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I'm continuing to work on my "semi-dead" line. Next up: A first generation Z-4000. I've had this transformer since it was issued. The fan is now making that wonderful groaning noise off and on, indicating its about to die. So I'm planning to open the case and replace it. I've found several threads on this Forum for doing this, and I have the tools. So far so good.

Second issue: Both variable post show voltage even when the handles are all the way down. Typically 2.3-2.5v. I checked with an independent meter, and the values are correct, as I see the same numbers at the outputs. I usually knock the voltage back to ~1v by adding a bulb across the terminals. But since I'm opening the case for the fan, is there any adjustment I can make to re-zero the outputs? I seems to recall that there is, but the thread was so long ago I cannot find it.

Any help would be appreciated.

Chris

LVHR

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OK, the fan is replaced. Several things I learned:

There are 6 screws in the bottom of the case that have to be removed. A long T-handle 3 mm Hex key works very well. These are definitely NOT Torx screws.

The fan is actually 60mm square, and 18mm thick.

The fan is wrapped on the edge with open cell foam. Its not worth trying to reuse it, so having some available is wise. Figure 1/4" thick, and ~1x 10".

I used a CPU cooling fan I picked up at my local computer store. The connector is not the same as what MTH uses. I ended up cutting off both connectors and splicing the old connector to the new fan. I insulated the solder joints  with heat shrink tubing.

I tried not to disturb the main transformer, but ended up having to so do anyway. The wire for the fan goes in a channel underneath it, and got tangled up with the other wires. I paid close attention to all the wires so that nothing got pinched in reassembly. Speaking of which, a clawed screw retriever is a very useful tool when reinstalling the screws.

 

To the voltage leak: I put a 18v bulb across each pair of posts for the variable output. With the bulbs in place, the outputs each read 0.5v. I guess as long as it does not climb further, I can live with it. I will keep an eye on it.

G- Do you have a diagram of the main board showing the locations of the pins you mentioned?

GRJ- I'm not up on ordering component parts, at least caps. I'll have to pay you a visit at Henning's sometime for an education.

 

When you had the cover off, on the gears that connect the geared wheel on the lever to the gear on the potentiometer have black marks on them which should align when the handle is in the zero position. If they don't, you will never get a less than 1 volt reading on the screen, and may have problems reversing locos with electronic reverse units. 

lehighline posted:

"They are soldered between pins 2 and 3 of U-1, 2, 5, and 6 on control board."

Does this mean U-1, U-2, U-5, U-6? Between pins 2 and 3 of each?  So I need 4 caps? Just seeking clarification.

 

Chris

LVHR

Yes,  Just those for micro chips get a cap, and the cap is soldered between the legs (2 and 3).  These chips are 8 leg (2x4).  The dimple on the chip is pin 1 and pin 2, 3, 4 on same side.  G

Luke,

 

On mine, the large gears have a black mark on it about midway in the travel. The small gear on the pot has either a black mark or an arrow molded in the plastic. With the handles about mid point, the marks line up. That's the way I found it, and that's the way I left it. I was tempted to purposely misalign them such that the pot would turn down further, but not knowing all the consequences of such a move, thought that might not be a wise idea.

G, Thanks for the information.

Chris

LVHR

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