Loksound 3.5 Micro Keep Alive

[Chinapig]

Has anyone managed to attach a keep alive to the Locksound 3.5 Micro sound decoder?  I've searched the web and can't find any mention of it.  If anyone has any idea of where to solder the wires I'd be grateful to hear from them.

[peteski]

I have not, but I think I still have one of those older decoders.  It should be feasible once we figure out where to connect it.  If nobody else has the info, I'll see if I can poke around the decoder to let you know where to connect it.

[tehachapifan]

What model decoders were 3.5? Was the much missed 73800 board a 3.5?

[reinhardtjh]

What model decoders were 3.5? Was the much missed 73800 board a 3.5?

No, the 73800 was a Select Micro which was a version of the V4.  The V3.5 was earlier than that.

https://www.esu.eu/en/products/former-products/loksound-v35/

[peteski]

No, the 73800 was a Select Micro which was a version of the V4.  The V3.5 was earlier than that.

https://www.esu.eu/en/products/former-products/loksound-v35/

The one I have is actually the micro version: https://www.esu.eu/en/products/former-products/loksound-micro-v35/
I just dug it out of the stash.  Amazing how large the electronic components on it look compared to what is used today!

[Chinapig]

Yes, that's the one, Peteski.  I've currently got it a BLI E6 but I originally picked it up second-hand in an Athearn Big Boy I picked up.  The BLI has awful pick-ups and is giving me trouble because of it.  It would be great to fix it, otherwise, I may have to move the decoder on.

[peteski]

Yes, that's the one, Peteski.  I've currently got it a BLI E6 but I originally picked it up second-hand in an Athearn Big Boy I picked up.  The BLI has awful pick-ups and is giving me trouble because of it.  It would be great to fix it, otherwise, I may have to move the decoder on.

Ok, I should be able  to figure it out in the next few days.  Also, some BLI models are famous for bad pickup, and while installing caps will somewhat mask the problem, it would  be the best if you also worked on improving the pickup.  I believe there are multiple threads about the problem and fixes for it.  The pickup can be improved.  I'm mainly taking about the E6 because I didn't think Big Boys had any serious pickup problems.  Mine seems to be ok.  Since you picked them up second hand, did you clean the wheels *REALLY* well?  There could be ther contact points needing cleaning too.,

[Chinapig]

Hi Peteski, I was feeling brave this afternoon and thought I'd see if I could work it out myself.  I wouldn't say I have the confidence to go ahead and install the stay-alive without any feedback, though.  So here goes...

In the photo of the decoder, I think the four components nearest the wires are the diodes making up the bridge rectifier.  Each has the number 26 stamped on it and one sloping end.  The middle two are placed so the slopes are furthest away from the wires and the outer two have the slopes nearest the wires.

The photo of the wiring diagram shows what I have deduced after testing the connections.  Where I have written Red, Black and Blue I have tested this with a multimeter.

I guess that I just wire the stay-alive to the blue and negative outputs of the bridge rectifier.

What do you think?

[Chinapig]

Oh yes, the wheels have had lots and lots of attention to make sure they are clean.  This is the last resort before I rip the decoder out and replace it with one with stay-alive outputs which are easily soldered to.

[peteski]

You figured it out correctly Ted.  Here is a diagram I created which confirms your findings.

[Chinapig]

Ok, I've managed to solder the wires to the decoder and the good news is that the decoder is still working as it did before.  The bad news is that the homemade keep-alive doesn't seem to have any effect.

I've tested my keep-alive on another loco and it works. Holding a multimeter between the +ve and -ve sides of the KA when the loco's running shows a voltage in the caps of about 13v.  I tip the loco so that one side of the loco's wheels is off the track and the voltage immediately drops to about 5v and the loco stayed running for about one-half of a second.  Doing this with the LS 3.5 Micro loco shows a voltage of about 13v when running which doesn't drop when the loco is tipped - it appears as if the caps aren't discharging but it's the very same KA I used in the first experiment.

What does it mean?

[peteski]

Is that a home-made keep-alive unit?  If yes, can you post its schematic?

[Chinapig]

Hi Peteski, It's one I've used lots of times.

[peteski]

Hi Peteski, It's one I've used lots of times.

That looks correct.  The only thing I can think of (of this decoder uses it) is CV11.  Some DCC manufactures use it, while others do not.
https://dccwiki.com/Packet_Time-Out_Value

See if you can read/write (on programminig track) CV11 and if it retains its value.  If it is readable, what was its original value?
Try setting it to zero, and see if the KA does its job.

[Chinapig]

The CV listing obtained in the Lokprogrammer has no mention of CV11.  Reading it using a Sprog gives a value of zero, so I reckon it doesn't exist.

This is a strange one as but I feel lucky enough to have gotten this far without blowing it up

I may very well leave it at this or try to obtain better pick-up using your previous suggestions.

Thanks for your help