KB0NLY wrote:
>I'm using GM3SEK's Triode Board for my 6m amp project using the GI-7B,
>i ran into a problem today with the power supply. According to his
>manual, i sent him an email as well waiting for a reply, for 2500v i
>should use 10 1M Ohm resistors in series from the B+ line, on the end
>of that string of resistors there is also two 100k 1W resistors to
>chassis ground. My supply is 2400V, measured with a HV meter i get 2380V.
>
>The problem is the output of that divider is supposed to be 12v or
>less.
>I put the positive of my meter on the end of the chain of resistors and
>i put the negative to chassis, 0V, nothing nada.
So you have a voltage divider with 10M in the top leg and two 100k
resistors in parallel (for safety) at the bottom. So the no-load voltage
at the divider tap has got to be 2380V x 50k / (10M + 50k) = 11.84V.
IF all the resistors are of the correct values, and are also wired
correctly, and you do have 2380V connected to the top end, then there
WILL be 11.84V at the tap, plus or minus a few percent.
That would be exactly as designed, to provide a "HV OK" signal to the
Triode Board.
We're also presuming that the B-minus rail is closely tied to chassis...
yes?
>I put the positive of my meter on the end of the chain of resistors and
>i put the negative to chassis, 0V, nothing nada.
Obviously there is something *totally* wrong here. A value of zero isn't
just "slightly wrong", as in "not quite the value I expected" - 0V
indicates a major fault, either in the construction of the voltage
divider or in the measurement
What kind of voltmeter is it? Have you checked each of the two leads
using the ohm-meter function?
When everything has been switched off and safely discharged, you can
also check the individual divider resistors with an ohmmeter.
>Then i put the negative to the 0V lug on the secondary of the
>transformer and i get 113V.
>
Sorry, I don't quite understand this part. Does the transformer have a
center-tapped secondary, meaning that the 0V lug should be connected to
the B-minus rail? If so, then 113V is another totally incorrect value.
Please be VERY careful with this power supply and voltage divider...
something is very wrong with either the wiring, the measurement or both.
Trust nothing in this power supply until you have verified it's safe.
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek/boards
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