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Old 18th November 2006, 11:57 AM   #1
rossdt is offline rossdt  Italy
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Default Quad II - Forty

Is there someone that it can send me the schematic of Quad II - Forty?
Thank you in advance.

Alessandro
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Old 21st November 2006, 03:50 PM   #2
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Old 21st November 2006, 07:29 PM   #3
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Thanks G-n Georgiev

No surprise it sounds worse than the original.
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Old 22nd November 2006, 09:02 AM   #4
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Dear Mr. Alessandro,
I haven't Quad II - Forty scheme. This scheme is the same Quad II mono amplifier (KT66) 1949-1970. I have followed and checked the voltages in this scheme and montage. I have to tell you that Quad II - Forty has higher anode voltage than Quad II mono amp anode voltage.

Regards, Georgi Georgiev, Bulgaria
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Old 24th November 2006, 10:58 PM   #5
rossdt is offline rossdt  Italy
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Thank you very much!
What is the black component under the rectifier?
Thanks

Alessandro
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Old 25th November 2006, 05:27 AM   #6
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Most likely a NTC thermistor for cheap protection and limit current inrush.
Bright idea! just in case the rectifier tube goes kaput, saving further damage to amplifier.
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Old 26th November 2006, 02:00 PM   #7
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Please tell me that amplifier didn't cost very much money.

I've got the original quad II schematic here:

http://quadesl.com/refurb/refurb_quadTube.html


Sheldon
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Old 30th November 2006, 11:26 PM   #8
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Quote:
Originally posted by rossdt
Thank you very much!
What is the black component under the rectifier?
Thanks

Alessandro
It is a very low value thermister in series with the rectifier (5U4) filament to give a kind of slow power-up.

The Quad II-40 circuit is essentially the same as the Quad II, with some slightly different value resistors to accomodate the 6SH7 drivers. The other difference is the separate cathode resistors (bypassed) for the KT88 power tubes.

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