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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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14th Apr 2022, 3:13 pm | #121 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: Another TV22
Thanks John, I'll make up one using 2x 0.33 and 1x 0.1 and see if it cures the problem. Previous TV22s I've restored have been fine without it but as always its possible one will be upset
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14th Apr 2022, 4:45 pm | #122 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
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Re: Another TV22
They are mostly snipped but it does remove the last traces of ripple on the HT line. To be honest 99% of owners would never have noticed its loss. I think Bush used its addition with a slightly different value on models up to but not including the TV105 series. See how you go. John.
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14th Apr 2022, 7:50 pm | #123 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
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Re: Another TV22
Hi.
Check for leakages in the tagboard and valve bases. Remember the TV22 was manufactured during the time the transmitter was locked to the mains and of course standards converters are not and neither are broadcasts, DVD's etc. This means any hum getting into timebases etc will modulate the frame or line. It can be a hard one to fix and can often be resolved by what's in the photos Good luck
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Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member |
14th Apr 2022, 10:27 pm | #124 |
Hexode
Join Date: Dec 2006
Location: Bromley, Kent, UK.
Posts: 332
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Re: Another TV22
STOP,,,, STOP,,,,, STOP you have muddled them up , Its a TV22 you are meant to be smashing up , not a TV 12 !
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15th Apr 2022, 9:12 am | #125 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
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Re: Another TV22
I wondered where my TV22s had hidden David but then I remembered we dealt with them some years back when you visited me. The fire brigade were very understanding.
David you need something bigger than a toffee hammer. We have here the next generation to light the stove next autumn. John. |
15th Apr 2022, 6:33 pm | #126 |
Octode
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
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Re: Another TV22
Trevor, luckily for this set it will just miss the lump hammer! Although the amount of work it's needed it would have been easier I've followed John's advice and replaced the 0.75uF capacitor. This has made an improvement, the problem is still there but it has cured the most of it and you need a sharp eye to spot it now. I have found that the supply for the Aurora is indeed a switch mode type so I will swap this for one of the more traditional transformer types and hopefully cure the fault once and for all. I presume this is probably the source of the issue and as my other working set is a late 50s GEC I can imagine it has much better smoothing and filtering that a humble old TV22 so the problem may not be noticed on that one.
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15th Apr 2022, 6:48 pm | #127 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,987
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Re: Another TV22
The PSU needs to be a regulated type, not just transformer with rectifier and capacitor on the output.
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Stephen _________"It`s only an old telly" ___ |
16th Apr 2022, 12:00 pm | #128 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
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Re: Another TV22
Indeed any Aurora or Hedghog needs a regulated supply.
Another way of reducing hum is with an RF transformer from the Aurora etc to the aerial socket.
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Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member |
16th Apr 2022, 1:58 pm | #129 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 4,985
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Re: Another TV22
The Aurora shouldn't need a regulated supply as it already has a regulator built in, hence it can run from anywhere between 7 to 14 volts, although a solid 14 volts would make the series regulator device within the unit work rather hard (and make it rather warm probably), so best to keep the supply voltage somewhere in the middle.
I run mine from a gash wall wart with no regulation, rated at 9 volts @ 0.3 amps and it runs cool as a cucumber and never had any hum bars or hum lines or anything else similar. What I would say about using one of these rather crude, but transformer type, unregulated wall wart supplies, is that off load it puts out around 15 volts, so it's important to always have it already connected to the Aurora BEFORE actually plugging it in to the mains so that it's already loaded down by the device and at the stated 250 mA current drawn by the Aurora, rather than the total 9 volt rated load at 300 mA of the supply, I'd guess that the stated 9 volts will probably be more like 10 - 11 volts (although I've not cut into the wire or opened it up to take an actual measurement, or applied a dummy load to actually measure the voltage), but the inbuilt regulator in the Aurora seems to be quite happy running on this supply. It could be argued that a proper stabilised and regulated supply should be used. However, I don't agree - how often have we known a series regulator to suddenly go down and give full DC line voltage of probably 30 odd volts straight to the connected device...that can't really happen with a basic non-regulated transformer wall wart supply, so much safer in my opinion. Finally, I would agree that it's probably a good idea to avoid most of the switch mode type wall wart devices available to minimise the problems the OP is having at the moment - it'll be interesting to see if this turns out to be the final answer to the hum line. Last edited by Techman; 16th Apr 2022 at 2:11 pm. Reason: Missing words etc. |
16th Apr 2022, 11:34 pm | #130 |
Tetrode
Join Date: Sep 2019
Location: Aalborg, Denmark
Posts: 97
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Re: Another TV22
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