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G6DTW > QUAD 15.08.14 01:00l 40 Lines 2160 Bytes #999 (0) @ GBR
BID : 7168_GB7CIP
Read: GUEST
Subj: ''complete '' quad mono valve system
Path: IW8PGT<CX2SA<VK2DOT<VK4TUB<NA7KR<GB7JED<GB7CIP
Sent: 140808/0251Z @:GB7CIP.#32.GBR.EURO #:7168 [Caterham Surrey GBR] $:7168_GB
From: G6DTW@GB7CIP.#32.GBR.EURO
To : QUAD@GBR
for less than 100 pounds i have sucessfully re-built, from non-workers a quad
qc2 controller/ an fm 1 mono valve tuner/ and a lw..mw..sw receiver but instead
of using a quad monoblock power amplifier i am using one channel of a
hybrid(i/c/ transistor/ valve ) fatman amplifier
i have covered the faults on the fm and am tuners before but basically leaky 8
uf 350v cap on ht but with the qc 2 controller which has the renowned varislope
bass / treble hf rolloff .... ideal for mf to cut the 9 khz whistle... the
fault was no more than poor contact on 6.3 v indicator lamp and o/c heaters on
ef 86 valve
that done the thing was to rewire as jumpers the 6 pole paignton plug ... all 6
pins parrallel... often wrongly named a jones plug which is similar but much
larger or a plessey which is newer and finer.
i wired to a 350v 300mA supply i had made when i was age 12 !!!!
however on testing all 3 units together there was smoke ! from the psu.
ht fuse in neg leg.
this really got me thinking.
it was obviously an ht short.. but where?
i had previously run a thin black wire from chassis of am tuner to ht neg as
there was no path
the ht neg is grounded via the phono output bplug normally.
well of course ! with the qc 2 unit (preamp/ controller )this wire was
superflouous so i remooved it and voila ! all works ok
from the 6 pole plug is an adaptor with 4 wires and output sctreened co ax to
phono plug . this is utmost bimportance if not using a quad monobloc power amp.
it comprises ht+/ ht -/ 6v ac heaters .
yes its more than 50 years old but hey its still very hi fi for mw/lw/sw then
fm vhf band 2 .
ntracking of front end and oscillator was av major job on the fm 1 tuner.. but
going back to basics the images were soon remooved and 88-108 achieved.
after correctly lining up the 10.7if with wideband 1khz sig from racal sig gen.
also discriminator tweaks to avoid distortion / max output
thats it .. a very rewarding session of multiple repairs .
total time was , wuith 2x fm 1 tuners and vone fm 1 stereo tuner has been over
40 hours but well worth the effort.
alvin
g6dtw@gb7cip.#32.gbr.eu
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