Focusrite RED II and RED III Schematics needed.
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pucho812
Well-known member
have you checked the technical documents section?
Can you describe the faults? Most Focusrites that I've had through the shop, especially ones that came from pro studios where they were left on 24/7/365 for years, were in serious need of re-capping. If you have a capacitor tester, I would start there.
pucho812
Well-known member
I concur.
Hi, after a certain time, the RED III begins to crackle and simmer quietly. I think you're right. I probably won't be able to avoid replacing the capacitors. With schematics it is much easier. Could also be a Transistor or ceramic cap. I'll start with cold spray. Maybe I can narrow things down a bit..
If the unit comes from the situation I described, some of the electrolytic capacitors will be so bad as to be virtually no capacitance. I would suggest doing some frequency sweeps through the unit. I have seen things like the sweep looking like the HPF and LPF were fully engaged, when they were bypassed. I have also seen some paths attenuated by more than 20dB because of dried out caps.
Disco Volante
Well-known member
That does indeed sound like bad caps, if not a bad solder joint or failing tracks under leaky caps (which still implies a full recap)...
Gareth Connor
Well-known member
You need to look at the power supply electrolytic caps as well as the audio coupling caps; not so much the PSU reservoir caps, but the low-value caps used around the regulators. When these go out of spec, it can affect the voltage rail stability, and hence the audio performance.
Audio coupling caps and some of their problems have already been dealt with in previous answers.
I don't recall the exact circuit topology of the power distribution of RED2, but if it's individual electrolytic decoupling of each chip, when the decoupling caps go dry, the EQ circuit can become a tunable oscillator
. This is a disturbing experience the first time around, but once learned, power caps are a go-to first check on any Neve-type of circuit.
Regarding RED3, I don't know what Focusrite did to it after I left in mid-1993, but I do recall most of the circuitry in the prototype designs.
If I were faced with the RED3 problems you have, I would make a note of how long it takes for the crackling and simmering to start.
Then check power supply voltages to see if anything is radically out-of-spec; repair if required.
Re-test to see if the crackling returns.
After that, check electrolytic cap values and ESR measurements throughout the unit. Replace any duff caps, test again. When does the crackling start?
With caps attended to, it's time to move on to other components.
Audio coupling caps and some of their problems have already been dealt with in previous answers.
I don't recall the exact circuit topology of the power distribution of RED2, but if it's individual electrolytic decoupling of each chip, when the decoupling caps go dry, the EQ circuit can become a tunable oscillator
. This is a disturbing experience the first time around, but once learned, power caps are a go-to first check on any Neve-type of circuit.Regarding RED3, I don't know what Focusrite did to it after I left in mid-1993, but I do recall most of the circuitry in the prototype designs.
If I were faced with the RED3 problems you have, I would make a note of how long it takes for the crackling and simmering to start.
Then check power supply voltages to see if anything is radically out-of-spec; repair if required.
Re-test to see if the crackling returns.
After that, check electrolytic cap values and ESR measurements throughout the unit. Replace any duff caps, test again. When does the crackling start?
With caps attended to, it's time to move on to other components.
