Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Tom -
OK. Next try V4. It, and V1 are controlled by the AGC #2 and are the
"other side" of the S-Meter bridge.
Your readings on V3 (I'm assuming you're referring to Pin 2, not Pin 3)
reflect a circuit change. There are at least two versions of the 2-C
that I'm familiar with, and the voltage/resistance charts weren't
updated to reflect the later version. Version 2 started at s/n 1000.
Your readings are correct for Version 2 units.
The AF collector voltage seems too low. A leaky Q6 can cause this.
What is the voltage at the top of C48? (The +12V power supply filter cap)
73, Garey - K4OAH
Atlanta
Drake 2-B, 4-B & C-Line Service CDs
<www.k4oah.com>
Tom Taylor wrote:
I tried swapping several 12BA6's (V5) at Garey's suggestion. All
caused me to recalibrate the s-meter zero and I was able to get -13v
at tp-1, but the s-meter is nearly unreponsive. It'll register S4 on
only the very strongest of signals. I replaced the 12BZ6 with a NOS
tube and that had no positive effect on the s-meter either.
I did a voltage and resistance check against the table in the manual
just to see if there was anything way off. Surprisingly, the case of
the output transistor was at 10.3v instead of 12.5v. Perhaps that's
why audio isn't ear blasting. I'll have to investigate further. As far
as the resistance checks, everything was within reason for a 35 year
old (perhaps older) radio, except for the resistances around V3, the
mixer and VFO. Pin 3 is supposed to be 330 ohms and I measure .6 ohms.
Pin 7 is supposed to be 7k and I measure 1m. Should I believe the
chart in the manual? The VFO certainly seems to work fine. With those
measurements so far off, I wouldn't expect the receiver to be so
operational, except for the S-meter.
I guess I'll dive deeper and try and understand why those couple
resistance measurements are so far from what's listed in the chart.
Tom n7tm
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