Ok, am going to describe some symptoms for my Crosley and just want to see what others think. I recently had this set restored electronically by Kamakiri. Set was working very well and he had put about 5 hours on it.

Transported the set about an hour away, and it still worked fine after some pic tweaks. It did develop an Audio Harmonic Hum ( which got worse with use) and was only getting audio on channels 6,7,8,9,11,12, and 13. Channels 2,3,4,5, and 10 had perfect picture, just no audio.

Then transported the set 8 hours. Got her home to MD, made sure ALL tubes in the set were seated properly and everything inside looked right after transport. Hooked up antenna, which pulls in an analog signal on channel 7 from my agile modulator which has my DirecTV fed into it. Turned on the set. Got perfect audio on Channel 7. Got raster and with a contrast tweak and pic tuning tweak got full stable picture. Thought all was well.

Then about 20 seconds later, hear a click. Along with the click sound, the picture signal was lost and the overall picture brightened. The audio was also lost. Heard the click again, pic signal and audio signal returned to normal briefly . . . then click noise again and pic and audio signal lost, but still a good raster. Pic and audio signals did not return after a minute, shut set down. After consulting with Kamakiri, figured the issue must be in the tuner section or audio. Went through audio tubes and tested them - all good. However I found the 6J6 mixer tube did have a slight H-K leak in it. So waiting on a good 6J6 to replace that as well as testing all tubes in set.

If no other bad tubes are found and the new 6J6 mixer tube does not fix the issue - anyone have any ideas???? I am very new to the hobby. :)

Thx.

Just to note, I didn't do a B+ adjustment on this set. I've been told that those who don't know how to do this shouldn't touch it, so I didn't :)

Which means I definitely am not trying it!!! :nono: Chassis is the RCA KCS-20J

Also to note: I picked up this yesterday on eBay. So if I need parts, I got em! :yes:

Plus wonderful to find an original stand!!!!

Hey guys, any thoughts on this? Has me kinda stumped, offhand.....at least to the theory of what could be going on here....

The problem seems to affect pic & audio signal equally, so that narrows things down.

Wild guesses follow:

-- Funky tuner? I have had tuners that blipped the picture & audio in and out completely if their contacts were dirty or worn out.

If the problem reoccurs when changing channels, try nudging the tuner, rocking it, etc., while changing channels. If the pic & audio come and go, that may be the culprit. I have even had tuners that only worked when you turned the tuner so that it "stuck" slightly off the normal detent position. The remedy is to pull the chassis and service the tuner.

-- Funky Picture control? The "Picture" control on a 630TS is a manual gain control. If it is dirty or worn out, that can have a major affect on the signal.

When the TV is playing, try turning the Picture control back and forth through its entire rotation. If that has an immediate effect -- either causing the problem or curing it -- you may have found your culprit. When pic/audio are present, note whether turning the control makes things change smoothly; if the change is jerky, the control may need attention.

Re-seating tubes and wiggling them is always worthwhile. Sometimes a tube or its socket will have stubborn oxidation or dirt (or the socket may even be loose) such that wiggling or re-seating only works when you happen to position it in exactly the right position. The remedy is to thoroughly clean every tube pin and socket hole so that you don't have to guess whether the tube is actually making contact. Dirty tube pins & sockets are an extremely common cause of intermittent operation and that's why I eliminate this cause before I do any recapping: http://antiqueradio.org/FirstStepsInRestoration.htm .

Those are a couple of not-very-scientific things you can try immediately. I don't know what instruments you have available, or how willing you are to pull out the chassis and get your fingers dirty. Smarter people may have better ideas.

Regards,

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

Tuner wasn't dirty, and all the tubes now test good.

Here's a video of the issue:

https://www.youtube.com/watch?v=lvxCIJcaqqM

I described the initial failure in the comments below the video.

The problem seems to affect pic & audio signal equally, so that narrows things down.[/url]

I agree with Phil's recommendations and suspect that the problem is either in the tuner or the picture (contrast) circuit.

You may have or may not have two problems here.

