Eiron wrote:
Phil Allison wrote:
Hi to all Quad lovers.

Anyone know why a DC voltage of 7.3 volts approx is present on pin 4
of DIN output socket of Quad 33s ?

It is derived from the dial lamp supply.

Quad label it with the letter " P " .

Goes nowhere on a Quad 303 power amp.

http://www.geocities.com/quad_esl63/...atic/pre33.jpg


http://www.geocities.com/quad_esl63/...c/power303.jpg


Presumably so you could have a relay in your power amp to turn on the
power,
a feature not found in Quad power amps.
http://groups.google.com/group/uk.re...6ce82af8aa0b6e

That pre33.jpg diagram is missing the earth connection on pin 2

I suspect that diagram was "re-created", as the original official circuits don't look anything like that. Hence the earth
connection was lost in the process. Interestingly the same re-created circuit appears on the Quad World website so one or t'other
has just perpetuated the error.
For the real circuit layout see: http://www.flashbacksales.co.uk/manu...rcuit%2033.pdf
This one IS the real deal.

With regard to the DC supply on Pin 4 of the 33, the Quad Service Manual states........

"The DC supply provided on Pin 4 of the output plug, derived from diode MR503, is used only as a switching supply for special
installations. Its regulation is poor and is nominally 7-8 volts at 1 ma maximum, intermittent rating. The DC supply is omitted on
sets after S/N 80000."

Here endeth the lesson