lARrybody Posted October 27, 2016 Report Share Posted October 27, 2016 Like many of you I have cleaned my fair share of original Atena-Pollak potentiometers with mostly success and a few disappointments. Sometimes the corrosion has eaten into the metal rendering them unusable, but more often than not they clean up well and with some little tweaking of the wiper they are quite usable. A few months ago the mid range pot on one of my rebuilt of 2ax's developed a sticky spot (more like a bump in the road) that just started. Upon removing the woofer and fiberglass I de-soldered and removed the offending Potentiometer and disassembled it. I could see nothing wrong. Reassembled and the hard spot remained. I finally replaced it with another rebuilt unit. These original pots compared to the Ohmite RHS15RE's that I used on my AR3a's, leave a lot to be desired in build quality. I know the Ohmite's don't have covers, but a couple Red Bull cans and some tin snips takes care of that. I have used L-pads on some 4x's and others, but they are not what AR intended. The main problem with the Ohmite's is that a set of four can run over $150.00 with shipping. There are some Chinese rheostats available on the auction site for less than one third the cost of the Ohmite's. http://www.ebay.com/itm/130697097827?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT The problem is these are 20 ohm and the original potentiometers were rated 16 ohm. I am not sure what the 4 ohm difference would mean installed in lets say some AR5's. Could someone explain the relationship of ohms verses impedance in these variable resistors? Link to comment Share on other sites More sharing options...
owlsplace Posted October 27, 2016 Report Share Posted October 27, 2016 I doubt the difference would be noticeable. It works out to less than half ohm in a parallel resistance calculation. There were some 15 ohm Chinese pots around for a while. I wasn't impressed so I picked up some 15 ohm -- 15W Russian pots which I haven't tried yet. Most people just go with the current industry standard 8-ohm/15-watt L-pads and a 25-ohm parallel resistor. Here is the Russian pot: Roger Link to comment Share on other sites More sharing options...
LouB Posted October 27, 2016 Report Share Posted October 27, 2016 With my 2Ax's I encountered Pollak green fuzzy corrosion, completely gone. I have wondered whether the porcelain in these might have been subject to an improperly rinsed acid bath during manufacture. For these, I used Ohmite 25 ohm 25 watt I had in the parts bin and with the added resistance they seemed to have an unusual attenuation pattern. I keep them at about 3/4 rotation. For the 3A's I have been working on, I purchased Ohmite 15 ohm 25 watt and then when I took the boxes apart I found the Pollaks to be corrosion free but needing the wiper spring wings to be re-bent. They worked fine afterwards. When the time presents itself, I'll put the 15 ohm 25 watt units in the 2Ax's. Regards, Lou Link to comment Share on other sites More sharing options...
LouB Posted October 28, 2016 Report Share Posted October 28, 2016 There are these on the auction site now, but the size sort of precludes them although the price is right; http://www.ebay.com/itm/50W-15-Ohm-Ceramic-Core-Wirewound-Adjustable-Rheostat-with-Knob-/181176533175?hash=item2a2ef680b7:g:kIgAAMXQRkdR49Ez Link to comment Share on other sites More sharing options...
lARrybody Posted October 28, 2016 Author Report Share Posted October 28, 2016 At 2 1/2 inches in diameter, those would be huge. I tend believe owlsplace's assessment of not being impressed with these Chinisse pots. You probably get what you pay for. I have two pairs of AR5's to be rebuilt to match, so I will probably bite the bullet and get the Ohmites. Thanks for the input. Link to comment Share on other sites More sharing options...
LouB Posted October 29, 2016 Report Share Posted October 29, 2016 Yes, the ohmite are expensive. As I had mentioned, I paid the Mouser price ( ouch! ) and then didn't actually need em for the project. I am generally not impressed with the quality of average Chinese stuff either. Lou Link to comment Share on other sites More sharing options...
DavidDru Posted October 29, 2016 Report Share Posted October 29, 2016 What would be your guys concerns about the LPads? Link to comment Share on other sites More sharing options...
LouB Posted October 29, 2016 Report Share Posted October 29, 2016 Ummmmm.... Other than a rigid adherence to tradition, nothing. With a strapping resistor, L pads could be just peachy. Link to comment Share on other sites More sharing options...
lARrybody Posted October 29, 2016 Author Report Share Posted October 29, 2016 L pads work great. I have used them on a set of 4X speakers with the 25 ohm resister. I recently added some to a pair of AR25's where no tweeter control existed before. Really makes a difference when the tweeters are backed off slightly. They have ferro-fluid tweeters so I left off the resister. Binding post also added. On the larger classic AR speakers I prefer to keep them looking as original as possible. Thus the rheostats over the L pads. Link to comment Share on other sites More sharing options...
LouB Posted October 30, 2016 Report Share Posted October 30, 2016 Nice work! I'll have to try using them as an alternative. Link to comment Share on other sites More sharing options...
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