Reminising Bose 901's

gdb

Easter's all about resurrection !

Schurkey

geoff727 wrote: »

I'd love to do some upgrades to the equalizer, and see how things change.

Just finished that about a month ago.

My limited electronics knowledge works against me. The only thing I did was rip out every electrolytic cap on the board, and replace with similar-value fresh, new caps. None of the original caps "appeared" to be defective. None bulged, none leaked.

Not a world of difference. Seems quieter in terms of background noise; and that itself was worth the effort. The location and intent of this music system doesn't lend itself to intense, critical listening. (They're hung from the ceiling in my garage)

About $20 and two hours well-spent. Someone with more knowledge of reverse-engineering circuitry would stuff in higher-grade resistors, a more-robust power supply, and perhaps find upgraded ICs; but that's all beyond me.

westmassguy

Schurkey wrote: »

Someone with more knowledge of reverse-engineering circuitry would stuff in higher-grade resistors, a more-robust power supply, and perhaps find upgraded ICs; but that's all beyond me.

That's would be me

Schurkey

westmassguy wrote: »

That's would be me

Photos of original circuitry, prior to replacement of electrolytic caps. I was wrong earlier, cost was $27.50, not $20.






12 electrolytic caps
C3 and C4 470uf 50V (Blue) P13134-ND 0.87 ea.` $1.74

C5 and C6 1uf 50V (Yellow) P4675-ND 0.68 ea. $2.72
C15 and C16

C101 and C301 10uf 35V (Blue) P14629-ND 3.84 ea. $23.04
C141 and C341
C147 and C347

All original capacitors rated for 85 C.
Total cost for 12 caps $27.50

2-RC4559N "High Performance" dual op-amp ICs
2-LS404CB "Filter" ICs

westmassguy

For a premium upgrade, the two 470uf get 35volt 1000uf Panasonic FM Series Caps, the four 1uf get the same value 50 volt Panasonic FC Series, and the remaining 10uf caps get 25 volt Elna Silmic IIs. The two quad op/amps rearly fail, howerver when they do, they are replaced in pairs with identical models. For the dual op/amps, if they fail, I prefer TL072CPs instead of the 4559s. The TL072s were designed as audio amplifiers, while the 4558 and 4559 (interchangable) are general purpose high frequency amps.

NJPOLKER

All said and done............................ the Bose 901's were and are amazing speakers. What company has accomplished more than Bose? I know what some will say but isn't that what Polk and others do? Selling to the masses is not for me but it seems to work well. In reality Polk is not in the same ballpark as Bose.

So let the animosity go and enjoy the tunes whatever speakers/components you listen to.

I just got done with a tune session which lasted about two hours and my system sounds better than ever. After a few more adjustments maybe I'll take the time to do a review of my system.

I do have very fond memories of the 901's which we were so fortunate to have back in the day. Thanks to the audio gods and my mother and father for buying them and the Rotel receiver Dual TT Bi-amp EQ for getting me started in my love for great sounding music.

GOD BLESS AMERICA

OldmanSRS

901 sound quality was proportional to weed quality

westmassguy

OldmanSRS wrote: »

901 sound quality was proportional to weed quality

That would apply to most other loudspeakers as well, supplimented with your choice of adult beverages of course :redface:

Schurkey

Finally found my "After" photos of the equalizer re-cap.





I copied and pasted an incorrect parts list earlier. What I actually used was from www.erseaudio.com.
MPX25-03-1.00 4 1.0μF 250v PulseX - Metallized Polypropylene Film $4.48
ANP10-05-470.0/PB 2 470.0µF 100v 10% D.F. Non-Polarized Electrolytic $6.64
ANP10A-05-10.0/PB 6 10.0µF - 100v - 3% D.F. - Non-Polarized Electrolytic $5.22

lanchile

Bose produces the best sound...for deaf people lol... Bose is the biggest scam ever!!! People think that they have the best of the best because they have Bose...When will they learn?

westmassguy

Schurkey, why did you use axial mount instead of radial?

westmassguy

lanchile wrote: »

Bose produces the best sound...for deaf people lol... Bose is the biggest scam ever!!! People think that they have the best of the best because they have Bose...When will they learn?

So you've heard every product Bose has ever produced since 1966? Wow, that is amazing.

gdb

lanchile wrote: »

When will they learn?

Maybe you can just make it your mission in life, chief. Begin by shouting from the rooftops !

Schurkey

westmassguy wrote: »

Schurkey, why did you use axial mount instead of radial?

Axial is what I could find at Erse, and I had a bunch of other stuff I was ordering from them at the same time. Radial leads seem...unpopular...compared to axial.

Radial leads would have been better; and probably easier to mount as long as the leads were long enough to lay the caps on their sides--the equalizer housing isn't tall enough to stand 'em up on-end.

As it is, my first testing of the equalizer was a disappointment, it had TERRIBLE hummmmmmmm. Had to go back in and re-solder an extension to one of the leads on one of the big 470uF caps. The leads weren't long enough, had to add an extension, and the first attempt didn't get appropriate contact (poor solder-job.)

All is well now, though. Still debating on replacing the ICs with new-production chips (LS404CB) and the TL072 upgrade to the 4559s. Cost of the chips is practically nothing; I'll probably order them and install 'em when I'm caught-up on some other re-cap projects. (ordered power-supply caps for my three JVC receivers; and still have to diagnose, repair, and then upgrade a dbx 118 which has been kicking my ****. I also own a batch of old cars in perpetual need of wrenching, that have taught me how to procrastinate VERY effectively.

westmassguy

Schurkey wrote: »

Axial is what I could find at Erse, and I had a bunch of other stuff I was ordering from them at the same time. Radial leads seem...unpopular...compared to axial.

Radial leads would have been better; and probably easier to mount as long as the leads were long enough to lay the caps on their sides--the equalizer housing isn't tall enough to stand 'em up on-end.

As it is, my first testing of the equalizer was a disappointment, it had TERRIBLE hummmmmmmm. Had to go back in and re-solder an extension to one of the leads on one of the big 470uF caps. The leads weren't long enough, had to add an extension, and the first attempt didn't get appropriate contact (poor solder-job.)

All is well now, though. Still debating on replacing the ICs with new-production chips (LS404CB) and the TL072 upgrade to the 4559s. Cost of the chips is practically nothing; I'll probably order them and install 'em when I'm caught-up on some other re-cap projects. (ordered power-supply caps for my three JVC receivers; and still have to diagnose, repair, and then upgrade a dbx 118 which has been kicking my ****. I also own a batch of old cars in perpetual need of wrenching, that have taught me how to procrastinate VERY effectively.

Me thinks you have axial and radial confused. The EQ originally had radial type caps, which are pretty much the standard now, with the exception of surface mount caps. Axial type capacitors are much less plentiful, and really aren't used anymore because they take up too much realestate in the circuit board. Most of the premium caps I use aren't even available in axial form.
Check out the photos I posted. That's a Series V with Panasonic and Elna Radial Caps.