1 Nov
2015
1 Nov
'15
10:42 a.m.
On Nov 1, 2015, at 12:37 PM, Robert Jarratt
<robert.jarratt at ntlworld.com> wrote:
...
Hmmm.... Until your email I was pretty confident this was a switcher. But
your description of a linear PSU seems to fit. I have posted three photos of
the main board here: http://1drv.ms/1KQkTBp can you tell from that what kind
of PSU it is?
The big TO-3 on the left is the one that I found had failed. The replacement
does not appear to be switching, but I don't know why.
I agree with Wulfman that it looks like a switcher. There's too much circuitry in
there for a linear. Also, that pile of small electrolytics is typical for a switcher.
That said, it's possible that there may be an auxiliary linear regulator in there.
That's common for additional outputs with modest current needs, especially in older
designs where the switching circuitry takes a lot of individual components. A TO-3 can
isn't what I would expect to see in a switching-only supply. In other words, that
particular transistor might be the pass transistor of a linear regulator.
paul