Hi John:
The U4226B chip operates at very high impedance levels in order to minimize battery drain in its main application,
battery powered clocks.
So some sort of buffer is needed on all the output pins.
The 333 model, with the analog meter, was made for the folks working for WWVB as a way for them to know the transmitter
was on the air.
http://www.prc68.com/I/timefreq.shtml#WWVBrcvr
http://www.prc68.com/I/Loop.shtml (WWVB)
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
-------- Original Message --------
On 03/30/2018 03:39 AM, Hal Murray wrote:
[email protected] said:
I updated http://leapsecond.com/museum/ulio/ with more manuals, and many
exterior / interior photos of the 301 module.
Thanks. My 301 says it is a 30TH Rev-A - mostly through hole parts. Same
layout.
Mine is the same. Circuit is very simple. The 20 pin IC is the U4226B receiver chip and it has two external 60 kHz
filter resonators. The 8 pin DIP is a TLV2770C op amp which seems to be a buffer to drive the S meter from the very
high impedance AGC test point on the receiver chip. And I am guessing that the 2N3904 transistor is a buffer for the
time code output.
The modular cable connecting the receiver to the decoder is wired straight through, not reversed as most telephone
cables are. My fear is that someone (like me) might at one point have used a reverse cable and thus put reverse
polarity on the board; I don't see any reverse power protection.
Later today I'll tap into the four conductors on the cable and see what signals I see on them, and also look for signs
of life on the receiver chip.
BTW -- Donald Resor pointed me to UTSource which shows several Chinese vendors as having them in stock. I get nervous
about whether they are the real thing or not, but will probably order a couple just in case. The chip is a 20 pin
TSSOP package, which isn't too hard to rework but before putting hot air on the receiver board there are one or two
surrounding parts one would want to remove to avoid collateral damage.
John
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