Hello all,
I also have had problems with the latest Hattons decoders. I recently bought some 6-pins to fit to DJ Models' J94s and have had exactly the same symptoms described by Jaggzuk. The locos run fine(ish) on DC, right down to a crawl, but stop-start-have a rest-start-stop-have a longer rest-etc when the chip is fitted. If the loco manages to get to maybe half speed, then it runs fine, but half speed is of no use if slow speed can't be relied on. To try and identify the problem I have:
* tried different chips
* tried different locos(I have two of the J94s)
* cleaned the track
* played with CV settings by turning BEMF off and on, ditto with momentum settings
all to no effect.
I thought the issue was with the coreless motors, but in the last week I've also had the same problem with an 8-pin in a Heljan Garratt, an 8-pin in a Hornby J15 R3230, and a 6-pin in a Bachmann 31-166 L&Y Class 5 .
I have previously fitted a dozen or so Hattons chips to Hornby & Bachmann locos and all have been quite OK, so this latest batch of issues was unexpected. I emailed Hattons who replied that they had sent some samples to DCC Concepts for testing. That was 2 weeks ago.
I've just ordered some DCC Concepts 6-pins with Stay Alive to see if that eliminates the problem. I suspect I shall soon be returning a number of decoders to Hattons as either faulty or not fit for purpose.