mc76 no difference between ratios / attack knob no effect

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Joined
Dec 27, 2005
Messages
7
Location
seattle, wa
I am in the troubleshooting phase of my purple mc76 project. Input and Output work. The meter modes all work. I have calibrated it according to the instructions in the MC76 manual. It does compress audio, but seemingly at a set ratio as if the audio takes the same path through the switch regardless of which button is pressed. Ive checked for shorts on the switchbank. The ratio switches each work to activate compression, but there is no apparent difference between them other than the fact that when switching between the ratios, there is a momentary jump or decrease in the level depending on if your are going to a lower or higher ratio setting. For example if you are on 12:1 and switch to 20:1 there is a momentary dip in the level and on the meter as if it wants to go to a higher ratio, but returns to a common static setting. If you are on 12:1 and switch to 8:1 there is a momentary jump in the level and meter. I notice on the schematic a resistor labeled (T&C). I havnt put this on my switchbank because I dont know how to test what value to use or what it is for. Also the attack knob doesnt seem to affect the attack speed of the compression. The release knob works. I am not using an attack knob with a switch and have just taken the 1st buss side of the ratio switch straight to point 23 on the pcb. Here are some links to pictures:

http://i156.photobucket.com/albums/t6/binaryapotheosis/DSCF1175.jpg
http://i156.photobucket.com/albums/t6/binaryapotheosis/DSCF1181.jpg
http://i156.photobucket.com/albums/t6/binaryapotheosis/DSCF1177.jpg

If anyone notices something that Im obviously doing wrong I would greatly appreciate the insight. I havnt done a lot of this kind of thing.
 
I haven't built the unit you're talking about but on the gyraf/mnats version (and the real 1176 for that matter) the ratio changes the threshold as well.

Soooo...you get the same about of GR on the meter regardless of ratio setting. (the sound changes though)
 

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