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Old 22nd Aug 2011, 12:05 pm   #1
FERNSEH
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Default Bush TV12 restoration.

Let's see if I can get this set working before the weekend.
The results so far are a narrow thin horizontal line and an indicated 4KV EHT.

DFWB.
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Old 22nd Aug 2011, 12:08 pm   #2
Andy Doz
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Default Re: Bush TV12 restoration.

I'll race you .. I've got a TV22 just arrived. Not powered it up yet , but I'm hoping the LOPTx is OK, so the line whistle will drive away the woodworm in the side panels
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Old 22nd Aug 2011, 12:52 pm   #3
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Default Re: Bush TV12 restoration.

Quote:
Originally Posted by Andy Doz View Post
I'll race you ......
OK the challenge is on.

David.
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Old 22nd Aug 2011, 3:49 pm   #4
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Default Re: Bush TV12 restoration.

I would turn the brightness down on that!

Peter
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Old 22nd Aug 2011, 3:58 pm   #5
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Default Re: Bush TV12 restoration.

Following my policy of Glasnost (openess) I can report that the line timebase has packed in.

DFWB.
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Old 22nd Aug 2011, 4:27 pm   #6
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Default Re: Bush TV12 restoration.

No excuses allowed! As soon a a challenge rears it's head you creep back into the workshop! I'm backing you David. Don't allow the TV22 brigade to intimidate you. .
The EHT on a TV12 is rarely above 4.9kv unless it is fitted with the later line output transformer. It still gives a good picture even with this very low EHT potential. Boost cap and coupling caps come to mind. It was a good first light. Pity the bulb in the lighthouse popped just before you crashed into the rocks.
Even with that minimum display it shows a good CRT and LOPT, the rest is easy. Regards, John.
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Old 22nd Aug 2011, 4:44 pm   #7
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Default Re: Bush TV12 restoration.

Has war broken out in the vintage community?
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Old 22nd Aug 2011, 4:58 pm   #8
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Default Re: Bush TV12 restoration.

Hi Trevor,
Not exactly war, let's say a difference of opinion. Eine Meinungsverschiedenheit

TV12 versas TV22, no competition. Everyone knows which is the better set.

DFWB.
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Old 23rd Aug 2011, 8:04 am   #9
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Default Re: Bush TV12 restoration.

... it's just I happened to have a TV22 to do at the same time ...

I can confirm my line stage doesn't work either, the top cap's fallen off my line bottle..
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Old 23rd Aug 2011, 8:16 pm   #10
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Default Re: Bush TV12 restoration.

A few caps. Repair the top cap on the line output valve ... and up with the volts!!

... there's all to play for.
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Old 23rd Aug 2011, 9:45 pm   #11
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Default Re: Bush TV12 restoration.

Nice to see the tube 'smiling'!

You know you're well on your way at that stage!

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Old 23rd Aug 2011, 10:34 pm   #12
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Default Re: Bush TV12 restoration.

I've been working on the TV12 today. The line oscillator failure turned out be be a broken tag on the EF50 valveholder. An easy fix. So it's back to the original line TB fault, lack of width. The 'scope shows that the sawtooth drive is correct: 30volts @ 100microseconds. Note the "sit up" on the flyback part of the waveform. The frame timbase needs some attention.
That's the next stage of the restoration.

DFWB
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Old 23rd Aug 2011, 10:37 pm   #13
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Default Re: Bush TV12 restoration.

Some pictures. The broken valveholder tag can been seen.

DFWB.
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Old 23rd Aug 2011, 10:52 pm   #14
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Default Re: Bush TV12 restoration.

The frame timebase turned out to be the same valveholder problem. Two broken tags. The FTB now works in a fashion but the hold control has a dead spot at one end. It's a 2.2Megohms lin pot.
The frame timebase employs a Miller Transitron circuit. The line time oscillator is a more conventional blocking transformer circuit.

Plenty height now but just look at the width.

DFWB.
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Old 24th Aug 2011, 8:17 am   #15
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Default Re: Bush TV12 restoration.

I think you're inchining into the lead now ....

Does someone have a TV22MKI schematic or trader sheet I can borrow?
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Old 24th Aug 2011, 8:25 am   #16
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Default Re: Bush TV12 restoration.

Try Dukes page here
Enjoy
Mike T
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Old 24th Aug 2011, 8:35 am   #17
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Default Re: Bush TV12 restoration.

Quote:
Originally Posted by Cobaltblue View Post
Try Dukes page here
Enjoy
Mike T
Unfortunately that's for a TV22A ..
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Old 24th Aug 2011, 10:16 am   #18
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Default Re: Bush TV12 restoration.

Think your Frame Osc Tx could be o/c Andy.

David
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Old 24th Aug 2011, 10:17 am   #19
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Default Re: Bush TV12 restoration.

Think i have MK1 sheet can scan and send.
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Old 24th Aug 2011, 10:24 am   #20
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Default Re: Bush TV12 restoration.

Just send me a PM with email address and its sat here on my desktop ready to go!
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