# JL HD900/5 potentiometer defect



## goodguyocom (Jan 19, 2011)

I have a jl hd900/5 that is having problem with the gain control on the sub channel. Everything work fine but when anything touch the gain control it start making cracking noise and if I turn the gain all the way down it still sound loud. So I'm guessing it the potentiometer that is defected. I called JL and told them about it and they told me the same thing. But they won't sell me just the potentiometer instead they told me that they charge a flat rate of 180 to fix the amp. I try calling Tocos which is the manufacturer of the potentiometer for the JL HD amp but they don't have it either. Can anyone here help me with locating a replacement potentiometer for the JL HD amp.


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## TrickyRicky (Apr 5, 2009)

Does it have a value on the top or any of its sides? Like 20k,50k? How many pins does it have (should have 6, but that's the common pot used for gains)? 

Have you done the usual diagnosing (switch: wires, speakers, rca)?

If your handy with the solder iron, then I would suggest removing it and testing it outside the circuit. ONLY after you determine it is in fact the amplifier that is faulty. 


You can also try DeoxIt to see if that helps any. Which I doubt since the amplifier is new (meaning its not over 5 years old).


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## goodguyocom (Jan 19, 2011)

The number on the trimmer is 20A502 94C. It is square with dual trimmer and 6 pin. I'm very positive it is the potentiometer. I just need to locate a replacement.


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## goodguyocom (Jan 19, 2011)

It is the one on the left.


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## goodguyocom (Jan 19, 2011)

Here another picture


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## TrickyRicky (Apr 5, 2009)

There's a replacement...trust me. Its a 5K AUDIO 20% pot, Bourns or Vishay should make one similar.


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## goodguyocom (Jan 19, 2011)

Can you help me find one? I would really appreciate it.


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## TrickyRicky (Apr 5, 2009)

Boom....who's your daddy?:laugh:


Mouser has it on ORDER, so you'll have to *wait about 6-8weeks* before you actually get it shipped to you. Check Digikey or other well know distributors. 



TIP: Make sure you measure the pin lay out for the original and check out the datasheet of the pot I suggested and make sure it fits properly. I WILL NOT BE RESPONSIBLE for it not been the same pin lay out (as I clearly don't have the amplifier in front of me). Also not sure if yours is Linear or Audio taper....I am assuming its Audio but confirm with the manufacture of the pot or JL.


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## goodguyocom (Jan 19, 2011)

But the estimated ship date is not till end of next month.


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## TrickyRicky (Apr 5, 2009)

I can see if I have one in my component box, I have a few pots but as you will find out they are all different in many ways (pin lay out, function: audio/linear, resistance, tolerance, material used, shaft size and length, and much much more).



Look around for it, Digikey or Arrow may have it. Just be advise some carry some very heavy S&H fees even on their smallest orders. Others will have a minimum piece or $$ before order can be placed (welcome to my world).


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## bbfoto (Aug 28, 2005)

OP, did you check with Digikey, Grainger, or MCM Electronics?

Ricky, is it typical for these to have a 20% tolerance? I knew that they weren't very accurate, but wow.


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## TrickyRicky (Apr 5, 2009)

bbfoto said:


> OP, did you check with Digikey, Grainger, or MCM Electronics?
> 
> Ricky, is it typical for these to have a 20% tolerance? I knew that they weren't very accurate, but wow.


All the amplifiers that I have had in front of me had a 20% tolerance pots on the gain section (besides those amps that have built in DSP:laugh just different resistance.


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## goodguyocom (Jan 19, 2011)

Thanks alot Ricky. I will desolder the pot again and get the measurement of everything and contact mousers. It was alot of help knowing the resistance value and and how many ohms.


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## TrickyRicky (Apr 5, 2009)

No problem, am glad I was able to help. Once you have it out you can test it to ensure it is the pot that's faulty. If you need further help testing it let me know and I'll help you further more. But its quite simple you'll see (both sections of the pot have to be IDENTICAL, for example if you have 100ohms between pin 1 and pin 2 (wiper) you should have the same (or very close to 100ohms) on the same set of pins but on the second section of the pot (each three pins is one section/pot). If they are the same while the pot is turn counter-clockwise, then set the pot to the middle and re-check, then turn it fully clockwise and check it again.

If both are the same when turning the pot, then its pretty balanced (both channels are getting the same amount of gain). Now check to make sure your reading atleast 10ohms one way and atleast 4.9k when turn the opposite way (gain control turned). If this is what your reading, then your pot is good and you may have other issues.


If you look at the schematics/diagram for the pots you'll see how exactly they work and you can verify if it is in deed properly working or not. You'll see that pin 2 is usually the wiper on most of the pots.


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## goodguyocom (Jan 19, 2011)

think the pot was lose. I desolder it then solder it back on now it work like it should. thanks for the help ricky


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## TrickyRicky (Apr 5, 2009)

Glad you got it working, maybe cold solder joint.


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## ndramountanis (Apr 23, 2013)

That was a cheap fix... How did you figure out it was the pot initially?


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## basshead (Sep 12, 2008)

TrickyRicky said:


> Boom....who's your daddy?:laugh:
> 
> 
> Mouser has it on ORDER, so you'll have to *wait about 6-8weeks* before you actually get it shipped to you. Check Digikey or other well know distributors.
> ...


JL wanted 180$ to fix my HD1200/1 with a bad gain pot, replaced it with the Bourns pot you mentioned and the amp is back in service.

Thanks!


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