TIU REV. L

Sounds like the aux input jack is not connecting but still keeping the Fixed 1 input disconnected. I am under the impression that the fixed 1 input gets disconnected when you plug in the aux connector. Could also be bad bridge rectifier at aux input. But maybe someone more familiar with the TIU could verify or have more accurate info.

Power supply section failure. How and what should be done by a pro. The last thing you want to do is kill your whole TIU.

There are 2 regulators associated, the 1 without heatsink and the one with heatsink. Further, there are 2 TVS diodes that could be shorted from voltage spike failures.

Again, the good- TIU can be powered by 5V input on the USB and logic and main processor still operating.

The bad- both AUX power and fixed1 not working- most likely a component in this power supply section, but this is pretty advanced for DIY repair.

Again, my guess, a component failed. The regulators I believe have thermal protection and shutdown.

The symptom:

@Jean Perusse posted:

The led will flash once and stay off when i apply power to the "Aux power input"

with a 18VAC power supply, the same thing if I use the "Fix voltage in 1".

Again, theory is, say one of those TVS diodes failed. Then the regulator would initially attempt to power the shorted load on first powering in a cool state. The shorted TVS then overheats the regulator or hits a current limit and the regulator shuts down- hence the once and done system. Blinks once, briefly, and then is dead.

This forum is great for information!

Thanks Aegis21 for your feedback.

Thanks Vernon for the detailed explanations and photo it's very appreciated,

I will come back for the follow-up.

Jean

This is one of those repairs where my FLIR Pro thermal camera could spot the bad device.

How I found a bad component on a PS3 board

@Vernon Barry posted:

This is one of those repairs where my FLIR Pro thermal camera could spot the bad device.

How I found a bad component on a PS3 board

I use my finger.

@gunrunnerjohn posted:

I use my finger.

Tsssss, aaaaahhhh, my finger.

And, yes, I did that once on that un-heatsinked regulator, on a TIU with 4 bad ACT244s, loading the 5V bus down and that regulator was smoking hot.

I've imprinted a finger with a perfect image of a TO-5 transistor top a couple of times, I did learn not to do that with a dry finger.

Hello,

The defective diode on my tiu is KE33CA.

Given that there are several variants of the diode on Digi-Key

is it possible to tell me which one I should order.

Thank you so much.

Jean

@Jean Perusse posted:

Hello,

The defective diode on my tiu is KE33CA.

Given that there are several variants of the diode on Digi-Key

is it possible to tell me which one I should order.

Thank you so much.

Jean

This one from digikey is a good replacement: https://www.digikey.com/en/pro...CA-TPMSCT-ND/1960025

@Jean Perusse posted:

The defective diode on my tiu is KE33CA.

Given that there are several variants of the diode on Digi-Key

is it possible to tell me which one I should order.

Why not replace it with the same part, the TIU makers probably knew what they were doing.

https://www.digikey.com/en/pro...inc/1-5KE33CA/688026

Hi,

Thanks H1000.

Thanks John, the diodes are ordered and when they are received and

installed I will follow up.

Thank you to all for your skills and expertise.

Jean

If you powered with the aux plug and it flashed once than LED went out, the board has a shorted component on the 5V or 3V buss dragging 5V buss down causing LED to go out.  This is not a hung up Aux jack, nor a TVS diode fault on fixed one which would short your transformer.  Good chance the Transmit chips failed, or there are other faults not repairable that can cause this.  G

Hi,

Thank GGG, I am waiting for electronic parts and

I will come back after replacing these parts.

Jean

@Jean Perusse posted:

Hi,

Thanks H1000.

Thanks John, the diodes are ordered and when they are received and

installed I will follow up.

Thank you to all for your skills and expertise.

Jean

If you removed the diodes that you think are shorted, wouldn't the TIU start up and led turn red and stay red? I would not run trains without the TVS replaced if it is the culprit, however it could confirm diagnosis and expidite repair. Just a thought.

@gunrunnerjohn posted:

I use my finger.

YUP and I have the burn marks to prove you response. LMAO

Hello Everyone,

This afternoon my son-in-law successfully replaced the diodes (KE51CA).

Result: Bingo, the TIU works as it should.

Once again thank you for your skills and expertise.

Jean