Rev H1 TIU worth fixing (or even possible)?

If it's just for the bench, I'd power it through the FIXED INPUT 1 and use one of the other channels on my test track.

Given the price of TIUs these days, it probably worth fixing beings the issue is this minor.

I don't have an H series on hand, nor are there schematics of any of them in public domain.

I realize your bodge job wire there kinda sorta works, but I would just replace the jack and resolder and reflow the joints. I think 90% of the problem is just that jack, and simply replacing it- (those riveted center pins are a known failure point on that style of jack) might be quick and dirty.

Otherwise, yes, just used fixed 1 input.

Forgot to mention that in my original post...yes, I tried to power-up through Fixed Input 1 but the indicator light is not coming on.  I've got voltage coming out the other side on the FIXED 1 output but no TIU light.   Something must be toasted on the board.  I can't see anything obvious, burnt, blown, distorted ??? 

It could be a blown trace. It might be on the backside of the board, or worse a middle layer you will never ever see.

You appear to be connecting to the bridge rectifier, and personally, I would solder to the terminal of that on the other side of the board to make your jumper.

One thing that is known- the AUX power jack and the Fixed 1 are both inputs to the power supply circuit. That said, I think there is also a connection that shorts out if the phasing or polarity of aux and fixed1 are connected together externally by a common on the transformer.

What I'm getting at- say someone was using one power source. It was connected to fixed 1 and AUX at the same time or otherwise had a common (like a Z1000 brick with also using 14V out of accessory). That could cause a serious short inside, maybe enough to blow a trace and likely not fuse protected. That damaging event might be what happened in the past to this TIU.

In fact, just tested on a Revision L.

Center pin of the AUX jack shows continuity to the Black post of the Fixed1.

Outer ring of the Aux jack shows continuity to the RED post of the Fixed 1.

Normally convention is we think center pin hot, or in DC it is sometimes the +, with ring outer being the negative or common. However, the internal connect puts this opposite to convention and so a Transformer with common like Z1000 or a Z4000, or many other transformers- if 2 channels were used, but then they thought they could borrow power from another transformer common output and feed that into aux power- and it goes horribly wrong.

@Vernon Barry posted:

It could be a blown trace. It might be on the backside of the board, or worse a middle layer you will never ever see.

You appear to be connecting to the bridge rectifier, and personally, I would solder to the terminal of that on the other side of the board to make your jumper.

That bare copper wire coming out the back of the power socket looks strange...is this factory installed this way or do you think this has been modified?  I don't think my Rev L has such a wire/connection?

The bare copper wire is solidly soldered to the center pin on the aux power socket but it is not connected (and has always been loose) on the other end under that black square component (bridge rectifier?)...has been this way since I got the TIU.

Here's a few pics with less zoom.  There's also a insulated black wire coming off the center pin going over to a cylinder component on the board by VAR1 OUTPUT.

I'm not sure what a "blown trace" is but it doesn't sound good!

I can't remember specifics but may have an early one to look at.  I do think some early TIU did jumper to the rectifier.  But in your picture, you seem to have a jumper off the TVS diode to the same terminal.  Bare copper looks like a home modification since MTH use stranded wire. Someone jumpered it with house wire.  The issue with F1 not powering TIU is most likely the round socket is damaged internally and has disconnected F1.  When oversized plugs used it deforms the spring metal connection and only Aux power works once plug pulled out.  I will be working on a TIU later today and will refresh myself on the Aux jack connection.  G

Just looked at a Rev I and Rev L.  The early version TIUs used the black wire from the F1 TVS AC ground side (black) to feed the rectifier using the center pin connector of the AUX port as the common junction.  The rectifier lead did not go into the PCB but was bent up and soldered to the center pin terminal also.   The other AC terminal of the rectifier goes to the board and gets power via the metal tab in the Aux port when the Aux power fitting is plugged in.  If no plug is installed that tab springs up and connects with the metal band that solders into the PCB to help hold the round port in place.  THAT band gets power from the Red AC side of F1.  There is an inductor in-between.

When you plug in the Aux jack, the tab moves down and disconnects fixed 1 Red from the rectifier.  That can be an issue if a TIU does not power up from F1 only Aux.  Small screw driver can lift it up.  This is how the TIU prevents your aux power supply from running in parallel with F1 transformer.

Later TIU had traces in the PCB and the rectifier had all 4 legs soldered to PCB.  That copper jumper tells me someone broke the rectifier lead.  I would remove rectifier and install a new one with that AC lead bent up and solder to the center pin.  I am assuming 2 issues.  Intermittent rectifier lead contact from that copper wire, and over sprung tab preventing F1 red from powering rectifier.  G

@GGG posted:

I would remove rectifier and install a new one with that AC lead bent up and solder to the center pin. 

Thank you for doing some investigative work on TIU antiquities!   The explanation above is great.

So....that bare wire from the center pin should actually be connected (soldered) to the AC lead from the rectifier that is bent out sideways?   That's why it often sparked when plugging-in power from the Z-1000 and was "sort of" resolved with my zip-tie jammed between the wire and the bottom of the rectifier.  I wasn't sure if they were supposed to be connected or if the center pin was connecting to something else under the rectifier.

I just plugged in the Z-1000 and shorted across those two bare copper wires with a small screwdriver and it sparks so I am hesitant to solder together thinking something else is not right.  Maybe the power socket (as you explained above) may be faulty or the rectifier is faulty?     Which brings up another question about your comment to replace the rectifier...just curious about what your reasoning is to replace it.

THANKS!

Kevin Mac

Hey, I think I fixed it (patched it back together for now) by soldering those two bare copper wires together...the one bent out from under the rectifier and the one coming from the center pin on the power socket.   Somehow, someway, I was able to get the tip of my iron down in there and solder them together.  It's not a good looking solder joint but it works.    Testing the TIU now with some remote backup & restore transfers and will connect it to tracks & loco here in a bit to see if it can make a loco go.

I assume over time, the jumper from the center pin socket just broke the original solder joint free after stress from multiple plug/unplug/plug activities.  Before soldering it, I noticed that jumper wire moving side-to-side down by the rectifier when plugging/unplugging the male end of the power cord into the TIU aux power socket so it was definitely stressed over time from repeated movement.

The leg from the rectifier would have been longer and directly soldered to the center pin connection.  No stress on it from plugging a socket in and out.  Somehow it got broke and someone had to solder a jumper into it.  Without that copper jumper, the rectifier never gets power since both Fix 1 black and aux power transformer feed that joint. 

Gotcha...makes sense now regarding replacement.  For now, it is working again and will handle with kid gloves when powering-up at the bench.

Thanks for your help!!!  I thought I was going to have to send this off for repair or drop in the scrap pile. 

Kevin,

        FYI,  the pic you supplied above where you circled the solder joint - the green line just to the right is a "trace"   If you pass too much current through it like from a short or a failed component, it will burn up usually in one spot and leave a black mark on the board.  That is referred as a "blown trace". There are thick traces usually for power that can carry more current and the thin traces are usually for the circuitry data etc, low current stuff. There you go - learn something new every day. So next time someone suggests to look for a blown trace, you know what to look for.

Hey thanks for that explanation Bill.   I wish I knew as much about PCB's, components, ohms, resistance, etc. as the rest of you guys on here.  I'm pretty good with basic wiring and soldering and working on this stuff if I have a schematic and pictures but when it comes to the laws and science of this stuff, I'm out in left field!

Thanks,

Kevin Mac

Design a few PCB's, after a few meltdowns, you'll learn all about trace widths and trace weight!