Z-4000 Repair

Without a load, the outputs probably show a leakage that is not something that can be eliminated. And when there is a load, the outputs are zero-ish?

I wouldn't spend any time trying to "fix" stray voltage indications with no load on any variable transformer.  If it functions properly with a light load, it's working properly.

First generation Z-4000 were susceptible to voltage leak and there is a modification that can be done to the board using .001uF SMD caps.  They are soldered between pins 2 and 3 of U-1, 2, 5, and 6 on control board.   G

hi George, where do you buy the .001 UF  SMD cap and do you get them from Digi key   MTH or mouser electronics '? What is the working voltage for the Cap?

Thanks

Alan

Yep, probably a 603 size would be appropriate to fit there.  I'm sure 50V or more would be fine as a voltage rating.

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.

Here you go, .001 100V 0603 chip capacitor.  They're 12 cents each, less in quantity.  Digikey has very reasonable shipping for small orders.

Thanks John , hope you had a great Christmas, and have a very happy new year!

ALAN

"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

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

Here is a shot of the Z4K control board. Where are the chips located?

Chris

LVHR

on the back side underneath the large heat sink for all the fet's for controlling the transformer voltage and current ! there is not an easy way to work on and if your not sure what you are doing you should leave a repair to the experts.!

Alan

P.s. what is your problem with the transformer?