Quote:
Originally Posted by staticmind
Hmm, there's something I don't get at ALL about the schematic and the voltages they show at the PCL84 pins.
For example Vg2= 145V, but this SHOULD equal the b+ voltage rail, as there is no dropping resistors as with EF80 in the image IF section.
As mentioned by PortugalTV, my b+ voltage rail is low, due to the selenium rectifier (maybe).
So why do they write 145V on the schematic, when it should be 180V? I don't get it.
Also according to https://frank.pocnet.net/sheets/030/p/PCL84.pdf there is no data for Vg2 below 170V. I'm really confused now.
Is the low (out of range) Vg2 the reason why Va equals the b+ voltage? |
for your first point i have no explanation....tvs and tube stuff have wayyyyy high tolerances so dont bother with that. 20% higher or lower will work perfectly.
Va equals b+ voltage beacuse the tube is not conducting so no drop occuring on the resistors from b+ to anode of the pcl84. missing bias or bad tube like i said above. dont worry you will find it out
you mentiond above some coils wrapped around resistors
they often get broken and often you can repair them or even bypass them. normally they measure very low dc resistance so if they measure high you are probably reading the resistor and have an open coil.
after reparing coat them in wax, no hot glue beacuse if they fail again then there is no more fix possible
the 1.8meg before the contrast control could be high in value. you are reading 4v instead of 15, it would explain that