frankmarsi Posted August 12, 2010 Report Share Posted August 12, 2010 8-12-10 3P.M.O.K. here’s an usual problem for all of you members. Three weeks ago the lower right channel of my system ‘s two amp, four speaker, set-up had stopped working.When the problem first started I un-hooked and then re-hooked the speaker's cables and fuses, changing all cables and interconnecting cables, pre-amp to amp cables and again changed the 'problem' speakers to new fuses and I had success the second time of this operation, after at first failing to prove good results yhe first time around, extremely frustrating at best. I had also changed the fuses five times using a new fuse every time on the problem speaker. All speaker leads and connections were traced, un-done and re-done (speaker cables are the originals made by me in 1990 and spaded 10 AWG, all soldered connected spades were ‘wiggled’ and pulled upon many times for tightness, removed and re-connected from the binding posts, I didn't see any (as per "Vern" and I learned from yrs. ago) green oxidation either. All amp volume and balance controls were rotated many times (amp fuses were checked too), all pre-amp balance and volume controls rotated many times, all pre-amp switches were tried many times). The LST's spectral control was rotated many times. Finally the whole system worked as it should normally. I was happy, but still wasn’t aware of why I had a singular speaker ‘fall-out’ on the ‘lower-right’ as the all the other three channels worked correctly and amp out-put meters showed the amp was putting out on all four channels, that's to say, two left and two right channels. This week the output of the lower right channel was out again just as before with no apparent reason (no amp over heating, no fuses blowing, etc.). I repeated all of the same above changes and installed new speaker fuses again, also checked the amp's fuses. Both amp’s meters were showing output This latest time I used a ‘test-speaker’ in line of the lower right channel as the system was playing with system speakers connected and to the ‘out’ channel of the amp. The test speaker played loud and clear, but the ‘systems’ speaker did not, out ruling the amp being 'out'. This is not a 'four-channel' system, but simply a vintage 'stereo' system with four separate channels, two lower left-channels and two upper right channels. No 'quad' or 7.1 here my dear, heavens forbid, just good old two-channel with four 'stacked' AR-LST's and two stereo high power amps. Any insight here? I just don’t get it? My speakers were originally from an “Broadway” theater here in New York City when first installed as theater monitors and 'PA' speakers since 1972 when in 1988 I first acquired them and I have been using them since 1990 with-out any problems other than re-foamed woofers, replacement tweeters, etc. No ‘cap’ or connectors changes have ever been made since they were originally manufactured ( I have read that 'cap' changing is not always needed, although fuse posts and terminals were cleaned in 1990. Strangly enough, there is still a very slight vibration from the 'out' speaker's mid and woofer, although this may be from the 'upper' speaker's cabinet vibrations sitting on top of it. Although I know a 'blown' fuse in LST's will give this effect of minimum output, I have changed the fuse many times with no positive results.After 38 years plus of being first manufactured are my LST’s prone to a new crazily enough ‘virus’ or some sort of major and unheard of ‘cap’ , or resistor or internal wire failure or strange other problem?The speakers in question are LST’s and the obviously still working amps are PL-700Series Two, both amps were rebuilt by Ed Blaclwood, one of the last PL guys in Wash. state who knows about these beasts better than any one else, however he's not replying to emails, oddly enough, although I'm doubting it's an amp problem as proved so with the test speaker. All input sources, two turntables, two CD players and a tuner were used in all tests, but to no avail.FMP.S. I’m not kidding this time! Link to comment Share on other sites More sharing options...
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