mark fader Posted July 13, 2019 Share Posted July 13, 2019 (edited) long story short - my dad bought theses new when i was a kid and its what i grew up on . now i have them but after 30 years or so i just decided to give them a little tlc . about 2 years ago i refinished the outside . i stained them black and put on a satin gloss finish and replace the grills with a frame and grill cloth . now i decided to do the inside about a month ago . the goal was to make them sound the way they did new , or as close as possible . of course i don't remember what they sounded like new because i was just a kid and i hadn't developed an ear yet , but at least restore them with new components . the caps were pretty straight forward but the challenge was the pots . i searched and searched and emailed anybody and everybody just to find more confusion and dead ends . as of right now there is no known direct replacement for the pots . so i just kept searching the net to see what others have done and what there results were . sill , not a whole lot of info . so here is what i ended up doing - new caps . the ones i chose are dayton 12uf caps . i chose dayton because parts express is only about 12 miles from my house and the caps were well spoken of and they were reasonable cost . i am still concerned about the L-pads because some say that they will change the frequency and the impedance a little . others say it won't . i can't get a real answer from anybody and i don't know this stuff enough to argue the point either way . i want a direct replacement but since i can't find one this is what i decided to try . i installed a parts express L-pad in the original holes . the L-pad is 8 ohms 15 watts . i attached pics so let me know what you think . Edited July 16, 2019 by mark fader Quote Link to comment Share on other sites More sharing options...
Mallette Posted July 13, 2019 Share Posted July 13, 2019 I wouldn't have worried over the pots. All Fraziers I have that feature them I run them in the middle, null mode anyway and the speakers are awesome. Dave Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 13, 2019 Author Share Posted July 13, 2019 so what you are saying is that the L-pads are fine ? there is no difference between the original pots and the new L-pads ? Quote Link to comment Share on other sites More sharing options...
glens Posted July 13, 2019 Share Posted July 13, 2019 Should be the only items in need of refreshment are the capacitors unless perhaps the speakers have seen excessive electrical abuse. Caps can be expected to change over time all on their own while the other components are quite stable. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 14, 2019 Author Share Posted July 14, 2019 The reason for the pot replacement was because 2 went bad. I have a total of 4 because I have 2 cabinets. All 4 were scratchy so I cleaned them.all 4 got better - 2 cleared up real good but 2 not so much. I took those apart and found the wire was broken on 1 and the other had a bad spot. So I just decided to change all of them. I just think it was age. Nothing last forever. That is my only concern because I’m installing something that wasn’t originally there. Quote Link to comment Share on other sites More sharing options...
avguytx Posted July 14, 2019 Share Posted July 14, 2019 Try them without the lpads and see what they sound like. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 14, 2019 Author Share Posted July 14, 2019 I will. I figured I would try them with and without. I’m even going to put the 2 original good pots in one cabinet and compare them to each other Quote Link to comment Share on other sites More sharing options...
glens Posted July 14, 2019 Share Posted July 14, 2019 30 minutes ago, mark fader said: I’m even going to put the 2 original good pots in one cabinet and compare them to each other That's some rational thought! Quote Link to comment Share on other sites More sharing options...
kevinmi Posted July 14, 2019 Share Posted July 14, 2019 I have a pair of original Model 7's in working order if you need to do a hearing comparison. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 14, 2019 Author Share Posted July 14, 2019 That’s a long way for you to drive and they are a bit heavy to carry around. but if you feel the need to come over than I guess it would be ok. Thanks for the replies but I still don’t have a real answer. Are the lpads going to change the circuit in any way ? I stuck my meter on the terminals and it’s reading 7.5 ohms. Close enough to 8 for me. Turning the lpads made no difference on the meter. I haven’t hooked them up too my receiver yet and I don’t think the lpads will harm anything but I’d like to hear from somebody who understands this more than me explain / tell me they will work or not and some expiation as to why. Just wondering because I want these cabinets to be put together the right way. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 15, 2019 Author Share Posted July 15, 2019 So I’ll answer my own question. After reading more forum pages the answer is yes lpads will make changes. However , since the speaker , crossover , amp , and lpads have so many variables anyway, it won’t make a noticeable difference. So in my mind I’ve come to the conclusion that lpads will be just fine. After all this very purpose is what they were made for. Thanks to the forum for all the great info !! Quote Link to comment Share on other sites More sharing options...
pzannucci Posted July 15, 2019 Share Posted July 15, 2019 The lpads will start to have dead spots and at minimum, need contact cleaner and lubricant. For their age, I had the Mark Va's of the same vintage, same crossovers, woofer, piezo, and mid, just 1 tweeter though. (piezos can get a little unhappy too though hard to find the old Motorola types). 4 12uf - dayton is fine. Much better than the originals Choke should be fine From what I remember, wired in a series type configuration lpads probably could use replacement or tlc outlined above at minimum. They seemed to burn though so mine ended up with some dead spots (I used to crank mine anyway). They will not sound good unless you like screechy highs and too much mid unless run around center or slightly higher on the lpads. Quote Link to comment Share on other sites More sharing options...
