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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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5th Jan 2003, 9:13 pm | #1 |
Heptode
Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
Posts: 693
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Bush VHF62 FM alignment
Having recently re-aligned the FM i.f. strip of this radio, I thought some readers might be interested in what appears to be an error in Trader sheet 1301.
It seems that L21 and and L22 have been interchanged - either on the sheet or by the manufacturer. These comprise the final FM i.f.t. primary and secondary and, as can be imagined, this led to considerable head scratching before the penny finally dropped! See below for details: http://tibblestone.users.btopenworld.com/Bush_VHF62.htm
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Keith Yates - G3XGW VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm |
5th Jan 2003, 9:29 pm | #2 |
Retired Dormant Member
Join Date: Jan 2003
Location: Redcar, Cleveland, UK.
Posts: 54
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Re: Bush VHF62 FM alignment
it just goes to show even the people who write the trader sheets can get it wrong.
moral of this story trustno1 |
7th Jan 2003, 11:57 pm | #3 |
Guest
Posts: n/a
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Re: Bush VHF62 FM alignment
Keith, Well spotted! I have just aligned one of these sets and didn't notice - perhaps I operate in automatic these days. The Bush service sheet is correct, however.
These sets do line up beautifully - almost perfect tracking if you do a few iterations. The solvent for the white paint used by Bush is acetone (nail varnish remover). Apply a couple of drops to a dust core, leave to soften for a few seconds, then gently screw the core inwards. The ratio detector balance is sensitive to diode matching in the EABC80, so align with the valve you intend to use, and replace the stabilising electrolytic before you start. Apart from tracking (the other sort) between the switch contacts, these sets are almost viceless - clean the contacts with switch cleaner and a cut down toothbrush to remove the dirt. The FM sensitivity is splendid for a valve set (the EM81 needs a 4:1 attenuator in the FM feed to make it useful on strong signals), but the AM performance is only average; my set almost overloads on strong signals despite a thorough overhaul and removal of those dreadful Hunts capacitors. Has anyone any bright ideas for restoring the knobs, which tend to deform? Last edited by Paul Stenning; 27th Dec 2004 at 1:19 pm. Reason: Fix link or code for vBulletin |