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R2400 RF Attn Damaged

This forum exists for the purposes for discussing service monitors (This includes but is not limited to Motorola, HP, Aeroflex, GD, etc). Additional topics allowed include test procedures, interpretation of test results, where to find information about specific tests, antenna VSWR, return loss testing, duplexer and filter alignment, etc.

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KRT-Hobby
New User
Posts: 3
Joined: Thu Nov 19, 2015 4:38 am
What radios do you own?: Motos,1959-2000

R2400 RF Attn Damaged

Postby KRT-Hobby » Thu Nov 19, 2015 5:15 am

I made that very wrong mistake of replacing the Antenna jack BNC fuse with a piece of wire . I was tuning up a 100 watt lowband radio into the antenna port,"by accident" and smoked the rf attenuator. The generate feature has me at the 40db area to get .3 microvolt test point. Can the attenuator be repaired.Is there a source for resistor values.I want to revive my 2400.

DJP126
Posts: 865
Joined: Wed Jun 18, 2003 6:41 am
What radios do you own?: What's a radio?

Re: R2400 RF Attn Damaged

Postby DJP126 » Sat Nov 21, 2015 10:56 am

Are the attenuators repairable? Yes they are. We used to repair (internally owned) monitor attenuators all the time but you needed other bad attenuators to canaballize the parts from. Your best bet is to try to find a new attenuator. IIRC the attenuators came from a company called RLC but I have no idea if they still exist or where they are.
Dave

jry
Posts: 371
Joined: Fri Feb 06, 2004 3:14 pm

Re: R2400 RF Attn Damaged

Postby jry » Sat Nov 21, 2015 6:13 pm

I have repaired the mechanical attenuators on the 20XXD series but have never had the need on the 2200 series.

IIRC the 2200 /2400 series was a bit more challenging to get to the attenuator due to the compact design.

You would have to look at the service manual but usually the attenuator is a combination of fixed pads of 10,20,30 and 2 40db ( this is for the 2001D the 2200 may be different but should be the same idea )

You probably blew the 10db pad which is normally the first in line. They are easily tested with just an ohmmter. Look up the PAD calculator to get the correct values.

Be careful if you disassemble since there is a bunch of small springs and little plastic actuators. You can replace the defective pad(s) with the correct value of SMT resistors or order a small attenuator from one of the online RF parts vendors. Once replaced you can do the initial tests with and ohmmeter but really should be tested with a sig gen and SA.

Of course the easy answer is to
1.buy another working unit
2.buy a parts unit and swap the attenuator and hope that one isn't blown as well.

Good luck

KRT-Hobby
New User
Posts: 3
Joined: Thu Nov 19, 2015 4:38 am
What radios do you own?: Motos,1959-2000

Re: R2400 RF Attn Damaged

Postby KRT-Hobby » Mon Dec 07, 2015 9:42 am

DJP126 wrote:Are the attenuators repairable? Yes they are. We used to repair (internally owned) monitor attenuators all the time but you needed other bad attenuators to canaballize the parts from. Your best bet is to try to find a new attenuator. IIRC the attenuators came from a company called RLC but I have no idea if they still exist or where they are.

"THANKS"

KRT-Hobby
New User
Posts: 3
Joined: Thu Nov 19, 2015 4:38 am
What radios do you own?: Motos,1959-2000

Re: R2400 RF Attn Damaged

Postby KRT-Hobby » Mon Dec 07, 2015 9:46 am

Awesome advice. I am using it in its crippled condition by knowing where a good radio stands on the RF dial but I'd rather fix it right so I can use the full range of the attenuator. Thank you.


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