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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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22nd Apr 2014, 11:18 pm | #1 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Marconi VT161: local distant control repair.
The local distant control in my Marconi VT161 has fallen to pieces. There's is no chance of course of finding an exact replacement so a conventional 2Meg pot will have to be used instead. This will involve using my favourite device, the adaptor plate.
The local distant control sets the delay voltage to the AGC supplied to the RF amplifier. When receiving very weak signals it is desirable to remove or delay the AGC voltage supplied to the PCC84 RF amplifier. Doing this can improve the signal to noise ratio. On strong signals no AGC delay is required and the full AGC voltage is fed to the RF valve. There are few other jobs to do the set before the chassis is installed into the cabinet. DFWB. |
23rd Apr 2014, 8:36 am | #2 |
Nonode
Join Date: May 2006
Location: St Albans, Herts, UK.
Posts: 2,193
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Re: Marconi VT161: local distant control repair.
Nice job (as always). It looks like it was there from new.
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All the very best, Tas |
23rd Apr 2014, 11:36 am | #3 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
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Re: Marconi VT161: local distant control repair.
A very nice tidy job.
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Simon BVWS member |
23rd Apr 2014, 12:09 pm | #4 |
Dekatron
Join Date: Jul 2008
Location: Charmouth, Dorset, UK.
Posts: 3,601
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Re: Marconi VT161: local distant control repair.
Yep very neat, looks like an RS pot.
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23rd Apr 2014, 12:42 pm | #5 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: Marconi VT161: local distant control repair.
The original component was a Morganite make and the replacement is a Welwyn. It does have a RS look about.
I've turned my attention to the sound. The original PCL82 was low emission and has been replaced. Also the 0.01mfd Hunts coupling capacitor to the grid of the triode section needed replacement. Much more sound now. The Marconi VT161 has direct line sync. This set is always prone to slightly ragged verticals, something I must look into to later. TV sets with blocking oscillators do seem less prone to ragged verticals than those with multivibrator line oscillators. Focus Diode (Brian) called around today and he noticed another adaptor plate, this one was fitted by the manufacturer. The metalwork allows the fitment of an octal line output valve, say a PL36, and as this set uses the PL81 which has the smaller B9A base an adaptor plate is called for. DFWB. Last edited by FERNSEH; 23rd Apr 2014 at 12:57 pm. |
23rd Apr 2014, 2:10 pm | #6 |
Octode
Join Date: Jan 2006
Location: Borough of Gateshead, UK.
Posts: 1,420
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Re: Marconi VT161: local distant control repair.
Lovely set and a great performer. David's done a great adaptor for the dropper too as can be seen in the photo below, a brilliant piece of work the manufacturer would've been proud of.
Cheers, Brian |