On Mon, 19 Oct 1998 17:25:58 -0700 "Jim Heath" <jimheath@foothill.net>
writes:
>
>Hello,
>
>I purchased for not much money, a Henry 2k that was probably made
>about
>1964. It still has 3B28 rectifiers and 3-400z's. I spent a day
>cleaning
>the RF deck which was more than dirty.
>
>One of the primary fuses was blown when I picked it up. After
>cleaning and
>looking it over, I applied HV with no big problem. The rectifiers
>glowed as
>I remembered from years gone by.
>
>On removing it from standby, the tubes idled within specs. The
>problem
>occurred with drive. After about 400ma (just a guess) the first time,
>the
>fuses popped. They blew big time (glass cracked). As the glitch
>occurred,
>I could hear the transformer rumbled from the demand for a lot of
>current.
>As a test, I replaced the tubes and ran into the same problem. This
>time
>putting it into the transmit mode with no drive, I could hear the
>transformer rumble again intermittently. Driving it with 10 watts,
>the
>fuses blew.
>
>It appears to me that the plate transformer had been replaced. I was
>told
>when I bought it that it was a Dahl transformer. Any ideas are
>welcome.
Is there any flash inside the rectifiers? If not they are likely OK. I
would next look to a partially shorted filter cap or something else in
the PS food chain.
Remove the 3-400's and do a DC current check, you will have to break into
the circuit to do this...use a HV rated meter such as a Simpson 260 with
a 5KV scale and plenty of caution.
You can calculate the expected PS current from the bleeder resistor
value, the filter cap should add a miniscule amount.
Next step would to put a resistor across the HV to ground...some value
that would limit the current to what you would get from the finals or a
bit more.....an underated resistor can be used if you have a small fan
available. Do a sniff and ear test...listen for funny noises.
If all OK then restore to original and test with one tube at a time at
reduced drive. From your brief description of the xfmr grunt AND the fact
it was replaced I suspect a PS problem...I'm correct once in awhile!
73 Carl KM1H
>
>73, Jim KB6SX
>
>
>
>
>--
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>
>
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