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Old 18th May 2017, 2:46 pm   #42
dtvmcdonald
Pentode
 
Join Date: Mar 2016
Location: Champaign, Illinois, USA.
Posts: 227
Default Re: Marconi 702 advice

A test of the MHD4 on a different tester shows an intermittent heater cathode short.
I thus need a new one. However, if vertical and not bumped it is OK, so that's
not the cause of the problem. That's why the first tester didn't find it.

In any case a grounded cathode would
increase gain, not ruin it. Putting 4 volts AC on the cathode
would result in an enormous hum and might blow the cathode electrolytic
bypass.

I suppose I could temproraily bodge in a 4AV6 which would be the "usual suspect"
American electrical equivalent and would work perfectly. Luckily these are cheap
as water because nobody used them.

Last edited by dtvmcdonald; 18th May 2017 at 2:52 pm.
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