Re: Two Ampliphone HV problem questions

On 02/16/2014 12:21 PM, Andre Huijts wrote:
> I think Mark from Cinelabs once explained why the heater voltage can't be really measured correctly with a DVM but I forgot the reasoning why.

I would think that considering it is 20khz AC for the filament that
meters may have trouble measuring that value - the diodes to rectify the
incoming AC to take the DC voltage may not be fast enough...

Thus one can expect the AC voltages to be difficult to measure with
anything less than a 'scope and a small load on the AC heater line to
stablize it.

If the transformer is putting out correct rectifier DC then the filament
voltage should be fine.

John :-#)#
>
> Verstuurd vanaf mijn iPad
>
>> Op 16 feb. 2014 om 08:12 heeft pj pj <pj1@shaw.ca> het volgende geschreven:
>>
>> The Cinelabs transformer uses the (white) wire wrapped a few times around the ferrite as the winding for the filament voltage.
>>
>> One side goes to the HV board directly, the other via a resistor in series. Start tracing from the socket to back to that winding.
>>
>> The tube if I remember correctly needs 6.3V for the filament, so it sounds like something is running open circuit.
>>
>> Hope this helps.
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