Well gang the T4XC is starting to sing nicely. A few
little things still to sort out but good for 100+ watts on all bands except 20.
Looks like somebody replaced the meter shunt resistor R59. The value fitted is
3.9 but the schematic I have looks like 3.3 but not clear, can anyone
confirm?
The 20m crystal really does seem to be dead. I have
tried it in two R4C's and a simple transistor oscillator breadboard circuit but
nothing seems to work. It doesn't rattle but just does not want to
oscillate.
I have three other questions at the
moment.
On power up the T/R relay seems to pull in within a few
seconds. This causes idle current to flow. After about a minute the relay drops
out and normal service is resumed, a soft tube?
Maybe related to this. After keying, PTT, Tune, or
spot, when returning to receive position the relay seems to takea good
half second or more to drop out. VOX is off. Is this connected with the question
above or something else?
As an example on 15m with the Tx in Tune, gain at 50%
gives 110 watts out, about the maximum. Switching to CW with no key inserted the
power drops to almost zero at the same setting of the gain control but can be
increased to about 125 watts at 75%V setting of the gain control. Is this
normal?
73 es thanks for all
the help so far.
Martin
HS0ZED
p.s. Eric, I can come to NC pretty much anytime. Just
send me the tickets, return from Bangkok for me and the xyl, hi
hi.
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Eric
WebnerSent: 07 September 2005 08:44To: Martin
SoleCc: DrakelistSubject: RE: [drakelist] T-4XC permanent
current problem
Hi Martin,
Glad you are making progress. When you are done, please come to North
Carolina and finish my C-line for me HI.
I learned a while ago that you may be able to get the crystal oscillator
going again by simply replacing the oscillator transistor. This is certainly a
lot less expensive than replacing the crystals.
Give it a try, and let us know how it works.
73,
Eric KA8FAN
Martin Sole [EMAIL PROTECTED] wrote:
"Martin
Sole" <[EMAIL PROTECTED]>made an utterance to the drakelist
gang--Found
it.A short inside the meter. I never did like the way those meter
studs werenot fixed like others. Obviously in dismantling everything and
re-assemblingthe lug on the inside got rotated and was touching the inside
of the metercase.Note to self: Don't unscrew the meter nuts to
remove next time, unsolder thewires.All is good now but looks like
the 20m and maybe the 80m crystals are dead.They will not oscillate in the
transmitter nor in the receiver. Any crystalsfrom a dead radio out
there?73Martin HS0ZED-Original
Message-From:
[EMAIL PROTECTED][mailto:[EMAIL PROTECTED]
On Behalf Of Garey BarrellSent: 07 September 2005 04:13To: Martin
SoleCc: 'drakelist'Subject: Re: [drakelist] T-4XC permanent current
problemGarey Barrell <[EMAIL PROTECTED]>made an utterance to
the drakelist
gang--Martin
-Something is shorting the final cathodes to ground, "South" of the
metershunt, R59.There are a limited number of paths that can get
the cathodes to ground,especially when that path has to handle the idle
current you are seeing inthe "key-up" condition.Heater-cathode
short in V7, (6AU6 AM Mod tube). ?I've never measured the key-up Final
cathode voltage, but I think it couldrise as high as the screen voltage if
the cathodes are "open" to ground?73, Garey -
K4OAHAtlantaDrake C-Line Service ManualMartin Sole wrote:"Martin Sole"
<[EMAIL PROTECTED]>made an u! tterance to the drakelist
gang--I
checked the bias voltage at the tube bases. The AC4 pot varies it
between about -44 volts and -85 volts. If I key the radio in SSB (No
Mic gain) and advance the bias pot until the meter shows 0.1A, bias
voltage measures about-55 volts,then release the PTT the
current increases to approximately0.12A.Same problem with
different PA tubes that were known good last time they were tried in
another radio.Looking at the cathode line it seems this is
taken to ground by a contact onK1 but when unkeyed should rise
up to cut off the tubes. How many volts should be on the cathode line
in the unkeyed state? On this radio the point at L5 sits around 0.38
volts in the unkeyed state and drops to 0.34 volts in the keyed state.
Voltages are the same with K1 removed.Ideas
appreciated.73Martin
HS0ZED-Original Message-From: Gary
Poland [mailto:[EMAIL PROTECTED]Sent: 06 September 2005
10:22To: Martin SoleSubject: Re: [drakelist] T-4XC permanent
current problemMartin, Sounds like you have lost a
capacitor in the AC-4 bias supply. The voltage is too positive causing
constant plate current.73,
