TV22 frame collapse - UK Vintage Radio Repair and Restoration Discussion Forum

mark pirate · 10th May 2013, 5:30 pm

I started on this set nearly three years ago, it was fully recapped but suffering from frame collapse due to the blocking tx primary winding being open circuit.
I have just fitted a good replacement, but the set still has frame collapse

I have replaced the ECL80 with a known good one, and the scan coils seem ok, but still no joy.

Any suggestions welcome, I can't seem to see the wood for the trees!

Mark

Peter.N. · 10th May 2013, 5:45 pm

Can't remember the circuit off hand but is there voltage on the oscillator and output valve anodes? Do you have a scope, if so check the anode of the oscillator and see if it has a sawtooth wave on it.

Peter

Freya · 10th May 2013, 8:51 pm

Does the replacement transformer read 540 and 480 ohms. R53 220k likes to wander upwards and causes collapse too.

Stephen

Heatercathodeshort · 10th May 2013, 9:04 pm

A very crude but effective check to see if the actual output stage is working is to connect a .01uf capacitor from the low end of the heater chain [pin 4 or 5 of an EF80 or pin 3 or 4 of a EF91]to pin 9 of the ECL80.
This should produce some sort of frame scan. Make sure you have the connections the correct way round on the transformer [correct phase]. Try reversing them to ONE winding and see what happens. All great fun! John.

mark pirate · 11th May 2013, 5:43 am

Thanks for the suggestions chaps, I will have a bit of workshop time this afternoon.

Quote:

Does the replacement transformer read 540 and 480 ohms. R53 220k likes to wander upwards and causes collapse too.

Yes, the replacement is fine, it has been 'borrowed' from my TV24, and is correctly wired in.
I will check R53, I have both the trader sheet and the Bush manual, it is the MK1
version with EF91's in the receiver.

John, I will try your method, if there is a problem with the scan coils, I can borrow them from the TV24, I assume they will work ok with the 9" tube?

Mark

Heatercathodeshort · 11th May 2013, 8:15 am

The two chassis are identical Mark but don't tell the Bakelite boys or they will all be wanting one. John.

Peter.N. · 11th May 2013, 8:38 am

Quote:

Originally Posted by Heatercathodeshort

A very crude but effective check to see if the actual output stage is working is to connect a .01uf capacitor from the low end of the heater chain [pin 4 or 5 of an EF80 or pin 3 or 4 of a EF91]to pin 9 of the ECL80.
This should produce some sort of frame scan. Make sure you have the connections the correct way round on the transformer [correct phase]. Try reversing them to ONE winding and see what happens. All great fun! John.

I remember doing things like that, didn't think 'proper ' engineers did.

Peter

mark pirate · 12th May 2013, 6:18 am

I checked R53 220k this had risen to 226k, but replacement made no difference.
John's suggestion of connecting pin 9 of the ECL80 to the lower end of the heater chain did change the line whistle, but did not produce a frame scan.

I am beginning to suspect the scan coils, but as usual these are stuck fast to the neck, so will apply a few DC volts to them to warm them up and hopefully free them off, the TV24 coils do not appear to have the 2uF cap on them, and will also be stuck fast.

It may be a good idea to put both sets back to back and try using the TV24 tube and coils plugged in to the TV22 chassis rather than risk removing the scan coils, will report back later.

Mark

Sideband · 12th May 2013, 8:47 am

Quote:

Originally Posted by Peter.N.

I remember doing things like that, didn't think 'proper ' engineers did.

Peter

Very common quick check in the field particularly, or in the workshop if you were feeling lazy and couldn't be bothered to get the scope out (or it was being used by someone else.....only one scope per workshop in those days)

Rich

mark pirate · 12th May 2013, 10:16 am

I have now tried the TV22 chassis connected up to my TV24 tube and scan coils, I got an unfocused blob on the screen, this was due to the lack of a 2uF cap across the scan coils, with one fitted I am getting the same frame collapse, so unless the scan coils are duff in both sets, the fault lies elsewhere.

At least this experiment proves the tube is ok in the TV24

Looks like time to dust off the scope and go through the frame stage.

Mark

mark pirate · 12th May 2013, 1:12 pm

I have tried John's trick again and now get a full scan which proves the output stage is now working, both the ECL80's voltages are close to the trader sheet.

