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Problem 'Rx65b' Receiver In O-Scale Loco
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 Posted: Sun Nov 22nd, 2020 12:13 am
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Bob D
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Starting to experience a problem with one of my BPRC engines.

I have an O-scale Williams/Samhongsa brass 4-6-2, this has a Rx65b installed.
I’m using a 2000mAh, 9.6v Ni-Mh battery.
Up until now it’s been running fine.


The other day I was running it and it suddenly stopped,
the RCS Australia Tx-3 throttle was set at 65%.

I turned the throttle down, waited maybe 30 seconds, and turned the throttle back up.
The engine ran again but stopped after about 1 minute. I can repeat this over and over.

I removed the boiler shell, disconnected the tender (Rx and battery),
and connected a 12v power supply directly to the motor and it ran fine, no stoppage.

I reconnected the battery and Rx, turned on the Rx and Tx and throttled up to 50% power. 
Ran for a couple of minutes before it quit again.


What I did notice was the LED on the Rx is blinking.
I didn’t notice a pattern, but there could be one.

I thought the only time the LED blinked was when receiving a signal from the Tx,
but the Tx was not being manipulated?

I tested the Tx with another (identical) brass 4-6-2,
and the Tx (and the other engine) worked fine.


I’m thinking it’s the Rx but not sure how to test to see what’s failing or being overloaded.
I swapped out the motor with a spare and still had the same issue.

Both motors maybe be pulling too much amperage,
the other engine has the same motor in it.

If the connector plugs are the same on both engines, I can swap the tenders,
which should eliminate or confirm a motor problem.




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BobD
O-SCALE BPRC
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 Posted: Sun Nov 22nd, 2020 01:22 am
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Rod Hutchinson
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As a side,

check the battery in the Transmitter.







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Rod Hutchinson
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 Posted: Sun Nov 22nd, 2020 07:06 am
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davecttr
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I had a similar problem some time ago,
it was due to voltage sag in the battery.


Under load battery voltage can drop and trigger the Low Voltage Cut-off (LVC),
with the LED flashing sequence you describe.

Switching off allows the battery to recover some voltage,
so on switch on, it will work until the LVC triggers again.


The Rx automatically selects LVC level depending on the battery voltage at switch on,
however this only applies properly to Li-Pos.

For other battery types you should program the appropriate value,
depending on the discharge characteristics of the battery type.



Yes Rod, check the Tx battery as well,
I have been caught by that a few times!



Just found this online, your Ni-Mh battery is 8 cells?

These don't discharge at the same rate,
so there might be some rogue cells in there.

They spend most of the discharge cycle at 1.2V
 
If the LVC is set to Li-Po voltages,
the 9.6V Ni-Mh pack will trigger LVC at 9V, with a 2% tolerance.




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 Posted: Sun Nov 22nd, 2020 08:04 am
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fallen
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As Dave says,
the LED blink can be an indication of low RX battery, as well as loss of TX signal.

The LED will blink on loss of TX signal, even when you are not moving the TX knobs,
as the link should be active all the time.

So, worth checking the TX battery as well.


If the RX loses the TX signal it may stop after a period of time,
depending on how it is set up.

You can program it either to stop on loss of signal (default),
or carry on at the same speed (useful if you have tunnels).

Frank


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 Posted: Sun Nov 22nd, 2020 09:51 am
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Bob D
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Thanks guys!

The battery is probably 4 years old, maybe older,
and I have not checked it yet.


Usually, when one of these batteries gets low, the engine will stop,
and if I throttle back and then up again, it will only run for a short distance.

This is letting the engine run a bit longer, but it could still be the battery,
even though it's not acting like it normally does under that condition.

I'll report back soon.




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BobD
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 Posted: Sun Nov 22nd, 2020 02:07 pm
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Bob D
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:moose:  What a newbie mistake.  :Crazy:  :doh:

Took over 2-1/2 hours to charge the battery, but that fixed the problem. 
Normally takes 2 hours max. 

Engine's running fine now.


It wasn't behaving like they normally do when the battery gets low,
but now that I've seen it, that will be the first thing I do. 

Last time I charged it was back in July and haven't run it much since then,
so maybe it's time I got a new battery.


At least opening the boiler and tender gave me an opportunity to tidy up the wiring.  :bg:




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BobD
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 Posted: Mon Nov 23rd, 2020 12:12 am
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Rod Hutchinson
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Not to worry Bob. 

My Deltang expertise has been preceded by a litany of mistakes and learning along the way. 

The Deltang system is quite complex.






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 Posted: Mon Nov 23rd, 2020 06:52 am
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davecttr
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Good news

And apparently that Ni-Mh battery has a faster self discharge rate than Li-Pos.


I have some cylindrical Li-Pos I bought several years ago and never used.
I tested one a couple of months ago and it still gave over 3.7 volts on the meter.

Thinks, they don't have any wiring,
maybe I could ask someone like Micron to add the connectors?


Deltang system, complex and adaptable.
It will be interesting to see what the replacements for the Rx6x offer.




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Dave
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 Posted: Mon Nov 23rd, 2020 10:20 am
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Bob D
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I have 20 or so engines converted to BPRC, most have 9.6v Ni-Mh batteries in them.

I have charged them and left them alone for 6 months or more before running them, and they usually run fine,
but now this one seems to be not holding the charge as long.

I have a log book where I keep the dates of recharge,
so maybe I can see a pattern developing.


It surprised me at how fast some of these engines go with only 9.6v,
I may try using a lower voltage pack, just to see how it performs.

I don't run them fast anyway, but I do want them to start and run as smooth as possible,
not sure if a lower voltage pack will give me the same slow speed performance.




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BobD
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 Posted: Mon Nov 23rd, 2020 03:04 pm
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davecttr
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Interesting if you lower the input voltage to the Rx and have the loco run at the same scale speed,
are PWM pulse widths sent to the motor longer ?

I did get a slightly better start response from a small loco, when I reduced the PWM setting to 120Hz from 16KHz.
The loco emitted a high pitched whine as it accelerated.




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