"crawfish" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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The 13DE7 could be a culprit. The TR-4 uses controlled carrier modulation
on AM(50 watts out). You can go to www.amwindow.org and go to Tech area and
click on Mods.Then go to T-4. The text there that the TR-4 uses the same
time of circuitry. The mod will change the modulator from controlled-carrier
to screen. Lower power, but audio will sound better.
Joe W4AAB
----- Original Message -----
From: "Peter Hoon" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, August 08, 2006 1:33 PM
Subject: [drakelist] No TR-4 Am Transmit
>
> "Peter Hoon" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
> ----------------------------------------------------------------------
> Need any and all diagnostic suggestions from list members who are familiar
> with the TR4.
>
> A blind ham, Max N0HU, will be bringing his TR4 with AC4 pwr supply to
our
> QTH repair bench Aug 17th, with a complete set of spare tubes.
>
> Unfortunately, cannot get my hands on a readable schematic or block
diagram
> until Max arrives with his printed manual (and we can enlarge the
pictorials
> on a zerox machine).
>
> Max reports that he gets (what appears to him to be) normal output on SSB,
> good SSB and AM receive, but no AM transmit.
>
> 1) Could it be that he missed the instruction from the manual that says:
> "For AM operation, set function switch to X-AM position, and set sideband
> switch to position X."?
>
> 2) Will test Max's AC4 power supply for ripple, correct bias and HV DC
> under load. Though it seems unlikely, since SSB is working, could his AM
> problem be due to AC4 not holding voltage under load (bad caps)? We have
the
> AC4R recap kit from Mike, ready to install if necessary.
>
> 3) Is another likely culprit a bad screen modulator tube, 13DE7? Other
> possible tube culprits to check?
>
> 4) Could you still get some SSB operation, but no AM, if one or more final
> 6JB6 tubes is bad?
>
> 5) Please send on other immediate (and less immediate) diagnostic hunches
> to check out, so we can hit the ground running, for this lack of AM
transmit
> problem.
>
> We will report progress notes to the list as we work on the TR4 next week.
>
> Ultimately, we hope to do a complete voltage check out and alignment
check,
> re-tube where necessary, since Max will be here for 3 days or so, testing
> the rig, but it would be great if we could quickly solve the AM problem
> straight off, which is our first concern.
>
> (We have a complete bench set up of test equipment: scope,
transconductance
> tube testors, VTM, counters, dummy loads, the alignment cap and resistor
> suggested in the manual, watt meters, etc. All suggestions and ideas
> appreciated.)
>
> 73s, Peter, VE1CHS, Nederland, Colorado
>
>
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