Paul -
Couple of things. One, be careful using a larger fuse than the 8 Amp
original. That fuse is to protect the wiring harness in case of a
filament short. Melted harness = parts radio. The early units used a
piece of #30 wire instead of a fuse.
There aren't many places in the transmitter where enough current can be
drawn from the +250 bus to heat up R3 in the AC-4 without smoking
something IN the radio itself. I believe I'd start with V7, as a short
here would put R35 across the +250 bus for approximately a 4.5 W load.
Of course a short anywhere along the +150 bus would give a similar
result, but all but the PTO/BAND OSC resistor paths are small, high
value resistors
So... Guessing shorted VR tube, V7 socket wiring shorted, shorted lead
to PTO.
Let us know!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Paul Gerhardt wrote:
OK and thanks to all. I just got back home and am going to try the
T4Xb troubleshooting again this weekend. Will pull the finals and see
if that is what is pulling the 250 B+ down. The R3 was in the AC4
sorry for not noting this before. I looked at the old one and the
schematic and was reading it as 1k but will look again and make sure
it I have the value correct. Auto parts store had some 10amp glass
buss fuses in packs of 5 so I got one for the fil fuse 8A and will at
least replace the #22 wire I put in there before I do any more. The
filaments are lighting ok with the wire in at this point.
73,
Paul
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