C.A.S Optimum II , 1200w power amp...

pat allen · 17th January 2007, 02:08 AM

Hi group.

A friend just gave me one hell of a heavy power amp. It is a C.A.S Optimum II. I do believe it is a Canadian made amp.

Rear of casing says it is capable of 1200wrms in 8 ohm bridged. It is in fact a double mono block amp. Very heavy and big. It uses several MJ15025/24 outputs.

It needs care, few outputs and capacitors.

And my question:

The power supply seems unusual. The transfo dont have a center tap at its output. The ground is taken from the mid tap of 2 bank of capacitors (see my attached short schematic).
Also, all the T03 outputs dont have any mica isolators. I tought at first it was wrong since a lot of peoples played in it before me. But after i realised the power supply, it makes me wonder what is its design.

If you have any idea, let me know, id like to fix it !!

thanks

Workhorse · 17th January 2007, 06:17 AM

Hi Pat Allen,

That amp must be then a copy of QSC amp...

As it has got the following...

Grounded Collector amplifier ....no mica insulators between Devices and Heatsink

AC coupled output as the Transformer has no center Tap..

Follow this link to QSC schematic..for help..

http://www.qscaudio.com/support/libr...ies/USA400.pdf

regards,
K a n w a r

pat allen · 17th January 2007, 03:50 PM

wow, super interesting !!

the schematics look a lot like what i have...

in the lot he gave me there is 2 Proximity model 500 and a Nikko Alpha 220, all dead, with missing outputs or main caps, but all fixeable with patience.

Any of these amps worth the time to fix them ? (inlcuding the QSC clone ) ?

thanks.

Workhorse · 18th January 2007, 03:23 AM

Quote:

Originally posted by pat allen
Any of these amps worth the time to fix them ? (inlcuding the QSC clone ) ?
thanks.

QSC Clone could be an intersting project as it could serve your friend with much more reliability....That design is the main key for the Success of QSC amps....

pat allen · 19th January 2007, 12:50 AM

Ok, thanks.

One question remains...i do believe the transistor needs to be "matched " ?
all the base of the transistors are common, there is 6 npn/pnp per channel.

thanks for any other inputs.

btw, i will do a complete reverse of this amp.

anatech · 19th January 2007, 01:50 AM

Hi Pat,

Quote:

in the lot he gave me there is 2 Proximity model 500 and a Nikko Alpha 220, all dead, with missing outputs or main caps, but all fixeable with patience.

What I am going to say is very important. Those Proximity amps are fire hazards. Don't even think about repairing them! They were made in Quebec. Count those as chassis for future projects.

The Nikko Alpha 220 should be rebuilt as something else. I have two and they don't sound great. The original outputs would be expensive to source. Main caps may have leaked. Alpha 440 and 450 are famous for doing exactly that. Someone here on teh forum built a leach clone in a 220 I think. The reports were that they turned out well. PCB layouts for your chassis too.

-Chris

pat allen · 19th January 2007, 02:06 AM

Quote:

Originally posted by anatech
Hi Pat,

What I am going to say is very important. Those Proximity amps are fire hazards. Don't even think about repairing them! They were made in Quebec. Count those as chassis for future projects.

The Nikko Alpha 220 should be rebuilt as something else. I have two and they don't sound great. The original outputs would be expensive to source. Main caps may have leaked. Alpha 440 and 450 are famous for doing exactly that. Someone here on teh forum built a leach clone in a 220 I think. The reports were that they turned out well. PCB layouts for your chassis too.

-Chris

Thanks for the advices for the Proximity amps, yes they were made in Quebec, well, in Montreal to be precise, which is 1 hour away from me. Those 2 amps were used in a disco mobile long time ago and they did the job well then, and yes, it looks like they turned into huge mess, nothing is good in them but the chassis, heat sinks and transfo. The guy who gave them to me is the original owner, he told me he used them for at least 10 years before they literaly melted

That is back into the 80's

I am defenitively rebuilding the QSC clone because it is far more simpler, and later the Nikko.

Thanks again.

anatech · 19th January 2007, 11:07 PM

Hi Pat,
I saw many in the 80's. Each took the speakers with them. The 250's seemed to be popular here. Flames? Yeah!

-Chris

pat allen · 22nd January 2007, 11:39 PM

wana get a good laugh ??

i took some pictures...

the dead caps from the QSC clone (C.A.S)

pat allen · 22nd January 2007, 11:41 PM

The proximity 250 and the 500.
The transfo next to the 500 is its transfo. Spec are 110v in/105v out with center tap and 500va.

17th January 2007, 06:17 AM	#2
Workhorse diyAudio Member Join Date: Dec 2004	Hi Pat Allen, That amp must be then a copy of QSC amp... As it has got the following... Grounded Collector amplifier ....no mica insulators between Devices and Heatsink AC coupled output as the Transformer has no center Tap.. Follow this link to QSC schematic..for help.. http://www.qscaudio.com/support/libr...ies/USA400.pdf regards, K a n w a r __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

17th January 2007, 03:50 PM	#3
pat allen diyAudio Member Join Date: Dec 2004 Location: Quebec	wow, super interesting !! the schematics look a lot like what i have... in the lot he gave me there is 2 Proximity model 500 and a Nikko Alpha 220, all dead, with missing outputs or main caps, but all fixeable with patience. Any of these amps worth the time to fix them ? (inlcuding the QSC clone ) ? thanks. __________________ Electronic engineer for automotive market.

19th January 2007, 12:50 AM	#5
pat allen diyAudio Member Join Date: Dec 2004 Location: Quebec	Ok, thanks. One question remains...i do believe the transistor needs to be "matched " ? all the base of the transistors are common, there is 6 npn/pnp per channel. thanks for any other inputs. btw, i will do a complete reverse of this amp. __________________ Electronic engineer for automotive market.

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19th January 2007, 11:07 PM	#8
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Pat, I saw many in the 80's. Each took the speakers with them. The 250's seemed to be popular here. Flames? Yeah! -Chris

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