On Sun, 21 Feb 2016 17:13:55 -0500, JC wrote:

On 2/21/2016 4:28 PM, JC wrote:
On 2/21/2016 3:59 PM, Cursitor Doom wrote:
On Sun, 21 Feb 2016 20:09:47 +0100, Dimitrij Klingbeil wrote:

On 21.02.2016 18:27, Dimitrij Klingbeil wrote:
On 20.02.2016 15:36, JC wrote:
On 2/20/2016 7:55 AM, Cursitor Doom wrote:
On Sat, 20 Feb 2016 01:14:09 -0500, legg wrote:


Thank you. If you've had the chance to read my follow up to JC (I
think it was) then you'll be aware that one of those BY208 diodes was
replaced by a BY134. If the design is that critical of the speed of
the diodes it uses then maybe it won't function properly as you
suggest. I can only imagine the technician who replaced it was unaware
of the critical nature of the part concerned.
I'm kind of unhappy with this design overall, to be honest. It was
critically appraised on s.e.d and found generally unsatisfactory. I'm
strongly tempted to just save the transformers, junk everything else
and start afresh with a modern design. The rest of the scope is mint
and untouched, it's only the psu section that's been butchered around
and shows signs of burning and scorching in places. Maybe the best
thing to do would be to bin it? :-/

Switching supplies are all designed with the diode (and other
component)
parameters in mind, its how they function efficiently. Bunging any old
diode in is asking for trouble. Same as the ESR and temp rating of the
caps used. Seriously you need to sit back and chill. These scopes were
very well designed and I would say exceptionally reliable. I'd like to
see you build a replacement. I've designed switching supplies,
everything needs to be right or it goes wrong fast.

FR107G seems to be the current equivalent for the BY208-1000

FR107G Ebay (UK) #390565307743 cheap enough.

Thank you, JC. You and Dimitrij have both given me some subs for suitable
replacements which I'm quite happy to go along with. But I'm not prepared
to spend much more time on this repair, to be honest. I'd relish the
prospect of a comprehensive re-design. Even if it's beyond me at this
stage I'd learn a lot from it.