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 Post subject: Tele-Tone blooming like crazy
PostPosted: Jun Tue 23, 2020 9:47 pm 
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Joined: Aug Sun 11, 2019 5:45 am
Posts: 19
Hi folks. I'm working on a Tele-Tone that came my way because the seller told me I "had to take the Tele-Tone" in order to get the TV I actually wanted. The TV was a MESS. I decided to just have a "quick look" to see if I could at least make the screen light up. Before long I was up to my eyeballs in the thing. No vertical deflection caused by open blocking oscillator transformer. I don't think I got the correct transformer, because I had to do a bit of a mod to the vertical sweep to get full deflection. Of course, I wound up replacing all the caps in the vertical circuit.
But I digress.
I have horrible blooming. I tried a couple of 1B3s. Turning up the brightness can reduce the 2nd anode voltage down to 3KV or lower. Horizontal drive is tweaked for max picture.
Anyone have any thoughts on this? Have you worked on one of these? In olden times, the "go-to" diagnosis was a defective flyback. I do have a low coil DC resistance compared to what Sams says.
This would be a neat port-hole TV if I could just knock out this last issue.
Thanks for any insight.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Tue 23, 2020 10:02 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2081
Location: Lafayette, CO
Which Teletone do you have? I have one that is similar to an RCA 721TS in style, it might be the same chassis or circuit? Craig


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Tue 23, 2020 11:20 pm 
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It appears to be a TV 250 or 254 according to the SAMS I have for it. Honestly, I can't seem to locate a model number on it at the moment. But I must have had one at some time or I could not have been able to find the SAMS for it.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Wed 24, 2020 1:33 am 
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Joined: Nov Tue 03, 2015 9:43 pm
Posts: 104
Location: Illinois, 60565
Greetings Jfleetwood:

You have one of those popular 1950s televisions that are compact with a wealth of data. You have a Sams but you can crosscheck with Riders Volume 4 Tele-Tone page 1. Parts and info are also available under the Sears Silvertone television models 9125 or 9126 depending on the CRT size. (see photo)

My question is what have you done our not done with the seleniums? Might be that your B+ isn't up to the load?

John

Attachment:
12_Silvertone TV Model 9125A.jpg
12_Silvertone TV Model 9125A.jpg [ 422.51 KiB | Viewed 796 times ]


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Wed 24, 2020 3:27 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 926
Location: Belrose, NSW, Australia
Sometimes there is a resistor in the 1B3 socket in series with the HV lead. This goes bad and the picture blooms.

Don't forget to set the Hor Linearity coil (if it has one) for minimum current through the Hop OP tube.

It could be a bad flyback. If so it will be a shorted turn in the HV winding. Does the HV winding get warm aftyer a few minutes running? What is the boost voltage and current at the Hor OP tube cathode?

_________________
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Last edited by irob2345 on Jun Fri 26, 2020 3:21 am, edited 1 time in total.

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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Wed 24, 2020 4:34 am 
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Joined: Aug Sun 11, 2019 5:45 am
Posts: 19
Not able to reply directly to "heterodyne" for some reason, but to irob, I will check that resistor. and to "heterodyne" I replaced the selenium stacks with silicon diodes and and increased the dropping resistor to achieve the only measurement point in Sams that traced directly back to the power supply. Glad there is more data out there. I will look for Riders info.
Thanks to both of you!


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Thu 25, 2020 1:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2081
Location: Lafayette, CO
If the output of the horizontal oscillator is low in amplitude (and on frequency), you will get this problem. Check plate resistors and supressor grid resistors. Craig


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Fri 26, 2020 4:39 am 
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Joined: Aug Sun 11, 2019 5:45 am
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This is a really enjoyable forum. Thanks, everyone.

