A Variac would be a big help here.
Then place a 100W bulb across the secondary with an AC ampmeter.
Also use a meter in a 240V leg.
Then crank up the voltage until the bulb has about normal brilliance.
Record meter readings, do the math to calculate efficiency.
If youre close to a transformer company have them reassemble if they
concur its an assembly issue.
Carl
KM1H
----- Original Message -----
From: "David Craig" <davidhcraig@verizon.net>
To: "Jim W7RY" <w7ry@arrl.net>; <amps@contesting.com>
Sent: Thursday, February 12, 2009 12:47 AM
Subject: Re: [Amps] Transformer heating (problem?)
> 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
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>>
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>
>
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