The earlier missing sound on some channels indicates more probably tuner and the clicking in and out suggests picture control or related circuit.

Since the contrast control sets the gain of the tuner, it can also muck up the sound.

If tubes make no improvement, download the RCA 8TS30 / KCS 20J-1 manual at

http://www.earlytelevision.org/tv_schematic_diagrams_postwar.html

and using a VTVM run the voltages tests on V!, V2 & V3 shown with the picture (contrast) control set at both maximum and minimum.

If any voltages are off more than 20% find out why.


Also, the set is quite heavy and if it accidentally slides into something while being transported and the channel knob gets pressed in, that can cause problems in the waffer switches. Inspect the switch for bending damage and carefully clean the contracts. Allow solvent to dry over night before turning set on.

James.

AGC (if it has one) get bumpped? never mind just looked too early no agc. agree with others seems like tuner.

Son of a B, I never thought of AGC. This has all the symptoms of AGC loss.

Now in the pic below, there's no AGC listed, just a "peaking" control. Is that the same as AGC?

Just a quick follow up - in the very first post on this thread I described the moment the set lost pic and audio. About how I heard the clicking and lost signals and raster brightened. Then clicking and all returned to normal, then clicking and lost again. Well I want to add that I had just used the channel fine tuning control to get a good picture in and was adjusting the set's contrast when this started. I see some folks above mention the contrast circuit as a possible issue. Well that is exactly what I was adjusting when the set went funky.

Thanks for all your replies. Really appreciate it. I am very lucky to have a good teacher and mentor to walk me through this too - thanks Kamakiri!!! Keep any ideas pouring in if you think you know what may be up with the set.

some early sets contrast adj is the same as AGC (adjust the gain of the IF vs the gain of the video amp) so it kinda makes since it would look like an AGC issue.

We're thinking possibly the contrast control at this point, not sure. It was VERY touchy before this, and now I'm wondering if it's the culprit.

The Sams gives no information on it at all, and the Riders only comes up with a part number of 73157 on the assembly. I have a KCS47 chassis here, and we're thinking that the contrast control on that should yield similar readings.....but not sure.

I don't remember if they affect sound as well as the picture, but bad IF coupling capacitors caused flashing video and brightness on my RCA 8TS30. There are about four of them, 270pF mica if I remember right. Phil's site has the details, I know.

We're thinking possibly the contrast control at this point, not sure. It was VERY touchy before this, and now I'm wondering if it's the culprit.


The factory manual was listed in my early post.

As you said, the control is RCA part number 73157 with no cross reference.

Picture half is 10K Ohms tapped.

Volumne half is 1 Meg Ohms tapped and with AC switch and dual shaft length to fit early RCA. (The same control is found in some clones, including Teletone look-alikes that were not clones.)

Correction (07/27/2013):

Sorry folks, I kinda put my foot in my mouth on this one.

I looked about for another same combination control with switch and could not find one.

I suspect the only commonly available replacement control would be from an RCA 8TS30. Before I'd go looking for a parts set, I'd first confirm that the control is at fault and, if so, open it and see if it can be repaired, possibly by robbing a 10K element from another control.

While some of the other early sets used similar circuits, but after this one, I don't think anyone ever put the volume and a gain-type of picture control on the same shaft.

It seems too many people accidentally bumped the picture control while adjusting the sound and could not understand what they had done to mess the set up.

Jas.

Thanks Jas. Wondering if the KCS-47 has same control?

The KCS-47 has a 1.5M with two taps for volume and a 2.5M tone control along with the AC switch.

Jas, thanks for the clarification to your earlier post. I am going to try and test my pot this week sometime. So, the values you list above for it are correct, you just think it is not a control that was common to other sets now?

I have a spare set coming, so if it is a bad pot and cannot be repaired I will have a back up.

THANKS!

It appears that the contrast control is okay.

Is there a way to inject a channelized signal into the set at some test point, bypassing the tuner?

Hi All;
Sure, If you have a B&K 1077 or something similiar..
THANK YOU Marty