IFR2975 Generator/Power Term investigation

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IFR2975 Generator/Power Term investigation

Post by VE2VXT »

Hello every IFR guru's,

I have on my bench an IFR2975 and I'm suspecting a trouble in Gen and Mon mode.

The generator output is bad and the Monitoring is bad too, when I look input levels on Spectrum mode their is a lot of attenuation.

In between the Power Term and Generator, their is a 110dB variable attenuator, this guy is 100% ok.
It is made with 6 Teledyne relay attenuators (20dB+20dB+20dB+20dB+10dB+20dB) for a total of 110dB.

Now, I do not know if the Power Term module work like it suppose to be.
I'm wondering if their a simple way to test this module, I do not know where to start and what kind of levels I'm supposed to get assuming I inject a signal like -20dBm?

Whats kind of RF connectors are on the back of the Power Term Module? they looks to me as SMB.
I would like to have 2 pigtails for troubleshoot, one for Antenna side and the other for for Generator.

On the Generator module, what is the range level in dB at the output, at the SMA connector?

Is their any service manual, including schematic and parts list somewhere or if it's punch secret?

So, as you can see I have some work in front of me and any help will be really appreciated.

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Joined: Fri Feb 06, 2004 3:14 pm

Re: IFR2975 Generator/Power Term investigation

Post by jry »

there are multiple items that often fail on the 2975 at the same time especially around the GEN and Receive.

I very rarely get a 2975 through calibration that does not have issues ...like 60 -70% have one or more items need repair. This is often the case with service monitors that are complex devices and multiple functions.

Normally you should be able to see -20dbm out max at the T/R port ...if not the GEN board is bad.
The GEN port should be able to hit +10dbm ...if not the PTA is bad on that port.
The ANTENNA port should be able to hit ~ -80-85 dbm for 10 db SINAD using the 3Khz Deviation and narrow IF with the audio filters enabled. There should be a SHIPCHECK setup to verify this but you need a working RF generator , jumper installed and GEN enabled to get it to pass .
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