mindlessstudio
Member
- Joined
- Oct 4, 2012
- Messages
- 23
So. As part payment for a mix job I did, I’ve gotten a nice boffinisland-made rack with ten Calrec PQ1785 modules. Overall it’s in pretty good nick. Phantom was erratic though. It turned out that the bulps in the lamp-switches were drawing a lot of the actual phantom current, so the more channels had phantom turned on, the lower the output voltage. I fixed that by basically bypassing the light bulps. Weird thing.
Anyway, one of the modules has a problem and I’m somebody here might be of assistance. Basically the input switch is dead until around mid position and then it works as expected. I’ve tried cleaning the switch to no avail. As far as I can tell there are two different gain stages in the preamp, there's a Hamlin relay right on the input, so I guess it’s the lo gain part that’s somehow messed up. Trouble is I can't really figure out where the lo gain part sits. I’ve tried finding schematics but there are none available online and Calrec can’t supply since they don’t own the rights to the modules anymore (!). The output stages that usually would sit at the bottom of the desk are burried deep at the back of the rack, as in inaccessible – so it’s really tricky to set up anything resembling a test bench, not least because of the missing schematics. Basically I’m a bit in the dark here. Does the problem described ring any sort of bell with any of you?
Interestingly, the modules are vitually identical (save the surface color) to the UA8000 PQs that Jakob Erland has posted schematics for, but unfortunately the component numbering is different on the PCBs so it doesn't help that much.
Anyway, one of the modules has a problem and I’m somebody here might be of assistance. Basically the input switch is dead until around mid position and then it works as expected. I’ve tried cleaning the switch to no avail. As far as I can tell there are two different gain stages in the preamp, there's a Hamlin relay right on the input, so I guess it’s the lo gain part that’s somehow messed up. Trouble is I can't really figure out where the lo gain part sits. I’ve tried finding schematics but there are none available online and Calrec can’t supply since they don’t own the rights to the modules anymore (!). The output stages that usually would sit at the bottom of the desk are burried deep at the back of the rack, as in inaccessible – so it’s really tricky to set up anything resembling a test bench, not least because of the missing schematics. Basically I’m a bit in the dark here. Does the problem described ring any sort of bell with any of you?
Interestingly, the modules are vitually identical (save the surface color) to the UA8000 PQs that Jakob Erland has posted schematics for, but unfortunately the component numbering is different on the PCBs so it doesn't help that much.
