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Hi!

I have been tracking the signal (unbalanced) in both channels, shorting ground with pin 2 (i think). Audio path works perfectly without sidechain signal.

TL074 pin 7 one channel signal ok, two signals wobbling (see pictures). This is channel independent. so i am assuming the sidechain vca that 2181 cannot deal with the two summed signals simultaneusly and hence it is faulty. I Exchanged this chip with one of the audio chain and the wobbling reapeared now also in audio path, in both channels which i find weird.

I scoped pin 7 and 1 of tl072 with bypassed sidechain and i get -10mV Dc instead of 0mV. Is this normal operation?

Thanks!
 

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THAT has better specs

but coolaudio, being sloppier, may have that "sheen" that some associate with the ssl4000

Most of the sound in this unit is sidechain function, not parts


..yes - the that 2150/2180 series are also marked like this:

https://www.thatcorp.com/datashts/THAT_2181-Series_Datasheet.pdf

/Jakob E.

edit: and no, usually only the vcas themselves gets damaged by this
Hello !

Got the new 2181's today and soldered them in. I also reverted to vanilla setup for now.

Now I have some other weird behavior. there is sound, but also only the makeup pot works in ON-position , like it should.

But here it comes, There is no compression at all. no Meter movement. But then I saw that the power led of the switch got lower , more dimm after a minute or little more. I turned the Unit off and on again , and to my surprise the Compression , the meter and everything , the whole function of the device fades in , like in a swell , and goes away again . like a big wave of normal behavior :) Wtf is that ??? is it some Power thing, capacitors , or ?? I don't get it . 15v on + and - stays constant all the time.

I could also upload a short video of the behavior if needed,

thanx again !
 
Thermal shutdown of 12v-line, we've had this before. Search?
I searched, and also heard before that the led can cause problems. should I try running it without the leds connected to check ?

UPDATE: Ok, disconnected leds. Even got back to the original stepped switch from ur ssl.pdf. just to get the pushbutton confusion out of the way for now ;)

Meter shoes movement, makeup is working. but no compression, threshold Poti no effect at all.
that's so frustrating... :)
 
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Little jumper on front assembly board is installed? Not sure tho all board versions still need it.
 
after a little brake I got back to it

ok, I checked everything again, I also changed and used the additional resistor, trimmer and jumper for the THAT2181C. still the same Problem. bypass works, audio comes thru. only makeup gain change output sound, also meter reacts to only high input level as it should. but I think this is adjustable via trimmer, right ?

However. I#m on the end of my knowledge here. And it feels more like searching in the dark here.

I can't spend so much time on it, and im afraid that means it will collect dust in my shelve....

So,... I rather give it away to somebody who is more experienced with trouble shooting. If someone wanna buy it from me, I#m sure we figure out a good price. As u can see in my pics before I have a white front panel and knobs from don audio/frontpanels.de. and super sidechain mod.

so sad, I managed to build the stereo Pultec EQ and the stereo Calreq EQ successfully

Anyway thanx for all your help !!!! and hopefully my unit finds a new home and gets back to working status asap :)
 

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