Altec Bolero 890c schematic
Hello everyone, my first post here. I just picked up a pair of Bolero 890c speakers (well about a year ago actually). I had thought they might be nice used in a 2nd system with a Marantz receiver. But when I hooked them up to my tube rig I was pleasantly surprised at what came out. A nice change from the studio monitors I was using there. Needless to say, they've stayed in that system since. I am now thinking of having the capacitors in the crossovers replaced as well as bypassing the 3-way switch in the back. Does anyone know where I might find a schematic?
One more question, should I rotate the woofers?
Thanks all.
Re: Altec Bolero 890c schematic
Re: Altec Bolero 890c schematic
I would definitely recap them.
Maybe put an alligator clip jumper across the switch and see if you like how it sounds? The switch itself might add some resistance, even in the WFO position. You might like how it sounds, or need to put a small resistor in place of the switch.
Good luck, and let us know how it turns out
Re: Altec Bolero 890c schematic
Hi,
I don't have a schematic ( & I've never seen one posted on the .net ) but typically the values are quite clearly printed on the body of the capacitors ( both the Callins & AC brands when present ) .
:)
Re: Altec Bolero 890c schematic
Each 890C crossover uses two 6uF and one 3uF caps. The switch controls three parallel resistors across the tweeter inputs. Not sure there's much sonic advantage to bypassing the switch. Also never seen a crossover schematic but you can find photos of the crossover from people that have recapped them.
Re: Altec Bolero 890c schematic
Re: Altec Bolero 890c schematic
Quote:
Originally Posted by
miker1
Each 890C crossover uses two 6uF and one 3uF caps. The switch controls three parallel resistors across the tweeter inputs. Not sure there's much sonic advantage to bypassing the switch. Also never seen a crossover schematic but you can find photos of the crossover from people that have recapped them.
Looking at the photo, the resistors connected to the switch aren't parallel. Each one connects to a different terminal. So each terminal appears to select a different series resistor for the tweeter.
Re: Altec Bolero 890c schematic
Seems like even the +3db setting has a resistor before the tweeter. So you could jumper from the switch input directly to the resistor of your choice. If you just solder a piece of wire in the mod would be reversible.
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Re: Altec Bolero 890c schematic
The three resistors controlled by the switch are 15, 15 and 30 ohm. It's a little confusing to me how the slide switch is wired. When I measured the resistance with the drivers removed (resistance across the leads going to the tweeter) I got 31.8 ohms at the +3 dB setting; 10.6 at the Norm setting; and 7.6 at the -3dB setting. Given some tolerance, it seems the -3dB setting parallels the two 15 ohm resistors, and the Norm setting parallels the 30 and one of the 15 ohm resistors.
- - - Updated - - -
Here's my crude schematic of the crossover with the switch details uncertain to me.
Re: Altec Bolero 890c schematic
I suspect you have it right. Looks like Altec did an EQ with the series resistor and cap across it.
As said, I doubt any sonic improvement from bypassing the switch.
Re: Altec Bolero 890c schematic
Thanks everybody. Looks like I came to the right place. After reading these posts I will most likely not bother bypassing the switch.
But I will go ahead and replace the capacitors. Are there any particular brand of capacitors that you would recommend? I don't mind spending a little more if it makes a difference. My first Altec purchase, and I'm really pleased.
Re: Altec Bolero 890c schematic
Also thanks to mike1 and mah for the photos and sketched schematic!
Re: Altec Bolero 890c schematic
Quote:
Originally Posted by
miker1
The three resistors controlled by the switch are 15, 15 and 30 ohm. It's a little confusing to me how the slide switch is wired. When I measured the resistance with the drivers removed (resistance across the leads going to the tweeter) I got 31.8 ohms at the +3 dB setting; 10.6 at the Norm setting; and 7.6 at the -3dB setting. Given some tolerance, it seems the -3dB setting parallels the two 15 ohm resistors, and the Norm setting parallels the 30 and one of the 15 ohm resistors.
- - - Updated - - -
Here's my crude schematic of the crossover with the switch details uncertain to me.
Thanks for taking the time to draw up a schematic Miker1 ! :Thumbs up:
