Repairing an AA ENT Phase Pistol

**tim** · Aug 9, 2009

About six years ago, I bought one of the AA Phase Pistol and Communicator sets and modified them, adding a laser diode + 2 LEDs to the phase pistol's emitter and replacing the green LED in the comm with a blue one.

However, in the intervening time, one of the phase pistol functions no longer works. Normally, when the pistol is opened and a power cell inserted, the power cell lights up for a while. Closing the pistol then allows it to be "fired" with lights and sound.

The power cell illumination on mine has failed, and I set about trouble-shooting today. Disassembling the toy, I verified that the LEDs, micro-switch, and wiring are all good. Moving to the circuit board, I verified that all resistors, capacitors, and diodes check out too. At this stage, it seems that the electronics are (partially) fried. Is anyone here familiar enough with the electronics on this toy to suggest other things I should check? If all else fails, where can I get a replacement sound board?

**RPF Support**

**tim** · Aug 10, 2009

Did some additional checking of the circuit board and have confirmed that the output to the power cell LEDs is kaput, presumably at the IC.

So, looks like I'll need another circuit board.

I have toyed with the idea of building a circuit to replicate the timed power cell illumination. I could rig up a circuit based on a 555 timer but would need to do a fair bit of rewiring to get it all to work.

**tim** · Aug 10, 2009

I was a bit bored at work this morning and so whipped up this 10-sec timer circuit based around the venerable 555. This can be used to replicate the function lost from the damaged original circuit but will require rewiring so that the timer output goes directly to the red LEDs that illuminate the power cell.

(Top wires: power; Right wires: output; Bottom wires: trigger)

The problem is that I will have to replace the micro-switch that gets closed when the power cell is inserted. This is because the toy will only fire if the power cell is inserted (thus closing the micro-switch) and the "breech" of the pistol is also closed within about 10 seconds, thereby closing another micro-switch and allowing the emitter light and sound to operate.

Therefore, the micro-switch at the power cell must remain in the original circuit. However, my timer circuit needs its own designated trigger switch. My best bet is to find a momentary DPST micro-switch that is the same form factor as the SPST switch in the pistol and replace it. Does anyone have a part number?

So, in sum, I'll need to install my circuit, replace the micro-switch, and add three wires running to the business end of the pistol to accommodate the modifications.

I still think a replacement sound board from a junked toy would be the better option!

Another un-pictured modification is adding reverse voltage protection. This is simply achieved by connecting a diode antiparallel to the battery holder. I fried the electronics on my first phase pistol toy years ago by installing the batteries backwards.

**Mr.Engineer** · Aug 10, 2009

Wow!

You're a genius! I wanted one of those long ago but the opportunity never came. And then the TV series got canned.

**tim** · Aug 10, 2009

^ Impatient, maybe.

Getting another stock circuit would be the preferred option, but at least I have this as a back-up.

The tricky bit will be the DPST micro-switch.

EDIT: I couldn't find a DPST switch with the same form factor as the original SPST switch, but I did find this close match that appears to be from the same manufacturer. I can Dremel the phase pistol parts to make it fit. Yay free samples! Still, a replacement board would be better.

**tim** · Aug 11, 2009

I've finished the repair project. I wanted to find a way to avoid having to replace the micro-switch at the power cell and after some testing of the AA circuit board, lucked out.

There were a pair of contacts on the AA board that went from 0V to 4.5V when the power cell micro-switch was closed. I used this to power an opto-isolator circuit (below and to the right of the AA board in the photo below). When the opto-isolator is active, it triggers the 555 timer circuit (in the upper left of the body in the photo) which then illuminates the power cell LEDs for 10 seconds.

Pros: only one wire added coming from the emitter, avoiding a possible failure mode due to stress at the hinge

Cons: opto-isolator remains active as long as the power cell is inserted (drains battery) and power cell LEDs stay on for 10 seconds regardless of whether cell is subsequently removed or the pistol's breech is closed (differs from original operation).

Probably biting the bullet and replacing the SPST switch with a DPST one would have been the best option in terms of maximizing battery life, but once I got rolling, I decided to finish.

I'll touch up the paint and install real spanner-type screws at the hinge to complete the repair/upgrade.

**thegreatgalling** · Aug 19, 2009

My hat is off to you Sir, that is pretty awesome. I have a lot to learn from the talent soaked in the pages of the RPF.

Repairing an AA ENT Phase Pistol

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