Cetec 20LM Channel strips.

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Cetec 20LM Channel strips.

Postby Futureman » Mon Dec 22, 2008 7:38 pm

Generally, I ask what others think before buying something old and cranky like this, but this time I bought some first..

any opinions?

http://cgi.ebay.com.au/ws/eBayISAPI.dll ... :IT&ih=002

Still 4 Left.

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Postby Futureman » Thu Jan 01, 2009 10:33 pm

Hey all, I got 4 of these the other day, from an old american console circa '74 and powered em up... 3 worked perfectly, 1 sounded real bad...

It had no top end or even mids.. lots of low end distortion etc..

The EQ when enabled, only the low EQ knob effected the sound, it seemed as though the high & mids did nothing..

The output from the Aux sends sounded the same as the output from the Bus & L/R outs..

Could someone please point me in a general direction as what components the more experienced techs out there would be blameing for this sort of fault?

Thanking you in advance
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Postby Futureman » Thu Jan 01, 2009 10:34 pm

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Postby Futureman » Thu Jan 01, 2009 10:38 pm

Futureman wrote:Hey all, I got 4 of these the other day, from an old american console circa '74 and powered em up... 3 worked perfectly, 1 sounded real bad...

It had no top end or even mids.. lots of low end distortion etc..

The EQ when enabled, only the low EQ knob effected the sound, it seemed as though the high & mids did nothing..

The output from the Aux sends sounded the same as the output from the Bus & L/R outs..

Could someone please point me in a general direction as what components the more experienced techs out there would be blameing for this sort of fault?

If you think it is the first or second LM-307, where would I get a metal can version of these? would a normal chip version on a bit of vero and legs be fine?

Thanking you in advance
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Postby rob » Fri Jan 02, 2009 2:54 pm

well there isn't too much in these. so that might help

can you monitor the signal before the fader?

are the ICs socketed? If so swapping out the two ICs in the bad channel with ones from a good channel would be a starting point.

Finding LM307s in a TO-8 package is going to be difficult. One option is to buy 8 way DIL wire wrap sockets ( from RS / Farnel ) and use the long legs to bend them into a circular pattern to mate with the pcb. Once you have a bog standard DIL socket in place, then all options on ICs open up and repairing is easier

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Postby Futureman » Fri Jan 02, 2009 6:39 pm

rob wrote:can you monitor the signal before the fader?


yes, the aux sends can be pre/post fader, but it makes no difference to the sucky tone..

all the IC's are can package & not socketed..

The fact that the pre & post fader output both sound the same tells me that the fault is not with IC A3, but earlier.. possibly A1 or A2 or their associated passive components..

So, if i get hold of a LM-307 thats not in a metal can, and get it's pin out etc, it'll be electrically the same? the can doesn't have anything to do with shielding etc?

Thanking you in advance
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Postby rob » Sat Jan 03, 2009 8:34 am

sure, pin out is the same. But you do need to correlate the pin 1 of a circular layout to pin 1 of a rectangular layout. And you will need some form of IC adapter as previously suggested.

Also that mod of adding the cap from the input transformer secondary to pin 2 of the first IC is really weird.

And will the limited brain power i can apply at 8am on a saturday morning tend to think it is a bad mod and could / will cause problems.

In fact there is very little in the entire design of these channel strips that is worth keeping.

I think I have one coming my way soon and will probably re-design most of the entire channel.

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Postby Futureman » Sat Jan 03, 2009 2:57 pm

I've had a good play with them, but not through any real decent monitoring, but they seem to sound fine.. I'll get back to you when I hear them through some good monitoring.

The EQ sounds pretty cool, I just don't like the low at 100hz.. it's a bit too high for me.. just my preferences tho.

On a side note, the knobs are exactly the same (well i'm 99% sure) as an 1176..

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Postby rick » Sat Jan 10, 2009 8:10 pm

hey mike you might want to "redate" this console
it looks much more like 1984 to me , very un-early seventies me thinks :)
although you may have cornered the market on knobs for 1176 clones !
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Postby Futureman » Sat Jan 10, 2009 9:48 pm

Ok, I was just going by the date written on the schems...
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Postby norm » Sun Jan 11, 2009 5:39 pm

Yes I ended up with 16 of them, for the price I could not resist and you are right Rob you will get one next week. Either I will have something of sonic worth or a batch of expensive parts. Norm
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Re: Cetec 20LM Channel strips.

Postby Futureman » Sat Nov 02, 2013 7:57 pm

Hi all!

Resurrecting this thread.

Norm, would you want to sell any of your strips? (assuming you still got some)

(planning on building a Frankenstein mixer with some that I have plus a few odds and ends.

Oh, and F me if I know where I put the schems!
I tried way back machine.. Funny seeing the wood grain T-rock thread again.. But the scans didn't get archived.

Rob, any chance you have a copy?

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Re: Cetec 20LM Channel strips.

Postby rob » Sun Nov 03, 2013 11:51 am

message from Norm as he drove his truck out of my driveway. ..... He is up for selling his Cetec channel strips. He is on the road for a week so contact him in a while. I also threw the schematics into the truck, so he has these.
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Re: Cetec 20LM Channel strips.

Postby Futureman » Sun Nov 03, 2013 12:22 pm

rob wrote:message from Norm as he drove his truck out of my driveway. ..... He is up for selling his Cetec channel strips. He is on the road for a week so contact him in a while. I also threw the schematics into the truck, so he has these.


Much thanks!
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