Old BGW 550D

sfox50 · 16th December 2009, 02:34 PM

I'm resurrecting an old 500D, it's the 7 inch version with the amp boards/heat sinks on the top of the case. I have replaced the PS caps with new Nichicon 21000 uf 80V , replaced the bridge rectifier (just to be safe), and installed an IEC socket for the power cable. The fan was quite noisy- I tried replacing it with a newer AC fan, but I still hear it at times. Would it be OK to run it with the top cover off & no fan? I'm running MMG's, so I do use the power that's available. Also- should I replace the Sprague electrolytic caps on the boards, or maybe bypass them with film caps? There is a single op-amp on each board- would it be good to update those? Thanks for whatever help you can offer!

djk · 17th December 2009, 09:04 AM

No fan=heat death.
Opamp, don't change.

Output stage on older ones will be quasi-comp, newer one shown here.

Replace the C1, C3, C11, C12 with new, and add a film bypass. Add a pair of 47µF bypass caps to main filter caps. Change all ceramin caps to film or silver mica (as appropriate for values).

sfox50 · 17th December 2009, 01:20 PM

djk- thanks for the quick reply. The fan & top cover will go back on! I have the manual & schematic ( generic, for the 500D & 750D). The C1 cap is shown as a 10UF 25V Tantalum, what should I use to replace that? What would be good to use for the film bypass? Thanks again!

16th December 2009, 02:34 PM	#1
sfox50 diyAudio Member Join Date: Jan 2005 Location: Central Maryland	Old BGW 550D I'm resurrecting an old 500D, it's the 7 inch version with the amp boards/heat sinks on the top of the case. I have replaced the PS caps with new Nichicon 21000 uf 80V , replaced the bridge rectifier (just to be safe), and installed an IEC socket for the power cable. The fan was quite noisy- I tried replacing it with a newer AC fan, but I still hear it at times. Would it be OK to run it with the top cover off & no fan? I'm running MMG's, so I do use the power that's available. Also- should I replace the Sprague electrolytic caps on the boards, or maybe bypass them with film caps? There is a single op-amp on each board- would it be good to update those? Thanks for whatever help you can offer!

17th December 2009, 09:04 AM	#2
djk diyAudio Member Join Date: Feb 2001 Location: USA	No fan=heat death. Opamp, don't change. Output stage on older ones will be quasi-comp, newer one shown here. Replace the C1, C3, C11, C12 with new, and add a film bypass. Add a pair of 47µF bypass caps to main filter caps. Change all ceramin caps to film or silver mica (as appropriate for values). __________________ Candidates for the Darwin Award should not read this author.

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17th December 2009, 01:20 PM	#3
sfox50 diyAudio Member Join Date: Jan 2005 Location: Central Maryland	djk- thanks for the quick reply. The fan & top cover will go back on! I have the manual & schematic ( generic, for the 500D & 750D). The C1 cap is shown as a 10UF 25V Tantalum, what should I use to replace that? What would be good to use for the film bypass? Thanks again!

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