See below...
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Steve Wedge wrote:
Yes on the caps - absolutely! That particular chassis can is really easy to
sub modern caps under the chassis because the points they're wired to are
really easy to access.
Now here's a funny thing: on 40, I can peak the plate current with the RF TUNE down below
"1". This one is looking to be one of those rare ones where I will actually
have to measure the slug heights to get to a starting point. Someone must have gone in
sometime in the past trying to peak it.
Sounds like either you have a coil failure or the slugs have been misadjusted. Watch for a broken
slug as well.
| The last trimmer to the back (which I believe peaks the driver) on 80 seems to need more
capacitance, so looks like I'll have to be replacing some fixed caps in there.
Yes, that sounds like perhaps another Dur-Mica failure! :-)
| Still scratching my head over why only 10m gives me a sidetone in either CW
or TUNE.
Probably a switching problem.
| I also hear the faint drone of the sidetone all the time if the gain is advanced - just like in
nearly every T-4X I've ever used (you have to listen for it).
SIDETONE 'backwave' is usually high esr in C132, allowing the tone to couple 'around' the keyswitch,
D8, via the Plate supply for V9a and V9b. D8 itself is also the problem sometimes, usually
indicated by a junction voltage increase (greater than -0.7 VDC) in receive.
Ah, well.
"We do this for fun ..."
There will be more time for this one later... 73, Steve, W1ES/4
-----Original Message-----
From: Garey Barrell<[email protected]>
Sent: Nov 29, 2011 10:10 PM
To: Steve Wedge<[email protected]>
Cc: Drake List<[email protected]>
Subject: Re: [Drakelist] T-4X: put on your thinking caps!
Steve -
Sure sounds like bandswitch. Don't forget to check bandswitch hardware for
wafer alignment, AND
check wafer center holes for oblong and not round holes!!
You DID disconnect the electrolytic caps from the old twist-lok when you tacked
in the tubulars....?
Verify the RF TUNE pointer is aligned properly.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Steve Wedge wrote:
I have not taken out the scope or meter yet. Observations are somewhat random.
My friend Keith's T-4X spent who knows how many years in a New Hampshire
cellar. Keith got it at
a hamfest long ago, from parts unknown. It was obvious to me that it had
belonged to a smoker and
was pretty grungy anyway, so it got the poolside view in my kitchen, followed
by the sauna.
I could "sort of" get output on 20m with it prior to its cleansing. It was
obvious by the fact
that it wouldn't work at all on CW that the can capacitor had dried out. I
replaced both caps
with modern units under the chassis. I had to sub an 80 uF for the 60 that was
there because
that's what I had on hand.
I haven't tried it on all bands yet, but there's some weird stuff going on here:
No output on 40& 15
60W is about all it can muster on 80& 20 despite tweaking the trimmers. The
rear 80m trimmer
needs to go in more but is against its stop
A couple of watts out on 10.
No sidetone - except on 10m. No real output on 10 (it's like 3 W). There's a
somewhat chirpy
sidetone on 10 only.
Neutralization must be way off, as max out on 20 doesn't match the dip.
I'm thinking the switch wafers need some Cramolin applied with a toothpick
(yes, I still have a
bottle of the stuff!).
The good news is that all the low-level stuff seems to be working as far as
frequency control.
All the tubes tested good on a TV-10 D/U except the finals which I can't check
on that tester.
Why would I only get any sort of sidetone on 10m?
Take your time, as I'll be setting this aside so that I can get to the two
R-4B's I have waiting
that I know I can clean, de-mod and align fairly quickly compared to this sad
rig. I was hoping
it was only going to be an alignment and a set of finals away from finishing,
but I'll have to
save this for later.
The R-4B's await - Keith told me no rush Smile emoticon
73,
I do suspect
Steve Wedge, W1ES/4
I swear by my life, and my love of it, that I will never live for the sake of
another man, nor ask
another man to live for mine.
-Ayn Rand.
All my computers have my signature with various pearls of wisdom appended
thereto.
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