Re: WG 6199 HV section help

I had a HV with a Bad 555 last year that I was looking at for a friend....
Some of the resistors smoked (not got the schematics to hand and disn't take
notes) and the little transformer was getting warm too if I recall...

I also had to replace the transistor which drove the little transformer
too... used a sub and I decided to make a little bracket to hold it in place
and keep it cool too (it didn't have a metal tab on it) ... bit of an
overkill .... its worked well since I'm told... It was all nicely recapped
with a few fresh resitors and a couple of modern ceramic caps on the 555
too...

There was a BIG hole in the board under one of the resistors from a past
failure. I also added an inline fuse for the little transformer (as
suggested on cinelabs) - You can see it (little circular brown device) to
right upper right of the pot.

http://www.jammaplus.co.uk/forum/uploads/70/Gav_HV4.jpg

http://www.jammaplus.co.uk/forum/uploads/70/Gav_HV3.jpg

Testing on the Bench off a dual power supply with HV probe ....using Andy
Welburns suggestion to measure HV...

http://www.jammaplus.co.uk/forum/uploads/70/Gav_HV2.jpg

Cheers, Col

----- Original Message -----
From: "Pat Danis" <patdanis@verizon.net>
To: <vectorlist@vectorlist.org>
Sent: Monday, February 11, 2013 2:17 PM
Subject: Re: VECTOR: WG 6199 HV section help

> Well, that was interesting. It turned out to be the 555 timer. After
> rechecking everything in the HV cage (and out of desperation), I replaced
> the timer with one from a pull from another cage I had. It worked. Then I
> still had low High Voltage at about 136v. Traced it back to ZD901.
> Replaced it and all is good now. The 555 I used as a replacement was of
> the CMOS variety the first time. Don't know if that would cause an issue
> or not. May have to get some regular 555's for next time. Thanks for all
> of the assistance. Sometimes you need another brain to make sure that
> yours is still working.
>
> Pat
>
> On 2/10/2013 6:15 PM, John Robertson wrote:
>> Pat Danis wrote:
>>> Like Ian, I have the same issue with my HV cage. P316 model. R903 gets
>>> fried and I keep frying q901 and q902. I have been thru the entire cage
>>> and can't find anything bad. Read the FAQ and checked or replaced
>>> everything suggested. I'm not a smart enough guy to figure out what is
>>> drawing so much current.
>>>
>>> I can only power up the monitor for a few seconds. (about 5-10) When I
>>> power up the monitor, it is very dim and then I get a high voltage
>>> crackle and R903 starts to smoke, then the transistors let go. The
>>> issue I was having before was the image was blooming. I replaced ZD902
>>> and I think that stopped the blooming. Now I need to know why I keep
>>> frying these parts.
>>>
>>> Can anyone offer some suggestions? I've been thru this cage so many
>>> times, I'm starting to forget what circumstance leads to what condition.
>>>
>>> Pat
>>
>> Do you have a ring tester for the flyback? One shorted winding can take
>> out the parts you are speaking about...
>>
>> A cheap and easy alternate tester is to use an multi-function audio
>> signal generator (all of us have these, right? - eBay, "audio signal
>> generator" look for Sine/Square wave within those) - hook up the output
>> to the transformer and fire up the generator (square-wave) around 15KHz @
>> 10 to 20V. You should see on your 'scope (you have these too, eh?) a nice
>> signal with a ring that rolls down after about five to more cycles after
>> each pulse.
>>
>> There is no reason you have to run the HV cage at the rated DC input, use
>> a variable power supply and dial it up slowly while you watch the
>> screen/focus outputs (not the HV lead!) on your 'scope. You may see
>> something interesting...
>>
>> John :-#)#
>> PS, I sell the ring testers as a kit, cheap @ $49.95, I'll knock $5 off
>> the shipping if you mention you post on Vectorlist.
>>
>
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Received on Mon Feb 11 13:42:56 2013