Hello! This pair of Quad II’s were the result of a "good bargain" win on EBay, by a customer in Italy. After spotting that my home town was Nottingham, UK and that the amps were situated in Mansfield, Nottinghamshire, the customer kindly asked if:
(a) would I mind collecting them for him and
(b) would I please give them a thorough service and "check-over" before sending them to him.
He would of course be paying all the fuel, servicing and
shipping costs that would be involved through-out. I
had no problem in doing this for him, and the amps were subsequently collect and
brought into the workshop.
Like most good old British-made amps, the first one fired-up almost OK. However
the second one wasn’t so good! There was a large amount of +ve grid
voltage on both the KT66’s, which told me that both the coupling caps were
very leaky. By the way, all four of the KT66’s were the original smoked-glass
GEC/Osram……….beautiful! I therefore suggested to the owner that all the
coupling capacitors on both amps should be changed, as the better working one
would probably give problems in time. There were only a total of six to change
in both amps, and afterwards everything came up wonderfully.
Although working fine now, and although all the resistors were 1 watt, a good
few of them had drifted considerably in tolerance with time. Now, I understand,
respect, and realise that with any kind of equipment like this it is always nice
(and preferable) to keep everything as original as possible. However, in the
case of guitar amplifiers, "drifting resistors" is a little more
expectable and in quite a lot of cases actually "adds to the sound"
making them sound like they do! But in the case of Hi-Fi gear I think this rule
should be ignored. The use of modern "high quality" components with
old tube amps can most certainly improve them, in some cases making them even
better than when they were new! I suggested that whilst they were on the bench,
I could simply change all the resistors (about 22 all-told) and that I could do
them just as neatly as the originals.
After being given the go-ahead, I proceeded on the above lines.
On completion, I could see some definite improvements on the 'scope, especially
in the drive balance. Everything now looking perfect, I moved on to the final
testing. As you will see in the photos, one of the amps had a GZ32 rectifier (as
original) and the other a GZ34. The owner had plenty of spares for both these
types so he asked me to just leave the odd pair of rectifiers in place.
On testing, both amps were identical. With the GZ32 (original) in either amp
they produced a good 18 watts (originally rated at 15 watts) whereas with a GZ34
in place they both managed about 22 watts! I suggested using GZ34 tubes as this
gives a bit more "kick and tightness to the bottom end", with the HT
being a little higher!
The amps are now back in Italy with their new and very satisfied owner.
Thank you for your interest in the site and projects…….enjoy the photos.
Cheers, John.
The two amps side-by-side. The lower one has a GZ34 Rectifier. The higher one is fitted with a GZ32.
Underside of both of the amps prior to component changes.
Underside of one of the amps following changes to the components.
Close-ups of the new components.
