ENC: [1000mp] Receiver Attenuator - defective

Wed, 24 Dec 2003 08:04:33 -0200

Hello Mike

Merry xmas ! Thanks for the posting.

The 47ohm resistor, which is put in the RX line by a relay,  I believe is my
1st suspect too. If it is opened, RX is gone when attenuating 6/18 dB.
Is your radio a 1000MP MarkV ? Mine is a Mark V field. I believe they have
similar circuits, but they are different inside.

If yours is a Mark V, what difficulties may I face to access the resistor ??
Another question, is it difficult to get these film resistors ? I was told
they are cheap, but sold by hundreds or thousands !!!

Many thanks Mike

-----Mensagem original-----
De: [email protected] [mailto:[email protected]]
Em nome de Mike Gilmer
Enviada em: ter�a-feira, 23 de dezembro de 2003 23:36
Para: [email protected]
Assunto: [1000mp] Receiver Attenuator - defective

There are two attenuator circuits in the MP - a 6dB and a 12dB (the 18dB
position uses both).

R1039 (47ohm, 1/10 W) on the RF unit (according to my service manual) is the
culprit (it's the series resistor in the 6dB pad switched by RL1003).

Now the fun part: The resistor is on the RF unit, which is located under the
poweramp's heatsink/fan, which in turn is under the top cover.  It's near
relays RL1002 and RL1003 on the underside of the board.

Mine popped last year - better that than the front-end!

Mike N2MG

PY2XB wrote:
> I have the same problem reported in the emails below. Per diagrams
probably
> resistor 1151 (47 ohms) opened. Anyone could give some tips on where these
> resistors are located, what a type of resistors and what to expect when
> replacing them.

> HA1AG wrote:

> > You have blown a few resisitors in your ATT switch. It's quite
troublesome
> > during the contest and they are easy to replace. They act as a sort of
fuse
> > so to say.

> > GW4BLE wrote:
> > >
> > > When switching in the 6dB or 18dB attenuator on my 1000MP
> > > signals disappear
> > > completely,  the 12dB position appears OK.   Same on all bands.
> > > Rest of the receiver runs as-normal.
> > > Any ideas?
> > > Maybe blown something running SO2R in last weekends' CQWW ?

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