Re: 454 fireworks


Sean Turner
 

John,

The -12V rail is spot on, and so is the +12. I did do a quick and dirty diode test on Q1197, which showed two good diode drops, but that was in circuit and at low. I suppose it could be breaking down at operating voltage? I agree, getting at it will be...interesting...if the fault with +75V regulation is narrowed down to that.

Sean

On Mon, Mar 15, 2021 at 12:57 AM, John wrote:


Let's hope it's not Q1197 gone s/c as it's a pig to replace (mechanically).
With the EHT unpowered at least you can trouble-shoot the PSU. NB the -12V is
the reference for both +75 and +12V rails so needs to be correct / set first.
Once you have the power-supply working fingers crossed the EHT section comes
good.
John

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