Paul -
Ripple on Calibrator signal probably power supply ripple, D6, C190, C192.
S-Meter drift is gassy tube (grid emission) probably V4 or V5, possibly V1.
Phones jack 'used' to be on the front panel, but interfered with the
controls on either side. Note small circle where phones jack USED to
be. The hole IS in the subchassis as well, so if you want it there,
yours won't be the first to have it!
AGC SLOW cap is C109.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Paul Christensen wrote:
Now that my Drake 1A restoration is complete, it's off to the races
with a recently-acquired R-4B. BTW, Hartzell re-painted the 1A
cabinet and it looks great. Also, Tom at HayseedHamfest.com provided
me with an exact replacement multi-section PS cap for the 1A, although
it's not listed on his website. Ready for this? The can is made from
copper and looks great against the copper chassis. Perfect retrofit
without any hassles.
My first R-4B operating impressions below. Keep in mind this unit
requires some TLC.
- Plenty of sensitivity on all bands. Easily peaks noise with no
antenna connected;
- High IMD on audio. Listening to the Xtal calibrator, I hear IMD
that sounds like perhaps either 60 Hz or 120 Hz is mixing somewhere.
It may also be the result of B-H distortion from the output
transformer into high quality headphones with a 40-ohm load Z. In any
event, I need to investigate further. Overall audio passband response
is mediocre. I was expecting a wider audio passband. At this early
stage of ownership, the audio is nowhere near the quality of my 1A nor
R-4C with Sherwood AF mods;
- Audio output tube way too microphonic. I do not sense this much
mechanical sensitivity with the 1A receiver and the output stages are
similar;
- The S-Meter starts at S8 then drifts to down to S0 after about five
minutes warm up. Is this behavior normal for the R-4B? Either a weak
tube in the AGC loop, leaky cap, or out-of-tolerance resistor changing
value with heat may be the root cause. More investigating needed...;
- Why the headphone jack on the side and not on the front panel? A
target point is marked on the panel for a 1/4-inch jack and the
chassis easily supports it. Very strange;
- AGC *way* too fast on both settings. Just my opinion, but AGC Slow
is more like where I would want the Fast setting. AGC Slow needs R/C
help to get its recovery slower. Easy enough to fix;
- Nice VFO feel, even better than early R-4Cs, and equal in tuning
feel to late R-4Cs with metal/Nylon gears. Excellent PTO stability.
I would appreciate any comments on the recovered audio and S meter
abnormalities before digging in. Many Tnx to everyone on this list!
Paul, W9AC
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