17 Apr
2012
17 Apr
'12
11:50 p.m.
Tony Duell wrote:
Isolation barrier? Hmm, there isn't really one.
If you look at this: http://www.tiffe.de/Robotron/TSZ07/nt-10.jpg
(http://www.tiffe.de/Robotron/TSZ07 for the directory index)
You see the cable going from left top to the middle of the bottom PCB
and left and right from its connector sits an opto coupler.
This may be the barrier...
The three wire cable from left bottom to upper rigt is going to the
transormer behind the sheet metal on the top pcb, it looks to me like
the drains from 2 FETs (on the heat sink) and 330V ... (don't know this
exactly in the moment, the PSU is back in the drive again).
The upper Board is looking like low voltage, the board at bottom to the
high voltage part.
Shadoo, which has two such drives and one of the defective with other
problems will look closer at the part values for me, specially the
resistance of this white resistor. I'll wait until he comes up with some
infos before I dismount this all again.
Wondering how his PSU would look from the inside..
Regards,
Holm
--
Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe,
Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583
www.tsht.de, info at tsht.de, Fax +49 3731 74200, Mobil: 0172 8790 741
No Tony, for
sure this is not such an circuit.
I've meausred the pieces of the wirewound resistor, it must had a
resistance with approx 4-5 Kohms before. The Place for the FET is marked
Ok, lets think for a second.. This wirewound resisotr is, perhaps, 4700
ohms. And it burnt up spectacualrly, so perhaps it disipated at least 5W.
Now, P=V^2/R, so V= sqrt(P*R). That implies a voltage across that
resistor of about 153V by my calculations. And a voltage that won't drop
even when supplying such a load.
Are you sure?
GDS on the PCB and lat but not least the circuit
isn't connected to the
Capacitors on the mains side.
What is it conencted to? Which side of the isulation barrier is it on
(mains or output side?)
-tony 