Hi Jim,
Purchased it from WA1JOF about 2 years ago when I started this project-
I can't recall if he ever used it, though I doubt it given the severe
current loop problem it had when I powered it up the first time.
Is a "Heritage", marked 240V on the primary & "common", "2800", "2875",
"2925" & "3000" on the secondaries. I have not checked primary current draw
on it, but with some work placing a meter between the transformer primary &
the relay/filament/etc I could do so. Guess that is the logical next step,
though it obviously is drawing more than the few mils from the equalizers &
the dropping R given the heat. It does this every time I power it up, or at
least I presume so given that I have only had it online for a couple weeks
and isn't on much given that 6m isn't exactly open regularly this time of
yr.
73 Dave
----- Original Message -----
From: "Jim W7RY" <w7ry@arrl.net>
To: "David Craig" <davidhcraig@verizon.net>; <amps@contesting.com>
Sent: Thursday, February 12, 2009 12:18 AM
Subject: Re: [Amps] Transformer heating (problem?)
> What is this transformer's history? Where did it come from? What was it
> used for? Some sort of intermittent duty type of device like an industrial
> welder or similar? Is it really 240 volt primary? How much current is it
> drawing on the primary when it does this?
>
>
>
> 73
> Jim W7RY
>
>
>
>
> ----- Original Message -----
> From: "David Craig" <davidhcraig@verizon.net>
> To: <amps@contesting.com>
> Sent: Wednesday, February 11, 2009 8:37 PM
> Subject: [Amps] Transformer heating (problem?)
>
>
>> Corollary to a previous issue with a B+ transformer I passed thru the
>> group a while back, which before I repaired it had a current loop due to
>> bad/no insulation on the core bolts. Transformer has a 240V primary,
>> 2800-3000V secondary rated at 2 amp CCS. Is installed & in use on a HB
>> GS35b 6m amp. When "module" testing the amp the transformer taps met
>> specs, measured with a Simpson 260. Calculations based on measurements
>> then indicated a 12.5 to 1 ratio.
>> Fast-forward to completed amp...After some occassional use (~30
>> minutes of total operating time) am having the following "issues." The
>> 3000VAC secondary tap is now only putting out 2700VAC with line voltage
>> measured at 243VAC (240V mains line is 10 guage wire, a 10 ft run from
>> the breaker box & then 6 feet of 12 guage line to the amp... original
>> measurement taken with same lines). The even more disconcerting problem
>> is that after a couple hours of sitting at "idle" (amp on, power to B+
>> but no RF) the transformer iron is getting hot- enough that you wouldn't
>> want to keep your hand on it for long, and particularly so near the left
>> & right sides of the core. (Yes, I checked the plate meter & no current
>> thru tube, bias relay fine).
>> Lamination bolts remain cold so no more current loop around the
>> mounting brackets.... I am baffled as to why this thing is getting hot
>> just idling. There is no "bleeder" per se on the PS, just 6 x 220k ohm
>> Rs across each of twelve 450V caps in series. The only other constant
>> current draw is a 5 MEG dropping R to the B+ meter. I am baffled as to
>> why the transformer laminations would get hot with almost no current
>> draw, and am concerned that once I really work this thing out during a
>> contest or Es opening the heat is going to short the secondaries.
>> Any ideas as to what could be going on? Is this normal, or as I am
>> beginning to think, an 86 lb misdesigned piece of junk??? Any input
>> appreciated.
>>
>> 73 Dave N3DB
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>>
>
>
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