Re: waveform at 555 + HV variance - amplifone monitor

That 555 waveform you described is what I saw when I scoped mine and that one has been rock solid for a long time now.....

Although I do not have more proof than just one working Wintron that I replaced, but I have a feeling the Wintron is actually not as good as its reputation. At least the one I replaced had a LOT more blooming during f.i. the death star explosion than the Cinelabs I have on my own HV board, and the Cinelabs type one that I put on the "customers'" board.

Verstuurd vanaf mijn iPad

Op 15 aug. 2012 om 15:45 heeft Karl Doe <karlcdoe@yahoo.co.uk> het volgende geschreven:

> Hi Mark,
>
> Thanks for your reply. If I'm absolutely honest with you it was purchased from ebayUK some time back and it does not have a cinelabs warranty sticker though it is similar in appearance. I would like to clear that up if anyone has any concerns about ordering any cinelabs products. I referenced 'cinelabs type' as it was the nearest commonly known flyback type, as opposed to red or wintron. Sorry about that...
>
> Anyhow, an update is in order as I fixed it last night: after deciding on changing the 555 timer and BU406D the problem remained so I hung the HV PCB outside the cab to rule out the noise coming from the tube itself and see if I could visually see where it was arcing. It was at that point I briefly saw an arc in the loom.... the input for the +- 24v regs from the deflection board had been damaged at some point giving an intermittent 60v short. Sounds like the sort of voltage used for mig welding :-) Anyway its rock solid now, better in fact than my amplifone with a wintron (athough I probably need to freshen up the deflection board on that one). So there you go, a really simple fault for once....
>
> Cheers
>
> Karl.
>
> From: Cinelabs Info <cinelabs.info@gmail.com>
> To: vectorlist@vectorlist.org
> Cc: Karl Doe <karl.doe@kcom.com>
> Sent: Wednesday, 15 August 2012, 14:25
> Subject: Re: VECTOR: waveform at 555 + HV variance - amplifone monitor
>
> Hi Karl,
>
> You mentioned you installed "a Cinelabs type flyback". If you installed an actual Cinelabs flyback, specifically a flyback with a Cinelabs warranty sticker on it, then you are fully supported and we are happy to provide specific assistance with troubleshooting your board. If you're replacement flyback is a dud, we'll get it replaced.
>
> If the flyback is a generic Cinelabs type (i.e. no warranty sticker), you should contact the place you purchased the part, for technical and/or replacement support.
>
> Can you check to see if your flyback has a sticker on it?
>
> Thanks,
> -Mark
>
>
> On Mon, Aug 13, 2012 at 5:29 AM, Karl Doe <karlcdoe@yahoo.co.uk> wrote:
> Hi all,
>
> Just a quick sanity check: Should the waveform from the 555 be a true square wave or do they vary a lot? I hooked up a dummy load (60w light bulb) across pins 1 and 9 in place of the HV transformer and connected a 'scope (10x probe, compensated) to pin 1 (ie the light bulb) and what I saw was a slow ramp up to the top of the wave (more like quarter of a sine wave) then a sharp cut off (more like what I expected), the frequency is still around 20kHz. I figure the data may be skewed because of where I am measuring it (or an effect of the lightbulb) and maybe I have to measure directly from pin 3 of the timer IC?
>
> Secondly (quite possibly related), I went ahead anyway and installed a cinelabs type flyback but I can hear occasional arcing and I think it's somewhere actually on the HV board. When this happens my HV probe shows a brief but significant increase in HV from, say 19.5 normally up to 25kV+. I can't decide if the arcing if the cause of the HV increase or if some other part of the circuit is playing up and therefore ramping up the HV and the arcing is just a side effect.
>
> So far all the electrolytics have been changed, +- 24v regs, 50 ohm resistors, 1n4001 diodes and the CR3 was missing so I used a sub. Old parts: the BU406D has not been replaced -tested okay as far as one can tell from the FAQ, and I haven't replaced the 555 timer.
>
> The output of the =- 24 regs is stable but a little out of spec on one rail like +2 volts or something with the lightbulb attached and I put this down to the 50 resistors. So logically speaking I think I shall replace the 555 timer, BU406D, and perhaps the frequency adjustment pot next.
>
>
> Thanks in advance.
>
> Karl.
>
>
>

---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com
Received on Wed Aug 15 15:22:15 2012