Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Ron / Jason -
The resistor is 5 ohms @ 2W, so should read 0.5 VDC for the recommended
0.1A idle current. The plate meter "should" also read 0.1A.
Actually, I'm not really sure why they bothered to short out the
resistor. It's actually in the negative lead of the HV supply, and even
at full plate current there is less than 2 V drop across the resistor.
Not that big a difference in the 650 VDC supply voltage, considering the
supply drops about 50 V from no load to full load.
73, Garey - K4OAH
Atlanta
Drake C-Line Service Manual
<http://www.k4oah.com>
Ron Wagner wrote:
Ron Wagner <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Jason,
I am not sure what you mean about measuring below the chassis.
- I couldn't make heads or tails of the TP-1 reading with the jumper
screw
removed.
You need to measure the *voltage* from TP1 to ground (TP1 ungrounded
of course). There is actually a voltage drop over a resistor below
the chassis. That voltage is directly related to the current flowing
through the resistor. I don't have the TR3 manual handy, so I can
not tell you exactly what voltage ratio would be. But the voltage has
a direct relation to the plate meter reading.
Ohms law says current is equal to voltage divided by resistance. And
what ever the values give, that is the current. Idle is all that
should be measured this way as leaving it ungrounded will create
distortion as the bias voltage will change as the voice peaks draw
more/less current.
As for being inside the MS4, well I had to remove the AC3 to change
bias any way. And you did this how often? :-) How lazy are we? :-)
See the two pictures at this link: http://www.dma.org/~wagner/ac3.htm
The TP1 is to the right and a bit up from the bias pot, between filter
caps. It used a screw from the filter cap to ground the TP. Second
pic is side view.
Hope this makes everything "as clear as mud" :-)
73,
Ron
----------------------------------------------------------------------
Submissions: drakelist@www.zerobeat.net
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net
----------------------------------------------------------------------
