PS-3 Upgrade Kit

PV - Positive Voltage

It's the 5V line, and it has power all the time.  The PCB ground comes over on the tether, pin 3. 

Thanks.

Off the top of your head, do you know what voltage is applied to the bulbs on a PS2 upgrade board, and on a 5-volt PS2 board?

The positive voltage is not the 5V line, it is actually Filtered DC converted from the AC input an runs around 22 to 24V.  The 5V line is the gray wire which runs tach reader and smoke fan.

One of the motor wires always is hot PV via the relay.  The return to ground is controlled by the motor FET.  That is why an engine with a motor lead shorted to chassis ground may start moving on it's own.  The DC voltage is present, and the other line if grounded to chassis will allow current to flow through the motor.

Normally PV is generated directly from the Bridge rectifier at the board.  But to get around wire limitations, the PV can be tapped off the motor leads.  One diode allows current to flow to the Purple wire when Yellow motor lead is hot, and the other when the white is hot.   G

Oops, you're correct, what was I thinking?

The way it's used for the lights and smoke is a PWM signal to ground to generate an effective power of 5-6 volts across the smoke resistor and the lights.

This is getting deep.  I'll have to open an upgrade kit (haven't done one in several years) and digest all this.

PWM?

GRJ, you're saying that lights in 3- and 5-volt PS2 installations run at 5-6 volts?

The lights are 6V bulbs, and the lights are controlled using a PWM signal to common to provide the proper power, about a 25% duty cycle.  When those FET's short, they usually take out the lights as they get the full voltage.

Gunrunnerjohn:

Is it possible to have a circuit breaker for boards?  Could MTH design a break into the boards in the future?

Anything's possible.

I'm looking into using PTC fuses for protection of boards.  Initial experiments have gone pretty well, but I have to get more mileage on the test locomotives.

Is the hazard to boards overcurrent, or the surge resulting from a spark?  I suspect the former is rare, since it requires a short in or downstream from the board, whereas the latter occurs frequently.  A breaker doesn't protect from the latter.

A voltage spike caused by a derailment could cause damage.  The audio amp seems pretty susceptible to this kind of damage.  Overcurrent is circuit related. Motors get power directly via the 8amp rectifier.  Lights, heaters and such get power via traces in the board.

The main culprit here is a pinched wire that overloads a small fet, or worse a pinch on the DC ground wire or the Gray DC 5V which puts the chassis AC signal directly onto the circuit of the microchips.  When that happens normally the Power Supply and Processor board get damaged.  Processor less likely a repair because of the number of chips and the main processor.  The Power Supply is normally repairable from that.  G

I had one of my beta ERR Cruise Commander Lite boards take out the FET drivers, a meltdown in a few seconds when the Interburban unit apparently got hung up on a switch.  When I asked ERR what could have happened, apparently a shorted or stalled motor can cause excessive current and take out the FET's pretty quickly.  I also had a PS/2 board smoke when a diesel threw a traction tire out of sight in a tunnel and jammed the works.  By the time I figured out it wasn't moving, it had taken the drivers out as well.

I'm experimenting with several values of PTC devices both in the motor leads and in the power pickup.  One thing I'm interested in is if they affect normal operation in any way.  I want to see how they react to long running times and grades with loads before I settle on a value.  Also, it'll obviously be dependent on the type of locomotive and what it's loading might be.

My RX for spikes due to derailments is still the TVS across the track pickups.

Would it be smarter to wait for PS3 upgrade or to continue to purchase PS2 upgrade.

That is debatable.  The ps3 will cost more, but no battery to bother with.  On the other hand, smaller batteries than what mth provides can be used.  I bought 3 ps2 kits to use when 5 volt boards fail.

I'm buying up some more PS/2 kits.  The battery doesn't bother me.

• PS/3 kits will almost surely cost more.
• PS/3 boards that fail are seldom field repairable, similar to the old 5V PS/2 boards.
• It appears that the PS/3 kit won't be that much smaller than the 3V PS/2 board set.

I'm sure you probably will, but I hope you post your findings when you finish your experiments. I would be very interested on your findings as I'm sure others would too. All your efforts put into these things are also really appreciated, at least by me anyway. I know very little about electronics, but learn a little every day around here.

While PS3 boards have a higher MSRP than do PS2 boards (at least right now), the PS3 kit price should be offset a bit by the non-inclusion of a battery, charging back and battery harness.

GRJ, in your opinion, would a stalled motor(s) take out any components of a PS2 (3-volt) board?

Can you say again what TVS's you use, and the source?

Well, it took out the 5V drivers, so I can only assume that it's likely to do the same on the 3V board.

