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ZS2ABF > MODS 04.07.10 19:47l 60 Lines 2707 Bytes #999 (0) @ WW
BID : 450617ZS2ABF
Read: GUEST
Subj: KENWOOD COMMON FAULT ?
Path: IZ3LSV<IK2XDE<DB0RES<DK0WUE<7M3TJZ<ZL2BAU<VE2PKT<F1BBI<CX2SA<ZS0MEE<
ZS0ELD
Sent: 100623/0853Z @:ZS0ELD.ELD.ZAF.AF #:1985 [1986] FBB7.01.35 alpha
From: ZS2ABF@ZS0ELD.ELD.ZAF.AF
To : MODS@WW
Hi ALL,
I have a Kenwood TS450S. Its about 16 Years old now and recently the set got
quieter and quieter. It was just as if the RF knob had been turned down,so
cutting down the signals or as if the audio amp was not giving out audio. It
seemed to come right after 5 minutes, and then it took 10 minutes and so on.
Eventually it did not come right at all and was just dead, and the S meter
gave a full Yellow/Red LED indication just as it does when you turn down the
RF knob to Zero position.
At this stage I decided to have a look see inside and fix the fault. I found
the fault and repaired the rig, which is working like new again.
I am writting this packet as I think this is a fault that several other hams
may be having with this vintage Kenwood and to save you much hunting for the
fault here is the answer. I draw your attention to this as it is the fourth
rig of this model that I have heard about with the same fault.
The cause is the Electrolitic capacitor C104 470uF on the output of the audio
I.C. IC5 uPC2002 pin 4, that has leaked it's electrolite and popped it's to.
This fluid may also have corroded several tracks and even caused the effect of
dry joints in the location of the spilled electrolite.To get to C104 turn the
rig upside down and remove the bottom. Look on the PCB and it is next to the
plug CN13.
The strange thing is that all the electrolitic capacitors in this rig are
coloured BLUE, but the C104 is a BROWN coloured one (Why the only brown one
and that's the one that was faulty in all 4 rigs that I know of). Did they fit
a reject batch of capacitors to this mode ?.
The capacitor sits next to the audio i.c's heat sink. Check to see if the
electrolite has corroded the very thin pcb tracks that run parallel to this
heat sink (Like happened to mine) it is hard to repair as it is difficult to
get the soldering iron in between the filter and the heatsink. You may have to
remove the PCB as the double layedr board's tracks may also need attention
underneath.
I hope this blog may help some one out there that is sitting with a similar
fault. If so I would like to know with a return packet to my local BBS.
73's Peter.
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