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 Post subject: Bell Imperial 1000
PostPosted: Feb Sat 18, 2017 3:23 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 90
Location: Colorado, USA
I'm very sincerely curious to hear from anyone who has any experience with the Bell Sound Imperial 1000 integrated receiver. It is a solid-state unit built by Thompson-Ramo-Wooldridge Bell Sound division in Columbus, Ohio in 1964-1965. It is nearly all solid state with the exception of three nuvistors in the FM only front end. The advertised power output was 80 watts (40 per channel). I own two unrestored 1000s and am wanting to resurrect them. Unfortunately I know little if nothing about them aside from the literature and manuals from the era. They have good build quality and seem to be similar in construction to the other Bell vacuum tube units I have from the same era. The 1000 was an expensive until for its day, costing about $595 new. That's about $4500 today. Wow, quite pricy!

Thank you for any information you all can give.

Regards,

Roy


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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Sat 18, 2017 5:12 pm 
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Posts: 89
Location: San Diego, CA
Attachment:
Capture.JPG
Capture.JPG [ 92.48 KiB | Viewed 258 times ]


These were very rare, and indeed very expensive for the time.
They were modular also, so you could buy it as integrated amp and add the tuner section later.

I have been looking for an example to restore as well.

The plated chassis and potted trannies were nice touches.

Are these completely point to point hard wired or to they use circuit boards as well?

I would love to see pictures of the internal construction...


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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Sat 18, 2017 5:27 pm 
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Location: San Diego, CA
The Imperial 1000 was reviewed by Audio Magazine in May of 1964 (see attached PDF)

They mentioned the unit could not withstand continuous power output at 40 watts (that was an optimistic "IHF" rated figure). Thus it was tested at 25 watts continuous power per channel.

I am guessing this thing was using germanium transistors as it features inter stage coupling transformers.

The review also mentions two different versions, the latter with revised tuner to prevent overload and cross modulation.

In all, I think Bell probably spent a fortune developing this line and never recouped it. Sales at that price were dismal for sure.


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Audio-1964-05-OCR-Page-0048.pdf [141.15 KiB]
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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Sat 18, 2017 6:39 pm 
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Joined: Aug Sun 01, 2010 1:12 am
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Location: Minnesota
This is interesting to me as I never knew that Bell was still making stereo gear this late. Their tube models are design classics and decent performers. The mid sixties were an interesting time in stereo gear, to say the least.


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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Sun 19, 2017 9:29 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 90
Location: Colorado, USA
Thank you to all for your replies. I have photos of the two units but they are too big to attach. I'll re-size them and add them soon.

The 1000 is a very well built receiver. The amp is point to point and PC board construction. The finals and power supply are point to point. The pre-amp and driver are all on a PC board. There is lots of room under the chassis to work on them so they don't feel cramped and tiresome to fix.


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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Sun 19, 2017 5:36 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 90
Location: Colorado, USA
Here a a few snaps of the Imperial 1000. Really good build quality. Chrome plated chassis is really nice.


Attachments:
File comment: Overall unit
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IMG_3978.jpg [ 69.62 KiB | Viewed 196 times ]
File comment: Underside with pre-amp board
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IMG_3973.jpg [ 111.92 KiB | Viewed 196 times ]
File comment: Power Supply closeup
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IMG_3975.jpg [ 115.99 KiB | Viewed 196 times ]
File comment: Chassis Rear
IMG_3971.jpg
IMG_3971.jpg [ 92.06 KiB | Viewed 196 times ]
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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Fri 24, 2017 3:03 am 
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Posts: 7121
Location: Beaver Falls, PA. USA
All of those black electrolytic capacitors are likely to be bad.

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Tim KA3JRT


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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Fri 24, 2017 4:56 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 24873
Location: Detroit, MI USA
Tim Tress wrote:
All of those black electrolytic capacitors are likely to be bad.


All of those black electrolytic capacitors were likely to have been bad a couple of years after the unit was built. They were horrible, Zenith liked to use them as well, and they had extremely high failure rates.

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Dennis

Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Sat 25, 2017 3:09 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 90
Location: Colorado, USA
Ah, darnsarnit! I was hoping to keep those "black beauties" for historical sake; they are so pretty....NOT! That is a major reason I haven't powered up either of the units in many years. I have a couple of Heathkit units from the same era that have those nasty caps too. They were so ubiquitous in many lines of products. Our family had a brand new Curtis-Mathes color TV from 1968 that had a mess of them in it too. The darn thing lasted about three years (just in time for the extended warranty to expire) before it started having horrible service problems due to capacitors. Dad finally ditched it for a more reliable TV. Believe it or not a Motorola Quasar II table model that lasted, yes!, 18 years with minimal service.

Anyway, I'm working up a BOM for the caps and related parts for a Mouser order. Is there a benefit in increasing the power supply and amp capacitance values?

Regards,

Roy


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 Post subject: Re: Bell Imperial 1000
PostPosted: Feb Sat 25, 2017 7:03 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 24873
Location: Detroit, MI USA
No, use the closest standard values to what the circuit was designed for. However, you may have difficulty sourcing electrolytics for the power supply that have the same ripple current capability and other ratings of the original parts, as they aren't made any longer and modern caps designed for use in switching supplies may not work as well (or as long). Stick only with a major brand like Nichicon or Panasonic, use only 105 degree caps, and watch the other ratings as well.

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Dennis

Experience is what you gain when the results aren't what you were expecting.


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