|[AMRadio] Any WRL Globe Scout experts out there?|
L at w0vt.us
Thu Jan 4 20:47:32 EST 2018
All I can tell you is I have replaced the pentacoupler with discreet
parts for the same reason as you describe. I used the same values as in
the pentacoupler and had no problem. The resistor is not going to lower
voltage very much as it draws very little current. That would not be
true if the circuit drew a lot of current. The speech amp tubes have
around 55 volts on their plates. Their source voltage started out at
around 500 volts. Just put in the discreet parts and if you are
concerned, check to see if you have around 55 volts on the plates of the
audio pre-amp tubes.
On 1/4/2018 7:23 PM, CL in NC via AMRadio wrote:
> The Globe Scout I am working on has an issue with the PC91 Pentacoupler. The main thing I am wondering is that, internally, the PC91 has a 4.7 meg resistor feeding B+ to the screen of the pentode section of the 6U8A. I do no recall ever seeing a screen resistor that high in any audio amp circuit. In this PC91, that particular resistor is reading 8 Megs, the other two are high in value, but not that high, only about15% off. Are there any mods out there for changing the mic amp circuit in this TX? Does it really need a change or just pull the PC91 out and put the right discrete components in the amp circuit as shown in the schematic of the PC91, and leave that section stock?
> Charlie, W4MEC in NC
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