I am helping a friend to repair her amplifier. A different friend took a look at it, and they were able to identify the circled part as being the one to blame. However, apparently this is a part that was made specifically for this amplifier and is no longer made, so my task is to figure out what to do. I have some electronics expertise, but mostly I was recruited because I am good at finding things.
However, it would be a good start if I knew what this component was. I’ve not been able to find it in any of my reference materials, so I was wondering if y’all might be able to help. The person who identified this part is not able to help clarify, as she’s off the grid for the next 3-4 months.
(On the off chance that someone here has some specific expertise on this particular amp, it’s the Kenwood KA-3020SE)
Edit: Now that I know it’s a potentiometer, the biggest challenge is understanding what 200KBH what is necessary to replace the part. It’s a 200kΩ one, that’s straightforward enough. It also seems that the “B” means linear response (found by checking my electronics reference book section on potentiometers, and cross referencing with other balance control pots for other amps, which specifies linear). I’m puzzling about what the H could mean though.
The big challenge, I’m told, is finding a part that will physically fit. There are 6 contacts on the part, which means it’s a dual ganged potentiometer. However, most that I can find online have the pins in a 2*3 arrangement, like this, whereas this one is 1x6, like this.
The person who identified this part is not able to help clarify, as she’s off the grid for the next 3-4 months.
based based waow
Yeah, she’s pretty cool. She’s studying crabs or something on a remote island somewhere. Living her best autistic life
This schematic symbol has only 3 pins, but you say the components has 6. Since this part is VR1-a, can you look around for maybe a VR1-b? That might explain where the other pins connect. If it’s a 1x6 arrangement, they may not be 2 totally electrically independent potentiometers.
First guess is that VR in that symbol stands for variable resistor (trimpot or potentiometer). The arrow pointing to the center of the resistor also makes it look like a potentiometer
Not sure if this is something you already found, but I found this from the service manual
Im very much a beginning hobbyist, so I cant make much from this, but I hope it puts you on the right path to an answer.
Here the link to the manual:
https://manualmachine.com/kenwood/ka3020se/2350744-service-manual/
It’s a variable resistor, commonly called a varistor. Probably metal-oxide and probably used for surge protection (which explains why is the part that fried). Unfortunately that’s all I can tell you.
I had to look it up myself - from Wikipedia:
A varistor (a.k.a. voltage-dependent resistor (VDR)) is a surge protecting electronic component with an electrical resistance that varies with the applied voltage.
Is there another identical part in the circuit, e.g. in a second channel, if stereo? (…dotted line?).
Then you can have a look at that to determine its behaviour.
Looks like a special kind of variable resistor, in that case has linear behaviour you might be able to conviently mimic with standard components.There is indeed an identical part — it seems that the balance control for amplifiers often has a “dual ganged” potentiometer
Linear behaviour is something that I had managed to conclude also, so it’s reassuring that you confirm this.
Do you know what the “H” in 200KBH means? That’s one of my big remaining puzzles. I agree that it seems likely that we’ll be best served by replacing it with something that is able to fulfill the same function due to not being able to find the specific part, but I’m not sure whether this could be something important.
Do you still have the component? You could try repairing it, there’s a youtube video where your last picture came from. edit: in case you didn’t already have the vid.
Not positive this is the right part, but it says 200k vr which to me reads as a 200k ohm variable resistor which is not a particularly difficult thing to find, but your friend may have more information about why specifically something like this wouldn’t work. The only thing I can think of is if the one in the amplifier was rated for crazy high wattage to handle plate voltage for a tube or something like that.
There’s 6 pins on the part in question, which I think means it’s a dual ganged potentiometer. The arrangement of the pins seems to be a big issue for other people online wanting to replace this part. I’ve added images to show what I mean in my main post.
The big thing I’m nervous of is not knowing that the other parts of “200KBH” means. 200K is resistance, and B seems to mean linear response, but I have no clue what “H” could refer to
I’ve looked at the manual again, and it seems to me you could do a drastic thing and drill a hole through the PCB in the place of the old component where you could put an axis of a different v-resistor through. This could then be connected to the board with wire.
This is purely a guess but might the H stand for horizontal? Or something along those lines. Since the way it’s mounted is different.
