Not so cheap solution to a pot problem

[musky]

The volume controls on one of my pachinkos started breaking down due to the load across them. Most pots used as volume controls can not handle the current on the output of the audio amp. Pots control volume in the pre amp stage. I know, I know, we have been using pots for years on the output, but the ones in my machine were heating up and breaking down causing them to open up and leaving no load on the final audio amp output. This can cause failure of the audio amp, not something I want for sure. My solution, RadioShack model 40-987 High Power In-Wall Stereo Volume Control. This puppy is designed to fit between the audio amp output and the speakers. It can handle 50 watts per channel, more then enough to tame those fever rounds. It controls in steps from full off to full on with steps 2-3 at 6 +/- 1 dB and steps 4-9 at 3+/- 1 dB. Installation requires 2 pairs of wires per channel or 8 total. I used a lengh of Cat 5 cable (8 wires) to connect the control between the speakers and the plugs that connect to circuit board. Everything works like a champ, one knob contolling both speakers in balance.
Price was a little high at $37.00 but I would rather invest that and save damaging my pachinko. There is probably a cheaper source for the same type device, if I find one I'll post it.

[birdbrain]

I thought the pot problem solution was to just say NO

[H20Dreams]

Its pretty much legal here in CA, but pachi's are not

[birdbrain]

you have nothing to fear but tokens themselves

[H20Dreams]

you have nothing to fear but tokens themselves

Isn't that just a shame!!! My new tag line!

[slothappy144]

Factory Volume controls on the Magic Lamp Girl are inline resistors that are decent sized to handle the less than 10 watts of power. The issue we might have is using the .25w or .10 rated trimmers in high output applications, like Julie.
Another problem I found is the 10K trimmers are difficult to adjust precisely. I use these for precise contrrol.

[musky]

Factory Volume controls on the Magic Lamp Girl are inline resistors that are decent sized to handle the less than 10 watts of power. The issue we might have is using the .25w or .10 rated trimmers in high output applications, like Julie.
Another problem I found is the 10K trimmers are difficult to adjust precisely. I use these for precise contrrol.

Right on Slothappy, my point exactly, the pots can't handle the wattage produced by some of the really loud machines. The pots in my machine were getting hot to the touch because of the load across them.

[slothappy144]

Thats what resistors do they convert electricity to heat.
Thanks for the useful info! a good bump for newer members.
I just wanted to add the tidbit about the 10k vs the 1k adjustability diffrance and the power rating note. all have been discussed previously.

[H20Dreams]

so where do the pashilso.com pots fit in here... Do they handle the newer machines like Julie?

[slotter]

I installed the pachislo.com pots in my Julie and they seem to be working fine.

[daverob]

so where do the pashilso.com pots fit in here... Do they handle the newer machines like Julie?

The answer is a most definite 'probably' , but only if the volume switch on the pachinko is set to the quiet setting before the pot is adjusted.

For those that are interested a technical description follows...

The speakers in a Lumina frame are rated at 5 watts, so you should be able to assume that the amplifier will not drive them at a higer power than this (it may well be less, but it should be safe to assume this value is the maximum).

If you use an inline resistor as an attenuator the worst case power dissipation in the resistor is when it's value is equal to the impedance of the speaker. If this is the case, then the overall impedance the amplifier is driving into is doubled and so the maximum power output will be halved. Seeing as this power will be shared equally between the speaker and the resistor, both of these will dissipate a quarter of the normal output power of the amplifier. So in the case of the Lumina frame this will be 1.25w, so the variable resistor will need a power rating of this value or higher.

However if the volume switch on the pachinko is set to a lower value then a lower rating could be used. I've looked at the attenuator circuit connected to the volume control switch on the Lumina frame audio board and calculated that if the maximum output is 5W in the loud position, then the medium position will be 2.75W and 1.8W for quiet. This would require a power rating of 0.7W for medium and 0.45W for quiet setting.

I don't know the exact spec of the pots that various installers use, but a typical rating for most small variable resistors is between 0.3W and 0.5W so they would definitely be overloaded on the loud and medium settings. On the quiet setting you'd probably get away with it as these calculated power values will only be present during the peak loudness parts of the audio, and the actual power output will be a little less. Also it is quite unlikely that the volume control will be set to exactly the same impedance as the speaker, and so the real world power dissipation will generally be less than the calculated worst case scenatio values.

Also note that it doesn't make much difference if you use one of the large volume controls with the mounting bracket, or the tiny PCB mount types, both of these usually have very similar power ratings. It's only the 'L-Pads' and the wirewound pots that are rated much higher than this.

[musky]

I have found on the net controls like I used for $19.00. I feel my solution is the safest one, when I say the pots were hot, I mean smokin' hot. Two trim pots at $9.00 a piece or High Power Volume control at $19. Just something to think about.

[slotter]

After reading this thread I decided to test the pachislo.com pots. Got Julie into a fever after running a lot of balls through. The pots never got even warm, let alone hot during the test. I have to think this isn't an issue at all. I did keep the machine set on the lowest volume setting as daverob suggested.

The only thing I noted was the sound might not have been as crisp and sharp as before the pot installation. But, then again, it was so loud beforehand that I wasn't able to judge well.

[daverob]

Musky solution is most definitely the safest, but might be a bit of an overkill. The small trim pots should be OK in most situations, but at Slotter has done, it's a good idea to check that they are not getting too hot in use, and if they are then replace them with something a bit more powerful.

Some pachis might put out more power than a Lumina frame model, even with the switch in the quietest position, and some aftermarket volume controls are too high a value, so that all the usable adjustment (and the heat dissipation) is tightly packed into a small portion of the track.

Slothappy's suggestion of 1k is a good value to use, I've also used 500 Ohm before with good results. (200 Ohm doesn't allow the volume to be adjusted low enough on some machines).

[H20Dreams]

pachislo.com's pots are 1k correct?

[johntofva]

The ones I purchased from them and placed on my "Thunderbirds" pachislo burnt up.

[Sid]

So if all your pots get burned out.. that would technically leave you without a pot to pee in...

[birdbrain]

go with the L-pads in the auction!