Author Topic: Quad II mono-block amplifier question  (Read 2054 times)

Offline Sweetsound

Re: Quad II mono-block amplifier question
« Reply #15 on: January 04, 2021, 04:41:18 PM »
Hi Johan,

I had a pair at one point and I thoroughly enjoyed their sound.
I did however found they needed the right speakers and pre-amp to get the best out of them. Call it "careful pairing" in a lighter sense.

Question: how do you manage to utilize an AU101 as preamp, since they were manufactured without pre-outs?

Cheers
Stef
God invented stereo, then the 2 ears...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #16 on: January 04, 2021, 07:32:21 PM »
Hi Johan,

I had a pair at one point and I thoroughly enjoyed their sound.
I did however found they needed the right speakers and pre-amp to get the best out of them. Call it "careful pairing" in a lighter sense.

Question: how do you manage to utilize an AU101 as preamp, since they were manufactured without pre-outs?

Cheers
Stef

Hi Stef, yes, I know - I bought them from you! Still got a free can of spray paint with them as well ...  :BWAHAHAH:
I later sold them to a friend who really wanted them, and he enjoyed them a lot.
Sadly, about a year later, the one stopped working.  :nfi:

Re the AU101 - I disconnected/separated the pre and main amplifier boards, and routed the connectors to the (unused) Tape 1 and Tape 2 RCA connectors: Tape one is now pre-out and Tape 2 is now Main In. Works like a charm!  :thumbs:

 
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #17 on: January 04, 2021, 07:33:18 PM »
Restoration started:



I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #18 on: January 04, 2021, 09:17:42 PM »
This is going to be a great topic!!


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline Hi-Phibian

  • Commercial Member
  • Trade Count: (+59)
  • *****
  • Posts: 14,205
  • Total likes: 868
  • I really prefer email, see my banner for address..
    • Croak Audio Exploration
Re: Quad II mono-block amplifier question
« Reply #19 on: January 04, 2021, 09:23:16 PM »
Restoration started:




That looks previously re stored?

I rebuilt some years ago.  If I were to do it again I would not use metal film resistors as I did then.  I would just hand select good carbon ones. 


 
Croak Audio
Analogue by birth, digital by design. Mostly a StereoType though known to enjoy some Mono too  http://www.croak.co.za https://instagram.com/croakaudio?igshid=1wzr83vlqtbyy

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #20 on: January 04, 2021, 09:45:40 PM »
Quote
That looks previously re stored?

They had been, electronically.
This is mostly a cosmetic refurbishment - metalwork
badly flaking and rusted all over.

Actual operation and sound appears to be 100%!
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #21 on: January 05, 2021, 07:14:37 PM »
I guess many knew this was going to happen, but I do have a few / lots of questions!

Today I stripped the paint off of the one PT can (the strange green one) and it is pretty beaten up,
dented and so on. Still, after a good paint job, it will be acceptable (to me).

What I discovered is that the PT was not "potted" in the can, and I suspect it is not the original,
but a replacement PT. Note how the wires "bolt on" and are not soldered on.

I measured the AC voltages, and found this:



Is this ok? Seems quite within spec...

The main problem I have with re-fitting this, is that the PT fits into the can, correct orientation, but there is an approximate 3-5mm
 gap at the top when fitted.

Like this:





So, when one turns over the amp, the PT drops to the roof/ceiling of the metal can, and when one rightens the amp, the PT drops down onto its "tag board" and, /my concern/ all the weight rests on the transformer wires (snaking under the PT body and between it and the tag board). This can't be good / or is it ok?

So I am thinking of:

A.  "potting the PT into the can. Would using this stuff be an option?



B. making 4 brackets for the PT to "stand on" and be "secured" to the amp chassis, like this:



C. Just putting something in the metal can between the top of the PT and the ceiling of the can, to stop/minimise the PT movement.
It will still "rest" on the wires when the amp is the right side up.
Is this a big problem?
It will have to be a heat-resistant material - such as what? Would thin wood "burn" / be a problem? Or what should I use? Leather? Rubber?

D. Or what other options do I have to fix this?

All advice, as always, greatly appreciated!

PS. I decided to do one at a time, so that, should I "haak vas", I can go back to the "unmolested" amp
for guidance.



 


I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #22 on: January 05, 2021, 07:20:32 PM »
Quote
Is this ok? Seems quite within spec...

