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Old 23rd May 2016, 7:10 am   #14
flyingtech55
Octode
 
Join Date: Nov 2005
Location: Ayrshire, UK.
Posts: 1,080
Default Re: Beovision 7102 CRT TV,schematic/advice please

Just a quick comment....

I don't want to be pedantic but the thing on the power supply PCB, although it looks like one, is not the LOPTx. It's the EHT generator. It also produces a number of other supplies including that for the sound output stage. The LOPTx is actually on the small PCB on the bottom of the cabinet under the CRT. As I say, I'm not being pedantic, it just used to cause a lot of confusion back in the day.

You mention that you have only 165V across 6C7. If that is the main smoothing block after the bridge rectifier comprising 6D1, 6D2, 6D3 and 6D4 then that is your fault. There must about be a solid 300V (or there about) across that capacitor. Do not bother doing anything else until you have 300V across that capacitor. It has probably gone O/C or the bridge rectifier is half waving. It wasn't common back in the day but age will take its toll. The set will not run with only 165V on the main HT rail. Get the fundamentals right before you start randomly changing parts. You must have the full 300V main HT rail up or you are just wasting your time.

After that, for tripping, the three most important things to check are dry joints, dry joints and finally, dry joints. These were particularly common on the little edge connectors that the larger boards plug into. If not these, then unplug the EHT cable. These are a common cause of the symptom you describe. The set starts up the then almost immediately shuts down. ISTR that the set shuts down and doesn't 'pump'. When you switch the set off and then back on, the behaviour is repeated. As Glyn says be careful not to pull the 'pip' off the end of the EHT cable. The EHT transformer is very reliable and the only ones I renewed were because of physical damage due to dry joints arcing (did I mention dry joints) or because the 'pip' had fallen down inside the stub and was causing 'brushing'. I never had one break down as such. However, these sets are getting on a bit now so I suppose these things can begin to fail.

HTH

TimR
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