I love the looks of the new Mallet, however, I am a Digitrax user, so need to know, will the DG583AR I bought for my Kays work in the NMRA socket in the Mallet.
I notice in the pictures that the same circuit board used in the Kay are also used in the Mallet. Has there been any improvement to the filter circuit to reduce inrush and prevent it from creating booster shutdowns.
I have wanted an afordable Mallet for years. Three of them would be a great addition to my railroad.
Dear Bob,
Glad you like it.
I'd address the decoder question to Digitrax directly.
Thanks!
the Bach-man
Quote from: the Bach-man on September 15, 2008, 11:12:17 PM
Dear Bob,
Glad you like it.
I'd address the decoder question to Digitrax directly.
Thanks!
the Bach-man
I do not have a question about the decoder, so there is nothing for me too ask Digitrax.
My question is about the Mallet.
Has the inrush and high current spiking problem in the Kay circuit been fixed or not in the Mallet.
Any modern decoder that is capable of delivering track voltage to the Kay without a lot of loss will have Schottky Diodes in the bridge rectifier. Any such decoder can not be used in the Kay because there are two 470 micro-farad capacitors three voltage regulators and 7 current regulators connected directly to the decoder's bridge rectifier output.
These components cause current spikes at every DCC signal transition through zero volts.
Any decoder that uses Schottky diodes have a very low forward resistance. These are used to reduce heat in the decoder and provide better control of the loco. They can deliver much higher current to the loco. However, the Kay design violates a simple rule, It does not limit inrush. Capacitors should never be connected directly to a decoder output. Schottky diodes will deliver enough current to instantly shut down most brands of boosters. Regular diodes, because of their higher internal forward resistance still SPIKE the booster but not enough to shut down the boosters. BUT THEY STILL SPIKE the booster if there are capacitors connected directly to the decoder. The spikes from multiple locos will combine. THIS SEVERELY LIMITS THE NUMBER OF LOCOS THAT CAN BE RUN ON A SINGLE BOOSTER TO WAY FEWER THAN WHAT THE BOOSTER SHOULD HANDLE.
On my Kay, I had to rewire the to capacitors into a twin "T" filter. This involved simply adding three resistors or chokes, one before the first capacitor, one between the two capacitors and one after the second capacitor. Going to a Twin "T" filter circuit also reduces the size of the capacitors needed, two 200 micro-farad capacitors will allow reduce the problems at power on.
This would have been a simple modification except that the first capacitor is in the tender and the second capacitor is in the boiler. I had hoped that I would not be required to open the boiler on the Kay to install a decoder.
If that problem has been fixed, then I can use any modern high current decoder, can run multiple Kays and Mallets without false booster shutdowns, and program them on any system without the need for special "programming boosters".
So, I will restate the question.
Has the circuit in the Mallet been changed from what the Kay had? Specifically, to reduce the inrush current so that high power, low impedance PNP decoders can be used and multiple locos with any decoder can be run without false shutdowns.? Yes or no.
Oh boy.......here we go again.....more questions that will probably not be answered....... :-\
And what " good reason" might that be??
chuck
Quote from: chuckger on September 16, 2008, 01:03:12 PM
And what " good reason" might that be??
Well, just take a look at the K-27 post that had many questions unanswered.......oh wait......that was deleted :-\
Look Guys. I don't want to start nothin.
I runing low on decoders.
I'm just trying to put together an order for enough decoders to get a discount.
If the board has been changed I'll order 3 with the plug and 7 with the screw terminals.
If the board has not been changed I'll order 10 with the screw terminals.
Dear Bob,
Sorry I misunderstood the question. I am trying to find out a specific answer for you.
Thanks!
the Bach-man