Musical Fidelity B1

Goetz · 16th January 2010, 05:09 PM

Dear All,

does anyone has a circuit plan from Musical Fidelity B1 ?
I want to make some mods...
Your advise would be highly appreciated !
Have a nice weekend.
Goetz

mjf · 16th January 2010, 06:18 PM

hallo.
with the search button you will find some threads for mf b1.........
e.g.
Index of /pdf/Service Manuals/Musical Fidelity
and so on.........
einfach search am ende der seite unten benützen
grüsse

Goetz · 16th January 2010, 06:57 PM

Dear MJF !

Herzlichen Dank nach Österreich !

Have a nice weekend.

dynoPort · 23rd May 2010, 09:02 AM

hi all I have a MF B1 bought off ebay

and the R68 resistor is smoking - getting very hot. I'm not too expert but I suspect a short in one or more of the 2N3055 bipolars? any thoughts?

Goetz · 23rd May 2010, 09:27 AM

Hi,

I just "achieved" the same condition during tuning by creating a short circuit. Are all 8 transistors getting hot or only one line(4pcs) ? (of course aside of hot resistor) I think in my case I have to exchange all 8 transistors after 20 years of operation.
Have a nice weekend.
Goetz

dynoPort · 23rd May 2010, 10:22 AM

Quote:

Originally Posted by Goetz

Hi,

I just "achieved" the same condition during tuning by creating a short circuit. Are all 8 transistors getting hot or only one line(4pcs) ? (of course aside of hot resistor) I think in my case I have to exchange all 8 transistors after 20 years of operation.
Have a nice weekend.
Goetz

I have to switch off the power before the transistors have time to get hot but I'm thinking of changing the transistors, just don't want the problem to be still there if I do

jez · 23rd May 2010, 12:33 PM

Output transistor failure is indeed the main problem with these amps. The 2n3055's fitted (Pecor if I remember correctly) are a cheap and nasty type and you would do well to replace them with better quality devices

dynoPort · 23rd May 2010, 01:30 PM

Quote:

Originally Posted by jez

Output transistor failure is indeed the main problem with these amps. The 2n3055's fitted (Pecor if I remember correctly) are a cheap and nasty type and you would do well to replace them with better quality devices

They are pecor I have easy access to some ST (ON?) types seem cheap tho! and would a blown transistor cause that resistor to over heat? thanks

jez · 23rd May 2010, 02:18 PM

Quote:

Originally Posted by dynoPort

They are pecor I have easy access to some ST (ON?) types seem cheap tho! and would a blown transistor cause that resistor to over heat? thanks

Yes it would indeed cause r68 to smoke...
ST and ON Semi are different companies. ON used to be Motorola.
Any reputable brand should be ok but watch for fakes and try and get all 8 from the same batch. Best go to the likes of R.S, Farnell, Digikey etc to ensure the above criterion.....

magnu · 23rd May 2010, 08:56 PM

Watch out for the 2N3055. This is a very wide spec, almost any chip can fulfil the spec. It is a popular part number to dump chips that are out of spec for other part nos.

I.e. you can get exactly anything in these parts. It has been this way since late 80s.

16th January 2010, 05:09 PM	#1
Goetz diyAudio Member Join Date: Jul 2007	Musical Fidelity B1 Dear All, does anyone has a circuit plan from Musical Fidelity B1 ? I want to make some mods... Your advise would be highly appreciated ! Have a nice weekend. Goetz __________________ Goetz

16th January 2010, 06:57 PM	#3
Goetz diyAudio Member Join Date: Jul 2007	Vielen Dank ! Dear MJF ! Herzlichen Dank nach Österreich ! Have a nice weekend. __________________ Goetz

23rd May 2010, 09:27 AM	#5
Goetz diyAudio Member Join Date: Jul 2007	B1 Hot resistor Hi, I just "achieved" the same condition during tuning by creating a short circuit. Are all 8 transistors getting hot or only one line(4pcs) ? (of course aside of hot resistor) I think in my case I have to exchange all 8 transistors after 20 years of operation. Have a nice weekend. Goetz __________________ Goetz

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16th January 2010, 06:18 PM	#2
mjf diyAudio Member Join Date: Jan 2009 Location: upper austria/near linz	hallo. with the search button you will find some threads for mf b1......... e.g. Index of /pdf/Service Manuals/Musical Fidelity and so on......... einfach search am ende der seite unten benützen grüsse

23rd May 2010, 09:02 AM	#4
dynoPort diyAudio Member Join Date: Oct 2004 Location: Cymru/Wales	hi all I have a MF B1 bought off ebay and the R68 resistor is smoking - getting very hot. I'm not too expert but I suspect a short in one or more of the 2N3055 bipolars? any thoughts?

23rd May 2010, 12:33 PM	#7
jez diyAudio Member Join Date: Jan 2004 Location: n.e england	Output transistor failure is indeed the main problem with these amps. The 2n3055's fitted (Pecor if I remember correctly) are a cheap and nasty type and you would do well to replace them with better quality devices

23rd May 2010, 08:56 PM	#10
magnu diyAudio Member Join Date: May 2010 Location: Stockholm	Watch out for the 2N3055. This is a very wide spec, almost any chip can fulfil the spec. It is a popular part number to dump chips that are out of spec for other part nos. I.e. you can get exactly anything in these parts. It has been this way since late 80s.

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