Thunders1988
Member
 Offline
Age: 36
Location: Belgium
Posts: 285
Conquistador of the useless.
|
 |
« on: November 21, 2019, 06:03:08 PM » |
|
The time has finally arrived for me to start working on a couple of Quad II’s I purchased a couple of years ago.
To get them working again, I need some help finding someone who can
rewind both powertransformers.
The first one has a problem in the primary 240v tap (dead)
And the second one has a fault in the secondary HT winding (no CT).
If there is anyone who knows of such person offering xformer services(Preferably in Belgium or Holland),
please do let me know!
Regards,
M.
|
|
|
|
|
Logged
|
Mathias
|
|
|
wer
Member
Offline
Location: Catalunya
Posts: 9,364
|
|
« Reply #1 on: November 21, 2019, 11:11:58 PM » |
|
There is a business in Holland that winds (new) transformers. I had one made for a Citation, and found the price quite reasonable.
|
|
|
|
|
Logged
|
Werner (wer - just my initials, not a nick!)
No esoteric audio equipment (except for my wife)
|
|
|
Thunders1988
Member
Offline
Age: 36
Location: Belgium
Posts: 285
Conquistador of the useless.
|
|
« Reply #2 on: November 21, 2019, 11:49:44 PM » |
|
That’s good news Werner! Do you happen to know the name of the firm?
Already emailed a company in Belgium, but no reply yet. Let’s see what they have to say.
|
|
|
|
|
Logged
|
Mathias
|
|
|
analogadikt
Administrator
Member
Offline
Age: 59
Location: India
Posts: 5,134
|
|
« Reply #3 on: November 21, 2019, 11:54:57 PM » |
|
It is the depotting and repotting that shall be tricky and increase the cost.
Regards,
|
|
|
|
|
Logged
|
|
|
|
Chris65
Administrator
Member
Offline
Location: Auckland, New Zealand.
Posts: 5,195
|
|
« Reply #4 on: November 22, 2019, 12:36:30 AM » |
|
AE Europe in Holland https://www.aeetransformers.com/products/audio-transformer.html#description(Moved this topic to Amplifiers as the information may be useful to others in the future and will be lost if left in the Wanted section) |
|
|
|
« Last Edit: November 22, 2019, 12:48:43 AM by Chris65 »
|
Logged
|
Chris
"The Blues is the roots, everything else is the fruits" - Willie Dixon
|
|
|
|
niclaspa
|
|
« Reply #5 on: November 22, 2019, 07:23:52 AM » |
|
You can remove the potting yourself by heating the whole transformer in the oven. Possibly, it will mess up the paint work. It appears that Majestic in the UK can supply a transformer that fits within the original can as described here: http://www.keith-snook.info/quad-ii-majestic-transformers.html |
|
|
|
|
Logged
|
Niclas
Ernst ist das Leben, heiter ist die Kunst
|
|
|
wer
Member
Offline
Location: Catalunya
Posts: 9,364
|
|
« Reply #6 on: November 22, 2019, 11:48:09 AM » |
|
As usual our Search-Wizard was spot on. (Sorry, but i did not have the time to look for it yesterday night.) |
|
|
|
|
Logged
|
Werner (wer - just my initials, not a nick!)
No esoteric audio equipment (except for my wife)
|
|
|
Thunders1988
Member
Offline
Age: 36
Location: Belgium
Posts: 285
Conquistador of the useless.
|
|
« Reply #7 on: November 22, 2019, 12:22:51 PM » |
|
No problem! Contacted a couple of firms, let’s see what the outcome is. In the meantime, might as well use this thread to post general progress...  |
|
|
|
|
Logged
|
Mathias
|
|
|
|
flyingmattyboy
|
|
« Reply #8 on: November 29, 2019, 05:03:23 AM » |
|
As someone else suggested already Majestic in uk is worth a phone call or email.
|
|
|
|
|
Logged
|
|
|
|
Thunders1988
Member
Offline
Age: 36
Location: Belgium
Posts: 285
Conquistador of the useless.
