In article
,
terry wrote:

Thanks Bruce for your reply.
Not absolutely su
We connected an oscilloscope to TP5 hoping to see white noise which we
could then adjust to 2 volts p-p. We understand TP5 is after the 60
meg IF strip but before the signal goes into the demod. cct. Not
seeing anything but low level (20 millivolts) general noise did not
adjust anything.
Connecting and disconnecting oscillator/mixer front end of the
receiver (which converts the 9.445 gig echos to approx 60 megahetz),
made no difference. Also trying to feed in a 60 meg signal from a sig.
gen. to the front end of the IF (where that front end of the receiver
plugs in) even at a relatively high level, we get nothing at either
TP5 or the so called video output lead that conveys the IF/Demod
output to the display unit. This with the receiver front end plugged
in and not plugged in.
BTW we don't have any other DC voltage info. on that PCB to check. But
something 'seems' dead in the IF strip??? Or the front end of the
receiver?
Any suggestions most welcome.
Terry and Alfred

What does your Scope see at the IF output from the Receiver Frontend?
You really don't need to unplug the Magnetron, as your Xband Power
Density at the Antenna Face is not significant, and adding the Inverse
Square Law Distance reduction in Power Density, you will get more
radiation from a the 100 Watt light bulb, over the table.

Well it sounds like you have blown the IF Strip, alright. It should
have about 60 db Gain, and be a Logarithmic Amp. These are fairly
straight forward Wide Bandwidth Amplifiers. Usually they have two or
three stages of gain, done in individual Amplifier Chips. YOu could
get the chip Idents, and lookup the pinouts, and check for Vdc Power
to the individual Gain Stages.

Check with the local Raytheon Marine Dealer in your area. They may
still have the Books on your unit, and maybe they will give you a copy
of the IF Strip subsection.

--
Bruce in alaska
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