Pentroller repairs

[Rod Cameron]

For those who might have guessed already, or not, here is one for sale

https://www.ebay.co.uk/itm/222912362861 ... 9#payCntId

[Jol Wilkinson]

Paul,

I bought a Bench Power Supply which is very useful for both testing locos (voltage and current readout), checking motors, testing electronic bits, etc.;

https://www.rapidonline.com/basetech-bt ... 5w-64-6084

Not much more expensive than the HH Pentroller for which Rod has provided the eBay link.

There are other types, brands and suppliers.

Jol

[Hardwicke]

Thanks,
Some great replies and I'm going to test the controller over the next few days for failed components.

[Hardwicke]

Found the problem ! A burnt out resistor to the right of the directional switch. Now to find a replacement !

[Hardwicke]

A better photo !

[Hardwicke]

And my spare pentroller is a different version!

[Hardwicke]

Can anyone identify the burnt out resistor/capacitor in the earlier picture? The alternative (working) one has a capacitor 1J63

[allanferguson]

The trouble is that if the resistor has burnt out, then something has sent too much current through it; If you just replace the resistor (not difficult or expensive) It's very likely the same thing might happen again.
I'm sorry this isn't a straightforward answer to your problem!
If you google "Resistor values colours" you'll be able to find the value of your component>

Allan F

[Hardwicke]

Yes, but the bands are unclear due to the burning. I think I know why it failed.

[Simon_S]

Could it be the same as the one next to the switch on your working controller? Mind you, that one looks 'thermally challenged' too...

[Hardwicke]

Hmm. As the photos show the design changed.
One has a blue resistor/ capacitor, whereas the other has a cream capacitor. It is the blue one I want to know about.

[grovenor-2685]

This is going to need someone with the same model to look at theirs. Those of us without Pentrollers are not going to be able to help.
Regards

[Jol Wilkinson]

I have opened up my HH Pentroller to find that it is the same version as Hardwicke's. And, guess what, the same resistor show signs of overheating.

So, no identifiable markings but testing with a Multimeter shows a resistance of 4.9 ohms. So it is probably a 4.7 Ohm rated resistor. As it is possible for the resistance measured installed to be affected by other components in the circuit I unsoldered it and got the same result when checked off the pcb.

It is probably a .24W or .5W resistance and it may be worth fitting one with a higher rating. That may not be possible in the same location but there is prabably space within the unit to fit one remotely near the motor selector switch with "extension" leads. I'll look into that when S4N is out of the way.

[Hardwicke]

Thanks Jol,
That's an excellent analysis. I may or may not be at S4N.
Michael

[Alan Turner]

4.7 R would have the first two bands as YELLOW, VIOLET. Form what I can see in the photo the first band is RED - suggesting first number is 2.

regards

Alan

[Jol Wilkinson]

Unless the red is the tolerance indicator, although 2% is unusual in most applications. The colour at the other end could be gold, which is 5% and more likely. There are no colours visible on the resistor on my HH unit, the outer case having mostly flaked off. I am satisfied with the reading I got, as a increase in resistance would presumably be more consistent with damage. It is also within 5% of the usual 4.7 Ohm rating for resistors.

I'll take a look at the circuit later to get some idea as to where this resistor is in the scheme of things.

[Jol Wilkinson]

Michael,

a further trip up to the workshop to investigate the HH Pentroller.

The delinquent resistor in question is in the -ve line from the onboard rectifier to the direction switch inputs (the switch is adjacent). So presumably acts as a voltage/current reducer. The problem may be that a short circuit will probably exceed the wattage rating of the resistor (.25W or .5W).

Or, as Tony Wilkins suggested earlier, is it a fusible resistor and has simply "blown", needing replacement?

Possible solutions;
* Fit a new 4.7 Ohm resistor
* Fit a new fusible resistor
* Fit a larger power handling 4.7 Ohm resistor.
* Add a resettable fuse to the AC input. (5A - 1.0A are available which should be about right.

A look at the Rapid Online site shows fusible resistors of 10 ohm value with variable power ratings, but they are all bigger than a standard resistor.

Also listed is a 2W 4.7 Ohm resistor measuring 12.0 X 3.9 mm which should fit or could be mounted elsewhere with extension leads (as could the fusible type.

The same site shows resettable fuses with various amperage ratings and trip times. That could be mounted in the PSU feeding the controller (all the transformer outputs in the London Road psu are so equipped). The downside is that you might not notice it has tripped. On London Road the control panel has a MES lamp holders with the bulb connected across the controller's output feeds into then box. No light equals no output from the controller.

I hope this helps,

Jol

[Hardwicke]

Yes, I believe there was a short in the layout before the unit failed.

[Hardwicke]

I thought I'd got the correct resistor in stock but no. Difficult to make out the colours under the burning. I have some 4.7Ω resistors but they have the wrong bands that are visible. The errant component is between the direction switch and this...

[Hardwicke]

Maroon band at top. Maroon or brown next. Don't know. Gold at bottom.

[Hardwicke]

I guess that is the onboard rectifier Jol. (Electronics are my weak point).

[Hardwicke]

An investigation into the post on the other place shows it as R29 2.2 (0.33 to 2.2Ω) on the "experimentroller".

[Jol Wilkinson]

Yes, the component with the polarity markings would be a rectifier.

[Simon_S]

I expect the burnt resistor acts as a current sensor and provides an input to the control circuit, needs replacing with a higher wattage rated part as suggested.

[Tony Wilkins]

The round component with the polarity markings is indeed a bridge rectifier. The ~ markings are the AC inputs and the + the positive output, the unmarked leg being the negative output.
As far as I can ascertain from my Pentrollers the burnt out resistor was 0.22R.
Due to precisely this failure mode, mine have been unofficially modified as follows.

The large green resistor in the foreground is a 0.22R wire-wound vitreous enamel 2.5 Watt resistor made by Welwyn. They have a high overload rating to cope with short high current peaks.

The underside of the PCB has a 1N4002 1 Amp diode soldered across the controller side of the switch to protect against reverse voltages damaging the controller circuity. Note the line marking the Cathode end of the device.
This can occur when two track circuits using controllers set to opposite directions become accidentally bridged.
Since my two Pentrollers were thus modified, I have had no further issues with failures.
However one should not allow a short condition to persist for any length of time or things will get hot, then very hot.

The .1j63 component would be a 0.1microfarad capacitor rated 63 Volts.
Regards
Tony.