QSI-DCRU LIGHTING CIRCUIT EXPLANATION HELP

There are several varieties of that board, here's one that was in some PS/1 diesels.  The two wires that go "off page" are the power and ground from the track.

It is not Head Light from the PS-1 board.  CV boards that MTH used in the ABA, AA slave sets up pickup a voltage off the Relay operation.  When the relay is active to drive the engine in a certain direction it triggers the directional lighting.  When Fwd relay active on the Lead PS-1 unit the lead HL goes on.  When the engine is reversed the Lead HL goes out.  The Slave board reverse relay is active and it triggers the reverse CV board HL and it goes on.

I never fully documented the circuit, but know where the leads are connected and that is the source to trigger CV board.  Hence the 6V bulb.

PS-1 boards have output for direction HL but at 1.5V.  Diesels use that and steam tenders for the Tail light.  G

Thanks John and George,    I'll check out that reverse relay today and take some voltage readings.     Bob

@GGG posted:

It is not Head Light from the PS-1 board.

Au Contraire George.  At least for the one I posted, the red input jack I labeled HL came directly from the PS/1 1.5V lighting outputs.  They went into an opto-isolator and switched the 6V headlight output.

Are you sure and did it work?  That output is about 1.2v, is that enough for those early isolators?  I have upgraded many of these units from 1994 through the end of PS-1 in 1999/2000.  The source was across the coil of the relays.  Much higher voltage drop.

I won't say never, but I have not seen it. Plus the DCRUs used in the trail A did not have the light mod added.  They were basic reverse unit, so there was no HL output to drive the CV board in the trail A.  G