Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Tom -
Yeah, that's typical. You're taking the right approach, since a failure
in the Bias supply can take out more than just the finals, even if the
unit is in Standby.
#4. Yes, this is a VERY early AC-3. I don't know how many were made,
but I've only seen a couple in 40 years of using/working on Drake gear.
They work just fine, but your plan is reasonable. Drake dropped the
choke, probably for cost / weight / not needed reasons. The primary
reason for it originally was to improve the regulation of the HV.
73, Garey - K4OAH
Atlanta
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Tom Taylor wrote:
I have a number of Drake A, B, and C twin combos. I decided to upgrade
all the power supplies with AC-4R boards. Since most of the caps are
now 30 to 40 years old, I don't want to risk a bias supply going out
and ruining the finals or some short ruining the transformers. I order
a bunch of blank boards since I already had some of the parts. The
rest of the parts I ordered from DigiKey. I assembled all the boards
at the same time and then started upgrading the AC-4s, one by one.
So far, all of the power supplies are different in one way or another
and all of them have been modified by previous owners. Here are some
examples:
#1) A previous owner replace the mid-voltage supplies' capacitors with
a bundle of three caps mounted to the upper end the supply.
#2) A previous owner replaced the sand resistor below the chassis with
two higher wattage resistors mounted to the upper end of the supply.
#3) A previous owner replaced one of the diodes in the HV supply. The
transformer in this supply has transformer bolts inserted the wrong
direction to mount the AC-4R board. Unfortunately, it's not as simple
as removing the bolts and inserting them in the other direction
because the bolts are just long enough to reach, but not long enough
to add the board spacers.
#4) This is an AC-3, serial #101. I've never seen a Drake power supply
like this. There's a large choke mounted adjacent to the transformer.
All of the other parts, including the capacitors, are radial lead caps
that are packed underneath the very low chassis. Has anyone else seen
an early AC-3 like this? I'm planning to remove the choke and
rebuilding the supply just like all of the others since all of the
circuitry is now on the AC-4R board.
Thanks,
Tom N7TM
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