"Mariusz Art. VE3PND" <[EMAIL PROTECTED]> made an utterance to the drakelist
gang
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Peter;
The negative potential is not sufficient to cut off the V10B on CW.
With the power off, the resistance to ground will consist of R69, R68,
R74 when measured with (-) at the grid. The R107 has a value of 6.8M so
it has a smaller effect. When tested with (+) at the grid the
resistance will be higher depending mainly on position of the pot R73.
To make the analysis little easier you may want to open the R71, CR16
and C99. I assume you've checked the pot R73 and it is OK... .
73 Art VE3PND
VE3AX wrote:
"VE3AX" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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HI all;
Been a while since I needed the technical services of this group but
after an evening of searching I am still buffaloed.
I have a late serial T4XC that goes into transmit mode c/w sidetone as
soon as the mode switch is placed in the CW position. AM & SSB
positions are fine but on CW the rig keys up with or without a key in
the key jack. There is no CW output until you close the key contacts.
Tube substitution of V-10 and the VOX preamp tube do not help.
All 5 diodes on the CW line and VOX circuit were replaced with new
ones. (I know, I know, this is not "troubleshooting" - I had a box of
1N4148's!)
This is a 6FQ7 Vox tube version. All voltages are within spec on the
tube pins and all resistances are on spec for this version (per Garey
Barrell's VERY useful C-Line Technical CD) with the single exception
of pin 7, the grid of V-10B. I am getting 1 megohm instead of 2
megohms. Guess more checking of resistor values in that area is
required.
Anyone else solve a similar experience and can shorten my bench time?
Thanks in advance!
Peter
VE3AX
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