[time-nuts] TRAK Model 8900-1 GPS Disciplined Freq Std

Greg Burnett gbusg at comcast.net
Thu Dec 16 06:08:12 UTC 2010


I bought the TRAK 8900-1 on eBay five years ago.  Because the 8901-1 GPS 
synchronizer module wouldn't lock, the seller sent me a replacement 8901-1, 
but I was unable to get it to lock either. My system didn't come with an 
antenna. One issue was that the system supplied 12VDC (instead of the more 
common 5VDC) to the active antenna. TRAK wanted a "fortune" for their 
replacement antenna, so that option was out. I finally figured out that, 
apparently, the 8901-1 had a current sensing circuit in its power supply for 
external antenna. The circuit was apparently configured to disable lock 
unless the antenna dc power supply current was within a specified "window". 
My substitute antenna apparently didn't draw enough DC current to make the 
circuit happy. So I ended-up soldering a 1k ohm resistor, on the board, in 
parallel with the antenna connector, in order to "trick" the sensing circuit 
into its "good" window.  That made it work, and it locked just fine. (Note: 
I no longer have the 8900-1, so I'm going by memory regarding the 1k ohm 
value.)

I might still have the defective, 2nd 8901-1 GPS synchronizer around here 
some place. But I just looked, and tentatively don't see it anywhere. I've 
moved twice since I bought the TRAK, so it might be misplaced or hidden in 
some box somewhere?

Best,
Greg


----- Original Message ----- 
From: "Alex Imas" <imasalex at gmail.com>
To: <time-nuts at febo.com>
Sent: Tuesday, December 14, 2010 3:07 PM
Subject: [time-nuts] TRAK Model 8900-1 GPS Disciplined Freq Std


Hello

I found Greg Burnett page with question about TRAK model and I have a
question, too.
Maybe you can help, where did you buy this unit cause I'm looking for GPS
synchronizer Model 8901-1 , for our  Trak Modular Frequency/Time System
Model 8900-50 and TRAK stopped produce it


Best regards
Alex
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