3rd Jan 2023, 8:03 pm | #121 |
Tetrode
Join Date: May 2009
Location: Hereford, Hereford and Worcester, UK.
Posts: 94
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Re: Fidelity transistorised Playmaster - reverse engineering?
Ben, Following this with interest, although I no longer have the machine.
Diagram in post 18 is for a different machine. Not sure it is the same. From memory, the Fidelity was positive to chassis but someone else will be able to confirm. Photos in post 1 and 105 show the rectifier location at the RH end of the board and you can make out the rectifier connections. The 16 volts that you have must be at the input to the rectifier - the heater and HT of course come direct from the transformer. Last edited by Borderer; 3rd Jan 2023 at 8:22 pm. |
3rd Jan 2023, 9:03 pm | #122 |
Dekatron
Join Date: Aug 2006
Location: Madrid, Spain / Wirral, UK
Posts: 7,500
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Re: Fidelity transistorised Playmaster - reverse engineering?
Thanks. Replaced missing rectifier bridge, 1000uF smoother (+ve gnd), replaced missing 1000uF cap on output stage. Replaced 1x 25uF/25v cap which had leaked and had leg hanging off.
Now there is hum and a slight crackle from speaker if volume adjusted. If REC selected green segment in magic eye lights up, but just as one dull blur. So, some progress but still not operational. Will keep at it.
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Regards, Ben. |
3rd Jan 2023, 9:13 pm | #123 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,607
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Re: Fidelity transistorised Playmaster - reverse engineering?
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3rd Jan 2023, 9:27 pm | #124 | |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,607
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Re: Fidelity transistorised Playmaster - reverse engineering?
Quote:
The TR8/9 are a 2 valve hybrid with EM87 Magic Eye and ECH83. David |
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3rd Jan 2023, 9:41 pm | #125 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,874
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Re: Fidelity transistorised Playmaster - reverse engineering?
. . .Oh dear, I'll have to get those Playmaster remains out from under my bed and get on with some more drawing–out me thinks – (it got put on one side because of holidays, eye–surgery, repair work for another Member, now complete), and the panel I got being only part–complete, hence me having to puzzle some of it out still!
Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
28th Nov 2023, 11:15 pm | #126 |
Dekatron
Join Date: Aug 2006
Location: Madrid, Spain / Wirral, UK
Posts: 7,500
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Re: Fidelity transistorised Playmaster - reverse engineering?
I recently looked at my moribund unit again. A dodgy design to begin with and an example which had missing parts and had been got at -a glutton for punishment am I!
One of the output pair was s/c, I replaced the AC128 and AC176 with an AC187 /AC188 pair which I had to hand, now there's quite a strong output but the signal is of terrible quality, very distorted/fuzzy and a bit of buzz. The winding for track 1 of the R/P head is o/c, so am awaiting a suitable replacement. Erase does not work. For all I know the erase head may be open too! The odd display on the EM87 was due to a green (signal?) and a yellow wire having detached themselves from the pcb. Now when Rec is selected the display is a bit jittery, but not blurred. I will do some more tests on the resistors and erase head if/when I get a new R/P head.
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Regards, Ben. |