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Old 12th Mar 2008, 9:35 pm   #14
Mullard
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Join Date: Jul 2007
Location: Clophill, Bedfordshire, UK.
Posts: 127
Default Re: Vidor CN426 HENLEY

The heaters in the Henley are series connected for both mains and battery operation. Any open circuit heater will therefore stop all heaters working. With no heaters there is no anode current and with no anode current the HT voltage could easily rise to 115 volts. The easiest way to check the valve heaters is with an ohmeter (Digital or analogue). If all are OK then then clean the valve heater pins. If this does not solve the problem look at the valve bases (check for heater continuity on the valve base. Check the heater supply from the mains transformer and check the 2 parts of the metal rectifier (ohmeter should read high one way and low with the connections reversed). The other thing to check is the switch. From the rectifier there are two resistors in series (1.4K and 700, check for open circuit) and these then connect to the DL94 heater via the rotary switch (battery, off, mains). Check for switch closure (ohmeter) or temporarily short out the switch. Trader sheet 1155 has all the info you will need (on CD 1).
Hope this is useful.

John
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