|
|
« Reply #9 on: November 29, 2019, 07:09:13 PM » |
|
So... Finally some time to update this post. Considering Majestic but I want to get these amps up and running on original parts first. Been soldering and painting the last couple of nights as well as reading up on tube amps and things related... This is how they look right now.  Just now I plugged em into the Variac, slowly turned it to 230v (won’t go any higher, old thing.) and I got some terrible feedback. A bit of cursing later, figured I might as well just lift the Feedback resistor and sure enough it sang. I know this isn’t a proper solution so I want to know... What’s wrong with the feedbackcircuit? Probably too much of it, so I need to raise the value? I blindly followed the circuit along with some of the information on Keith Snook’s webpage. Used original values to replace all the components. Only changes I made where to split up the KT66’s bias. Used 360r resistors with 10uF capacitors. Added a grounded plug, a virtual ground (10r + 47nF) to the E tab on the power transformer and upped the 16+16 cap to 50+50uF to use a GZ34 rectifier. Anyways. Not a specialist. All input welcomed! Have a nice weekend all. |
|
|
|
|
Logged
|
Mathias
|
|
|
Thunders1988
Member
Offline
Age: 36
Location: Belgium
Posts: 285
Conquistador of the useless.
|
|
« Reply #10 on: December 01, 2019, 12:16:21 AM » |
|
OK. So spent a little more time soldering on the second one tonight. Still needed to change some resistors around. Hooked it up to the variac, slowly turned it up and away she sang. No feedback problems, clean as a whistle. Started scratching my head a little more and took the multimeter to the first one again. Measured all values again... Like they say, assumption is the mother of all f*ckups. R7 measured a healthy 680K but R9 was about 770?! Came from the same strip as all the others. I suspect this to be the source of the feedback since these go to the grids of the KT66’s. Anyway. Ordered a new set of resistors... Let’s see if this guess is a bit more educated.  Also: Saw a powertransformer come up on eBay so bought it. Came in last friday. Already repainted and sitting happily in the second one. |
|
|
|
|
Logged
|
Mathias
|
|
|
rfgumby
Administrator
Member
 Online
Location: Minneapolis, Minnesota, USA
Posts: 18,470
|
|
« Reply #11 on: December 07, 2019, 04:44:56 AM » |
|
That’s a nice job on the rebuild of those Quads. Paint in no the chassis and trannys in place is tricky. Good luck with the new replacement!
|
|
|
|
|
Logged
|
Scott
These days, if it walks like a duck, and quacks like a duck, it's probably a fish
|
|
|
Thunders1988
Member
Offline
Age: 36
Location: Belgium
Posts: 285
Conquistador of the useless.
|
|
« Reply #12 on: December 08, 2019, 06:16:20 PM » |
|
 And we have 15 glorious watts in STEREO. Resistors changed out to the correct values. Connected the faulty one and got the same problem, just a slightly different tone. Checked everything against the working one and spotted my mistake. Switched two wires to the OPT. Corrected and it sounded fantastic. Very happy everything is functioning perfectly. Keith Snook’s website notes there is slight leaking from coupling caps to ground which adds stability to the amp. I replaced those caps with plastic bodied Vishays so no leakage to ground. Don’t know if I should add a couple of 22nF caps. And where do they go? No idea. we’ll see. They do seem stable. Also, the chokes appear to run quite warm as well. Is this normal? Don’t want to fry those... |
|
|
|
« Last Edit: December 08, 2019, 06:24:28 PM by Thunders1988 »
|
Logged
|
Mathias
|
|
|
nigel
Member
Offline
Age: 58
Location: Isle of Wight, UK, Europe
Posts: 4,132
|
|
« Reply #13 on: December 08, 2019, 11:28:35 PM » |
|
Also, the chokes appear to run quite warm as well. Is this normal? Don’t want to fry those...
When I had my Quads, everything ran hot. Mine were rebuilt, but to the original circuit. They used to eat output valves fairly regularly (I didn't have any KT66s, sadly - I tried various brands of 6L6GC). I think my high mains voltage didn't help - often around 250V. In the end I used a buck transformer to reduce it to around 230V, that made everything a little cooler. So, I wouldn't worry too much, I think it's normal. Just watch those KT66s for redplating - that's the danger sign. Nice rebuild, by the way - enjoy!  I still miss mine  |
|
|
|
|
Logged
|
Tofu-eating Guardian reader.
|
|
|
Firebottle
Member
Member
Offline
Location: Dudley, West Midlands
Posts: 369
|
|
« Reply #14 on: December 09, 2019, 10:12:56 AM » |
|
Nice job Mathias, good to see in such fantastic condition.
As soon as I read you were getting oscillation I guessed the feedback was connected incorrectly, useful having two to compare.
|
|
|
|
|
Logged
|
I'm Alan, an avid valve amp designer.
I don't bite, ask any question you like.
|
|
|
|
