[Clegg] Shooting troubles in the Clegg 22'er (long)

[milcom@softhome.net]

Thanks to Greg and Paul for their responses...
Had been to 6mt.com before and d/l'd the file,
but after several tries with corrupted ZIPs I'd
moved it to the back burner...

Here lays the pic of the problem.

http://www.hfradio.org/kb6lwn/ResHunt1t.jpg

  (schematic: hfradio.org/kb6lwn/Sch02.gif)
                         hfradio.org/kb6lwn/Sch01.gif

Arrow in jpeg points to the BBQ'd resistor.
Left end of resistor is lifted (for measurement) from
it's home on the ground lug visible just above the
resistor that is at the 9:30 position.
Right axial lead connects to lug #4 (L-to-R) on
the terminal strip above the component, where
there is also a Wht/Blue wire attached that goes
to pin-3 of the keying relay.  (a pinout of this rly
would have been helpful)-:

Problem: Subject resistor overheats and leaks smoke
whenever power is applied and energized by PwrSW.
Resistor is too charred to read bands, measures out to
240 Ohms, with the 'ground end' of the component lifted.

W.W. resistor (Ward Leonard, value rubbed off) that sits
to the right also warms up (too much in my opinion), but
may be conduction from failed resistor.

I've looked at the data from the 6mt' site and from what I
could read (of the sch and the pl), I don't see anything in
either place that designates a ~240 ohm/5w carbon comp
connected to the relay.  Perhaps I'm just not looking in
the right place :)

Searching out all sections of the relay (4PDT), the only
resistor I see that it MIGHT be is R67, if THAT'S it - then
it's only reading 240 ohms because it's BBQ'd...  And it's
definately NOT a 2w component in there, might that be
one of the things that was done to this to unit in order to
drive the 6146B final ?  (have replaced w/proper tube).

Does that sound right to the experienced among us ?

If it IS R67, then that means it's shunting 300+ volts to
ground, and I can see why it's getting hot at a value of
only 240 Ohms.  <sly grin>  Can you say 450+ Watts ???

Measurements: with the resistor lifted and voltage measured
with R67 not included, the potential to ground should be
about the same as it is on the other side of T4 primary,
right ?  ~330 V DC ?  (haven't measured that, yet...)

According to P=E2/R, the dissapation is ~1.945 watts,
so one would thnk that more than doubling this to 5w
should handle the load.  Or should a 7 or 10w be used ?

I'm presuming that the purpose of this switched load is to
enable the dual use (R/T) of the 6AQ5 audio stage pair ?!
(Rec Audio Out -and- Transmit Modulator)

See ???  This is why I was looking for a former Clegg-Tech :)
Sure is nice having those still around for the Swans ;)
                  (next project after this and the 66'er...)

Btw, one 6AQ5 (V10/V11) tests out OK on my B&K 606,at
80 quality, no shorts, no leakage...  The other has a quality
of 75, no grid leak, but a short on 2 and 11.  I presume one of
these is the plate and hence what overloaded the resistor...
Unknown which position the failed tube was was in :(

Or was it the other way-around, when the reisitor failed
it took the tube out ?!

Hmmmmmmmmmmmmm.......

73 4 now,
          Bruce - KB6LWN/RCC
                           Lake County CA [CM88]
                                      AMI-1302, SC-1520, SAM 058
-- 

-=- What is RCC ?  Find out at: www.arrl.org/awards
                    You DO! 'chew, Don't you ???