Quad II monoblocks

[RochaCullen]

Hi,

I've too many projects on the go at the moment, but I've had a set of Quad IIs in a box in my study for a while now. Apparently one of them is fully working, but the other is a little temperamental. Is there any resource on the web that supplies directions on how to overhaul these amps.

Any pointers would be appreciated.

Regards,

Nathan

[anthonyTD]

hi Nathan,
these amps are relitively simple to service/repair etc.
here are some pointers.
Cathode resistors tend to fall off or fail if output valves have drawn excesive current etc. Interstage coupling caps are almost always a failier in these amps, so change them without question, if you dont and you fit a new set of output valves then dont be surprised if they fail again within the first hour or so of firing them up!
Mains transformers are prone to failing on one of a pair as Quad decided it was a good idea to run the preamp, plus the tuner of one power amp only hence the one transformer has a harder life than the other which can lead to premature failer.
It goes without saying that all valves will need to be fully checked and tested before asuming the amp on initial inspection dosent work.
i hope this helps.
regards,Anthony,TD...

[jantheman]

Have a look here....loads of info....you may need to ask but you should be set.....
http://tech.groups.yahoo.com/group/quadhifi/

[RochaCullen]

Mains transformers are prone to failing on one of a pair as Quad decided it was a good idea to run the preamp, plus the tuner of one power amp only hence the one transformer has a harder life than the other which can lead to premature failer.


Hi Anthony,

If I recall correctly I think my friend mentioned something about the transformer on one of them causing a problem. So once the transformer is fixed, I assume this reliance on one poweramp would be overcome by simply using a different preamp than the original Quad?

Nathan

[RochaCullen]

Have a look here....loads of info....you may need to ask but you should be set.....
http://tech.groups.yahoo.com/group/quadhifi/

Thanks Ray,

I will have plenty of food for thought here, I am sure.

Nathan

[anthonyTD]

Hi Anthony,

If I recall correctly I think my friend mentioned something about the transformer on one of them causing a problem. So once the transformer is fixed, I assume this reliance on one poweramp would be overcome by simply using a different preamp than the original Quad?

Nathan
Correct!:)
Anthony,TD...

[Rare Bird]

I agree with Anthony, so simple.

Just rebuild but don't be tempted with silly mods or flashy parts

[BTH K10A]

Hi Anthony,

If I recall correctly I think my friend mentioned something about the transformer on one of them causing a problem. So once the transformer is fixed, I assume this reliance on one poweramp would be overcome by simply using a different preamp than the original Quad?

Nathan

Just remember the Quads are earthed via the preamp. ;)

[DSJR]

A quicky here...

It always seems to be one of the pair that gives the most trouble and it's usually the one which fed the preamp and tuners...... The potted chockes used to be set in tar and if this assembly became hot over many years, the choke could work its way down the molten or softened tar compound and eventually short on the terminals . A suggestion has been to remove the chokes and oven bake them at low heat with the terminals uppermost, returning them to the top of the cans and away from the terminals.

Have a look here as well - http://www.dc-daylight.ltd.uk/the-Hi-Fi-stuff.html

[anthonyTD]

Just remember the Quads are earthed via the preamp. ;)
Good point!
when i alter them to be run without the original preamp i usualy keep the two pin mains sockets but run a three core cable with the earth fitted with a soldered or crimped tag that i fit under one of the screws nearest the plug.
this ensures that you are not reliant on the preamp or source output connectors being earthed.
Dave's point about the chokes is also a valid one.
Anthony,TD...