Brass GHB L1 tender circuit- need help understanding it

[peteski]

Well if you are interested, I think that I have an brand new ( still in it original bag) a TSU 750 Soundtraxx decoder that used a cam for chuff.
Don't think that I WILL EVER USE IT?

No thanks, I'm more into ZIMO, QSI, and ESU decoders. But current most sound decoders (or the ones I have) still have a cam input lead, so that should not be a big deal.

[Lemosteam]

@peteski what is used to sense the position of the cam for that decoder, is it a wire that makes contact at a high point?

[peteski]

@peteski what is used to sense the position of the cam for that decoder, is it a wire that makes contact at a high point?

I don't know yet.
I haven't taken the model fully apart yet. Too many other active projects. But just a quick external inspection told me how poorly-made that model was!  I also followed some thread about fixing it (probably yours) which reaffirmed my evaluation.  That cam might have been one of those half-baked ideas they had while designing the model. For all I know there might not be anything contacting the cam - I'll have to add some sort of wire whisker to contact the cam.

[woodone]

yep, you are gong to have to install a wiper to operate on the cam. Only the Cam is there on the rear driver.

[peteski]

yep, you are gong to have to install a wiper to operate on the cam. Only the Cam is there on the rear driver.

I know - it is visible through the opening in the bottom gear cover. Does that create a problem?  I'm thinking of installing a small piece of thin PB wire held on some insulator (like a piece of a PC Board.

[woodone]

Yes that will work. Make sure that you make some provision so you can move your PCB forward or aft so you will have some type of adjustment.
Hard to bend the PB wire to adjust. Moving the PCB is a bunch easier. This is so you can get the chuffs in sync with the driver location.
Better use some small PB wire- or you will get a  point bounce and a double chuff.

[peteski]

Yes that will work. Make sure that you make some provision so you can move your PCB forward or aft so you will have some type of adjustment.
Hard to bend the PB wire to adjust. Moving the PCB is a bunch easier. This is so you can get the chuffs in sync with the driver location.
Better use some small PB wire- or you will get a  point bounce and a double chuff.

That's the plan. I'm sure there will be some fine-tuning needed. Fun stuff!

[Altoona]

Any luck in in getting the tender trucks to roll freely. Have flat spots on a wheel set.

Judd Barton

[Lemosteam]

@Altoona , @cbroughton67 told me he replaced the trucks with Kato or Bachmann and rewired them. I am going to use my scale Kiesel trucks with my home grown electrical contacts to do the same.  I also have Keisel trucks available with shorter axle centers for the Bachmann tender trucks as a truck frame swap.

[cbroughton67]

@Altoona , @cbroughton67 told me he replaced the trucks with Kato or Bachmann and rewired them. I am going to use my scale Kiesel trucks with my home grown electrical contacts to do the same.  I also have Keisel trucks available with shorter axle centers for the Bachmann tender trucks as a truck frame swap.

The pickups on the tender trucks was PB wire contacting the (IIRC) the wheel treads. The wire was stiff and flexed very little, so it either made good contact and kept the wheels from rolling, or it didn't make good contact at all. So, I decided to compromise ascetics for performance and used Bachmann tender trucks (this was pre-K4) as replacements. Now that @Lemosteam has Keisel trucks available, I may have to get motivated and replace the Bachmann trucks.


Chris

[woodone]

I removed the .015 wire and replaced with .010 phosphor bronze wire. Tweeted abit and got good contact and still have the wheels to turn freely.

[Lemosteam]

I removed the .015 wire and replaced with .010 phosphor bronze wire. Tweeted abit and got good contact and still have the wheels to turn freely.

Understood, but wipers do not compare to needlepoint contact in reliability, particularly in this case as the wiper contact the wheel diameter which will collect dirt over time and deposit it onto the wiper wire.

Not trying to argue, but that is why Chris chose his method.

[woodone]

I went this way because I don’t have any Bachman trucks. If I just used the truck to power up the frame I would loose the 8 wheel pick up.

[mmagliaro]

Okay, I'll jump in here.

Actually, whatever that wire was on the GHB tender trucks, it wasn't phosphor bronze.  So it would easily deform or break off, and it had no springiness whatsoever, so it was horrible as a wheel contact.

I replaced it with .008" phosphor bronze, because, like others here, I wanted to preserve both the look of the PRR trucks *and* the all-wheel pickup.  Yes, the wires can collect dirt and are not as robust as axle-point pickup, but by and large, riding on top of the treads, they do a very good job (until they get dirty).
In the first picture below, my replacement wire is at the top of the truck and the original is at the bottom.

Here are a few pictures of some of my fix-up on one of these turkeys.  Like many of you, I replaced ALL the harness wires and all the wiring going down to the trucks from inside.  If you don't do this, you are just beating your head against a wall.  One or more will break off - not "sooner or later", but SOONER.  The wire is horrible.

[nstars]

I was lucky with my L1,Hans reengineered the tender truck completely. They are now free rolling and picking up power.  It now runs beautiful. The second L1will be done shortly.

Marc