This TV is an interesting project because it has been consistently calling into question "stuff" that one might have accepted as fact over the years. Like "check the high value resistors. They drift." Well, that's certainly true, but the first actual improvement I made here was finding that the 3.3 Ohm filament resistor on the 1B3 was 12 Ohms. The 1 MEG was OK, although as soon as I scare up a 1 Watt 1 Meg, I'll get back in there and replace that too. That got the 2nd anode up to about 5 KV.
So following the forum advice, I looked into the H Drive.
I might have mentioned that this TV was barely more than a piece of electronic junk when I took it in. That said, the TV has had various parts substituted throughout. So yes...the H. O. screen resistor was "bad" because it was the wrong value. So was the cathode resistor. Replacing them with the correct value got the DC voltages back to where they are supposed to be on the H.O. tube, but no joy on HV improvement.
Back up one section to the H Osc. Plate voltages low. A 10K resistor off the damper was 16K. (Again, I don't find many 10K resistors that drifty) That helped. Not enough. A 120 K resistor was out of tolerance. That helped too much!
A check of the damper output had it significantly high.
THIS is where the H Drive adjustment started having a desired effect.
I'm not nearly done yet, and have not re-measured the HV, but it is looking WAY better.

I remain concerned that one winding on the flyback is measuring 1 ohm when it should be 6 ohms. All other windings are close. If anyone has ever documented the winding DC resistance on this set, kindly post it.

I've already gone on too long. But anyone who works on stuff like this does so because when you stare at a schematic, suss out what you think is ailing the beast, replace the part you suspect, and are rewarded with an improvement....well I guess that's why we take on a junky thing like this particular TV.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Fri 26, 2020 5:17 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 26155
Location: Detroit, MI USA
My thinking is that if a flyback winding which was supposedly 6Ω actually measures 1Ω, the set wouldn't work nearly as well as it does, and in fact currents would be excessive and HV low to say the least.

Therefore the 6Ω reading could have originally been recorded in error, or a production change made which made the original resistance reading no longer applicable.

Do you have a flyback tester, or a way to ring the flyback using a scope to look at the decay of the waveform? That will tell you immediately if there are shorted turns or not. But I never saw one which was that bad, that would work even remotely like it was supposed to.

_________________
Dennis

Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Fri 26, 2020 6:10 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 926
Location: Belrose, NSW, Australia
I agree with Dennis re the flyback winding DC resistance, if it was really that far out it wouldn't work at all. Stated DC resistance on transformer windings generally shouldn't be relied on too much.

I think a series filament resistor on the 1B3 that measured 12 ohms instead of 3.3 would certainly have caused your blooming.

I was pretty close, huh?

Remember that these things keep working with tolerances we would consider outrageous these days, like +20%, it was a matter of the materials they had to work with.
Hence my signature byline.

Do take my advice and tune the Hor Lin for minimum voltage on the Hor OP tube's cathode. Saves tubes and flybacks as well as generally giving you the best horizontal linearity. If some tweaking of the Hor Lin is really needed, don't go more than 2 turns either way of the minimum current setting.

_________________
Wax, paper, bitumen, cotton, high voltages - what could possibly go wrong?


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Fri 26, 2020 10:58 pm 
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Posts: 19
I agree with the flyback comments. The winding in question is the one with the H Width coil across it. Width is fine. HV is now up to around 8KV. Blooming is minimized. Yep! You were right to have me look at the 1B3. I'm really surprised at how many really out of tolerance resistors are in this thing. I'm not just checking them for the sake of checking them. EVERYTHING associated with H Drive was 30 to 60% out of tolerance. Enough to make me go get a precision resistor off the shelf and measure it with the trusty old Fluke. (And this is out of circuit!) They must have REALLY been having a "bad resistor day" down at the old "ohmage plant" they day they mixed up that carbon. that first bad 10 K I found really helped with the H problem, but the next one in line was double its value (across the osc coil).

On that topic, anyone have any recommended sources for a 1 W resistor kit? I hate like crazy to put in an order to Mouser for 1 ea: 220K 1 W resistor, and so on and so forth.

More questions, folks....if you have the time:
How would you select a dropping resistor to replace the original, given that the set now has 4007s instead of selenium rectifiers? I set the line voltage for 117, and fiddled till I got the voltage listed in Sams at an early point in the power supply.

And the big question: I have seen several old TVs with the H Osc tube shock-mounted off the chassis. This is one such set. Why why why???

Thanks folks.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Sun 28, 2020 6:09 am 
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Location: Pewaukee, WI
Tubes can be microphonic. The vertical and audio can vibrate the H osc and disturb horizontal opperation so shock absorbent mounting was common.

