[Collins] KWM-2

[Mac McCullough]

check and make sure the index pin for the power cord is still in place and 
the right place ... this is what happens a lot when some dufus plugs emm 
together wrong ...

mac/mc  w5mc

Located 46 miles due North of the Alamo, and 121 miles due South of the 
Western White House.   see my website at  www.collinsandharrisradios.com
----- Original Message ----- 
From: "Gerald" <geraldj at ispwest.com>
To: <collins at mailman.qth.net>
Sent: Wednesday, August 03, 2005 8:17 PM
Subject: Re: [Collins] KWM-2


> On Wed, 2005-08-03 at 21:20 -0400, W4BYG wrote:
>> I have obtained a very clean KWM-2 which was not working, but very much
>> worth the effort to repair.  I've never had one before, so I'm just
>> learning about it.
>>
>> I first found bad tubes as follows, 3 - 6U8s, 3 - 6AZ8s and 2 -
>> 6BN8s. Several had open filaments, one was shorted.  I've never seen a
>> radio with this many bad tubes, so I suspect a previous owner did
>> something wrong in powering it.
>
> Shorts aren't so likely to come from heater circuit abuse, though
> running a heater way up in temperature from over voltage could break
> down heater cathode insulation to show up as short in testing. The
> standard Collins Power supplies do the proper interconnection of the
> four 6.3 volt heater circuits in the radio to run them from 6, 12, or 24
> volts. However applying 12 volts (like from a Heathkit power supply)
> with the tubes wired for 6 would be hard on heaters.
>
> That is not to say that heaters going open can't happen, its not all
> that rare, though normally multiple tubes should have wildly different
> failure times.
>
> Tubes overheated can have lost a lot of cathode material and so not work
> very well either.
>>
>> After applying a siggen, I now have a very weak signal going thru it,
>> but the sensitivity is way down.
>>
>> I have a manual for it.  The schematic seems to indicate several jumpers
>> should be in place when operating without any accessories and yet the
>> hookup diagrams and installation instructions show or say nothing, about
>> any jumpers.  It does not have a NB.  The 100kHz calibrator also does
>> not work.
>
> Unless the options of noise blanker, 62S1, or switched receiver muting
> (as if used with a separate receiver or transmitter) are used normally
> those jacks are jumped together with a piece of wire inside the chassis.
> Sometimes I've seen it as a piece of solid bare wire. Instruction with
> the optional accessories tell to cut that wire between the jacks.
>>
>> When bench testing the rig with only the 516 AC power supply only, are
>> any jumpers necessary to make it functional?
>>
>> Anyone else ever experienced a similar multi-tube failure in a KWM-2 or
>> have any helpful suggestions?
>>
>> You attention is appreciated.
>> Ray, W4BYG
>> Naples, FL
>
> Another scenario is that the last owner had multiple radios and picked
> the working tubes from this one filling the holes with tubes from other
> radios. Or assorted tubes from a flea market, low priced and untested.
>
> -- 
> 73, Jerry, K0CQ, Technical Advisor to the CRA
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>
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