Looking for Altec Lansing 2204A-SP schematics

[avincenty]

I go my hands on two Altec Lansing 2204-SP for almost nothing, on one all the 4 channels worked and on the second only 1 channel worked. I opened up the second unit and cleaned the connectors with deoxit, all three remaining channels came back to life.

My original plan was that I could use these as donors for putting in 4 new channels per chassis. The transformer is very large and from what I found on the internet it is used in other Altec units that yield up to 600 audio watts.

I have been searching for the schematics but do not find anything online. I wonder if these 2275 amp modules can be improved. The unit has balanced inputs into transformers with some relays and input matrix selector. It looks very well made.

There is turn on and turn off thump on all channels with no hum. There are two pots on each board, probably bias and dc balance. Not sure what the relays I hear do.

Anyone out there with schematics or a service manual willing to share?

The end goal is to use the amps for 4 way dipoles using dsp.

Thanks

Alfredo

 

[avincenty]

Traced the 2275 amp module

I think it is going be difficult to get a real copy of the schematics. I painstakingly started tracing last week, after many back and forth revisions I have not found more mistakes. Doesn't mean it may not have errors, the board now always looks the same

There is an input board feeding the amp modules, i will try doing that next. There is a diode CR15 pointing back to the input board, not sure where it connects to. All DC measurements show predictable values except the Q7 and Q8 pair that with shorted inputs and with music appear to be turned off. What is that pair supposed to do?

Going back to my original question, could this circuit be improved? The inductors do not have any values printed on them. Also, notice that the board does not have R31 and C8 which appear to have been part of a feedback loop into Q3. Possibly those are used on the 2200 series amp that comes rated at 16ohms vs 8 ohms for the 2204A. Also two of the 8 amp modules I have contain a pair of RCA3773 the other 6 have the MJ15024.

Any suggestions are appreciated.

Thanks

Alfredo