1.5KE36CA at Digikey

 That remains to be seen, right?

Missabe, regarding your question about whether to wait, you may wish to review another ongoing thread regarding PS3 locos locking into a direction.  As I've said before, my 3-volt PS2 locos are rock solid.

I think the board would shutdown before that motor fet would go.  A spike might get it, I think I have seen one bad Motor FET on a PS-2 3V of the hundreds make that a couple hundred boards I have tested or worked on.  That motor fet is rated at around 40+ amps I believe.  Trying to protect a circuit board from internal over current seems a little interesting to me.

I rarely even see heater FETs go bad.  G

I'd like for the board to shutdown, but since the 5V board cooked the driver, and the Cruise Commander Lite did as well, I'm giving the issue some thought.

GRJ & GGG, do you have any idea of the ampacitry of the HO board motor circuit?

Not really, but I'm guessing a lot less than the O-gauge boards.  

5V are a whole different beast being so old and built closer to operating specs.  Lionel stuff has also had the motor Triac, and FET built a closer to operating specs.  MTH is using a relay to switch polarity and PWM on the return.

I guess if you think it is necessary I would try it with a slave unit.  Those motor FETs can fail, though it might have more to do with both fets being active at the same time.   G

I think it is/was mentioned at school.  I believe it around 1 amp.  The boiler board carries the motor for steam and that is very small.  G

It might have been mentioned, some of the HO stuff was lost on me as I don't really get any HO repairs as a rule.

The beauty of using a PTC is it shouldn't affect anything if it's not pushed beyond it's specifications, it's just pretty invisible.  If a motor is drawing more than 2-3 amps in the typical locomotive, something is usually seriously wrong.  Even on grades with a large consist, I don't get that kind of power draw.

Reason I asked is that you surprised me by saying the O-gauge board FETs could handle 40 amps.  If that's correct, why can't the PS2 board handle 4 motors?

Unless it trips? This sounds like it could end up like my grandson figuring out how to use the Legacy 'Brake' slider a few days before I did and then using it to park the train.  Kids these days are quick!

The rectifier is an 8 amp rectifier.  There is a difference between continuous current verses instantaneous.  You also have the voltage drop across the motor leads in the tethers which results in a lower voltage at the trail motors, so you are now dragging a powered unit vice having it contribute.

I don't think the limiting component is the FET, rather other operating characteristics and component issues.  Believe even K-Line used an additional DCDR in the trail A slaved to the lead DCDR and R2LC.  G

The rectifier is said to be the limiting factor, which is why I was a bit surprised when the drivers went in two different cases.  Jon Z. said that for the Cruise Commander Lite that the diodes would limit the power before the output FETs, and I respect his opinion since he's responsible for the design.

 The PTC is self-resetting when you remove the overload.

They have started shipping the 5V replacement boards, it's a PS/3 board with a piggyback board that adapts the outputs to be compatible with the incandescent bulbs of the PS/2 locomotives.  That's what I get now when I replace 5V ps/2 boards that have died.

So, it seems that other than the making up of the kit, they could be shipping these.

GRJ,

Is that a PS-3 boards that your installing on the DM&IR Doodlebug.

I installed one in my UP DC3 Track Inspection Car, I have another one for a repair as soon as I get to it.

I just got the PS/2 boards I ordered for other repairs.  The PS/3 are only for replacing 5V boards as they have the 5V board connector shells.

Has anyone actually done any 'audio testing of the PS3 to see if they produce a fuller better sound?

In the ones I have, some sound better and some not so much. I have heard that not all of the sound files have been fully upgraded? None of mine are upgrades, all my PS3 engines were purchased new starting about the time PS3 came out. I have noticed that the newest ones do seem to sound better. I have an SD45 and an RS3 that sounds really good to me. Still think I have to rate Lionel a little better in sound quality though. Barry, GRJ, Marty F, GGG or others may know for sure on what is upgraded and what is not?

The only PS3 engine we have is the recent Texas Special F3 which sounds really nice. It is considerably louder than several Legacy diesels we have...

I posted the question of when the PS-3 upgrade kits would be available to the MTH website and received the following response...

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Thank you for contacting MTH Electric Trains. We appreciate your interest in our products. We hope to release the ProtoSound 3 upgrade kits in the summer of 2015.  Additional information will be on the MTH website as it become available.  Please let me know if you have any questions or if there is anything else I can help you with.

Thank you,

Kirstin Martinez

MTH Electric Trains

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Hopefully, this will finally happen.  I have a couple of old engines that I like and want to upgrade.

PS2 upgrade kits would work fine, and are cheaper than the projected price for the PS/3 kits.  Why wait?