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Old 17th January 2013, 09:47 PM   #1
stenak is offline stenak  Norway
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Default Quad 303S

I have a quad 303S. All capacitors are replaced with new ones, and some resistors will be replaced with new ones. The amp is in mint condition. I have searched the internet to find some information about the 303S, but I can`t find anything about the "S" model. The production number is around 22000.
The curcuit diagram I found on the internet is different is not the right one....
Anybody who knows anything about the "S" model?....
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Old 18th January 2013, 01:30 AM   #2
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Are there physical differences in the 303S that lead you to believe they are a different circuit?
It appears to be in the standard serial number series so any differences should not be great.
Some pics for interest:QUAD 303 Amplifier modification to general purpose Lab amp from 303 A2
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Old 18th January 2013, 08:05 AM   #3
stenak is offline stenak  Norway
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Quote:
Originally Posted by Ian Finch View Post
Are there physical differences in the 303S that lead you to believe they are a different circuit?
It appears to be in the standard serial number series so any differences should not be great.
Some pics for interest:QUAD 303 Amplifier modification to general purpose Lab amp from 303 A2
I can only find two transistor om the powersupply curcuitboard, one small and one bigger, but on the scheme I found on the the internett, there are two. Some of the capaciotors are also different, compared to the one found on the net.
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Old 18th January 2013, 08:18 AM   #4
Mooly is offline Mooly  United Kingdom
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The PSU has three transistors in total, one will be on a large (or the main) heatsink.
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Old 18th January 2013, 02:11 PM   #5
stenak is offline stenak  Norway
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Quote:
Originally Posted by Mooly View Post
The PSU has three transistors in total, one will be on a large (or the main) heatsink.
The PSU board on my 303S has only two!
One small round transistor, and one with a heatsink.....There is not a third one!!! Perhaps my 303S is something special?
Are there any Quad specialists out there? ............
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Old 18th January 2013, 02:44 PM   #6
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If you look at the schematic(s), the dashed line indicates which components are mounted on the circuit boards. You'll see that the third transistor (tr3, part #40411 which is in a large TO-3 case) for the power supply is outside of the dashed lines, and is, therefore, not mounted on the circuit board, but rather on the heat sink. (I just went and checked my 303, which is a serial number in the 60 thousands, and it only has 2 transistors on the PS board) Beyond that I can't tell you what the 'S' means, but since the amp was made from 1967 to 1985, in a quantity of 94,000 units, there were changes to AC input, DIN versus RCA, and speaker outputs so I guess your 'S' is one of those.
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Old 18th January 2013, 02:55 PM   #7
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Try e-mailling Quad.

S in the UK usually means Special. It's possible it's had a few tweaks but I woulndn't expect it to deviate too far from the original.
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Old 18th January 2013, 04:33 PM   #8
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by stenak View Post
The PSU board on my 303S has only two!
One small round transistor, and one with a heatsink.....There is not a third one!!! Perhaps my 303S is something special?
Are there any Quad specialists out there? ............
Can you post some pictures of it ?
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Old 18th January 2013, 09:03 PM   #9
stenak is offline stenak  Norway
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I will take some pictures this weekend. The guy who gave me the Quad set bought it in the late sixties. He also bought a Thorens 124 II. The Thorens did not work, because the motor was defect. A SME3012 arm was mounted, and I sold the Thorens and arm, to a collector who had six others 124, for about 10000 Nkr, about 1100 British Pounds.
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Old 19th January 2013, 11:02 PM   #10
stenak is offline stenak  Norway
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Have taken some pictures of my 303S. I will take some more pictures tomorrow....
Have you seen one of these before----the "S"-type?
Attached Images
File Type: jpg Quad 303s komprmert bilde 1.jpg (46.0 KB, 186 views)
File Type: jpg Quad 303s komprmert bilde 2.jpg (41.4 KB, 172 views)
File Type: jpg Quad 303s komprmert bilde 3.jpg (50.2 KB, 165 views)
File Type: jpg Quad 303s komprmert bilde 4.jpg (39.6 KB, 165 views)
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