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Mission PCM II DC offset issue?
Mission PCM II DC offset issue?
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Old 19th January 2019, 07:35 PM   #1
humanbenIlkley is offline humanbenIlkley  United Kingdom
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Join Date: Dec 2008
Exclamation Mission PCM II VDC on line out?

Hi folks,
I have recently acquired a Mission PCM II cd player in working order however, when it's switched on my speakers pop (also does this when you turn it off too.) So i'm thinking there must be some dc leaking through?
Now i've tested it from cold, turning it on with a meter (300mV) on the outputs, it goes off scale & finally settles after about a minute or so to approx. 4mV on right channel & 1mV on left.
My question is does anyone have this player & willing to test it & or is this normal for a PCM II?

Thanks

Last edited by humanbenIlkley; 19th January 2019 at 10:03 PM. Reason: didn't make sense
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Old 21st January 2019, 03:49 PM   #2
Mike P is offline Mike P  England
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Join Date: Jan 2012
Location: South Yorkshire
The PCM II will likely have a pair of coupling capacitors in series with the output which are there to block any DC from getting through to the amp. Usually in players of this level they will be a pair of electrolytics of between 22uF and 220uF (sometimes bipolar).


If you think there's too much DC on the output the first thing I would do is check that someone hasn't removed the DC blocking output coupling caps. Sometimes people remove them and replace them with a wire link because having no caps in series with the output sounds better. You don't need DC blocking caps in both the output of the CD player and the input of the amp.
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Old 21st January 2019, 04:26 PM   #3
humanbenIlkley is offline humanbenIlkley  United Kingdom
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Join Date: Dec 2008
Hi Mike, It's driving me nutz! I stripped the player down completely, the only problems I've found are typical of Philips based players, those blue axials were shot. Cyrus added there bit to it which is where I think the problem lies, As its part of the output stage & volume, It does have 2 sets of bipolar capacitors;
a pair of bakelite Roe eku 47uf in series with the output & 470uf (same bakelite Roe) near the input of the cyrus pcb, both show good esr but have gained some uf.
My amp is a Sansui AU-217II if that makes any difference?
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