I think I've just killed my AKF12 :(

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I think I've just killed my AKF12 :(

Post by Trapper » Mon Aug 28, 2017 9:09 pm

I think I've just killed my AKF12. I picked it up last year from the original owner, it had been in his loft for a few years.

It's been working fine apart from the broken power button. I used an A30x0 Castle ADFS IDE mini podule backplane to keep it pushed in.

Today I reconnected it as it had been on my office floor for two months whilst I've been unwell.

Played the MegaDrive for a few hours today and suddenly the picture went and was replaced with a high pitched whining.

I assume this means the tube is dead?!

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Re: I think I've just killed my AKF12 :(

Post by philb » Mon Aug 28, 2017 9:44 pm

I doubt it's the tube. Something in the power supply or line output circuit seems more likely.

If you can find a local TV service engineer who still knows how to fix CRTs then I imagine they can probably sort it out.

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Re: I think I've just killed my AKF12 :(

Post by flaxcottage » Mon Aug 28, 2017 9:47 pm

The CRT will probably be OK.

The high pitched whining is likely to be the EHT circuit oscillating at the wrong frequency. It is likely that somewhere in the horizontal oscillator circuit right up to the line output transistor there will be a fault meaning that the circuit oscillates at the wrong frequency and produces the wrong output. It is probable that many of the other voltages are also derived from the EHT transformer and so the whole device fails.

For a competent CRT engineer this will be an easy fix but these engineers are few and far between nowadays.

Edit: As philb says - he beat me to it.
- John

Why do I keep collecting Acorn gear? I'm going to need a considerably bigger man-cave. :?

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