I'm rebuilding a McIntosh C27 preamp and I'm having trouble discerning the orientation of eight, small, 2.2uf electrolytic caps in the pushbutton assembly. The schematic is too large to upload completely, so I've enclosed some pertinent pages. It appears to me that the schematic and pcb outline board are in conflict as to orientation. If I'm wrong on that, please set me straight. If there is a conflict, then could someone tell me which of the two exhibits is correct. Thanks in advance.
I had a look at the full schematic. Ray is correct, McIntosh uses the symbol you refer to for non-polarized caps. Polarized caps have a "+" indicating orientation. This was one common way to draw schematics back then.
Do you know they are electrolytics from looking at the actual preamp? Do not assume they are electrolytics from the schematic.
Do you know they are electrolytics from looking at the actual preamp? Do not assume they are electrolytics from the schematic.
My evidence is that the existing caps are aluminum cans (without markings). However, it possible those caps had been replaced. Looking at the overall schematic, there are many, non polarized, film caps that had symbols with two straight lines. I'm not sure how to proceed. If I've got the polarized caps in backwards, then they will cause problems. Non polarized would not be a problem. Guess I could try to find out if the old ones were non polarized.
You definitely should use either nonpolar electrolytics, or film types (always nonpolar
but will likely be physically too large). Trust me on this.
Polar electrolytics in these positions will not function properly.
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I would love to see a schematic section where DC is present to make certain.
In my youth, non polar caps (plastic, paper, etc.) were drawn using 2 parallel lines, the classic capacitor symbol used since forever.
Electrolytics were drawn using a straight line and a curved one, which indicates that terminal is also the (aluminum) case.
Certainly there was a difference between US/UK way of drawing and Euro one (basically DIN rules) and another way was to use a flat line and a largish dot.
As to Purists, yes you are right stricto sensu, but polarized caps have been used by the millions , since forever, with no DC applied, and worked very well.
Like on most capacitor discussions, one important and often ignored factor is voltage drop *across* capacitor.
Nil voltage drop? ... nil problems.
In my youth, non polar caps (plastic, paper, etc.) were drawn using 2 parallel lines, the classic capacitor symbol used since forever.
Electrolytics were drawn using a straight line and a curved one, which indicates that terminal is also the (aluminum) case.
Certainly there was a difference between US/UK way of drawing and Euro one (basically DIN rules) and another way was to use a flat line and a largish dot.
As to Purists, yes you are right stricto sensu, but polarized caps have been used by the millions , since forever, with no DC applied, and worked very well.
Like on most capacitor discussions, one important and often ignored factor is voltage drop *across* capacitor.
Nil voltage drop? ... nil problems.
I've just reviewed my full C27 service manual and, in spite of my memory, I cannot find a parallel line symbol anywhere - schematic or diagram. I know that I've looked at parallel symbols in the last 24 hours (maybe some gremlin sneaked into my computer last night and changed them all.) And McIntosh seems to have followed a consistent pattern throughout the documentation.
As to the issue, it looks like the clear answer is to install non polarized caps. Hopefully, I'll be able to find caps that fit. Thanks for straightening me out on this.
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