Problems with 2 old Sony TV's ( Tripping )
Michael Kevin Drummey
I've got 2 old Sony TV's, both in good condition. One is a KV1820UB,
the other a KV2000UB.
Both sets are tripping. The power supplies both run OK when a 100W
lamp is used as a dummy load ( 135V output measures OK )
The same is true even with the line output stage in circuit, i.e.
power supply seems to be tripping due to lack of load.
The KV2000 once came on when an attempt was made to measure the drive
to the output device ( a GCS, type SG613 ). The CRT was OK, and the
picture seemed fine, apart from being slightly narrow.
Can these GCS devices go open-circuit, removing the load from the
power supply. They seem to be expensive, rendering the sets
uneconomical to repair. ( I have read about them going short-circuit,
this is not the case this time )
Could there be a problem with the line drive?. There seems to be a
reasonable waveform at the gate of the GCS ( when PSU is loaded ). I
don't have a manual to check this correctly, but it is at line
frequency.
Someone now tell me how stupid I am for missing the obvious,
unfortunately, this is not one of my favorite chassis designs, and I
don't know anything about GCS's. I do however like Sony Recievers and
feel that the trinitron tube produces a far better picture than
conventional types (at least a good one does!)
Any help would be apprieciated, including a cheap source of the SG613
if this is to blame (possibly surplus or obsolete stock)
Thanks in anticipation.
M.Drummey
Alan
know of any cheap source for these that I would consider reliable as the
generics and the substitutes seem to inflict problems or generrally not
hold up.These sets are very touchy and if you dont have everything
working correctly they can blow right back out.My suggestion if you wan
to repair the sets-take out the Gcs device and then find a decent sized
heatsink to mount a conventional to-3 type horizontal output
transistor.wire it into the set where the gcs was-A=collector,G=base,K=
emitter.this will allow you to fire the set up with Hv for
troubleshooting purposes.I use a heatsink from an old Zenith
foldown(titan) chassis.Dont forget to put a damper diode across it.This
procedure will save you from destroying more expensive components while
troubleshooting.Any loss of drive to the Gcs will cause it to fail so if
you have intermittant connections,an unstable drive signal in any way
such as jitter from a dirty h.hold control poor filtering on any of the
supply lines fix them.also test run the set for intermittant crt arcing
wich was a common occurrence in some of these.Yous said it had a width
problem,Look into it,Usually bad caps in pincusion circuit.width
problems may be a little tough to find this way because this jig will
cause the pix to pull in from the sides a little bit,more on the left
than the right.I have personnaly never left one of these jigs installed
in the set but i know of others who have with good results,I wouldnt
recommend it.
good luck
Laurence Taylor
In article <5ij35i$o4c$1...@news.enterprise.net>
mkdr...@enterprise.net "Michael Kevin Drummey" writes:
-> Any help would be apprieciated, including a cheap source of the SG613
-> if this is to blame (possibly surplus or obsolete stock)
There is no such thing as a cheap SG613! I did see someone - I think it
was Willow Vale - advertising them on "special offer" a while back for
ś10 each, normal price twice that.
There was an article in "Television" a while back that described how to
replace the line output device with a BU208. I don't know how this would
fiollow for the power supply, but in the set I have, I think it's a
KV1800 or 1810, the GCS is simply used as a glorified series regulator
for the HT line, so could probably be quite happily removed and the
circuit redesigned more simply. I hate doing that though, I must admit I
prefer things in their original condition.
rgds
LAurence
cgw...@itmco.net
> I've got 2 old Sony TV's, both in good condition. One is a KV1820UB,
> the other a KV2000UB.
>
> Both sets are tripping. The power supplies both run OK when a 100W
> lamp is used as a dummy load ( 135V output measures OK )
> The same is true even with the line output stage in circuit, i.e.
> power supply seems to be tripping due to lack of load.
>
> The KV2000 once came on when an attempt was made to measure the drive
> to the output device ( a GCS, type SG613 ). The CRT was OK, and the
> picture seemed fine, apart from being slightly narrow.
>
> Can these GCS devices go open-circuit, removing the load from the
> power supply. They seem to be expensive, rendering the sets
> uneconomical to repair. ( I have read about them going short-circuit,
> this is not the case this time )
>
> Could there be a problem with the line drive?. There seems to be a
> reasonable waveform at the gate of the GCS ( when PSU is loaded ). I
> don't have a manual to check this correctly, but it is at line
> frequency.
>
> Someone now tell me how stupid I am for missing the obvious,
> unfortunately, this is not one of my favorite chassis designs, and I
> don't know anything about GCS's. I do however like Sony Recievers and
> feel that the trinitron tube produces a far better picture than
> conventional types (at least a good one does!)
>
>
>
> M.Drummey
probable the emf diode