View attachment 312191

BC548 Manufacturer is Micro-Electronics

 

View attachment 312194

Here are power Darlington BJT pin assignments.

 

Here are power Darlington BJT pin assignments

The Darlington is now obsolete - replacing with a MOSFET would be the way to go, but there doesn't appear to be an upgrade path?

 

View attachment 312194

The connector at lower right is chopped off. I need to be able to trace where each wire enters the connector
(to identify the connector pin number) and trace it to the pins/devices on the transistor heat sink.

Can you post a better (non-blurry) shot of this?

 

BC548 Manufacturer is Micro-Electronics

Thank you.

 

Can you post a better (non-blurry) shot of this?

I can try in the morning with some natural light. They are quite faded though, and difficult to see.

 

The Darlington is now obsolete - replacing with a MOSFET would be the way to go, but there doesn't appear to be an upgrade path?

The Darlington can be replaced with a different manufacture if you want but I would recommend using mosfets.
The mosfets would be in a different package.

 

I can try in the morning with some natural light. They are quite faded though, and difficult to see.

OK...I suggest using some PCB cleaner spray (preferred) or rubbing alcohol and clean the boards.
Especially the bottom of the main board so we can clearly identify traces, then repost.

 

The mosfets would be in a different package.

Can you translate that?

 

Can you translate that?

The existing MJ2501 Darlington BJTs are in a TO-3 case. Mosfets don't usually come in that style case.
So the mounting of the mosfets to the heatsink would be different footprint.

However, ST-Microelectronic makes an MJ2501 Darlington transistor that should be a drop in replacement.

 

Also, Can you describe anything about the LED lighting patterns this produced?

 

OK...I suggest using some PCB cleaner spray

Ordered - will be here on the 'morrow.

 

Also, Can you describe anything about the LED lighting patterns this produced?

I put LED on the schematic as I couldn't find anything to simulate the actual rear lamps - although it would probably be a nice feature to add LEDs to the board. The existing unit powers ordinary incandescent bulbs so needs to handle 10 amps or more per line out.

Not sure of the pattern (not my unit) so we are going to set up a video either on a vehicle or with bulb holders/bulbs and a car battery.

 

So the mounting of the mosfets to the heatsink would be different footprint.

Ah-ha - so the metal container is a heat-sink! I wondered why it was separate to the PCB - is there a way to add a heatsink to the board to neaten it all up? I know that processors use heat sinks and thermal paste, but it didn't dawn on me that a transistor would - learning all the time.

 

Can you post a better (non-blurry) shot of this?

 

Ah-ha - so the metal container is a heat-sink! I wondered why it was separate to the PCB - is there a way to add a heatsink to the board to neaten it all up? I know that processors use heat sinks and thermal paste, but it didn't dawn on me that a transistor would - learning all the time.

Yes...that metal plate is heat sink. The transistors get hot, so with them mounted to the heat sink, with a thermally conductive paste, the heat is transferred to the heat sink and dissipated. The size of the heat sink can reduced if the right Mosfet is chosen.

 

I put LED on the schematic as I couldn't find anything to simulate the actual rear lamps - although it would probably be a nice feature to add LEDs to the board. The existing unit powers ordinary incandescent bulbs so needs to handle 10 amps or more per line out.

Not sure of the pattern (not my unit) so we are going to set up a video either on a vehicle or with bulb holders/bulbs and a car battery.

Adding LED indicators to the board is no problem.
So...is your intent to retain the original functionality of driving incandescent automotive lamps?

 

So...is your intent to retain the original functionality of driving incandescent automotive lamps?

1. Only very new vehicles have LEDs as original - aftermarket ones have resistors to emulate the original lamps, so in either case it will need to handle the output.

2. When the unit is not switched on the lights will still work as intended.

 

1. Only very new vehicles have LEDs as original - aftermarket ones have resistors to emulate the original lamps, so in either case it will need to handle the output.

Do you mean it needs to drive either LED's or Incandescent lamps?

2. When the unit is not switched on the lights will still work as intended.

I don't understand. Please clarify.

 

Do you mean it needs to drive either LED's or Incandescent lamps?

Incandescent. I over complicated that answer.

I don't understand. Please clarify.

It will be inserted into the vehicles wiring.