Any suggestions where to go from here would be very helpful.

Mark

Steve_P · 12th May 2013, 2:14 pm

Are the controls OK? If one went open circuit, then that would cause it.

R53 on the trader sheet is on the Sound O/P. But do check the resistors as well.

I hope T4 is OK.

Cheers,

Steve P.

Freya · 12th May 2013, 2:53 pm

Sorry Steve_P, was looking at 1003/T15 sheet when i quoted R53.

Steve

mark pirate · 12th May 2013, 3:05 pm

All controls are working, I checked them when I got the full scan on screen.
I checked all transformers and they are fine, I have checked and rechecked but cannot seem to find what is causing this fault

The receiver has not been recapped yet, but appears to work fine, but this would not cause this problem.

I do get a reasonable testcard on the screen when linking the heater chain to the frame o/p valve.

Mark

Steve_P · 12th May 2013, 3:29 pm

Wiggle the valve in it's socket and watch the screen. Also check the valve base.

Cheers,

Steve P.

mark pirate · 12th May 2013, 5:03 pm

All valve bases have been cleaned, as have the valve pins.
So waggling the valves makes no difference, this really has got me stumped!

Mark

PJL · 12th May 2013, 6:05 pm

I am not surprised you are having trouble getting the frame oscillator working without replacing the old leaky paper caps.

mark pirate · 12th May 2013, 6:19 pm

If you had read the whole thread, you would have seen that all the caps on the upper deck have been replaced, It is only the receiver deck that has not had the caps replaced, this would not cause the frame collapse fault.

Mark

thermionic · 12th May 2013, 7:49 pm

Hi Mark.
I would re check your work around the frame stage. As you would have been unable to test your work when re capping due to the blocking TX being OC, then It could be due to something being disturbed here.

Please don't take this as a criticism, we've all done it!

This could be one of the very few TV22's that provide you with a bit of a challenge! Make the most of it Mark!

Good luck. SimonT.

Heatercathodeshort · 12th May 2013, 8:20 pm

Mmm. There are only a few components that can stop the oscillator.
A faulty ECL80 valve. [Rare to have the triode section pack up completely]
Faulty blocking oscillator transformer but you have checked this. Worth a double check to make sure it has not been taken apart and reversed. Just a hunch.
Preset controls that have gone O/C. [Very common as mentioned by Steve]
A wiring mistake. [I've done it dozens of times]
A blob of solder shorting something out.
A broken valve holder connecting socket very close to the valveholder.
Way out capacitor value due to possible miss reading.
Failing that Mark, haul it up the A24 to my place and we can sort it out together!
Regards, John.

10th May 2013, 5:30 pm	#1
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	TV22 frame collapse I started on this set nearly three years ago, it was fully recapped but suffering from frame collapse due to the blocking tx primary winding being open circuit. I have just fitted a good replacement, but the set still has frame collapse I have replaced the ECL80 with a known good one, and the scan coils seem ok, but still no joy. Any suggestions welcome, I can't seem to see the wood for the trees! Mark

10th May 2013, 5:45 pm	#2
Peter.N. Dekatron Join Date: Jul 2008 Location: Charmouth, Dorset, UK. Posts: 3,601	Re: TV22 frame collapse Can't remember the circuit off hand but is there voltage on the oscillator and output valve anodes? Do you have a scope, if so check the anode of the oscillator and see if it has a sawtooth wave on it. Peter

10th May 2013, 8:51 pm	#3
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,991	Re: TV22 frame collapse Does the replacement transformer read 540 and 480 ohms. R53 220k likes to wander upwards and causes collapse too. Stephen

10th May 2013, 9:04 pm	#4
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: TV22 frame collapse A very crude but effective check to see if the actual output stage is working is to connect a .01uf capacitor from the low end of the heater chain [pin 4 or 5 of an EF80 or pin 3 or 4 of a EF91]to pin 9 of the ECL80. This should produce some sort of frame scan. Make sure you have the connections the correct way round on the transformer [correct phase]. Try reversing them to ONE winding and see what happens. All great fun! John.

11th May 2013, 8:15 am	#6
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: TV22 frame collapse The two chassis are identical Mark but don't tell the Bakelite boys or they will all be wanting one. John.

