Hi all, first post here! Looking for help properly sourcing a replacement part I need to repair my amp.
I have a PrimaLuna Evolution 400 Tube Integrated Amplifier that is out of warranty, and I have taken it upon myself to repair it.
The issue is that the volume control on the remote control does not work -- the volume knob itself does work when you turn it manually. It has a motorized potentiometer that should react to the remote but doesn't.
To diagnose, I took off the bottom cover, located the potentiometer's motor terminals, and hooked up a multimeter. Saw +2.5 V when pushing volume up on the remote, and -2.5 V when pushing volume down. So, it would appear that the potentiometer motor itself is dead, and I'm hoping that replacing it solves my problem.
The potentiometer is a blue motorized ALPS potentiometer, and it has a sticker on it that says "848G 100KAX2". Googling shows me that this part seems to come in many flavors (motorized vs non-motorized, KAX2, KAX4, KAX6...).
I have not found anywhere selling something labeled "848G 100KAX2" exactly.
Partsconnexion has this one simply labeled 100k: https://www.partsconnexion.com/ALPS-71668.html
Aliexpress has this one which doesn't exactly look like mine but says it is 100KAX2: https://www.aliexpress.com/item/2255800877149088.html?gatewayAdapt=4itemAdapt
Is the "848G" part of the designation important? Or is it just the 100KAX2 part? Is the one simply referred to as "100k" on partsconnexion the right part? Are the ones on Aliexpress authentic?
I don't need to find the cheapest price or anything, I just want to find exactly the right part and get it here 🙂 Any advice here is appreciated!!
I have a PrimaLuna Evolution 400 Tube Integrated Amplifier that is out of warranty, and I have taken it upon myself to repair it.
The issue is that the volume control on the remote control does not work -- the volume knob itself does work when you turn it manually. It has a motorized potentiometer that should react to the remote but doesn't.
To diagnose, I took off the bottom cover, located the potentiometer's motor terminals, and hooked up a multimeter. Saw +2.5 V when pushing volume up on the remote, and -2.5 V when pushing volume down. So, it would appear that the potentiometer motor itself is dead, and I'm hoping that replacing it solves my problem.
The potentiometer is a blue motorized ALPS potentiometer, and it has a sticker on it that says "848G 100KAX2". Googling shows me that this part seems to come in many flavors (motorized vs non-motorized, KAX2, KAX4, KAX6...).
I have not found anywhere selling something labeled "848G 100KAX2" exactly.
Partsconnexion has this one simply labeled 100k: https://www.partsconnexion.com/ALPS-71668.html
Aliexpress has this one which doesn't exactly look like mine but says it is 100KAX2: https://www.aliexpress.com/item/2255800877149088.html?gatewayAdapt=4itemAdapt
Is the "848G" part of the designation important? Or is it just the 100KAX2 part? Is the one simply referred to as "100k" on partsconnexion the right part? Are the ones on Aliexpress authentic?
I don't need to find the cheapest price or anything, I just want to find exactly the right part and get it here 🙂 Any advice here is appreciated!!
You never know, but when I read a catalog, the 100kA means 100k resistance and A taper (Audio) The X2 means times two, or "stereo" if you like. It means a dual pot.
Likely they make a selection of 100kA pots, even in dual. I don't know how universal the motors are. I saw on your onhe data sheet motor was 4-6v supply. Your unit shows less than that. If you have the pot out, you ,might feed it 5v from a bench supply and see if it moves.
Likely they make a selection of 100kA pots, even in dual. I don't know how universal the motors are. I saw on your onhe data sheet motor was 4-6v supply. Your unit shows less than that. If you have the pot out, you ,might feed it 5v from a bench supply and see if it moves.
Most motors will work between 3 and 12 volts.
See the control voltage with the motor disconnected. Can use paper pins in socket (it works, do not laugh)...be careful not to short anything out.
That will tell you if it is a control problem or a stalled motor.
Check the supply before checking the pot, maybe motor is in need of cleaning and lubrication.
Alps are good, so unlikely to be a bad motor.
See the control voltage with the motor disconnected. Can use paper pins in socket (it works, do not laugh)...be careful not to short anything out.
That will tell you if it is a control problem or a stalled motor.
Check the supply before checking the pot, maybe motor is in need of cleaning and lubrication.
Alps are good, so unlikely to be a bad motor.
Thanks for responses and suggestions, all.
I'm still trying to determine -- can I know for sure that this is the exact right part? Is the "848G" on the label of my part a model designation that meaningfully distinguishes it from others, or are all 100KAX2s going to be the same?
I'm still trying to determine -- can I know for sure that this is the exact right part? Is the "848G" on the label of my part a model designation that meaningfully distinguishes it from others, or are all 100KAX2s going to be the same?
Paper pins to be able to use meter leads to check voltage in the socket.
Can use excess parts wire (leads) as well, or anything stiff and the right size.
First determine the fault, tell us about it, then do the repair.
Can use excess parts wire (leads) as well, or anything stiff and the right size.
First determine the fault, tell us about it, then do the repair.
I'm not sure what you mean by "socket". But I checked the voltage across the motor terminals while pushing volume+ and volume- on the remote, and saw +2.5V and -2.5V respectively, but no movement by the motor.
This tells me that it seems that the problem probably lies with the motor, no?
See Post #3 above.
Disconnect the motor, then check the voltage that is coming from the control circuit, to the motor socket, use pins / wires if your probes are thick.
If it is still the same, fault is in control board.
If it goes up, means motor stuck, drawing too much current, which could be possibly repaired by carefully cleaning, lubing and reassembly.
I hope this makes things clearer.
Disconnect the motor, then check the voltage that is coming from the control circuit, to the motor socket, use pins / wires if your probes are thick.
If it is still the same, fault is in control board.
If it goes up, means motor stuck, drawing too much current, which could be possibly repaired by carefully cleaning, lubing and reassembly.
I hope this makes things clearer.
Frequently manufacturers use custom part numbers on otherwise normal parts to get you to think they are special and must be purchased from them. They charge four times the price for nothing but making money on you. A 100k audio taper pot is a 100k audio taper pot!
Disconnect the drive wires to the pot and measure the voltage when you turn it up and down. If it is there take a 9v battery and use it to quickly try and make the pot motor turn, disconnected of course. If one or the other fails you know what to look at and replace. If it is the motor in the pot and you are worried about the new one being different you can take the pot elements off them and put the old pots on the new motor.