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 AWA 206CY
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 Return to top of page · Post #: 16 · Written at 8:10:37 PM on 16 February 2019.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 5791

Photo uploaded to Post 13.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 17 · Written at 12:18:54 PM on 17 February 2019.
Unknown's Gravatar
 Location: Shepparton, VIC
 Member since 19 June 2011
 Member #: 931
 Postcount: 24

By those tests its very bad.
At 6.3v it takes 5 minutes from cold to stabilise at 0.865v, at 7.3v I get 1.82v, at 10v I get 4.6v.
Warm it takes 2 minutes to stabilise at 0.86v.
The glass around the heater is browned and the heater/cathode is very blued.

if the kinescope was changed in 1973 and the set was retired a few months later the discolouration and the emissive readings i'm getting suggest the tube is original and not replaced.
Is there any hope of finding a 21alp4a kinescope is usable condition?


 
 Return to top of page · Post #: 18 · Written at 1:40:57 PM on 17 February 2019.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1490

Those readings look workable for a CRT that's been in hibernation for a while. I did a resto on the 17" version of that AWA that had an original CRT that tested worse than that. It's now in almost daily use in a museum and it gets better all the time!

From your results, it looks like your tube has shipped a little gas over the years (quite normal) and it needs the cathode to be heated to bake it out. You can do this by letting it sit on 10 volts for a few hours, perhaps overnight.

Looking at the picture, I would NOT discard this tube! You are going to be hard pressed to find another as good or better.

You said you were looking for a 21ALP4. That's the original tube number. There are a few alternative types that will drop in. Most common will be the 21CGP4.

Does your tube have an ion trap? That's a little magnet strapped or clipped around the neck near the socket. If not, it is DEFINITELY a replacement and will most likely be a 21CGP4.

As I said before, discolouration in the neck glass or on the gun itself is NO indication of hours in use. It's not a light bulb! Things that are done to the tube when it's made will cause these things.

Oh, going off the picture, you have some bad electros on at least one B+ line and around the vertical amp, notably in the vertical, the cathode (C119B) and B+ (C231C) bypasses. As has been said before, good vertical linearity is not this chassis' long suit, but it should be MUCH better than that.

As well I'd suspect C442 and C119C (in the power supply) of being bad, causing the pulling of the picture.

V206 is commonly low emission in these chassis. That will cause low contrast, a "dull" picture and a slow warmup. You can check this by measuring its anode voltage as it warms up, WITHOUT changing the test pattern. If it drops by more than 10 volts over 10 minutes, replace it.

A weak V302 (6SN7) can also cause pulling, as can V204 (6CB6).

Looks promising, keep at it!


 
 Return to top of page · Post #: 19 · Written at 3:21:18 PM on 17 February 2019.
Unknown's Gravatar
 Location: Shepparton, VIC
 Member since 19 June 2011
 Member #: 931
 Postcount: 24

Thanks for the reply, None of the IF section is in circuit at this point for testing purposes, aside from the audio section I have a signal and video amp at pin 2 of the 12BY7 with l204 disconnected.
the only caps in the vertical that are original at this point are the multisection cans I will bypass with new and substitue the 12BY7 and upload a new photo of the results, I don't really have that much hope at this point but I will see what happens. The tube is a 21ALP4A with an ion trap.
It has the black RCA cap and 21ALP4A silkscreened on the neck.


 
 Return to top of page · Post #: 20 · Written at 3:38:42 PM on 18 February 2019.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1490

Those can electros will almost certainly be bad, especially if they are UCC brand.

I regularly use 50 + 50 μF clamp-fit cans made in the Czech Republic from Tube Depot in the states to replace those multi-section twist-lugs. A 50μF half of these caps can replace anything from 20μF to 100 μF and they are rated to handle the ripple current as well as the voltage. Good and not too expensive.

https://tubedepot.com/products/jj-can-capacitor-50uf-x-50uf-500v?taxon_id=1

For the low voltage caps (esp. the 50μF in the vertical) I use axial or radial caps, 63 volt. Because of the current I usually go to double or 4 times the μF rating so the cap will be bigger and will last. It wasn't unusual for the tolerances of those electros to be +200% or even more when new.

There is a 4μF cap in one of those cans that is a slight problem. It has to be 600 volt and cannot be over 4μF because the height will be slow to come up.

The pulling in the picture MIGHT be due to the way you are biassing the 12BY7 with the direct input. If the sync pulses are crushed that will happen. The 12BY7 anode should run at about half the B+ voltage, it will vary with picture content. If it's up close to the B+ the sync will be crushed. Bias the grid up a bit in this case.

That CRT DOES certainly sound like an original, although it might have been a re-gun from e.g. Sure Brite. They often used the original base. RCA tubes were a lot longer lasting, generally, than the AWV ones. I would stick with it.

You will get a good result from this TV.


 
 Return to top of page · Post #: 21 · Written at 7:28:28 AM on 19 February 2019.
Daro's avatar
 Location: Tanawha, QLD
 Member since 22 December 2012
 Member #: 1263
 Postcount: 45

"The tube is a 21ALP4A with an ion trap. It has the black RCA cap and 21ALP4A silkscreened on the neck."

Funny an RCA 21ALP4A CRT in this set, I'd hardly think its a rebuild in the case of that CRT as most rebuilt CRT's in Australia were from Thomas in that time and most likely would not be using a replacement electron gun that requires an ion trap magnet.


