Rob Ineson Posted April 27, 2011 Report Share Posted April 27, 2011 Hi there, this is my first post on here. first of many i hope. I have just removed my dads LST-2's from his garage with the hope of restoring them to their former glory. The first thing I want to do is check all the drivers. The problem I have is that the woofer surrounds have all perished so I obviously dont want to power those up. Is it safe to plug the speakers in with the woofers removed to check the other speakers? I can see from there how good or bad the situation will be. Cheers, Rob Link to comment Share on other sites More sharing options...
dynaco_dan Posted April 28, 2011 Report Share Posted April 28, 2011 Hi there, this is my first post on here. first of many i hope. I have just removed my dads LST-2's from his garage with the hope of restoring them to their former glory. The first thing I want to do is check all the drivers. The problem I have is that the woofer surrounds have all perished so I obviously dont want to power those up. Is it safe to plug the speakers in with the woofers removed to check the other speakers? I can see from there how good or bad the situation will be. Cheers, Rob Hi RobGreat speakers.Depending if you will be up to the task of refoaming the woofers or not.If not, do not do anything just yet as more members read this topic and can offer much more advice.If yes, go to library and read up on the AR-3A repairs.If yes, remove and check the fuses for continuity and verify that they are the correct amperage rating or slightly less, never more.If yes, very carefully remove the woofers and unsolder one wire or both, do not let the ends touch each other.Turn the switch a few cycles to clean the contacts and with a low level signal to them, listen to each driver foroutput.More advice to follow. Link to comment Share on other sites More sharing options...
Rob Ineson Posted April 28, 2011 Author Report Share Posted April 28, 2011 Hi Dan, Thanks for the quick reply. I checked the tweeters and mids on a low volume earlier this evening. One unit was fully functioning but when I tried the other i got absolutely nothing through any of the drivers. I thought this to be strange so I changed the fuses over. When I tried again I got some sound! but only for a few seconds then nothing again. I have checked both fuses and they seem to be fine, and from what i have read on here, even if the fuses are dead there would still be some sound but at a lower level. This has somewhat confused me. I spoke to my Dad about it and he vaguely remembered that the selector switch on one was "abit dodgy". I went to look into this and found what looked like some DIY work on the crossovers. It was only the speaker wires that had been extended for some reason. i asked about this too but my Dad said he had never touched them and he bought them new. hmmmm... the plot thickens... hehe. i'll get some pics up tomorrow. Link to comment Share on other sites More sharing options...
deek Posted April 29, 2011 Report Share Posted April 29, 2011 Dead fuses = no sound. No exceptions.An intermittent sound from the drivers suggests dirty level switches.-Deek Link to comment Share on other sites More sharing options...
Rob Ineson Posted April 29, 2011 Author Report Share Posted April 29, 2011 Dead fuses = no sound. No exceptions.An intermittent sound from the drivers suggests dirty level switches.-Deekwhen you say level switches, are you referring to the spectral balance switch? Link to comment Share on other sites More sharing options...
deek Posted April 30, 2011 Report Share Posted April 30, 2011 Yes, the "spectral balance" switch cuts the level of the drivers depending on the position. It's a switch that has contactors that can corrode to the point they don't make enough contact and will cause one or more drivers to not receive signal.Unlike most "level" switches that only attenuate one driver, the LST-2 "spectral balance" switch attenuates all the drivers to a certain level depending on the positionTom Tyson's excelent schematics are here: http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/Page two of the LST-2 drawing has the switch detail and lists the attenuation levels for each drivers at each switch position.-Deek Link to comment Share on other sites More sharing options...
KlausDK Posted April 30, 2011 Report Share Posted April 30, 2011 Dead fuses = no sound. No exceptions.An intermittent sound from the drivers suggests dirty level switches.-DeekThat is actually not correct for the LST's, due to their construction with transformers i guess, they do have sound even with the fuse blown, I suspect that is the case for the LST-2 as well. That said, I don't think it is a fuse problem either, sounds more like a bad connection somewhere e.g. in the spectral level switch.BRgds Klaus Link to comment Share on other sites More sharing options...
Rob Ineson Posted April 30, 2011 Author Report Share Posted April 30, 2011 Thanks for the replies, much appreciated. I was wondering about the wires coming from the crossover to the speakers, can I just change them for good quality speaker cable? The diy extensions were on there for a reason so I thought just changing the lot for some decent speaker cable would be worthwhile. I'll probably change the speaker binding posts for gold plated ones too. I really can't wait to get these beasts up and running Oh.. and one more question... is there a particular brand of foam surround kit that I should go for? Link to comment Share on other sites More sharing options...
rjr513 Posted May 1, 2011 Report Share Posted May 1, 2011 Me personally I prefer the kits from MSound,I also like the "Boston" smooth filled fillet, MSound kits can be found on ebayOn the restores I've done I have used 14awg wiring and I would stay with same color code wiring,so I would use the other good working speaker crossover to make proper changes to the non-working speaker and also you can download the wiring diagram from the libary section.Owning a pair of LST2 I can say you want regret the time spent to bring these speakers back to life again Link to comment Share on other sites More sharing options...
deek Posted May 1, 2011 Report Share Posted May 1, 2011 How very odd... the fuse is after the transformer. I wonder what that's all about. Should have looked at the schematic more closely!-Deek Link to comment Share on other sites More sharing options...
Rob Ineson Posted May 1, 2011 Author Report Share Posted May 1, 2011 talking of schematics..... look at this crossover and tell me what the hell went wrong when they put this together? :sThe yellow tweeter wire is coming from the fuse holder. bizarre. Link to comment Share on other sites More sharing options...
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