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Magnevox CDB486 CD Changer
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Author:  moestevens [ 29 May 2018, 11:12 ]
Post subject:  Magnevox CDB486 CD Changer

Looking for anyone with experience with this CD changer.
I picked it up at a flea market, and powered it up before buying it. I had to buy a magazine from eBay to test it and was disappointed. I bought a reprinted repair manual, disassembled it, and found 2 broken micro switches. I am in the process of replacing them, and found a obvious after-market modification: 2 ea 1N914 diodes and a cut trace. They form an "or" gate which adds TCMP (Turntable control motor pulse) to the QDA (Q channel data signal) normally sent separately to the microprocessor. I have scoured the Internet and found no clue as to the purpose of the mod. Why these two seemingly unrelated signals have been joined is puzzling. I hesitate to remove the mod until I get the transport working.
By the way, IMHO, do not try to disassemble the changer mechanism without a manual (or contacting me) You will almost certainly break something if you don't know the procedure.
Thanks in advance for any help.
Moe

Author:  moestevens [ 17 Jun 2018, 16:29 ]
Post subject:  Re: Magnevox CDB486 CD Changer

Just a follow on. I found broken micro switches in the changer mechanism, and tried to replace them with similar generics (the originals are constructed of unattainaium). Much trouble trying to get it to load and eject disks, and finally gave up, as timing of the microswitches and the programming of the controller are both in question, and after hours wasted, ordered a working one from ebay. I now have a ton of spares. I will be bypassing the internal DAC and sending the I2s to a new preamp I am designing, based on the one in Fred Nachbauer's (RIP) RA100 Design. I already have built a Pavouk DAC using 4 TDA 1543's that work nicely. It will be incorporated into my new preamp. I will post my progress there shortly in another thread.

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