cdu failure?

[ESAERR]

I've used a circuitron snapper for switch machines for over a year.  Recently it failed.  I've replaced it and the rreplacement also failed.  Why? Bypassing the snapper worked but machines were vulnerable & one under the table did melt.

[BroadwayLion]

LION tried snapper. It too failed. Him replaced it not. Him has no more twin coils, him is 100% Turtle switch machines.

ROAR

[ESAERR]

thanks lion. Would rather not go to the turtle just now (very difficult but still possible). The snapper did work for an extended time and the replacement failed out of the box. If I knew why the failure, I could address the problem better, else just about starting from scratch.

[mlehman]

First thing I'd check was what's the instructions say about the max number of machines operated? May not be an issue, but worth verifying if you don't recall.

How is the Snapper failing? If it's the caps melting down, these are usually easy to replace. I've never needed a CDU, but that seems like a common failure point with other electronics and it would seem to be a potential issue for a CDU.

[ESAERR]

I'm assuming it's the Snapper that failed since I bypassed it & connect the switch machine directly to the AC (all Atlas coils). They then worked but would now be vulnerable to 'cooking'. Nothing looks out of place w/ the snapper(s) but it seemed like the juice did not go through and on to the turnouts' circuit.

[Alantrains]

The Electrolytic capacitors in CDUs can dry up and not provide the burst of current needed to throw the solenoids in twin coil switch machines. If the new one you bought was old stock, the Caps may have dried up a bit and a few discharges finished them off. New capacitors from a source that rotates their stock is the best fix I can think of. Try connecting up an automobile tail light instead of a turnout motor and see how bright a flash you get.

[ESAERR]

Sorry, dropped the thread. Again, thanks Alan & I will try the test you suggested ASAP. I would like to keep as many of the coils as possible in undecorated sections and move to 'turtle' machines under the table (will lose sleep over doing that). Are you familiar w/ BLOCKsignaling products & might it produce a better CDU?

[richg1998]

What filled on the CDU? The full wave bridge, series resistor or the caps?

I made one for a local club some years ago using those components and has yet to fail.

Troubleshoot the device. Very easy. I seriously doubt the cab would fail.

Edit.

Ok, not so easy. I see Circuitron uses an SCR. I would look at the part number and try to order a more robust version and also contact Circuitron. They are in the USA the last I knew and must be aware of this issue.

You should be able to troubleshoot this device with a multimeter.

I have replaced SCR's in the past in different equipment.

Circuitron link.

http://www.circuitron.com/index.htm

Rich

[ESAERR]

Not totally sure if the CDU failed. Just know when I did a bypass 'juice' was transferred. I will run another test at the earliest. Alan from Queensland suggested Snappers can fail even out of the box. On my unit(s) all looks ok visually w/ resistors intact. They have a printed circuit on a base. I've heard good about building your own but I'm a newbie to electronics (not a newbie to this earth - 69 yrs.) I've found another manufacture (BLOCKsignaling) that may have a better product. I want to keep as many coil machines as I can. I know the 'turtle' machines are better but it will be very hard to convert. Thanks for your help. Bob