12th May 2013, 6:18 am	#8
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: TV22 frame collapse I checked R53 220k this had risen to 226k, but replacement made no difference. John's suggestion of connecting pin 9 of the ECL80 to the lower end of the heater chain did change the line whistle, but did not produce a frame scan. I am beginning to suspect the scan coils, but as usual these are stuck fast to the neck, so will apply a few DC volts to them to warm them up and hopefully free them off, the TV24 coils do not appear to have the 2uF cap on them, and will also be stuck fast. It may be a good idea to put both sets back to back and try using the TV24 tube and coils plugged in to the TV22 chassis rather than risk removing the scan coils, will report back later. Mark

12th May 2013, 10:16 am	#10
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: TV22 frame collapse I have now tried the TV22 chassis connected up to my TV24 tube and scan coils, I got an unfocused blob on the screen, this was due to the lack of a 2uF cap across the scan coils, with one fitted I am getting the same frame collapse, so unless the scan coils are duff in both sets, the fault lies elsewhere. At least this experiment proves the tube is ok in the TV24 Looks like time to dust off the scope and go through the frame stage. Mark

12th May 2013, 1:12 pm	#11
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: TV22 frame collapse I have tried John's trick again and now get a full scan which proves the output stage is now working, both the ECL80's voltages are close to the trader sheet. Any suggestions where to go from here would be very helpful. Mark

12th May 2013, 2:14 pm	#12
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: TV22 frame collapse Are the controls OK? If one went open circuit, then that would cause it. R53 on the trader sheet is on the Sound O/P. But do check the resistors as well. I hope T4 is OK. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

12th May 2013, 2:53 pm	#13
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,991	Re: TV22 frame collapse Sorry Steve_P, was looking at 1003/T15 sheet when i quoted R53. Steve

12th May 2013, 3:05 pm	#14
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: TV22 frame collapse All controls are working, I checked them when I got the full scan on screen. I checked all transformers and they are fine, I have checked and rechecked but cannot seem to find what is causing this fault The receiver has not been recapped yet, but appears to work fine, but this would not cause this problem. I do get a reasonable testcard on the screen when linking the heater chain to the frame o/p valve. Mark

12th May 2013, 3:29 pm	#15
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: TV22 frame collapse Wiggle the valve in it's socket and watch the screen. Also check the valve base. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

12th May 2013, 5:03 pm	#16
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: TV22 frame collapse All valve bases have been cleaned, as have the valve pins. So waggling the valves makes no difference, this really has got me stumped! Mark

12th May 2013, 6:05 pm	#17
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: TV22 frame collapse I am not surprised you are having trouble getting the frame oscillator working without replacing the old leaky paper caps.

12th May 2013, 6:19 pm	#18
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: TV22 frame collapse If you had read the whole thread, you would have seen that all the caps on the upper deck have been replaced, It is only the receiver deck that has not had the caps replaced, this would not cause the frame collapse fault. Mark

12th May 2013, 7:49 pm	#19
thermionic Heptode Join Date: Apr 2003 Location: Cornwall, UK. Posts: 989	Re: TV22 frame collapse Hi Mark. I would re check your work around the frame stage. As you would have been unable to test your work when re capping due to the blocking TX being OC, then It could be due to something being disturbed here. Please don't take this as a criticism, we've all done it! This could be one of the very few TV22's that provide you with a bit of a challenge! Make the most of it Mark! Good luck. SimonT. __________________ The honesty of imperfection.......... Last edited by thermionic; 12th May 2013 at 8:01 pm. Reason: Tv 22 excitement!

12th May 2013, 8:20 pm	#20
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: TV22 frame collapse Mmm. There are only a few components that can stop the oscillator. A faulty ECL80 valve. [Rare to have the triode section pack up completely] Faulty blocking oscillator transformer but you have checked this. Worth a double check to make sure it has not been taken apart and reversed. Just a hunch. Preset controls that have gone O/C. [Very common as mentioned by Steve] A wiring mistake. [I've done it dozens of times] A blob of solder shorting something out. A broken valve holder connecting socket very close to the valveholder. Way out capacitor value due to possible miss reading. Failing that Mark, haul it up the A24 to my place and we can sort it out together! Regards, John.