Orban 111b reverb bias troubleshooting help

[jasonguitar]

I acquired one of these units recently sold as is for parts. It originally had good functioning signal but bad hum in right channel and the other channel was dead which turned out to be a bad IC in the output side of the left channel. With a new chip and new electrolytics it is now working except that the bias adjustment and distortion null trim pots on the left channel aren’t doing anything to the signal. The trim pots themselves are good and the other chips, diodes, resistors, caps all appear to be good and all connections seem to be intact. It seems as though the limiter on that left channel isn’t working and that is why these controls are having no effect? Hoping someone might be able to give me some pointers here as to what parts in particular might cause this condition. Hoping there’s not something burned out in the limiter module itself on that side since it’s an epoxied black box with no schematic or replacement part available to my knowledge.
Schematic/manual: ftp://ftp.orban.com/111B/111B_Manual.pdf

[g1]

Are you using the alignment procedure in the manual?
Alignment should not have been required for output IC replacement so I'm not sure what lead you to those trimpots, some other symptom?

[jasonguitar]

Yes I was getting a much brighter reverb on the left channel and less reverb overall. In tracing the signal it seems there is a weaker signal hitting the reverb tank input so I tried the bias trims and saw that there was drastic effect on the reverb and dry mix on the right channel and zero effect on the mix on the left bias trim.

[g1]

Can you swap the spring units? A defect in the input transducer could make it seem like the drive signal was weak.

[jasonguitar]

sorry I forgot to mention that I had tried swapping the spring unit and they behavior is exactly the same. Spring units are all good.

[g1]

Then I'd be inclined to think the limiter module is faulty, thus the unit being sold 'as is for parts'.
The schematic shows the module pinout, you could slice some traces and swap sides to verify.