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Old 29th August 2006, 04:55 PM   #1
Leisner is offline Leisner  Denmark
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Default Rotel rb850

Hi

Does anyone have a schematic for Rotel rb 850 Amplifier?
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Old 30th August 2006, 03:31 AM   #2
anatech is offline anatech  Canada
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Hi Leisner,
PM me. I have a fragment that may help. It's not complete, and it's not great but it may help you out.

-Chris
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Old 12th September 2006, 06:30 PM   #3
gni is offline gni  United States
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Default Rotel RB850 Schematic Errors

I have been researching the Rotel RB850 amplifier for several years.

I have compared it to the schematics of similar Rotel amplifiers.

I saw a schematic on this forum that seems to have at least one error.
It looked like a scan of a photocopy that had things erased.

I have redrawn the schematic based on the one on this forum,
similar ones found elsewhere, and my RB850.

I will answer any questions you may have (as far as I know).

There is a thread with this similar question on this forum

Sincerely,

Chris Browne
Ground Noise Industries
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Old 12th September 2006, 07:57 PM   #4
gni is offline gni  United States
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Default Rotel RB850 Marked Schematic

This was posted by member "transducer" and marked in red
by "gni"
Attached Images
File Type: jpg rb850_errors.jpg (99.2 KB, 881 views)
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Old 4th October 2006, 10:29 PM   #5
gni is offline gni  United States
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Default Rotel RB850 Pictures

http://arts2001photo.lifepics.com/a/v.cfm?h=CB59E3A7

Until December 2, 2006
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Old 5th October 2006, 01:18 AM   #6
routhun is offline routhun  United States
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Default What are the mods you did on this amp?

Hi Gni,

What are the mods you did on this amp? I have a vector research integrated amplifier VA-100 with exactly the same power amplifier stage, and would like to tweak that amp. How does this amp sounds? and the tweaks improved the sound?

Thanks,
routhun
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Old 13th September 2007, 01:34 AM   #7
gni is offline gni  United States
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I emailed Rotel for the Technician Manual and they sent me one. . .it
has the Schematic and Bias Voltage (4mV across 0.22 ohms = 18.2mA)

I replaced the single turn bias adjust pot with a 15 turn unit. . .
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Old 14th September 2007, 12:45 AM   #8
anatech is offline anatech  Canada
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Hi Chris,
Quote:
I replaced the single turn bias adjust pot with a 15 turn unit. . .
I am doing my best to figure out why you would do that.

You should install a new 270 unit at the very least, or put the old one back in after cleaning the slip ring and wiper.

What you people fail to realize is that the multiturn types generally have a much smaller contact area and are not intended to pass DC current.

I'm actually getting tired of hearing about this ill informed "upgrade".

-Chris
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Old 14th September 2007, 07:21 AM   #9
srh is offline srh  New Zealand
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Hi Chris,

The inability of multiturn pots to pass DC current explains why some of my projects won't work. Thanks for that, a great weight off my mind.

Cheers,
Steve.
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Old 14th September 2007, 07:30 AM   #10
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Anatech??, a multiturn trimpot is nothing but a single turn with a screw and a cog to allow easier adjustment than a very cheap open frame single turn trimpot. Its the same thing, just imagine a single turn, sideways and enclosed in a pretty sealed case thats helps protect from dust and dirt buildup.


Colin

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