"Byron Tatum" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Thank You Garey for the excellent help and service!
----- Original Message -----
From: "Garey Barrell" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, April 29, 2008 3:19 PM
Subject: Re: [drakelist] TR-4 TX Hang-Up
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist
gang
----------------------------------------------------------------------
Byron -
OK. Relays take more coil current to "pull in" than they do to "hold in".
It takes a certain amount of current through the coil (pull) to drag the
armature from it's non-energized position to the energized position. It
takes much less current to (hold) it once there, so slight leakage might
NOT be sufficient to pull, but more than enough to hold.
I don't know of any good way to touch up the panels. The original "paint"
is so thin, (I actually think it is more a dye (anodize?) than paint, but
don't know for sure,) and as a result any sort of paint ends up looking
worse than the mark! For a small mark or two, it might be possible to
just "fill" the mark to the level of the panel, but a string of numbers
would be a real challenge. Never could understand people that do that
sort of thing, especially on the front panel!!
I just saw your order. There are scans of both the 34-NB and the 34-PNB
manuals, with quite a bit of information, plus I have added a photograph
of the board itself with active components and alignment info annotated.
There is also a Voltage table for the NB, which has not been previously
published. It's really a straightforward design, and most units in the
field benefit from an alignment.
A lot of the components are common between the TR-3 and TR-4, but every
once in a while they threw in a curve like that cap to keep us off
balance! :-)
Your CDs will go out tomorrow. Thank you!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Byron Tatum wrote:
"Byron Tatum" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Hey Garey-
Thank you for the comments and help. I start nights at work and will
have several to complete, then I will get back into the TR-4. I will
measure voltage as you suggest, looking for a slight voltage drop. Then I
will check out relay itself.
I am beginning to think that it is the magnetizing of pole piece and
relay wear that is the problem. If it was a leakage to ground on the 6EV7
pin #1 lead you might think the set would go into TX on its own (relay
energize) every now and then, of which I have never saw it do.
One other thing- I bought a nice TR-4 from a fellow, based on several
pictures, but the photo angles, due to glare, covered up (of all things)
a ham's DL # engraved on the front panel in tiny lettering , immediately
to the right of "TR-4" on front panel. Do you know of a touch up paint
that matches the darker grey of that front panel area?
I got the set for a decent price, it was nice and had the built in NB,
but had a problem (as advertised). I found T-9 to be burned out in center
area of coil form. I had a spare T-9 from a parts unit TR-3. Thank
goodness I opened up the TR-3 T-9 transformer before I installed it -- it
had a 56 pF cap in it that was not in the TR-4 T-9. Otherwise the coils
looked the same. Anyway, I clipped out the capacitor and all went OK
after the repair. That is not a fun repair for sure!!
CUL, Byron.
----- Original Message ----- From: "Garey Barrell" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, April 29, 2008 1:46 PM
Subject: Re: [drakelist] TR-4 TX Hang-Up
Byron -
Well things were going well until you pulled the tube out of the socket!
:-)
There are a limited number of possibilities in that case. The relay
coil leads go through the feedthrough bypass caps _under_ the power
connector. Of course the relay lead to the 6EV7 is the one UNDER the
Jones connector, the last one in the "arc" of feedthroughs there.
(C92) There are no more components between this feedthrough and the
6EV7 tube socket. The other relay coil lead goes directly the +250V bus
via the next feedthrough cap along the arc, (C91). So the voltage
measured at the tube socket pin with the tube out should be exactly the
same as the +250V bus. Any drop would indicate leakage. See attached
photo from my CD (at reduced resolution).
So..... Leaky C92, leaky tube socket, pinched wire. One possibility I
have seen a few times is the "down" stop on the relay gets hammered down
over the years, allowing the armature to actually touch the pole piece
of the coil. The pole piece is slightly magnetized, and if the armature
physically is in contact with it, it will "stick". An easy check is to
slip a piece of paper in to prevent metal to metal contact between the
two. The "down" stop can be bent back up to prevent this contact.
Let us know what you find!!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Byron Tatum wrote:
Hello-
I have an unusual problem perhaps someone could shed some light on:
I have a TR-4 in 29K serial range that functions normally
except it will not go back into receive, until after approx 30 second
delay, after the mic button is released or the function switch turned
back to "SSB". This condition worsens (longer delay) the more you
frequently you transmit. The sidetone disappears but T-R relay will
not release.
I have tried different known-good 6EV7 tubes, have replaced a lot
of the coupling / bypass caps in T-R circuits, did resistance /
voltage checks, adjusted the VOX / VOX delay controls, tried other
tubes in T-R circuit, etc. to no avail.
What is real curious about this is that while waiting for it to go
back into receive and T-R relay is engaged, IF YOU PULL THE 6EV7 FROM
ITS SOCKET THE T-R RELAY STILL DOES NOT RELEASE. I suspect the issue
is with the lead that goes from T-R relay coil to pin #1 on 6EV7
(somehow allowing enough leakage to ground?) or could it be the T-R
relay coil itself?? I made sure socket / pins and all are clean on
6EV7.
Any help appreciated, thanks.
Perplexed,
Byron WA5THJ.
----------------------------------------------------------------------
Submissions: [EMAIL PROTECTED]
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in
body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net
----------------------------------------------------------------------
----------------------------------------------------------------------
Submissions: [EMAIL PROTECTED]
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net
----------------------------------------------------------------------
----------------------------------------------------------------------
Submissions: [EMAIL PROTECTED]
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net
----------------------------------------------------------------------
