Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Tom -
I don't think so. I'm one of the worst for keeping things "original",
but I don't think these units are THAT rare. I guess you could keep the
removed choke and try to avoid extra holes, but in all honesty I don't
think it's worth losing any sleep over. I guess you could stick it on
"E*ay" and see if someone like Sindre wants to "preserve" it.
The TR-3 was introduced in early 1963, probably at Dayton in April. By
October, it looks like they were up to about 3000 units, most of which
were probably sold with an AC-3. By September they were up to 2500
AC-3s, and that MAY be when they dropped the choke. By June 1964 they
had built 10,000 TR-3s and were still using the "chokeless" AC-3 power
supply.
The AC-4 came out in 1965, about the same time as the T-4X. My VERY
early T-4X was shipped with an AC-3 in September 1965.
73, Garey - K4OAH
Atlanta
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Tom Taylor wrote:
Would I be destroying something of historical worth by converting that
early, and perhaps rare AC-3, to a modern supply? That would mean
removing the choke and essentially all the parts underneath the
chassis? The AC-4R (as I'm sure you're aware) replaces everything but
the transformer, the cables, the connectors, and the bias pot.
On 12/11/06, *Garey Barrell* <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
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 <http://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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