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Quad II work

chiily

PFM Special Builder
Recently, this week, I purchased a fabulous pair of Quad II amps from @John_73 of this parish. https://pinkfishmedia.net/forum/threads/pair-of-original-quad-ii-amplifiers.261545/#post-4543836

They really are in lovely condition and date from 1966 based on their serial numbers. One has a few marks on the paint, not scratches just blemishes. If I can find a blemish that is hidden away I may try either some Brasso on it, or maybe a little TCut, just to see if the blemish can be lifted.

These are the first Quad IIs I've seen in the flesh, and ain't they heavy for something so little! Their simplicity is quite astounding, such a long way from the SS amps I've previously built. I can't wait to get these up and running playing through my Quad ESL 57s (another PFM buy from @foxwelljsly)

John_73 was kind enough to throw in not just the Quad book, but also a box full of new cables, connector shells, Russian PIO capacitors, a huge assortment of both carbon and carbon film resistors, etc. And this afternoon I couldn't help myself but to plug in my soldering iron and start to put in to practice all the information I'd read over the week about servicing and maintaining Quad IIs.

The Plan

Working from this schematic:
Quad II cct by Garf Arf, on Flickr

The Plan was/is to refresh:
C2 and C3 with Russian military K40Y-9 0.1uF capacitors
C1 with a Mallory 150 series 0.1uf capacitor,
C5 with a Kemet/Rifa 22uF electrolytic capacitor

For C4/C6, they are in the grey box, tucked away underneath, I am going to use one of Keith Snook's replacement boxes to keep in the theme of the original Quads.

Resistors; I'm having an internal struggle over them. Most sites say that they have no bearing on the sound, so get those carbon comps out and get those metal film resistors in. And certainly from a reliability PoV then yes; but they don't quite look right. John's little box of stuff has a replacement set of Carbon Film resistors, but I'm tempted to try some Takman carbon films...hifi collective has them in stock...tempting...

The only resistor that needs something that Takman can't provide is a replacement for R12, which has to have a power handling of more than 5W. John's box held three Mills MRA12F 180R resistors and three Rifa 22uF caps for C5.

Valve-wise - for the moment I'm going to buy a set to get me going from Watford valves, but I have on my birthday list a quad of of Gold Lion KT66s :)

What's not in the Plan is cutting any metal work. I'll keep the two pin power connector and the Jones plugs. I think they suit the style and mark the era that these amps come from.

Progress
As I said above, John's box of stuff had components that needed fitting, I mean they were just itching to be soldered in to the amps. In went the Russian K40-Y, 0.1uF caps for C2 and C3, and the Mills resistor for R12 and the Rifa cap for C5.

PXL_20211211_180059541 by Garf Arf, on Flickr

What is interesting about these amps is that no one has been in them before. The three cheese slot screws I undid where Linn tight, and the heads were completely unmarked
 
As a follow up. What would be the best way of testing and/or reforming the PSU caps (C4 and C6), the ones in the little box to the right of the picture above?

Ta.
 
I'd split the bias if I were you. Maybe try -72 teflons, too, and check the values of the CC resistors, all can be measured in situ except for one. I'd replace them with CC's. Guitar amp repair shops have them.
Never did it myself but matching the components after the phase splitter really well might bring rewards.
 
As a follow up. What would be the best way of testing and/or reforming the PSU caps (C4 and C6), the ones in the little box to the right of the picture above?

Ta.
Just put a 33+33 in there and chuck the box or keep in a drawer if you sell the amps
 
Shame your doing anything to them.Only original once,wished I’d seen the advert earlier they would have remained original and unmolested.
 
I tend to agree with you, and if I felt they required a service I would send them to Quad UK.
Let Rob Flain decide what’s required.
 
Shame your doing anything to them.Only original once,wished I’d seen the advert earlier they would have remained original and unmolested.
I agree, but to keep them going for another 50 years things have to be maintained. Without it it could be a boiling power transformer, or something equally as bad, requiring more intervention.