Marvel Posted July 15, 2019 Share Posted July 15, 2019 22 hours ago, mark fader said: Turning the lpads made no difference on the meter. LPads are designed to have the same input and output resistance over their range of rotation. That's what they do, while changing the level of the signal that goes to the particular speaker. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 15, 2019 Author Share Posted July 15, 2019 I agree. That’s why I’m so confused as to why the originals were pots. I just don’t understand. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 16, 2019 Author Share Posted July 16, 2019 (edited) good news . i just received some info on the pots . yes they are in fact potentiometers . they are a 30 ohm 2 watt linear pot . not L-pads or t-pads or rheostats or anything else . I stress this because I've been told all sorts of things . honeywell bought out clarostat many years ago . they have documentation of the original clarostat stock . the value listed above came directly from honeywell . now the problem is i can't find a 30 ohm 2 watt linear pot anywhere and honeywell doesn't have a direct replacement . however , they are able to make these pots from the parts they have on the shelf . i don't know what is involved in all that but I'm getting more info on that tomorrow ( hopefully ). anybody else need pots ? if there is enough need maybe i'll get an order put together . so i have to take a step back . above i was sure L-pads were the way to go but after this info i'm not so sure . i don't claim to be a guru with this kind of stuff , but as i continue to reason on all this , jack frazier did it this way for some reason . i don't know his reason , but it had to be based on something . if L-pads were the better way to go then wouldn't he have done that ? but he didn't . he used pots . so the search continues ... i haven't shut the door on using L-pads . but if i can get my hands on a direct replacement pot then that's what ill do. Edited July 16, 2019 by mark fader Quote Link to comment Share on other sites More sharing options...
glens Posted July 16, 2019 Share Posted July 16, 2019 How's it wired in? Crossover output to the outsides and driver to one side and the middle? If so, it would make a difference. If one of the outsides isn't connected to anything then the specific 30 ohm value is unimportant except for the knob or whatever lining up with markings on a label. Even if it was the first possibility, you could go with something with a lower value and make up the difference with a fixed resistor wired between the one outside terminal and the wires from the crossover and driver. You just wouldn't have full range of adjustment but everything else would be right. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 16, 2019 Author Share Posted July 16, 2019 all three terminals are wired . the center ( wiper ) goes to the speaker positive . one of the outside is connected to the crossover positive and the other one of the outside is connected to negative . btw - dark brown is + and light brown is - attached are some pics . the pot wiring pic is the tweeter pot still in circuit . the pot top and pot bottom pics are the midrange pot cut out of the circuit . i cut the wires and left a little on the ends of the pot . that is the original solder job . apparently by Ed himself because the cabinet is signed " may " right by the tweeter . Quote Link to comment Share on other sites More sharing options...
pzannucci Posted July 16, 2019 Share Posted July 16, 2019 Pots vs lpads... maybe it was too long ago :-) . From what I remembered, they used to have the woofer in parallel with the caps and mids in parallel with the coil. If they didn't worry as much about impedance for crossover frequencies, perhaps you should. Doesn't look like you have the original electrolytic caps which is good (unless you just replaced them). Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 16, 2019 Author Share Posted July 16, 2019 I just replaced the caps. The pics at the very top show what I did. I just mounted everything on a board and copied the circuit. The cabinets were completely stock when I opened them. The choke is original. So you are basically saying to go with the lpads because they try to keep the resistance as constant as possible ? Quote Link to comment Share on other sites More sharing options...
babadono Posted July 16, 2019 Share Posted July 16, 2019 So if i understand correctly the pots allowed the varying of the power to the driver but since it was a pot and not a pad this would reflect a different total load back to the crossover which in turn would vary the crossover frequency and slope at least somewhat. Sort of a "sound shaping" control and not just a level control. Quote Link to comment Share on other sites More sharing options...
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