No track power from Elite

[ff2nd]

Hi all. I am hoping someone can advise me on this. My Elite failed recently, quite spectacularly! It went to a dead block. I opened it up, and it became clear that I wasn't the first in there (it's an old Elite, so I am not worried about that.)

I re-flowed the power socket soldering, but nothing changed. I then changed the transistors at Q1 and Q3 (I have some identical ones), and the Elite sprang to life! "Great!" I thought. So, I tested it, and while it reads and writes perfectly well, there is nothing coming out of the track port at all. Unfortunately, I am not well versed in Electronics (monkey see, monkey do), so I don't know what fault I am looking for next.

Can anyone please suggest what tests I should be doing, and on what? I have spoken to Hornby CC for advice, but they cannot do this test, and due to the age of the Elite, I would be looking at a serious bill. Thanks.

[96RAF]

This may be of use . . .

http://www.halton96th.org.uk/page12.html

Q2 and Q4 also drive Track output.

Also in the Track output circuit is L4 a dual common mode choke. If faulty this can be linked out of circuit.

L4 COMMON MODE CHOKE 8P 300R CM3032V301R-10 or alternative - see Teardown.

There is a self test you can do to check general state of play. Press and hld LOCO button as you power up then release when you see Hornby on screen. It will self test and report then you can press all buttons in turn to check response. What we are looking for here is response to each speed knob which should confirm states of those track drivers.

To recover from the test state simply power down and reboot.

[ff2nd]

Sorry, I should have said, I already did the Loco button test, and it reported that all was well. Encoders are turning and registering correctly. I have just checked the resistance on the transistors that I fitted, and Q1 is giving some weird results. I will swap that one out again, and see where we go from there. Thanks.

[ff2nd]

Ok, Q1 and Q2 removed. When I test the board now, I have resistance of 107 ohms between the left hand and centre sockets for both of them. That can't be right, surely? Sounds to me like something else in the circuit has failed, yet the L4 choke meters the same resistance as the ones on my scrap Elites. Have to admit, I'm beginning to wish I'd never started!

[96RAF]

There are several resistors and capacitors in the Track circuit as well as Inductors L1 & 2 (7μ0) and drain transistors Q5 and Q6 (which are both BC847).

Unfortunately due to my NDA with Hornby I am not allowed to post the wiring schematic in the public domain.