 
 Return to top of page · Post #: 22 · Written at 10:28:26 AM on 19 February 2019.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1490

Did you ever visit Sure Brite Picture Tubes? Or any of the other small operators at the time?

Sure Brite would replace the cathode in the existing gun as I recall.


 
 Return to top of page · Post #: 23 · Written at 11:13:46 PM on 26 June 2019.
Unknown's Gravatar
 Location: Shepparton, VIC
 Member since 19 June 2011
 Member #: 931
 Postcount: 24

Thanks again to everybody who responded and helped out here.
I have an update - Good News!

The set is now almost fully functional.
But first before I get into that I have to eat some humble pie.
The RCA kinescope is good. I made a serious error there. over the past months I picked up a donor set, a newer model with the same kinescope, just AWA branded. This is a bad tube. Its a rebuild at some point, overly bright washed out and terrible focus. the image actually inverts when setting the ion trap. Now I know rebuilds should not have an ion trap, however this one came with the tube and I get no pic without it.
Before any talk of restoring the second set arises I must point out that the lopt, vertical and horzontal transformers are open circuit, and the tube is truly bad.

I was also wrong about the video amp circuit, it overdrove and created most of my picture issues, I now use a jvc top loader vhs through the IF as nature intended and get an excellent picture. although not with vhs as the heads are shot.

Further more I have found what caused my cramping issues. I had replaced all the vertical caps and resistors as I had found them, but after many hours of nutting out the circuit diagram fixed it. A mistake made sometime in the past but I did not catch as I was not looking for crossed components.

If anybody is still interested I am happy to provide pictures and am hoping someone may be able to tell me where the vertical blanking circuit is as I cannot identify it, I have retrace lines I can't get rid of even on a blank raster.

As it is now I am watching Blue Heelers on it happily.


 
 Return to top of page · Post #: 24 · Written at 10:40:09 AM on 27 June 2019.
Irext's avatar
 Location: Werribee South, VIC
 Member since 30 September 2016
 Member #: 1981
 Postcount: 268

Just a quick note. Did you replace the B+ filter electrolytics?
It's worth noting that it is unwise to leave the old ones in circuit with new ones bypassing them as I've seen sometimes.
Those old UCC ones can become leaky and drag the B+ down and in the worst case case even explode.
They will become hot to the touch before this happens.
Nice to hear of an 50's AWA up and running.
That model was one of the 1st sets I ever worked on as a teenager.
Fond memories.


 
 Return to top of page · Post #: 25 · Written at 6:25:22 PM on 27 June 2019.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 671

Hi, I can see an R/C network coupling the plate of the vertical output to the control grid of the pix tube.
That has to be the blanking path. Check those parts are in spec.

Fred.


 
 Return to top of page · Post #: 26 · Written at 1:22:05 AM on 28 June 2019.
Unknown's Gravatar
 Location: Shepparton, VIC
 Member since 19 June 2011
 Member #: 931
 Postcount: 24

I have replaced the B+ caps by disconnecting them and hiding replacements underchassis.

Thanks for the pointer I'll look into it.


 
 Return to top of page · Post #: 27 · Written at 9:59:09 PM on 20 July 2019.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1490

Re the retrace lines, have a read of my earlier post here:

https://vintage-radio.com.au/home.asp?f=6&th=214#1627

Old TVs can't blank some of the stuff seen in more recent signals.

I also added hor retrace blanking to my slightly newer AWA. Very effective at removing colour burst that can be seen as a vertical "watermark" in the image. Post or email me for how to.

If your player has Y-C outputs you may be able to use the Y signal in place of the composite video to get rid of this effect.


 
 Return to top of page · Post #: 28 · Written at 5:33:33 PM on 11 September 2019.
Unknown's Gravatar
 Location: Shepparton, VIC
 Member since 19 June 2011
 Member #: 931
 Postcount: 24

I'm still having issues with retrace lines.
They are visible on a blank raster if I get the tube bright enough for a picture,

After much research and testing, I have a rebuilt 21alp4a that's dead, inverted washed out image until heater is a 10.5-11 volts for a 6.3 volt filament.
And the original RCA branded 21alp4a that has dull picture and inverts for 5 minutes until warm up but shows some life.
The original tube has to be run at 7.5 to 8 volts for a good picture. it's left as factory as of now.

Today I hope that someone may be able to point me towards a compatible tube. I feel the value of this set warrants replacement, and as far I can find out this design is unusual. there are very few to my knowledge of AWA sets of this era with doors.

As well as that I enjoy watching it, more so now that I can get HDMI audio and video to it off my media pc.

Is anyone able to point me towards somewhere in AUS I could get a compatible replacement to the 21alp4a?

I have asked for a pic as the set is now to be uploaded to this post.

AWA 206CY Valve Television


 
 Return to top of page · Post #: 29 · Written at 12:27:05 PM on 14 September 2019.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 5791

Photo uploaded to Post 28.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 30 · Written at 11:48:19 AM on 16 September 2019.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1490

If you have retrace lines that come and go when playing a DVD, you have macrovision encoded video that the TV won't be able to fully blank.

Read my earlier post.

Your JVC HR7200 VCR was a very good model, back in the day....


 
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