I am trying to be sympathetic to the originals. I've measured resistors and they are the majority are within their 20% original spec, so I won't change them. But I will keep an eye on them in case they begin to wander high.

Like with everything of "vintage", do you use it and maintain it as close to the original as possible, or place it in a cabinet to just look at? How much is too much, everyone has their limit.

I'm sure some classic car owners enjoy nothing more than their head suck under the bonnet of their car with feeler gauges in one hand and an Emery board in the other trying to get a spark out of a 1960s distributor cap and points rather than driving their car. Maybe that is all part of the "fun". :)
Having lived the same problem with classic bikes in the past I had to resort to electronic ignition, because I wanted to spend more time going places than stationary at the side on the road, but that was my choice :)
 
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I went through much the same thought process with the PYE amps. 12 years older than these and not in mint or untouched condition so an easier decision. But what I can say is that ‘valve noise’ turned out to be resistor noise and the difference in sound quality was far from subtle. Interestingly, the resistors made more difference to the sound than capacitor changes. If you’re not running a museum, as long as the servicing doesn’t modify the fabric of the originals, a dose of suitable new components will tell what these old things are really capable of.
 
I giggle when I think about people listening to Quad IIs with dried out caps and out of tolerance components. It's just a thing, an object, and the components aren't even visible. :D
When I replaced the old elcos the amps sounded so good that I took a day off to just listen to music.
Then I bought four matched NOS GEC KT66 valves. Sublime. But I also bought four Saratov KT66s for "everyday" use. I would recommend to split the bias, because sometimes one valve can run amok.
 
I giggle when I think about people listening to Quad IIs with dried out caps and out of tolerance components. It's just a thing, an object, and the components aren't even visible. :D
You can't win though when selling them. Some time ago I sold a serviced pair (by toprepairman of this parish) and the buyer then wanted all the original caps etc so a quick scramble around in Henry's bin!
Got one now to sell, 100 % original and untouched Do I get it serviced or sell as it is?
 
That's why I kept all old tired components in a bin in case a future buyer would want a museum piece rather than a good sounding amp. I would sell it as is and let the buyer worry.
 
I've labeled and bagged up all the components I've taken off, and it would be relatively simple to swap the old for the new, there is a way back :)

I've read up on splitting the bias for the KT66 and I may do it in the future, but for the moment want to hear the Quads as originally configured. I just want to to swap out tired components for something sympathetic, (or underrated, I'm looking at you R12) to the age of the amp.

Anyway, I've ordered some pretty, coloured, twisted, cotton covered cable to make up the mains cables with.

I'm a complete newbie with valves and having read Tony's thread on his Leaks I realise I have a lot yet to learn about valves :) One EF86 is not like another EF86!
 
You can't win though when selling them. Some time ago I sold a serviced pair (by toprepairman of this parish) and the buyer then wanted all the original caps etc so a quick scramble around in Henry's bin!
Got one now to sell, 100 % original and untouched Do I get it serviced or sell as it is?
Do you know if the buyer refitted all the original components?
 
As a follow up. What would be the best way of testing and/or reforming the PSU caps (C4 and C6), the ones in the little box to the right of the picture above?

Ta.
A common trick for "soft starting" a vintage item is to get hold of an old type TFL light bulb and wire a bulb holder in series . It limits start-up current and gives everything an easy time while you look for the magic smoke.
 
Imagine if you had an original, unmolested, out of spec and soon faulty car? It wouldn't last long and that applies to any machinery that you can think of. The components in some of these old amplifiers were nothing special even when they were new and time has done nothing to improve them. A sympathetic restoration is entirely in order I would have said.
 
Keeping/using new carbon comp (CC) resistors is the best (and if you want the "old" sound). I replaced all CCs with metal film first and the amps sounded awful. They say CC is noisier, but my two pairs of IIs were dead silent. CCs are readily available and I think 1/2 W where enough, except for R12.
And why not go all the way and replace the elcos with film caps? Not cheap but you never need to worry about them anymore.
A cheaper alternative to the QII sound is to get a 303. Similar but with better bass punch.
 
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