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Jinxie, here is my guess as to what is wrong with the attenuator. Below is part of your post from a previous thread.
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This attenuator has three sections, 10, 20, and 40dB. Each section is either in line or it's bypassed. Various combinations of these three values will give 0-70dB in 10dB steps. Ignoring your measurements at 60 and 70dB for a moment, it looks like 50, 40, 30? and 20 are switching in and out correctly. The 10dB section is not properly bypassed in the 0dB setting. It's also not in-line in the 10dB setting. Thereffore:
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- One or both plungers in the 10dB section are not working, likely because of one or more bad/missing o-rings.
- The solenoid logic is not working. If this attenuator has the mechanical logic, I would look at the Y-contacts.
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You can determine if the solenoid is doing anything by listening for clicks when going between 0 and 10dB. Also listen for the type of sound when comparing the non-working 10dB section to another (working) section.
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Regarding your 60 and 70dB observations, you don't say if you left the display in the 1dB/div setting, or if you changed to 10dB/div. You also don't say where on the screen the noise is. If you were observing with a 10/ vertical scale, and the noise was way down, then this would confirm that the path through the 10dB section is interrupted while in the 70dB setting. Similarly, if the 60dB setting shows noise near the bottom of the screen, that would imply that the path around the 10dB section is also open.
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You can repeat these experiments by recallung reg. 8 and then changing the scale to 10dB/div. It's usually better to post pictures than to give verbal descriptions.
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Vladan
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