14db attenuator pad for R2001D RF module

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cahighwayman22
Posts: 193
Joined: Sun Jul 20, 2008 11:43 am

14db attenuator pad for R2001D RF module

Post by cahighwayman22 »

Hello

I have an R2001D that has a bad 14DB attenuator in the RF module. The service manual has no part number, the component itself has "ACR 1032" then "CR1113."

These part numbers don't turn up anything on google. Anyone know if there is a replacement part available?

-Trevor KI6KGN
cahighwayman22
Posts: 193
Joined: Sun Jul 20, 2008 11:43 am

Re: 14db attenuator pad for R2001D RF module

Post by cahighwayman22 »

Part number btw is 17-80377A95

Obviously it's NLA on the Motorola website.

-Trevor
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: 14db attenuator pad for R2001D RF module

Post by jry »

The best approach may to replace the input attenuator pair with a more standard value.

If you look at the manual you have a high power 14db followed by a lower power 16db with the connection in between used for the high power detector / wattemeter.

The combination is 30db so replacing with a 10db /20db and adjusting the wattmeter may be the easiest approach. So a 100W 10db followed by a 15W 20db should be easier to find at one of the RF component sellers.
cahighwayman22
Posts: 193
Joined: Sun Jul 20, 2008 11:43 am

Re: 14db attenuator pad for R2001D RF module

Post by cahighwayman22 »

Just noticed too that the attenuator part is soldered, or welded to a metal block with the over temp sensor.

Probably gonna have to cut it off if I can't find an exact replacement.
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: 14db attenuator pad for R2001D RF module

Post by jry »

it's soldered.

I have used plumbing tools ..flux, silver solder and propane torch to CAREFULLY remove and replace the primary attenuator. Apply heat to the back of the mounting bracket only and protect the attenuator connections with another piece of metal to shield them. Only takes a very brief amount of time to un-solder ....20-30 secs IIRC.

The secondary input attenuator is just normal mounting HW and thermal paste.
cahighwayman22
Posts: 193
Joined: Sun Jul 20, 2008 11:43 am

Re: 14db attenuator pad for R2001D RF module

Post by cahighwayman22 »

So just to confirm, both attenuators have to be replaced for proper operation?
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: 14db attenuator pad for R2001D RF module

Post by jry »

In order to get the correct total attenuation of 30db yes. use a 10db high power and a 20 db lower power ...wattmeter will need to be adjusted to compensate since the tap is now 4db higher.
Two adjustments on the RF I/O board to re-align the wattmeter so not that challenging.

Unless you can find a high power 14db one ...which does't seem to be readily available.

You can try and contact the usual suppliers of RF components but they typically only stock the standard values.

Motorola hasn't had this in stock forever and the D series is really obsolete so even the third parties are very limited on the repairs given the current commercial value of that monitor.

You could contact the old motorola test equipment repair facility ( still in business to support the GD stuff ) in IL but their minimum was $500 for a more current R2600 without parts.

Other choice is to find a junked out D series and hope the attenuator isn't blown as well.
cahighwayman22
Posts: 193
Joined: Sun Jul 20, 2008 11:43 am

Re: 14db attenuator pad for R2001D RF module

Post by cahighwayman22 »

Ok got it.

I tried using the 10db pad with leaving the 16 db one in place, the wattmeter adjustment doesn't do much.
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: 14db attenuator pad for R2001D RF module

Post by jry »

Did you follow the calibration process for the wattmeter in the manual ?

You may have to increase the value of R3 if you cannot get the wattmeter to calibrate. Normally a 56 ohm resistor but factory selected depending on the diode in the detector.

You may just want to use a 200 ohm multi turn variable and adjust for the to get the calibration correct .

Normally the wattmeter gain and offset adjustments interact so you usually have to go back and forth a bit between a 1W and a 50W and adjust. You may need to adjust the value of R3 to minimize the interaction. Once you get the correct adjustment you can replace with a fixed resistor and do a final adjust.

Once you get that correct you could just add a 4DB T pad using SMT resistors on the output of the 16 db attenuator. This will get the gen and receive levels correct.
cahighwayman22
Posts: 193
Joined: Sun Jul 20, 2008 11:43 am

Re: 14db attenuator pad for R2001D RF module

Post by cahighwayman22 »

Ahh, it makes sense now! Okay, i'll give that a try.

Thank you so much for your help. I have always had a heart for the R2000 series service monitors. My dad use to fix them when I was a kid, and thats what sparked my interest in Radio.

-Trevor
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