube in and it's the same , what I didn't know was that pin voltage varries with the rotation of the contrast control , unsure if it should do that

What's the pin 1 voltage range with contrast turned from end to end? While you're at it measure the voltage range on the cathode too. Have you replaced the .1uf cap between the detector and pin 1 of the video amp?

With contrast rotated for full contrast pin 1 reads -3.1 volts , pin 7 the cathode reads 171 volts , with contrast turned down all the way pin 1 reads 18 volts , pin 7 the cathode reads 27 volts ...... Yes I changed the .1uf , perhaps the new one is no good ?
I did notice SAMs voltage readings are taken with focus control counter clockwise , this I didn't try .
What I will try is injecting video from a DVD into pin 1 and see what happens .

Well I hooked to pin 1 with a .1uf and plugged it into a DVD player , I have an image , there are bars on the left side of the screen but that can be dealt with later , the first DVD player I used the image was ok but when you tried to put more black into the image it would cause black lines to reach across from the left and turn it higher it was like overloaD and smeared , so I tried a different player and a better image that if you turn the contrast up you get blacks and if up all the way a slight overload in the whites and a buzz in the sound , a video type buzz.
So it would appear that what ever is wrong it is before the video tube , I will try further but if I give up I can just feed to the video and audio , question is what would happen if I reduced the .1 to a .01 ? What would happen if I went from .1 to.5 ? Any ideas ?

So with the contrast control around center, pin 1 is not too far off from the 1 volt Sams calls for? The coupling cap value should only affect the video frequency response. No harm in trying other values, but you can assume .1uf is good because it's the coupling value used before and after the video amp.

Just to note the voltages on the 6ah6 are the same when feeding the video into the tube and they read the same at both ends of the contrast control .
Problem has to be before or at the 12au7 because that's where the picture and sound splits and there's no sound , only sound that can be heard is a buzz in the audio when contrast is at full and there's a slight overload on the screen plus way to black.

Does anyone knows why a 10k resistor in the audio area ? Wouldn't something lower like 1k or 100 ohms allow louder audio from the input ? Is the 10k to prevent frying of the DVD player ?
The audio is quiet , even if you overload the video with too much contrast no hint of a buzz .

I'm getting a 404 file not found when trying to download the schematic, but the volume control is likely a few hundred kohms or more, so using 10k resistors on the input will only reduce the signal by 5% or less. Tying the L and R to the volume control with 10k resistors prevents the L and R DVD outputs from overloading each other.

If you have disconnected the TV volume control / audio amp circuit from the detector, varying the video level should have no effect.

Thanks , I was just pointing out how directly feeding the audio is much more quiet