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Hi Richard,
I don't doubt that you have a well equipped acoustics lab....
By the late 1970's, Altec was already in trouble. They were paying horrible amounts on the debentures LTV had dumped them with. They had already spun off Altec Service Corp. (which I worked for later on), the stoplight company, etc., and were struggling to hold on to the Altecom line and University Sound.
Their QC began to decline rapidly as the 70's ended. By 1982, when they filed, it was really awful. Most of the time, it was we sound contractors that repaired and corrected the QC problems with the items - right out of the box - before we took them to the jobsite.
I believe that the variances you have measured may be due to QC problems - certainly the difficulties with uniformity - something Altec didn't used to have to worry about - are part of the problems they were having at the time....
As for the Tangerine.... True, it WAS easier to build and install into the HF drivers, but it DID make them sound different. In the large 288 driver, though, a dip at 10 kHz appeared in the "H" that wasn't present in the "G" series. Jerry Hubbard and I talked about this a lot in the middle to late 1980's - he wanted to design a new phasing plug for the Altec drivers, but EV (aka BOB PABST) wouldn't allow Altec to do ANYTHING that might improve their products (after all - they were already VASTLY superioir to ANYTHING Extra-Viscious made then or now, so why let Altec make products that outpaced the EV product line even more?).
I know where the tooling for the Tangerine phase plugs (large and small) is, but I think that a new phase plug needs to be designed and built if these products are ever reintroduced...who knows? - maybe they could be offered with optional phasing plugs on special orders.... wouldn't THAT be neat?
Todd W. White, Owner & Webmaster
Altec Lansing's (unofficial) Homepage
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todd-------since you obviously have connections is there any way you can help me locate a schematic for a 351-B amp??????-------yea its the one with light bulbs on the emitters!!!!!!------i love to collect and restore old amps and i remember these from over three decades ago but hadn't seen one for a long time------i remember them being real junk------i recently found a nearly mint pair on e-bay and i want to go through them--------i don't mind paying whatever someone asks.............RC
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Geez Richard, how about restoring my MC2125 for me. You can even use it for a year afterwards. http://www.hostboard.com/forums/
It's a spare now.
Anyway the Altec 351 was perhaps the worst amplifier ever designed, but of course the 1611 was a close second. I guess you like the light bulbs in the emitter trick, but that went away in all the C's I used to repair weekly or was that weakly.
I really wish I had access to all the schematics I had from the 40's on up to the final days from where I used to work they had everything on file. Long gone now.
The Altecom intercom systems were known for a whole slew of lightbulbs used as current limiters for the control circuitry, stepper motors. 200 and 300 series. Those things drove me nuts. lol http://www.hostboard.com/forums/
Good luck with your search. http://www.hostboard.com/forums/
salvageV6 on your site. http://www.hostboard.com/forums/
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nice to meet an old friend---------i also have some of the C's------by the time they produced the C they finally got it right------so good in fact that i would allow it in my amp challenge-------do you know if there was an "A"------if so it must have really been awful----------i love collecting old amps and restoring them-----there must be a way to find a schematic for the "B" amp-------i too had one decades ago but must have misplaced it------i remember the B's failing so often that i finally quit fixing them and they piled up on the shelf in the shop till finally i threw them all away-------the transistors would fail just fast enough to protect the light bulbs!!!!!!--------altec, western electric and Macs are my favorites to restore and collect-------whats wrong with your 2125-----i have several of them too and am pretty familiar with fixing them.........RC
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You have to get the C's quiet enough to work in the Amplifier Challenge. http://www.hostboard.com/forums/
Don't mention that over here we have many happy tube afficiando's here. http://www.hostboard.com/forums/
In the field they made lots of snaps crackles and a few pops on distributed systems.
Then again we all know nobody has ever hung and 8 ohm horn or ceiling speaker on a 70 volt system either, which always distresses the little green box. http://www.hostboard.com/forums/
Actually on the MC2125 I use for mids. I bought another one on Ebay about 2 years ago and have forgotton what exactly is wrong with the first one. Old age moment here I guess.
Got it used from the Stereo Shop in Hartford. I shall plug it in this weekend to double check the problem.
I appreciate the help in troubleshooting.
It is greatly unfortunate my relationship with my former employer did not last as they had most every manual and tech. update since the 40's perhaps earlier.
I am sure there was an A model or at least a plain old 351 designation. Not big enough for a boat anchor. http://www.hostboard.com/forums/
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allan------my "C's" are very quiet and exhibit no extraneous noises...........RC
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Have experimented with replacing phase plugs circumferential with tangerines in the larger Altecs. Can be done without opening them up!! Used an old couple of beat up 290Ds which can also be altered to 288C type diaphragm fairly easily. Would not recommended doing this. Not only is it tedious but 290Ds are such a good sounding MR drivers which combined with a tweeter (902 etc) makes a very good power tolerant fullrange. The smaller drivers can not be so altered. Richard's testing results are interesting. I have NOT performed freq response tests on these before and after phase plug changes. This would be the ultimate test.
That is same driver, same diaphragm (288C) just different phase plugs. Maybe some day I will get to it.
Roland
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Richard, just plugged in the old MC2125 and it's dead. Fuse is good 8A. No lights nothing.
I guess I should pull the bottom off of it and try to get at the switch wiring and test it.
