On Mon, 7 Mar 2016 13:46:27 -0000 (UTC), Cursitor Doom
wrote:

On Sun, 06 Mar 2016 23:34:55 +0100, Dimitrij Klingbeil wrote:

It's only my guess, but I think that they intended this supply to run
rather somewhere below resonance than somewhere above. This would mean
that adjusting the pulse frequency down to 17.35 kHz should do no harm
as that value would be lower than the setting right now.

I've just noticed that towards the bottom of (true) page 106, it states
the following:-

"The oscillator frequency is approximately 25kHz, determined by network
C1811, R1823 and is adjustable by means of R1824."

It then goes on to specify the duty cycle. Two things stand out as
requiring further investigation here. Clearly, the 25kHz clock frequency
mentioned is *miles* away from what my clock is running at - and the
frequency adjustment is made with R1827, not R1824 (which is fixed
anyway). I'm guessing the reference to R1824 is just a typo, but can we
say the same for 25kHz??
Since this *completely* changes our former assumptions, I'm going to
confine myself to just replacing the flaky polyester caps for the time
being. Be interested to hear how you think I should proceed now in the
light of this...

You are refering to manual component numbers from the 3262 manual and
schematic. The 3264 does not have the same schematic or part numbers.

The schematic is functionally similar, but uses a different control IC
and different components are present/selected to set the IC's
function. Part type for the main transformer/size and pinout, the size
of resonant/snubbing components, along the actual supply power
ratings may vary with model number, as well. One example is the
different resonant cap size used.

3262 PSU adjustment begins with para 3.4.4 on 3262 manual page 115.
(do not ignore preceding setup instructions re scope settings)
You can assume the sequencing and intention of these instructions to
mirror those needed for 3264, however numbers and test conditions that
reflect operating power and typical frequency can be expected to vary.
This includes chip reference pin voltages - TDA1060 internal reference
is 3V62.

The converter runs at a fixed frequency, above resonance. The
frequency only needs adjustment if the output voltages lose full power
low-line voltage regulation. This is also the protective power limit.

The two model control circuits do not limit in a similar manner. The
3262 manual describes a latching power limit that occurs after
repeated continuous overload. This does not appear to be present in in
3264, as it is chip-based feature.

RL