Bose 901 equalizer
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Blue Shadow
Waiting for Vintage Gear from this century
The eq should be in a tape monitor loop. If the volume is all the way down and the system makes noise it is not in a tape loop.
check connections verify 2230 tape out to eq input and eq output to 2230 tape input.
retry in tape loop
Could have been the 2230 squealing cause it knows it is short of power to fully drive 901s.
check connections verify 2230 tape out to eq input and eq output to 2230 tape input.
retry in tape loop
Could have been the 2230 squealing cause it knows it is short of power to fully drive 901s.
Is there a buzzing sound if you remove the equalizer?
PioneerPro
Active Member
A couple of 901 EQ Questions
Is there any difference in sound from the 3-4 Equalizer to the 5-6 Equalizer? I bought a set of series FIVE 901's and the seller gave me a Series 4 Equalizer. I was told they are the same.
Not only that but what are the most common issues with the Equalizer going bad. I see nothing inside that generally goes bad but the capacitors. Everything else looks pretty bulletproof.
Is there any difference in sound from the 3-4 Equalizer to the 5-6 Equalizer? I bought a set of series FIVE 901's and the seller gave me a Series 4 Equalizer. I was told they are the same.
Not only that but what are the most common issues with the Equalizer going bad. I see nothing inside that generally goes bad but the capacitors. Everything else looks pretty bulletproof.
Regarding your series V 901's, they should be used with the series V EQ or (at the least) the VI EQ's, not the series IV EQ. Series III and IV EQs are considered interchangeable with the Series III and IV 901's. Series V and VI EQs are considered interchangeable with the Series V and VI 901's. That being said, I've not noticed any appreciable negative audible difference between these EQ's, having owned all four and having used a series III EQ with and series V 901, etc... They sound good to my ears, but my ears are older.
I don't believe you'll have issues with the EQ, no more than you would have with your typical speaker crossover. There may be a need for some DeoxIT on the controls, but that's about it. However, I would consider a recap as yours are original and aged. You'll notice a sound improvement.
I don't believe you'll have issues with the EQ, no more than you would have with your typical speaker crossover. There may be a need for some DeoxIT on the controls, but that's about it. However, I would consider a recap as yours are original and aged. You'll notice a sound improvement.
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PioneerPro
Active Member
Thanks Guys, New caps are on the way. Went to remove the 2 larger caps and one lead on one of then was almost deteriorated.
Good find!
PioneerPro
Active Member
My 901's are series 5. I have a Series 5 EQ and a Series 4 EQ.
I recapped the 4 and it works perfect and sounds great. For the hell of it I bought a Series 5 EQ just because it is the actual EQ that came with my 901's and I listened to both and in my opinion the Series 4 EQ sounds better for some reason.
Can anyone tell me why I feel this way and what is the big difference between the two EQ's?
I recapped the 4 and it works perfect and sounds great. For the hell of it I bought a Series 5 EQ just because it is the actual EQ that came with my 901's and I listened to both and in my opinion the Series 4 EQ sounds better for some reason.
Can anyone tell me why I feel this way and what is the big difference between the two EQ's?
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whoaru99
Epic Member
There isn't necessarily a clear "why" to preference of some things.
I've not seen a concise plotted graph(s) of comparison between all the curves. I know that Ser I and Ser VI are pretty different because I've measured those. But, stands to reason they are. Ser I (and II) are sealed designs the rest are ported.
I've not seen a concise plotted graph(s) of comparison between all the curves. I know that Ser I and Ser VI are pretty different because I've measured those. But, stands to reason they are. Ser I (and II) are sealed designs the rest are ported.
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Blue Shadow
Waiting for Vintage Gear from this century
The series 3-6 EQs are very close. The recap of the IV eq might make it sound better than a non-refreshed V eq. Or the slight difference in the two leaves you preferring the sound of the IV eq.
PioneerPro
Active Member
As you see above I have a Series 3-4 and a series 5-6 EQ and I recapped the series 4 and like they way it sounds better. The power light on it is flickering but on with the cover off but as soon as you put the wood cover on it goes off. I checked the foil on the inside of the wood cover and its not grounding anything out, but this makes no sense.
tadawson
Well-Known Member
Classic neon lamp behavior! When they get "on the edge" the energy from room light causes this (I've had multiole neon based indicators, night lights, etc.) do exactly this over the years. (Scientifically, the presence of light alters the striking voltage of the neon lamp - search if you want more detail). Likely an NE-2H (or close) - replace it if it bugs you.
ernieS
Well-Known Member
I recapped my series V as well. It sounds wonderful.
Ronretired
New Member
Just finished recapping my series V equalizer with original caps. Sounds the same. The old caps are original to the unit and according to measurements were in accordance with specifications. None of the transistors are bulging or show signs of degradation. I might replace some of them for fun.
According to a person on another forum, he switched out the 470 uf 50V caps to 1000 uf 35V for improved performance. Does anyone have experience with making this switch? change?
According to a person on another forum, he switched out the 470 uf 50V caps to 1000 uf 35V for improved performance. Does anyone have experience with making this switch? change?
PioneerPro
Active Member
I still think mine has a short in it. Every so often the sound goes off and comes back on.
