J-Retro Pot Question

[BobKos]

Hi All:

I'm new to the club. Nice place.

I have a question regarding the pots on a J-Retro Jazz Bass Preamp. I recently bought a used J-Retro off eBay. The buyer assured me that it operates 'as new'. I got it today. I noticed that the first two sets of stacked pots operate very smoothly. They also operate independently and do not affect each other - ie turning the outer knob does NOT turn the inner knob and vise verse. The third stacked set is not so. The knobs will react together at the extremes of rotation. IOW - if the pots are both set at half way, they do not interfere. At full on or full off, they will drag each other part of the sweep. Can anybody who owns a J-Retro confirm this to be normal or abnormal behavior? I expected that all the pots should operate as the first two sets. Any advice appreciated.

[McCalister999]

I have a j-retro and all knobs interact independently from one another.

[xbradx]

Just loosen the set screws on the stacked knobs and lift the top knob just a little bit and re-tighten the screw and check.

[DaveAceofBass]

If you need layouts for what the controls do, check John East's website. They all work independently but the mids and lows can seemingly cross frequencies a little bit.

[brandonwong]

Originally Posted by xbradx

Just loosen the set screws on the stacked knobs and lift the top knob just a little bit and re-tighten the screw and check.

+1

[BobKos]

Thanks for the replies. I followed your advice and checked the knob clearance. It is / was OK. I looked closer and have discovered that the upper knob wobbles a bit, causing me to believe that the center shaft is bent. This seems to explain the dragging in certain positions. Yuk. I don't know why I mess around with eBay anymore.....

[xbradx]

I'd suggest contacting John East about a replacement. I just installed one of his custom 3-band MM pre's and he's great to deal with and could probably advise you on replacing the pot.

[John East]

Originally Posted by BobKos

Thanks for the replies. I followed your advice and checked the knob clearance. It is / was OK. I looked closer and have discovered that the upper knob wobbles a bit, causing me to believe that the center shaft is bent. This seems to explain the dragging in certain positions. Yuk. I don't know why I mess around with eBay anymore.....

If the shaft is bent, check it without the knob on it to be sure, you'll be able to see a difference in the gap, between the inner and outer shafts, as you rotate the pot.

If this is the case, it is possible to straighten the inner shaft using a large pair of pliers.

You have to be very careful with gentle but firm tweaking. The metal is not very hard and a sharp jerk could fatally break it.

[brandonwong]

There he is... as always to the rescue.
John never amazes me with the care and service he gives to any of his customers, whether new or used.

[BobKos]

Originally Posted by John East

If the shaft is bent, check it without the knob on it to be sure, you'll be able to see a difference in the gap, between the inner and outer shafts, as you rotate the pot.

If this is the case, it is possible to straighten the inner shaft using a large pair of pliers.

You have to be very careful with gentle but firm tweaking. The metal is not very hard and a sharp jerk could fatally break it.

Thank you for your reply John. I appreciate that you responded to this thread.

I have given some thought to doing what you have described. I am an auto tech by trade so I feel that I can accomplish what you suggest at minimal risk to the shaft. My thought and concern lies with the internal wipers of the pot assy. I am concerned that putting unnatural pressure on the shaft may cause one or more of the wipers to become deformed and inoperable. How delicate are the pot components?

[John East]

Originally Posted by BobKos

Thank you for your reply John. I appreciate that you responded to this thread.

I have given some thought to doing what you have described. I am an auto tech by trade so I feel that I can accomplish what you suggest at minimal risk to the shaft. My thought and concern lies with the internal wipers of the pot assy. I am concerned that putting unnatural pressure on the shaft may cause one or more of the wipers to become deformed and inoperable. How delicate are the pot components?

Having done this a few times, it doesn't seem to affect what goes on inside. You're pushing/pulling against the bearing of the shaft. So the inner workings are kind of isolated. The contacts between the wiper and track are tiny springs too, so any flexing while you make the adjustment won't cause any damage as any movement of the internal mechanism will amount to just the play/tolerance in the bearing.