Repairing a Gaugemaster P controller - Help needed !

[Renato]

Hello,

I am an Italian railway modeller and I need help to apply a simple fix to a Gaugemaster P controller bought back in the '80s in order to restore Inertia/brake simulator functionality.

The controller works but Inertia/Brake simulator does not, most likely because of a broken wire solder.

I am not keen enough with electronics and simply don't know where the wire should be reconnected. So I reverse-engineered the circuit diagram and ask some kind advice where to solder the wire.

In the attachments you can see the controller data sheet, the controller open with visible interrupted wire and the circuit diagram

Thanks for any advice,

Renato 

 

 

Edited November 25, 2017 by Renato

[dhjgreen]

As no-one has come back to you, have you tried looking for the frayed end of the wire on the board or one of the components?

[smokebox]

My (slightly educated) guess is that it should go to the positive supply rail.

[dhjgreen]

Certaintly it would do no harm to try it

[smokebox]

Looking further, is this a hole in the PCB where the wire came from?

[Tricky Dicky]

I thought Gaugemaster offered a lifetime guarantee, send it back to them.

 

Richard

[Renato]

thank you all for advice. Answering to suggestions in order:

 

there is no frayed end on the pcb side unfortunately

 

I will try to connect the wire to the positiver rail and report reults, thank you

 

no the hole is or a bolt that holds the pcb in place on top of an isolator column

 

Lifetime is remarkable but shipment cost from and to Italy probably is quite high.

 

thank you all, I will report result of trial

Renato

[Dunsignalling]

I thought Gaugemaster offered a lifetime guarantee, send it back to them.

 

Richard

Void once you open them up.

 

John

[John ks]

 

Hello CC,

 

Out of interest further Googling brought this circuit up, ostensibly from a Codar (never heard of them) controller. 

 

 

Looks as though S1 switches in the 'inertia' and R7/C1 regulates the ammount, I guess :-)

 

Cheers - Jim

 

While this is not the same as your controller it is very similar

 

 

Firstly is the area I have circled been correctly back engineered?

 

 

The connection of the 2 capacitors across the output transistor is not where(with my limited knowledge electronics) I would have thought they should be connected

 

C2 & C3 seem to correspond to the 2 capacitors (circled) in your diagram

 

 If these controllers are so similar then I would expect the loose wire to go to the negative (Black wires are often used for negative (maybe a red herring))

 

​Hope this helps

John

 

​John

[Butler Henderson]

Have you thought of contacting Gaugemaster - they probably will be able to advise you what goes where. I foolishly stuck a drill into a dcc accessory decoder and the supplier (not Gaugemaster) was a great help, advising on the components I needed to replace and providing a couple of resistors free of charge. Thankfully I had only destroyed those resistors and damaged a couple of transistors which I replaced, although it did take a bit of pestering to get the relative extract of the circuit out of them.

Edited December 1, 2017 by Butler Henderson

[Renato]

DId not have time to try yet.

Thank you John, I will look once more into my diagram

And thank you Butler, If my attempt fails I will write to Gaugemaster

 

Renato

[royaloak]

would it be possible to lay the cable in its normal position and see where it ends up, as long as you havent bent the wire too much it should return to (near enough) its original shape which would at least roughly give you a clue where it connects too.

[cliff park]

One puzzle that nobody sees to have asked (or dd I miss it) :- how or why did the wire come off?? Wires don't just fall off inside a sealed box. If there was movement of the potentiometer I would expect the wire to come off at that end. The point is if we knew what prompted it to 'fall' off there might be a clue as to where it came from.

[Renato]

Hello, the wire came off at the circuit end, long ago, probably because of an accidental collision. The controller had been used with open cover (it was installed on a sort of a wooden rack). 

The wire laid off was close to the printed circuit but there are many possible connections in the range of a coulpe centimetres. And no evidence of broken wire on the PCB.

However I think I could find the solution (or A solution at least). I soldered the wire to the brush of the "regulator" pot, as you can see on the schematic attached below. When "Simulator" switch is in  OFF position there is a sort of a direct feedback connection between the central point of the capacitor partitioner and the brush of the "regulator" pot which controls current to the base of the leftmost transistor. With the connection I made, "Simulator" switch ON intruduces a variable resistance in series to this feedback circuit, thus providing slower evolution of the operating point, so to say (My English probably sounds horrible, hope you can understand).

I tested the circuit and it works fine. The 100 kOhm position of the pot is marked "Brake OFF" on the front panel and this way when turning the regulator pot upwards from zero the locomotive hums a bit (some pulse oscillation I think) and slowly picks up speed. If I turn the regulator pot down to zero the loco continues at same speed and slows down in a very long time (more than 15 s). When at zero speed it hums until I turn regulator pot to zero. I then turned regulator pot up again, let the loco catch speed and returned regulator pot to zero. After that I turned brake pot up towards the "FULL brake" position and the loco speed slowed down faster. The more brake rotation up, the faster deceleration. When loco is stopped if I turn brake back to zero it will start again, until I turn regulator down to zero or brake pot up again. And this works both in forward and reverse direction. THe only worry I have is that the humming at stop is quite noisy so probably there is a high current ripple. To be safe I turned the regulator quickly down after loco stopped.

Here below the schematic with the wire connected (I also added wire color indication for my convenience).

Maybe this is not the best fix, don't know, I will keep locomotives monitored for overheat.

Thank you all for advice and support.

 

Renato

 

[kevinlms]

Hello, the wire came off at the circuit end, long ago, probably because of an accidental collision. The controller had been used with open cover (it was installed on a sort of a wooden rack). 

The wire laid off was close to the printed circuit but there are many possible connections in the range of a coulpe centimetres. And no evidence of broken wire on the PCB.

However I think I could find the solution (or A solution at least). I soldered the wire to the brush of the "regulator" pot, as you can see on the schematic attached below. When "Simulator" switch is in  OFF position there is a sort of a direct feedback connection between the central point of the capacitor partitioner and the brush of the "regulator" pot which controls current to the base of the leftmost transistor. With the connection I made, "Simulator" switch ON intruduces a variable resistance in series to this feedback circuit, thus providing slower evolution of the operating point, so to say (My English probably sounds horrible, hope you can understand).

I tested the circuit and it works fine. The 100 kOhm position of the pot is marked "Brake OFF" on the front panel and this way when turning the regulator pot upwards from zero the locomotive hums a bit (some pulse oscillation I think) and slowly picks up speed. If I turn the regulator pot down to zero the loco continues at same speed and slows down in a very long time (more than 15 s). When at zero speed it hums until I turn regulator pot to zero. I then turned regulator pot up again, let the loco catch speed and returned regulator pot to zero. After that I turned brake pot up towards the "FULL brake" position and the loco speed slowed down faster. The more brake rotation up, the faster deceleration. When loco is stopped if I turn brake back to zero it will start again, until I turn regulator down to zero or brake pot up again. And this works both in forward and reverse direction. THe only worry I have is that the humming at stop is quite noisy so probably there is a high current ripple. To be safe I turned the regulator quickly down after loco stopped.

Here below the schematic with the wire connected (I also added wire color indication for my convenience).

Maybe this is not the best fix, don't know, I will keep locomotives monitored for overheat.

Thank you all for advice and support.

 

Renato

It does appear that you have found the correct location for this wire - well done.