The Al Bundy wrote:
"Thierry Delaitre" wrote ...
Hi,
I've replaced the 2 bax17 in the detection part by by281 but no
success. I've posted the schematic at
http://www.cpc.wmin.ac.uk/~delaitt/PM3240/circuit.jpg
and the following pictures taken with an oscilloscope:
1) http://www.cpc.wmin.ac.uk/~delaitt/PM3240/P1010339.JPG
collector of TS1308 when intensity is in maximum
voltage goes from 7v to 75v (using 1/10 probe)
2) http://www.cpc.wmin.ac.uk/~delaitt/PM3240/P1010340.JPG
collector of TS1308 when intensity is in minimum
voltage goes to 50v
3) http://www.cpc.wmin.ac.uk/~delaitt/PM3240/P1010341.JPG
emitter of TS1306
voltage goes from 8v to 28v when intensity is in maximum
4) http://www.cpc.wmin.ac.uk/~delaitt/PM3240/P1010343.JPG
emitter of TS1306
voltage is 8V when intensity is in minimum
Cheers,
Thierry.
Hi,
What I don't trust is the oscillation that is on the collector of
TS1308. The signals on TS1306 seems to be correct.
Did you try to disconnect the fillament from its supply? It can be
that there is a short between the fillament and the grid or at the
supply of the fillament voltage, and then lighting up the neon lamp?
I've disconnected the fillament, R1337, G1, G3, R21, K and neon is
still blinking. I've checked R1341, R1339, R1338 and there are
correct.
Anyways, I dont know if the by281 (correct nr btw??) is a good
replacement. The BAX17 cross reference shows up this diode:
http://www.fairchildsemi.com/pf/FD/FDH400.html
When you put back the original diodes how is the signal at the
collector of TS1308? Still oscillating?
I meant BY218! I've now put back the original BAX17 diodes and taken
pictures.
The following shows the signal at the collector of TS1308 when
intensity is at its maximum (up to 75v).
http://www.cpc.wmin.ac.uk/~delaitt/PM3240/P1010350.JPG
The following shows the oscillating signal (6us) at the collector of
TS1308.
http://www.cpc.wmin.ac.uk/~delaitt/PM3240/P1010352.JPG
The following picture shows the board with neon lighting up.
http://www.cpc.wmin.ac.uk/~delaitt/PM3240/P1010353.JPG
Should i believe that the crt is not displaying anything due to the
fact that the voltage of the wehnelt is too negative relative to the
cathode ? Could it be that the neon is faulty ? Do they normally light
up above a particular current threshold ? In my case, it seems the
neon is lighting up when the current is 0.16mA (1300/8Mohm).
Cheers,
Thierry.