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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Tue 17, 2021 3:45 pm 
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Joined: Aug Thu 12, 2021 3:09 pm
Posts: 19
Seeing how close I am to getting it to display properly, which part of the circuit would you all recommend addressing first? Being as close as I am, I would rather try to get it going before doing a complete chassis re-cap.

Thanks!


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Tue 17, 2021 7:30 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2459
Location: Lafayette, CO
For you, adjust the horizontal frequency. The user adjustment is on the front panel. If that doesn't do it, put that control in the center of its range and leave it. Serviceman's control is on the rear panel. That's the coarse one....this should get you spot on. Any stability issues ought to be addressed by the re-cap. You're lucky that has a good picture tube. By the way, the cabinet face is painted woodgrain, not veneer. Craig


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Wed 18, 2021 12:26 am 
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analog.tv wrote:
For you, adjust the horizontal frequency. The user adjustment is on the front panel. If that doesn't do it, put that control in the center of its range and leave it. Serviceman's control is on the rear panel. That's the coarse one....this should get you spot on. Any stability issues ought to be addressed by the re-cap. You're lucky that has a good picture tube. By the way, the cabinet face is painted woodgrain, not veneer. Craig


Thanks Craig. I'm going to be able to get into it tomorrow. I will let you know what happens!

I want to watch me some Twilight Zone and I Love Lucy!


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Wed 18, 2021 1:17 am 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
The only picture you posted of the TV on shows "snow", a sign that the TV is not receiving or properly processing the RF input. Snow is just video noise. Actually it looks like the sweep circuits are providing approximately the correct frequencies. The screen sweep cannot lock onto a weak signal.
What did you use for a RF (antenna) signal?
You do realize there is no longer any TV broadcasts that work with vintage TVs like this.
A VCR, DVD plus a modulator, a digital to NTSC convertor or something similar is needed.

By the way, I would NOT tamper at this point with the horizontal adjustment coil on the rear of the chassis at this point. RCA used a Synchoguide circuit that is best adjusted using an oscilloscope, which I doubt you have.

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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Wed 18, 2021 1:33 am 
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Posts: 19
Notimetolooz wrote:
The only picture you posted of the TV on shows "snow", a sign that the TV is not receiving or properly processing the RF input. Snow is just video noise. Actually it looks like the sweep circuits are providing approximately the correct frequencies. The screen sweep cannot lock onto a weak signal.
What did you use for a RF (antenna) signal?
You do realize there is no longer any TV broadcasts that work with vintage TVs like this.
A VCR, DVD plus a modulator, a digital to NTSC convertor or something similar is needed.

By the way, I would NOT tamper at this point with the horizontal adjustment coil on the rear of the chassis at this point. RCA used a Synchoguide circuit that is best adjusted using an oscilloscope, which I doubt you have.


Hi Friend

If you go back and look, I attached a couple video clips showing the image being received but rather "collapsed"

I broadcast via a Blonder Tongue Agile Modulator.


Last edited by TVee on Aug Wed 18, 2021 2:53 am, edited 2 times in total.

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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Wed 18, 2021 1:55 am 
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Here are the videos:

https://imgur.com/NIsMDma
https://imgur.com/Y3cYt4X


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Wed 18, 2021 4:18 am 
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Location: Dallas, TX
Oh yes, I remember seeing them now. I'm trying to help with several TVs plus some things of my own.

So that does look like the horizontal sweep frequency is off quite a bit.
I'm sure the service manual has the procedure to adjust the coils. I believe there is a method to adjust them that doesn't use an oscilloscope but it isn't recommended by RCA. Maybe someone else remembers what that is.
Of course since the capacitors and other components were not replaced the adjustments may not work.

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It's not the Destination, It's the Journey.


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Wed 18, 2021 7:07 pm 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
I took another look at the service manual. It does explain adjusting the horizontal without using an oscilloscope.
Of course the manual assumes that the adjustments are not far off and that the majority of the TV's parts are good and not some 70 years old.
I'm fairly sure the coils are adjusted using non-metallic tool, probably hex. Service info assumes that you are familiar with working with TVs and have most of the correct tools.
You are lucky that the CRT and the cabinet are good. I still think you should do the recommended approach and do a re-cap and possibly replace other parts before expecting things to work fine and not go poof.

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It's not the Destination, It's the Journey.


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Wed 18, 2021 8:05 pm 
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I got in there today and tried again - put the horizontal hold into the center spot and tried adjusting the horizontal freq in back and nothing is opening up the image.

I have the service manual here. So basically I should go through and replace all the caps on the horizontal circuit to start?

Latest vid:
https://imgur.com/SbuNCHq


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Thu 19, 2021 12:52 am 
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Location: Dallas, TX
Well you can see that you have some video signal getting to the CRT which is good. You can't tell too much about the vertical sweep at this point but it is there.

Actually the best section to start replacing capacitors in is the power supply area. It feeds the power to all the other sections, so it is sort of the foundation of all the circuits. If the voltages are wrong or contain too much hum (ripple) the sections being fed won't work correctly. Also since the power supply is the source of all the power, it handles a lot and a fault there can do damage.
After the power supply you could take on the horizontal section.

Here is a link to Phil's work on a later model RCA. It just happens to have had a horizontal problem (among others).
https://www.antiqueradio.org/rca15.htm

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It's not the Destination, It's the Journey.


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Thu 19, 2021 1:43 am 
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Notimetolooz wrote:
Well you can see that you have some video signal getting to the CRT which is good. You can't tell too much about the vertical sweep at this point but it is there.

Actually the best section to start replacing capacitors in is the power supply area. It feeds the power to all the other sections, so it is sort of the foundation of all the circuits. If the voltages are wrong or contain too much hum (ripple) the sections being fed won't work correctly. Also since the power supply is the source of all the power, it handles a lot and a fault there can do damage.
After the power supply you could take on the horizontal section.