PS This was with the VAC input at exactly 230VAC via my variac.
At 240 VAC it goes up a little.
My normal VAC from COCT is between 234VAC and 237vac.






I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #23 on: January 05, 2021, 08:22:43 PM »
That transformer has been worked on, the original transformers are potted with a tar=like substance. Only way to remove that was to heat the transformer up on a hot plate and dig it out, a little at a time. I had a Quad with a 110v AC power transformer so had to do this in order to remove it and fit a 220v transformer in its place.

I do not know that sealer you depict but it looks like it could do the job, just make sure it definitely is very high resistance to electricity.

The voltages are good, the HT is actually 310 - 0 - 310v.

One fact I forgot to mention earlier is that it is a good idea to replace the GZ32 rectifier with a GZ34, which supercedes the now obsolete GZ32 and runs a bit cooler as well.


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #24 on: January 12, 2021, 07:02:47 PM »
Completed work on one of my two "new" QUAD II power amps today. Now playing, and sounding very, very good!

In order to hold the power transformer in place, I manufactured 4 brackets that I bolted onto the transformer and shaped to fit between the tag board and the recessed corner blocks in the transformer cap. Now the tag board is still properly recessed (so that the PT cap can be fitted flush with the amp's top deck), the PT does not sit on the wires (which was my main concern) and, when one turns over the amp, the PT does not drop into the cap, as before.

The biggest curve-ball was finding that the 4 bolts holding the power transformer cap in place were not imperial, but substitutes, and had
stripped the thread in the 4 brass corner blocks inside the cap.
So I drilled them out with a 4.2mm drill bit, and tapped them for 5mm metric bolts.
Fitted 4 new brass M5 bolts, and everything is hunky dory!

I also replaced 3 x 0.01uF 250v caps with 0.01uF 630v caps, and, because I am running GZ32 rectifiers, went back to 2 x 22uF PS caps.
Changed a 3W resistor out for a 10W resistor. All vanilla components, nothing exotic.

Currently playing one restored, and one original mono block.
They both sound wonderful!









Next, the other one!

(Thanks to everyone, especially Jean, for the help and advice)  :thumbs:





I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #25 on: January 12, 2021, 07:56:33 PM »
Nice job Johan, that amp looks as good as new!

(Pangs of guilt... I have a couple of these that I should also devote a little Tender Loving Care to, cosmetically good and electronically I have no idea as I have never fired them up.)


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #26 on: January 12, 2021, 08:09:51 PM »
Nice job Johan, that amp looks as good as new!

(Pangs of guilt... I have a couple of these that I should also devote a little Tender Loving Care to, cosmetically good and electronically I have no idea as I have never fired them up.)


-F_D

Thanks Eric!

They are such a pleasure to work on - reminds me more of my beloved meccano sets of my childhood that HT electronic valve equipment!
On these two the work was more cosmetic than electronic, but I would not mind having a go at restoring an original set, doing more
electronics as well!
Slowly slowly catchy monkey...


 



I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Qualityten

Re: Quad II mono-block amplifier question
« Reply #27 on: January 12, 2021, 10:09:48 PM »
(Pangs of guilt... I have a couple of these that I should also devote a little Tender Loving Care to, cosmetically good and electronically I have no idea as I have never fired them up.)

Now is the time! I've never found a pair at a price I could afford, but they are surely one if the classics you should experience for a while? Dig them out and start another thread, please.

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #28 on: January 13, 2021, 06:40:58 AM »
I need to do it, together with a couple of vintage Sansui amps and some other retro gems all eagerly awaiting their turn. This is why I enjoy Johan's topics, he actually does what I only think about.   :clap:


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #29 on: January 13, 2021, 10:26:23 AM »
Earthing my QUAD II amps:

I am making up a new set of power and signal cables for my amps.
as they will be used without the Q22.

The signal will be Amphenol RCA - Mogami cable - original Jones plug.

The power cord will be 3-prong wall plug - Cabtyre 3-core power cable - original Bulgin plug (L and N) and a pigtail lug
for the Earth (see pic).

I have reversed one of the male Bulgin socket chassis fixing screws (and fitted a longer screw, that has solid chassis contact)
and plan on fitting the earth pigtail to this with a nut, next to the Bulgin power socket. (see pic).

Does this sound all right, or should I change anything?









I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...