|[AMRadio] Want Ranger pwr xfmr|
Mike Dorworth, K4XM
k4xm at arczip.com
Fri Nov 25 14:17:55 EST 2005
Hello John. The filament windings should be on the outside and should be
fairly easy to remove and or replace. I have done it many times. You have
nothing to lose. Drive out a coupla laminations and pull the e and i out.
Then peel it like a onion and fix it.Use Scotch plastic tape and put er
together again. It will work as new. 73 Mike k4XM
----- Original Message -----
From: "John Lawson" <jpl15 at panix.com>
To: <johnson at mailman.qth.net>
Cc: <amradio at mailman.qth.net>
Sent: Friday, November 25, 2005 12:36 PM
Subject: [AMRadio] Want Ranger pwr xfmr
> Anyone happen to have a NOS or Good-Used Ranger power transformer for
> sale? I need one - or a Good-Used Ranger - or, a new hobby... ;}
> After several hours on the bench last night - it is apparent why this
> old girl was shelved - it came to me with a 5R4 in the HV socket, but the
> fils didn't light, tho the tube was good. So sure enough - someone had
> tied the 5V fil lines back, and there was a 10-ohm 10W resistor in series
> with the B+ lead.
> I made a plug-in SS rectifier, installed it, switched the rig on - and
> blew both diodes and both line fuses to little bits.
> So I restored the original circuit - there is a definite 'under-load'
> short from the HV rect fils to the HV winding.
> Disconnected all that - the LV side works fine, Osc runs, buffer runs -
> can 'zero-beat' to a receiver, frequency of VFO seems accurate.
> Tansformer voltage and resistance checks are within 10% of spec.
> Put new diodes in put a Variac and ac ammeter in the mains line, turned it
> up slowly - POW. Actually, with the diodes in cicuit, it appears to the
> Variac / AC Ammeter that the power transformer has a dead short. Having
> replaced the filter caps, and checked the plate choke - it ain't them. The
> B+ line resistance is slightly over 20K.
> In this process the power transformer has begun to get slighly warm, so
> I went back to checking the LV side - as I was testing, the transformer
> started to arc internally - and resistance measurements now show the
> fil-to-HV short. So: It's toast.
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