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Pilot TV-37 comments...
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During the restoration of a Pilot TV-37 for a friend, he asked about the idea of
adding a filament transformer for the CRT to protect it from inrush current via the series heater string. In asking around about this idea, various bits of information surfaced: The heater strings of some sets are wired differently [to address the inrush problem?]; In some sets to which a transformer has been added, the CRT still appears to light brightly momentarily then settle down to a 'normal' level. In the set I've been working on the heater wiring matches the SAMS schematic. With the mod described below, the heater now seems to light normally without an initial surge. It consists of a small 6.3 V@0.6 A transformer mounted on the rear of the HV enclosure with some power resistors wired to replace the 10.5 ohm CRT heater in the string and another in series with the transformer and the CRT heater. In place of the CRT heater, I wired a 10 ohm in series with a 1 ohm, both 10 watt resistors, and in series with the CRT heater a 1 ohm 10 watt resistor. The line voltage here at home [and where my friend lives] is high, in the range of 123 volts. Now, across the CRT heater, I measure 6.32 volts and across the 11 ohm combination, 6.94 volts. The 11 ohm combination is dissapating slightly less than 4.4 watts and does run warm. Pic of transformer, etc. attached... |
First let me apologise for posting this in the Color forum. Too much egg nog, I guess.
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I haven't turned on my TV-37 for quite some time. It bothers me greatly to see the filament of the CRT to light up as bright as a light bulb. (that's never good) I recall that some years ago an article was written on this very subject about adding a filament transformer and was highly successful. I forgot what value(s) of resistor(s) to add in place of the CRT filament.
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