TIU output only 50% on Fixed 1

If this is one of the early TIU Rev. G models, that may be last rites for that channel.  They have a trace that burns up with over current.  Turn the TIU over, is there no version sticker?

Weird you only get 8 out.  IS this stand alone not attached to the track?  Maybe a contact in the relay has burned up adding resistance.  G

John, the version is H2.

GGG, ok I have removed all wires from it except the ones going into fixed1.  I took the cover off, at the terminals inside on the input I get 18volts.  On the output terminals I now get under 1 volts.  Still hooked up to the aux power.  Visually the fuses all look fine.

when I moved the wires to fixed 2, got 18 on both input and output.

Do i just have a 3 chanel TIU?  Going to the Midwest train show this weekend, so might have to pick a new one up.

I would check the output of the tiu with no power applied and use a vom meter and check for continuity maybe one of the tvs diodes has almost shorted or very low resistance which would load the output? if you see low resistance its probably a tvs diode bad or almost shorted!

let us All know what you find out ok!

Alan, I would say if the TVS was a load like that you would see high amps too.

One other thing to look at, do the Fix1 output terminals look melted.  Are the leads corroded? If the wires are soldered on to the terminals, is one cracked?  If screwed on, and partially melted, you may have plastic between the terminal and wire ring.  If your actually measuring at the red wire leads inside the terminal, then look for the burned trace John mentioned.  May be under the TIU.  G

GGG -

When I opend it up, it looked brand new.  I can post a picture later.  Even though it is probably 13 years old, it was in the box for probably 10+ years.  I did not lift the board to look under it, is it easy to lift up?  

Easy it a relative term.  you have to loosen all the banana jacks in order to pick the board up.  If the trace cooked, you'll see a dark line under the surface of the PCB.  That's curtains for that channel, at least I know of no way of fixing it.  Apparently, you can't simply bypass it like most circuit board flaws, don't know why for sure.

OK, came apart pretty easy.  

Picture 1 - Output plugs for fixed 1 - They look fine to me.

Picture 2 - Underside of fixed 1 output, looks ok to me.

Picture 3 - Underside of fixed 1 input, looks ok to me.

Picture 4 & 5 - Underside of middle of board, not sure if this is a problem.  You can also see this is picture 1 for reference on where it is.

Not sure if any of this helps anyone with more knowledge of this.  

Seems like no one has the TIUs in stock.  

Thanks

Tony

That is not fixed 1.  Fixed 1 and 2 are the middle two outputs.  VAR1 and 2 are the outer two outputs and the can be adjusted to any output desired via the remote.  To control them, TIU must have power via F1 or Aux power. G

Sounds more like the output FETs to me given that it's a variable channel.  You never did tell us what rev this was.

John,

 He did say version H2 above. Time for new reading glasses....

Chris

LVHR

I missed that Chris.   And yes, probably past time for new glasses.

Ok, I should have said output 1, not fixed 1.  I have the two variavble set to fixed on both of my TIUs and both TIUs are powered by aux power.  

So it's the VARIABLE 1 channel (set to fixed mode) that is putting out 50%.  There's a good chance it's one or more of the so-called FETs that is blown.  There are 4 FETs circled below in yellow associated with VAR1.  And it even appears one of them was already replaced.

These are 10 cent devices if you are willing to do eBay and wait for parts from Asia - otherwise $1-2 each if purchased in US - see this thread:

https://ogrforum.com/...13#81678117883279013

This might not be your only problem.  One of the MTH techs who posted above could surely repair this.  Not sure how the $ numbers for a repair would work out vs. just buying a new up-to-date unit.  OTOH, if the alternative is to only have a 3-channel TIU, I suppose it might be worth rolling the dice and replacing the FETs yourself on a rainy afternoon.

I bought this new from my LHS, so nothing was replaced by me since I owned it, 12+ years, unless it was done by my LHS which I would doubt, but who knows.    

I can solder wires, but I have never tried to solder to a board.  I am guessing all 4 would need to be swaped out.

I can get a new one from a LHS for $189 all in, when they get them in late February or early March, so I was probably going to do that anyway, move up to a new one, but if the one I have could be repaird and keep it for a spare, or if I need a third TIU, that might be an optinon if it was not crazy in price.

Well, shipping is probably the biggest expense, the actual repair involving swapping the four FET devices isn't that expensive.  I'd certainly consider it if it were mine.  Of course, if it were mine, I'd just swap them myself.

I am guessing these would be fine.  If so, I will give it a try, can’t make it worse.  Anything special with the soldering?  I have a larger iron but also a smaller one, a pencil type one, I think they are called.

thanks all

https://www.amazon.com/IRFZ44N...1271088375&psc=1

Well, for PCB work, you want the small iron, that's for sure!  Truthfully, what you really want for PCB work is a temperature controlled iron.  Remember, too much heat will kill the PCB, then you're really done.

My technique for these would be to nip the leads right at the part, leaving a bit of component lead projecting from the PCB.  Then I clip my forceps on the lead and let it hang down and heat the other side.  The lead drops out, then I can clear the holes for the new part.  Trying to unsolder a whole part is harder, and you risk having too much heat for too long on the PCB.  Obviously having the right tools for the job is important when you're working on PCB stuff.

 I can fix this for you.  Not all 4 are required.  It can be isolated to a pair.   E-mail in profile.  G