Here is a link to Phil's work on a later model RCA. It just happens to have had a horizontal problem (among others).
https://www.antiqueradio.org/rca15.htm


Thank you!

Now the service manual doesn't stipulate any sort of discharge procedure at all when removing the chassis....really?


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Thu 19, 2021 12:11 pm 
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Location: Belrose, NSW, Australia
Don't replace anything!! At least, not yet.

The video shows clearly that you have vertical sync and that the horizontal oscillator is off frequency - but not by much.
The video also shows me there is nothing wrong in the power supply - caps look good, there is no ripple.

Do this:

1. While watching the screen, turn the horizontal hold in the direction that makes the lines broader.
2. If you get to the end of its travel, there are 3 possibilities:
(a) It makes no change at all.
(b) The lines get broader but there is still no locked picture.
(c) You now have a picture!

If (a), check the components around the horizontal hold pot. Measure the voltage on the pot as you adjust it.
If (b), does placing a metal screwdriver in the core of the Lock coil affect the number of lines?

Please resist the temptation to replace stuff by guesswork. You will probably make a mistake and end up with a new fault which will be very hard to find.
The time will come when you will need to replace various parts. When you do, replace them 1 or 2 at a time and check the TV again after each small step. Doing this WILL save you much heartache!

I worked on this kind of TV since I was a kid at school, up until the mid '70s. I trained TV technicians for a large service company.
I now design electronic equipment with a team of engineers. So I do know what I am talking about!!

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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Thu 19, 2021 5:09 pm 
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irob2345 wrote:
Don't replace anything!! At least, not yet.

The video shows clearly that you have vertical sync and that the horizontal oscillator is off frequency - but not by much.
The video also shows me there is nothing wrong in the power supply - caps look good, there is no ripple.

Do this:

1. While watching the screen, turn the horizontal hold in the direction that makes the lines broader.
2. If you get to the end of its travel, there are 3 possibilities:
(a) It makes no change at all.
(b) The lines get broader but there is still no locked picture.
(c) You now have a picture!

If (a), check the components around the horizontal hold pot. Measure the voltage on the pot as you adjust it.
If (b), does placing a metal screwdriver in the core of the Lock coil affect the number of lines?

Please resist the temptation to replace stuff by guesswork. You will probably make a mistake and end up with a new fault which will be very hard to find.
The time will come when you will need to replace various parts. When you do, replace them 1 or 2 at a time and check the TV again after each small step. Doing this WILL save you much heartache!

I worked on this kind of TV since I was a kid at school, up until the mid '70s. I trained TV technicians for a large service company.
I now design electronic equipment with a team of engineers. So I do know what I am talking about!!


Thank you very much for taking the time to help me!

I'll get on it today, do what you said and report back the results!


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Thu 19, 2021 7:44 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3509
Location: Dallas, TX
I don't think anyone was saying to replace components by guesswork.
The OP said he has some experience with working on solid state TVs, but not something this old. With a little guidance I think he would be up to the task.

Fixing just the problem of the moment may lead to fixing something else next month, and the month after that, and the month after that...
The object should be to have something with better reliability.
A piece of consumer electronics built in 1951 isn't the same as something built in 1990. Many vintage parts deteriorate with age. This is something commonly known by most people working on vintage electronics.
These forums are filled with cases of vintage electronic products with many faulty components in each one.
Unless the set is intended for a technology history museum I don't think there is any need to keep it pristine under the chassis.

There are many posters on this forum that have a long career in engineering and/or repair.
Most don't see the need to make an issue of it.

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It's not the Destination, It's the Journey.


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Mon 23, 2021 9:27 pm 
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About to get back into this....

Can someone tell me their discharge procedure on an old tv like this? The original service manual doesnt mention anywhere needing to discharge. IS this true?

Thanks


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Mon 23, 2021 10:19 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2459
Location: Lafayette, CO
Take a jumper wire from ground and touch the bell of the picture tube with the other end. Do this every so often until there is no arc. Now it's discharged. The bell of that picture tube you can find with a magnet. Craig


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Aug Mon 23, 2021 11:06 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3509
Location: Dallas, TX
TVee, you have to understand that service information is not meant for the TV owner, it is for a service technician, one who has had some training. Discharging a CRT is very basic info (like how to use a meter) that would have been covered in the training. Many times you had to go through an apprenticeship to work on radio and TV repair at a shop.
BTW, on this set mostly what you will be discharging is C197, which is mounted on the outside of the metal horizontal sweep cage. It is probably a ceramic capacitor, ceramic capacitors don't hold a charge quite as well as the glass of an all glass CRT. In your efforts to reach the CRT bell don't get near C197.

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It's not the Destination, It's the Journey.


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Sep Wed 08, 2021 6:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Rockaway , nj 07866
So what ever happened with this tv ?


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Sep Sat 18, 2021 4:12 pm 
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Kramden66 wrote:
So what ever happened with this tv ?


Had to take a pause due to life obligations but i'll be back at it soon!


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 Post subject: Re: RCA Victor 17T172 Help Needed
PostPosted: Sep Sun 19, 2021 12:10 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1796
Location: Phoenix, Arizona
Looks to me like the horizontal frequency is a little off. may be as simple as adjusting the front panel controls.

Since you have powered it up I would try running it a few hours under careful watching in case something shorts.

Sometimes electrolytic's can survive the decades. The other problem is RCA used a lot of can electrolytisc's which are expensive.

The metal CRT can be discharged with a screwdriver and a clip lead to the chassis. I recommend you discharge because the shock will make you break something like your hand.

We all know about old dried up capacitors but we all can't resist trying it. :) :)

Jim


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