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Philips MFB speakers

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jul 2021 at 8:00am
But without the motional feedback?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jul 2021 at 8:09pm
That would be interesting too. If you have a pair that work, you could use the service manual* to fix then and fine tune the servo feedback which is (ta dah!) the special feature of the MF series.

*available online or I can e mail you it if that would help?

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jul 2021 at 7:30am
I didn't get round to the recapping but did remeasure the supply caps and got similar readings in 2021. Then I listened ti them and found they were working!

Jon

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jul 2021 at 10:12pm
After a busy day I had a few more hours of enjoying old music on old speakers including The hounds of Love which sounded great.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2021 at 12:05pm
Several hours ago I serviced my 544's. In each case a good hoovering with a soft brush came first. Visual inspection and physical stuff like unplugging replugging connectors.

Power up and 10 minutes warm up before adjusting the two amps' bias. Both had the mid/high amp bias close to correct whereas the woofer amp bias was low. Leave and recheck.

Then I set up the test signal and adjusted the MFB servo gain. The test was quieter than I expected and easy enough once my analogue signal generator settled on 125 Hertz.

I am now two hours into checking my work with some music. Currently I have Who's Next playing. It just reached Won't Get Fooled Again. Great as always and just older than my MFB speakers. Philips have earned more of my respect!


Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2021 at 12:21pm
Originally posted by Fatmangolf Fatmangolf wrote:

Philips have earned more of my respect!



I should think so too! Otala did tons of research for them in the '70s - something lost on the back scratching hi-fi press.
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2021 at 1:30pm
The fact both active speakers are still working well 45 years later with the original parts inside is very impressive. That's worth respect as much as the excellent R&D Philips were known for and demonstrate in the circuits and drivers here.

To be fair I have looked after these speakers. They were the flagship model when my father worked for Philips in the seventies but too expensive even with staff discount. We had various bits of their kit including a music centre. So I was delighted to pick up a pair of MFB speakers second hand.
 
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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