ESU 58741 Kato FEF Jumpy Slow Speed Behavior

[EL3632]

Installed two different decoders into this FEF-3, neither one wants to give any good slow-speed performance, making the loco act all jumpy on speed step 1-5. I have previously installed decoders in two other FEFs and neither exhibited this issue. Was curious if the collective had any ideas for this jumpiness, why it exists, what it is caused by, and how to fix it:

[RBrodzinsky]

It is acting as if something is binding the motor or drivers.  What is weird is the chuffs following the wonky behavior

[peteski]

Chuffs simply track motor RPMs (BEMF), so I don't think it is all that wonky.  Similar to what I observed couple of years ago after installing a V4 decoder in friends FEF-3 Unlikely a mechanical problem, since ESU decoders have a problem controlling the Kato cordless motor in this loco (and auto-tune does not fix that - makes it worse).  There is another recent thread showing CV values to make this loco run better.

Actually it was Rick.
https://www.therailwire.net/forum/index.php?topic=52261.msg731728#msg731728

[jdcolombo]

Yes, almost certainly a motor control issue.  I tried both an ESU and a Zimo decoder in my FEF; I ended up using the Zimo, because it provided somewhat better slow-speed performance than the ESU.  The ESU was close, but it required about two hours of trial and error adjustment of CV's 51, 52, 54, 55, and 116-119.  Rick has fortunately already done a lot of this for you - start with his settings, and then if you are still not satisfied, do some minor tweaking, particularly on the slow-speed CVs (51, 52, 116 and 118).

Note that CV53 is the voltage reference CV.  Don't play with this one, at least not at first.  What it does is adjust the voltage "spread" between SS0 and SS128, and should be used if you find that your engine reaches max speed before the throttle is turned all the way up, or doesn't reach max speed even with the throttle turned all the way up.  In general, CV53 should be set to 10x the DCC track voltage (e.g., if your track voltage is 13v, set CV53 to 130).  That's usually the only adjustment you'll need for this one.

John C.

[Cajonpassfan]

Calling @RBrodzinsky . Rick set mine up with the ESU and it is a sweet, smooth runner.
Otto K.

[RBrodzinsky]

@EL3632 responded in the earlier thread immediately following my postings of the settings used to smooth out then low speed jumps, so I assume they’ve tried them in this unit.