[Boatanchors] Nasty Collins Problem

[Al Parker]

Hi Wilson,
	If that's a 70E series, it's like what's used in the 75A/51J rcvrs, 
plus other stuff, I expect.  It's not a horrible job to get into them 
and refurb them.  There are 2 bypass caps & one feedback cap that can be 
problems ad should be replaced whenever you're into one.
	Take a look at <http://www.boatanchors.org/75A2.htm> for work I did in 
a 75A2, there's a section with pix & dexcription inside the PTO.  I've 
done many of them similarly.  Span is the usual problem that gets one to 
go into them, but those caps get replaced no matter what.  You can back 
up to my home page & find more Collins stuff & PTO work in them.
	I don't know what I'll get going for CX, hope to cu then.
73,
Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 1/28/2011 12:20 AM, Wilson Lamb wrote:
> I got out my trusty Collins 310-B to get ready for CX this weekend. I
> knew it had had soft keying for a while and I was able to fix that
> quickly, although it's not clear just what was happening. The time
> constant in the grid block circuit was wrong, even though the components
> seemed OK. I can wait to get to the bottom of that.
>
> BUT, I've also had low drive to the 2E26 on 80M, but fair drive on 40.
> Historically, these have been high, with drive to spare. The manual is
> fine for alignment instructions and there's a good schematic, but no
> typical supply or signal voltages. After much adjusting and hand
> wringing, I convinced myself that the PTO was not putting out the
> requisite drive to the first 6AG7. While contemplating the tedious task
> of pulling the PTO and opening, it dawned on me that I had a similar PTO
> I'd been carrying around for the last 40 years or so. The PTO is
> connected to the circuit with a four pin plug, so I tried the old one.
> WOW, ten or fifteen times the output voltage and plenty of drive to the
> buffer string!!
>
> So now the nasty part. Pulling the pto is not easy, but not hard, just
> tedious. And when I get it out it will have to be opened. Maybe I can
> put the other one in. It looks to be the same mechanically, but I'd
> really like to fix the original. Has anyone still alive had one of these
> open and does anyone know likely failure points? It's been sealed up
> since 1947, when my dad's radio club bought the 310-B, so who knows what
> I'll find in there. And yes, both tubes are fine!
>
> Lastly; it won't help with this CX, but does anyone have a 70E-8 lying
> around for possible sale?
>
> I may have to drive my 1930s amp with an Icom 730, which won't get me
> many points.
>
> Thanks for any info you can provide,
> Wilson
> W4BOH
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