ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I'm just coming into this fascinating discussion as a latecomer to the party.
There was indeed an issue with servo system "ringing"or more correctly instability.The notorious C2103 figured in the argument even then
B&O were well aware of it when the units were still relatively new.
I have some notes regarding this,but they are unfortunately buried in storage at the moment.
There were several suggested "fixes",but often we just replaced the entire cd module,as customer satisfaction was paramount.B&O even provided the module on a part exchange basis.
I think that it's quite likely that C2103( and it's optimum type) is critical because any noise in that particular servo would surely end up in the laser beam,confusing the decoder?
Thanks to everyone for your input to this long running debate.
Nick
Well, the plot thickens.
My unit is a CDM 4/33, which I guess means the 33rd iteration of something. Hmm.
I have done a few very simple calculations based on my old rule of thumb of 1nH/mm parasitic inductance. Has the servo board layout anything to do with the problem? I can easily get up to 40nH in series with C2103 before it gets anywhere near a decent earth. That would put a resonant frequency somewhere in the 100kHz region. Without a scope I'm struggling to investigate, and I don't want to keep taking the unit apart to fiddle with it. Any thoughts anyone??
Also, I have noticed a previous bodge, where a 1.2nF capacitor has been soldered directly between the output (pin 1) of the focus motor amplifier (IC6104) and the far side of the input R3136//C2135 (ie connected to the -ve input, pin 8, of the op amp through R3136). Clearly that is there to reduce the high frequency gain of IC6104 on the focus motor drive. Has anyone seen this bodge before??
Thanks for all the inputs, loving the debate, making me think.