HP-IL device Seal s5801c

[Paul Berger (Canada)]

This is you picture of the back with some annotations, please note the annotations are just educated guesses from comparing the top and bottom of the boards. The Rifa caps have a Y on top of them which would lead me to believe that they are Y safety caps which are typically connected from the AC line to the ground. The two white caps next to them may be X caps and would be marked as such they are typically connected across the AC lines. The fuse holder would appear to be in line with what is likely one of the AC lines. You mentioned that the transformer is mark as having two 6 volt secondaries and it would appear that one end of both of them it tied together to effectively make it a center tapped transformer with the two leads that are tied together connected to the DC ground, and the ends tied to rectifier diodes. Q1 one appears to likely be a 3 terminal regulator something like a 7805 or a 340-5 it should be marked. it looks like Q2 and Q3 are probably triacs, again they should be marked. From what I can see it also looks like Q2 controls the AC to the transformer. If Q2 is a triac then the gate lead goes off to something that is obscured by the heatsink. One last guess looking at where the Rifa caps are connected I suspect that the large area at the bottom right is the ground (note it is also connected to a pad around one of the screws holding the heatsink.) then just left of that there are two groups of three pins the would seem to be the AC inputs, but again just a guess use a meter to verify.

As mentioned before Rifa caps like the ones on this board have been known to emit large amounts of smoke, the problem with them is the plastic shell on them cracks and moisture get in, so if they lokk at all like they are cracked I would remove them before applying power. As mentioned previously I suspect they are Y safety caps, it is ok to power up to test without them but is you where going to use this for the long term they should be replace with caps of a similar rating.

As Dave mentioned using the continuity check function of a meter to ring out the connections on the board is a good way to start. If that function is related to the resistance scales use the lowest range. Be aware that the transformer windings and the toroids will have very low resistance and may easily be mistaken for a connection. My usual approach to something like this is to ring out the connections and use that to sketch out a schematic of the board.