Author Topic: Quad II mono-block amplifier question  (Read 2052 times)

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #30 on: January 13, 2021, 06:44:12 PM »
I made the cables this afternoon...


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 charles

Re: Quad II mono-block amplifier question
« Reply #31 on: January 14, 2021, 08:38:06 AM »

Well done. It looks very good.

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #32 on: January 14, 2021, 12:02:34 PM »
Firefox blocked all these pics after an update, sorted it out now. Seems they might be hosted on a FB server?

Agree with Charles now that I can see the pics once again, the cable looks good indeed  :thumbs:


-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 #33 on: January 14, 2021, 12:20:19 PM »
Firefox blocked all these pics after an update, sorted it out now. Seems they might be hosted on a FB server?

Agree with Charles now that I can see the pics once again, the cable looks good indeed  :thumbs:


-F_D

Thanks Eric.

Yes, they will do the job. It is surprisingly difficult to get good "normal" 3-prong wall plugs these days.
Most seem to be cheaply-made, brand new screws are rusted on the insides (ACDC) and more than a few times the
set-screw strips in the post (Builders and Brights) when one tries to tighten it on the wire!

What / where do people buy decent quality (but not audiophile) wall plugs?

 
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 fdlsys

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Re: Quad II mono-block amplifier question
« Reply #34 on: January 14, 2021, 12:34:18 PM »


... where do people buy decent quality (but not audiophile) wall plugs?
Believe it or not, Chinese electrical supplies shops. Not all shops of course, you have to search and search...
Thick rubber or old style bakelite bodies, solid brass prongs and screws. Amazing.
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
Come back when youíve lived a little. Miles Davis

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #35 on: January 14, 2021, 01:27:45 PM »
Thick rubber or old style bakelite bodies, solid brass prongs and screws. Amazing.

Now THAT is exactly what I am looking for!
Thanks Mike, will hunt around.
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 #36 on: January 14, 2021, 05:16:43 PM »
Completed the Jones-RCA connectors just now.

Will try them out when it cools down a little, later -
boiling hot here at the moment!

(I am keeping the "look" of the Jones plugs original, but I have cleaned the
blades with an eraser, and they cleaned up nicely)



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 jerkyaudio

Re: Quad II mono-block amplifier question
« Reply #37 on: January 15, 2021, 06:39:47 AM »
Hello Johan,

Nice job again - I would however put a "groundlift" resistor +/- 1K ohms in series with the chassis earth i.e the tag that you have factored for from the wall plug.

This is to prevent "earth loops" should you plugin other earthed equipment.

Offline Ampdog

Re: Quad II mono-block amplifier question
« Reply #38 on: January 15, 2021, 06:47:09 AM »
Came onto this late:

I have also restored a few dozen Quad IIs over decades - yes, the power transformer runs hot. Some heat is also transferred from the closeness of the KT66s - Dr. Walker almost made the unit too small!  In this sense using the smaller GZ34 as rectifier helps (also runs cooler than GZ32.)

[Technically this amplifier was somewhat ahead of its time, further prestigious in that it was designed during WW2 with the resulting lack of quality materials at the time. Perhaps I may quote the opening statement of the circuit description: "The Quad II main amplifier differs from contemporary practice both in the output stage and the penultimate stage contributing materially both to performance and efficiency in a manner that will delight the engineer."]  Indeed!

One aspect to be attended to is the closeness of the mains voltage selector to its mounting screws. Flash-over often occurred with the least amount of dirt on the inside screw (sharp points there!) and placement needs to be attended to. Further, the loudspeaker banana sockets could form an oxide layer over time which would influence contact with the plugs. (Many people replaced these with screw terminals.)
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #39 on: March 24, 2021, 06:11:24 PM »
I finished the restoration work on my second Quad II valve mono block late this afternoon.

I think it looks great.

I plugged it in, switched it (them) on, and they both started playing beautifully!

For just over 60 minutes. Then there was a dull "pop" sound, and the mains earth leakage switch tripped. And the fuse in this newly-restored mono block blew.

I am not sure what the problem is - I double-checked everything, and it corresponds 100% to my "before" photos, and it looks exactly like the other (earlier-restored) and still working one.

Where to start looking - any advice from the Quad II / Valve gurus on the forum?








 
All advice greatly appreciated.

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 #40 on: March 24, 2021, 07:10:51 PM »
Sounds like a fault in the primary section of the 220v AC transformer. Check resistance readings of the transformer, specifically if any on the 220v side are "leaky" to chassis ground.

If you have a cap across the AC mains to filter out plops, check that carefully, or disconnect it for further testing.


-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 #41 on: March 25, 2021, 06:58:21 PM »
After a friend pointed out the possibility of the voltage selector strip in my Quad II valve monoblock amp arcing and blowing the fuse, this afternoon I bypassed the voltage selector, and hard-wired (nothing irreversible) the AC input to the 240V tap on the power transformer with a short, insulated piece of copper wire. I have now (and yes, there is basically a heatwave outside) been playing the Quad IIís for 3 hours solidly, with no problems at all. Holding thumbs!
PS. It is so hot, I have put my Cabernet Sauvignon in the fridge!



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...