[time-nuts] 3325A attenuators

Normand Martel martelno at yahoo.com
Tue Feb 20 23:06:20 EST 2007

Do you hear the relays working when you change the
signal level?

If yes, and that's probably the case, i definitely
suspect burned-out attenuator resistors/modules
(HIGHLY probably due to excessive reverse power
(Signal generator directly plugged to a transceiver
which has been accidently keyed)).

If your attenuators use resistors, you may try to
substitute nearest 1% precision resistors.

Theorical values for a 50 ohm system:

10dB attenuator:
Pi attenuator:   Series resistor: 71.151246 ohm
              Parallel resistors: 96.247531 ohm

 T attenuator: Parallel resistor: 35.136419 ohm
                Series resistors: 25.974692 ohm

20dB attenuator:
Pi attenuator:   Series resistor: 247.5 ohm
              Parallel resistors: 61.111111 ohm

 T attenuator: Parallel resistor: 10.10101 ohm
                Series resistors: 40.909091 ohm

40dB attenuator:
Pi attenuator:   Series resistor: 2499.75 ohm
              Parallel resistors: 51.010101 ohm

 T attenuator: Parallel resistor: 1.001 ohm
                Series resistors: 49.0099 ohm

For 40dB, i suggest to use two cascaded 20dB units
instead of a single 40dB unit (values much closer to
50 ohms for the single resistor)

73 de Normand VE2UM
Montreal, Qc. Canada

--- "Paul S. Linsay" <linsay at comcast.net> wrote:
> Hi,
> I have a 3325A and the amplitude attenuators are not
> working.  I  
> opened it up and it has sealed black relays, not the
> unsealed ones  
> mentioned in the maintenance manual.  When I run the
> front panel self- 
> test everything passes.  Any suggestions on what to
> do next?
> Thanks for your help,
> Paul--
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com

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