Carbon composition resistors are very sensitive to moisture. If the set wasn't stored in an environment with low humidity it will probably have some drift... I've worked on some sets that sat outside in the rain for a prolonged time and the drift was insane nothing even close to tolerance, and many 2-3x rated value.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Sun 28, 2020 10:41 am 
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Joined: May Sun 07, 2017 11:35 am
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Location: Belrose, NSW, Australia
The reason I didn't answer your question about shock mounted tubes was I was looking for a source of 1 watt resistor kits, I felt sure I'd seen them at either Altronics or Jaycar in Oz - OK to order on-line, shipping is cheap.

I found a good one for half-watt metal film resistors, 1700 of them, the full range of values, but not with 1 watt resistors so far.

_________________
Wax, paper, bitumen, cotton, high voltages - what could possibly go wrong?


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Sun 28, 2020 3:56 pm 
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Location: Beaver Falls, PA. USA
The resistors used in the 1940s and early 1950s often drift way out of tolerance, so it's a good idea to check all of them.

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Tim KA3JRT


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Sun 28, 2020 10:59 pm 
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Thanks folks. Yeh, I guess the H Osc could be disturbed by audio vibrations. I had not thought of that. I ordered some resistor kits from justradios.com. We shall see what I get. The values in the TV are indeed crazy off-spec in any area that I examine. I never had in mind swapping out ALL the caps, and measuring at least half the resistors on this when I started it. This particular TV has turned into a money-sink. But what the heck??? I'm stuck in the house, or masking up and going to the grocery store....I have not much else to spend money on at the moment. The Foxwoods Casino keeps sending me email inviting me up, but I'm just not ready to put my health on the line for a weekend of losing money. I'll dump it all into this TV.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Mon 29, 2020 12:01 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Phoenix, Arizona
Resistors and Capacitors have almost become one in the same in these 40's TV's.

The capacitors seldom change value but as they warm up they become more leaky.

I find the high resistance resistors tend to go off further than the low ones but they should all be suspect. They get noisy as well.

Some TV sets use trick voltage regulator circuits using the audio output tube as a voltage regulator (Admiral 19A1 7" set). a couple of innocuous grid bias resistors make that set go nuts.

Although I resisted in earlier years, I have found all capacitors need to go to the after life and more resistors than we think.

Taking this opportunity to plug the newly manufacture of can electrolytic s.

I like my old ancient Solar capacitor bridge as It puts a good high voltage on the leakage test.

Oh BTW they are all money pits and not worth our love and care :)
Jim


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Tue 30, 2020 5:17 am 
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Posts: 19
Yeah, but I still love them and care about them. I've been sending pictures flying through the air for a long time, and it still amazes me.


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jun Tue 30, 2020 2:58 pm 
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Location: Pewaukee, WI
jimmc wrote:
Resistors and Capacitors have almost become one in the same in these 40's TV's.


More like try to trade places. Capacitors try to develop resistance, and resistors try to go open....


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jul Wed 01, 2020 12:30 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 926
Location: Belrose, NSW, Australia
Yes and wax paper caps that become batteries!
The best I've found so far is 1.2 volts! I hooked up a string of them I removed from a TV chassis one time and I got just under 15 volts. The chassis hadn't been powered for at least 20 years so it sure wasn't stored charge...

Re carbon comp resistors, we have at least one brand here (Ducon) that goes LOW. Especially values that are supposed to be in the hundred ohms. Cathode bias resistors of course. The hotter they get, the lower they go. And the special IRC high voltage BTAV resistors that are all guaranteed to be twice their marked value and jumping around all over the place. Morganite resistors are the best of the bunch but even they go noisy. Noisy resistors are horrible things to track down, a long term intermittent in a horizontal oscillator circuit where the phase locked loop was trying to cover up the fault comes to mind.

Now even mica caps are suspect, at least those with a voltage across them.

Wire-wound resistors? Generally OK!

Well I guess in another 60 years they'll be laughing at the folly of us trying to make something reliable out of the materials we have available to us today. We already have the tin whisker time bomb....

_________________
Wax, paper, bitumen, cotton, high voltages - what could possibly go wrong?


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 Post subject: Re: Tele-Tone blooming like crazy
PostPosted: Jul Wed 01, 2020 2:34 pm 
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At the risk of taking this too far off-topic, thanks for the "tin-whisker time bomb" comment. I performed the task that passes these days for "research" and Googled the term. Fascinating. I had no idea. That lead to a discussion of a mandate to use COTS components in military gear. I already know of perfectly acceptable gear in the broadcast business that is relegated to the junk pile because a particular IC or other part is "NLA".


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