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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 22nd Jul 2018, 6:07 pm   #61
rogerdup
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Default Re: white horizontal lines Firestone tv

Thanks very much David. Should I put the 0.45mf capacitor between the diode cathode and the ground as in the Argus 25 circuit? What kind of diode will be suitable? I have choice among OA80 germanuim type and silicium type 1Nxx.
Sorry you told me already about silicon diode..

Last edited by rogerdup; 22nd Jul 2018 at 6:12 pm.
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Old 22nd Jul 2018, 6:19 pm   #62
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Default Re: white horizontal lines Firestone tv

Hi Roger,
The capacitor will keep the reference voltage stable. I'd choose the 1N4002 type of diode.
The theory of operation is that the diode conducts only on the positive going sync tips. Operates in a similar manner as the grid and cathode the sync separator valve does, except that the sync valve DC reference is the chassis.
DFWB.
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Old 22nd Jul 2018, 6:24 pm   #63
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Default Re: white horizontal lines Firestone tv

Hi David,
That's great ! I will try this tomorrow and see what happen. Thank you very much for your help.
Take care !
Roger
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Old 22nd Jul 2018, 8:40 pm   #64
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Default Re: Firestone 13G3 Television

Hi David. I made the change. The images are quite good (despite they look green because my cam).
Thanks again for the help!

Regards, Roger
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Old 22nd Jul 2018, 11:05 pm   #65
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Default Re: Firestone 13G3 Television

Hi Roger,
has the DC restorer modification solved the flyback lines problem?

DFWB.
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Old 23rd Jul 2018, 6:54 am   #66
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Default Re: Firestone 13G3 Television

Hi David,
I say yes, some very tiny spaced lines appear sometime, but very discreet and depending of the broadcast station. So, I say probem solved. In addition the contrast seems better. I had no 1N4002 diode in stock, but UF4007 in place. They are fast recovery and appear to be good for the application.
I have to check carefully the 12SN7 tubes. Some are capricious, even the new ones I bought!
Roger
I am glad. Steve MC Voy found knobs for my Firestone set.
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Old 23rd Jul 2018, 5:29 pm   #67
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Default Re: Firestone 13G3 Television

Found the solution to put a good vertical linearity for this set. The R96 resistor originaly 27 meg has to be lower to 10meg.
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Old 23rd Jul 2018, 11:37 pm   #68
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Default Re: Firestone 13G3 Television

Quote:
Originally Posted by rogerdup View Post
Hi David,
I say yes, some very tiny spaced lines appear sometime, but very discreet and depending of the broadcast station. So, I say probem solved.
I haven't seen your full schematic, but in my Admiral set with the came CRT and an RF power supply for the EHT, these lines are caused by interference from that supply, even though it is a shielded case. If you take the shield off, they increase by a factor of 10 or 20. I found that I could not eliminate them completely, even with extra power supply decoupling, it is due to EM radiation through or around the shield fittings it seems.
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Old 24th Jul 2018, 6:44 am   #69
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Default Re: Firestone 13G3 Television

That's interesting. I know that static crt's are very sensitive to field radiations, but not imagined that the eht supply could have been in cause because of the shield.
Perhaps an induction in the two wires which give DC power to the 12SN7 oscillator. May be trying a decoupling on these wires after the 150 ohms serie resistors would be useful. I would say 1n to 5n / 630v capacitors to the ground. Could be also an interference coming through the 12SN7 heater?.. I will try that.

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Old 25th Jul 2018, 7:07 am   #70
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Default Re: Firestone 13G3 Television

The Shield is about 98% effective, but not 100%. If you remove the shield, if the interference is coming from the RF power supply, you should see exactly the same type of interference, but greatly increased.
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Old 25th Jul 2018, 9:36 am   #71
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Default Re: Firestone 13G3 Television

I would concur with George, looks like a single line that's out of focus.

Peter
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Old 25th Jul 2018, 7:32 pm   #72
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Default Re: Firestone 13G3 Television

?
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