Author Topic: Restoration of Leak 12 Point One mono-blocks  (Read 893 times)

Offline peterc

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #15 on: December 05, 2018, 06:56:48 AM »
Good luck Charles, lovely project.

Peter

Offline charles

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #16 on: December 05, 2018, 02:41:14 PM »
Thank all of you for the encouragement regarding the restoration process.

Tested the second mains transformer.

Powered it up: All voltages present.

Offline Family_Dog

  • Administrator
  • Trade Count: (+26)
  • *****
  • Posts: 8,568
  • Total likes: 53
  • STEEL & GLASS - Everlasting Beauty!
    • Repcom 2-way Radios
Re: Restoration of Leak 12 Point One mono-blocks
« Reply #17 on: December 05, 2018, 04:01:21 PM »
That's good news, I was a bit concerned about how they looked in those pics.

To this day I have never even held a Leak 12 in my hands but it sounds like a fun project and I should guess easier to work on than the Quad IIs of the same era.


-F_D



-Eric

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

Offline El Sid

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #18 on: December 05, 2018, 04:01:37 PM »
Great stuff Charles! So both mains transformers have passed the insulation tests and are making the right voltages?

Offline charles

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #19 on: December 05, 2018, 06:05:18 PM »
^^^^

That is correct.

Size wise, one Leak mono-block is about the size of two Quad II amplifiers.

These mono-blocks have some rust spots underneath the chassis so it may be a better option to remove the wiring loom
and components from the chassis to restore the chassis.

An easy option is to use the spare chassis and populate it with one mono-block's OTF, MTF and Oil Capacitor Block.

This spare chassis will be my test jig to test all the OTF's, inductors and other components.


 

Offline Family_Dog

  • Administrator
  • Trade Count: (+26)
  • *****
  • Posts: 8,568
  • Total likes: 53
  • STEEL & GLASS - Everlasting Beauty!
    • Repcom 2-way Radios
Re: Restoration of Leak 12 Point One mono-blocks
« Reply #20 on: December 05, 2018, 07:50:25 PM »
I would concur with the above, remove the wiring harness and do it properly. Will make for a very professional quality product when you've finished.


-F_D



-Eric

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

Offline KNL

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #21 on: December 06, 2018, 04:13:26 PM »
Great news on the transformers, looking forward to future posts..

Offline VALVAGLO

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #22 on: December 06, 2018, 11:39:45 PM »
@ Charles,   Never mind the voltages and such,  What does it sound like?

Just pulling your leg.
"A man without tools is like a fish without a bicycle" Quote from Jim Gore

Offline Ampdog

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #23 on: December 09, 2018, 05:46:52 AM »
Hi Charles,

Apology that I do not always respond to your restoration projects as enthusaistically as others. They don't know: We two setlle that sort of thing at a Sea Food restaurant together with a botlle of .........  ? Much better restoration job after that!

But this matter of using original components af far as possible. Obviously - until they are no longer obtainable. Is my question irrelevant:  Would e.g. H.J.Leak not have used a 'more modern' version of say the dotted resistors if he had lived today, Why do using better modern parts change the 'intrinsic value'?  I can understand Great-Gran's wash table which he used to dunk Marie-Antoinette's head in; it does not need to still be fully operational and all that. But (and I am asking honestly): When guys restore ancient cars, do they go scavenging the boxes and surroundings for the same rusted possibly half-stripped bolts and nuts used in the time in pursuit of originality?  (Not that I have noticed)

In other words, between Gran's toilet table and the restored Ford XYZ, is there not a difference in the intrinsic value?  "Here; I got this Model T with all the original bolts, but unfortunately it does not run ..."  I always ask: "Would the designer not have used newer exact same components if he were to 'restore' his product 60 years hence?"

I am not making a statement one way or the other; I am not a judge with experience in thi field. But in this field you read up more than I do (I hope you do!), so in what actually lies the "value" of a restored say 1938 Excelcior amplifier?  (For that matter, how is the 'value' of any ancient something actually determined?)

Not trying to go off on a different tangent, but it always puzzled me: What are the end requirements regarding any valuable piece of restored "ancientry"?
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)

Offline charles

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #24 on: December 09, 2018, 07:20:54 PM »
Regarding the original components.

One has to test each resistor to check if it changed its value significantly or is it within the say 10% to 20 % applicable tolerances.
Then keep it. If changed make sure, if possible, that it is the same value, same type, size, etc.

The cathode bypass capacitors have to be changed as well as the coupling capacitors..

The oil capacitor bank is so reliable that in most instances it stays.

I have some 12.1's that has most of its original components and it still has a 0.1 % THD at rated output.

Very important when replacing the components, keep the original components.   

Bear in mind that lots of these 12 Point One's have been serviced in the past, so some of the original components
have already been replaced with modern ones.

The first ones were produced at the end of 1948. These Leaks are very old valve amplifiers. 

The market determine the value of a collectible vintage valve amplifier.

"What are the end requirements regarding any valuable piece of restored "ancientry"?"
At a later stage I will try to answer your question.
« Last Edit: December 09, 2018, 07:38:10 PM by charles »

Offline charles

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #25 on: December 12, 2018, 02:53:30 PM »
Fitted the MTF, OPT and Oil Capacitor Block onto the spare Leak chassis.

This chassis was already fitted with some replacement components so I did a spot check on most of the resistors. I still have to check all the
capacitors.

I used a variac to slowly reform the oil capacitor block (these are four capacitors housed in a big metal enclosure).

Some good news, according to preliminary tests the amplifier produced an output.

Offline 2wice

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #26 on: December 12, 2018, 03:40:51 PM »
Nice one Charles.

Hope to see some more photos soon.

Offline charles

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #27 on: December 13, 2018, 04:45:47 PM »
Amplifier could not produce rated output.

Found the fault. A previously replacement electrolytic cathode bypass capacitor had the wrong value.

Replaced it with the correct value capacitor.

Amplifier output now correct.

I still have to check the coupling capacitors for leakage.

Measured also the THD and output power.

I will post some photographs of the restored amplifier.

Now for number two. 

Online fredeb

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #28 on: Yesterday at 07:04:37 AM »
Progress seems fast Charles - well done !
...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts

Offline mygoggie

Re: Restoration of Leak 12 Point One mono-blocks
« Reply #29 on: Yesterday at 11:59:18 PM »
Photos will be excellent! Love the thread so far!
Herman

~ To heal the soul is to embark on a new journey. ~