Analog Maintenance And Upgrade Considerations - Locating parts, improving power and ground distribution

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Great River

Figure 1: A new copper bus bar distributes a robust ground to each module via the green wire to the motherboard below.

Figure 2: The newly added Barrier Strip is fed from the power-input connector on the rear panel from the top. Below, wires are “multiplied” to feed each of the motherboards individually.

Figure 3: Ground distribution on the Master Module is beefed up by using a bus wire in parallel with the main PCB trace. Three black wires reinforce the “distant” areas.

Figure 4: ICs 23 and 24 are the buffer amplifiers for the Stereo Master Fader directly above.

Here’s a recent upgrade story. Dan Kennedy, of Great River Electronics here in the Twin Cities, recently acquired two Trident Series 65 consoles, one with 24 and one with 16 modules. Kennedy combined the two with some fine and fancy metal work and improved the power and ground distribution in the process. He also modified the Master Module, which includes the mix bus and control room monitor
section.

In Fig. 1, the motherboard appears across the bottom, where a wire bundle—red, black, white and blue (hidden)—delivers power and original ground. Above is the new copper bus bar, distributing ground to each module connector via the green wire, when previously only the circuit board trace did the job. Power and ground were formerly distributed from “momma to momma,” via jumper wires until a barrier strip was installed, as shown in Fig. 2. Now, each motherboard gets its own power connection. (Note: Some liberties were taken with the wire colors.)

A similar approach was taken on the Master Module. Highlighted in yellow in Fig. 3, a new solid ground wire is paralleled with the original ground trace. In addition, note the three black wires that branch off from the connector to reinforce the ground for the more “distant” areas in need. You really can’t have too much ground.

On the flip side of the motherboard, two Burr-Brown OPA602ap op amps replace ICs 23 and 24—the stereo fader buffer amplifiers—as seen in Fig. 4. The Burr-Brown part has a minimum slew rate of 20 volts/microsecond and a quiescent (idle) current of 3 mA min to 4.5 mA max when hot. Both of these parameters are about twice that of the original TL071 part. Replacing just these two op amps in the Master Module might not be cause for worry—in terms of power consumption—but there are 23 op amps on this PCB alone! Kennedy felt the Master/Monitor module was very important. The old power supplies were replaced with a single redesigned supply with more than enough reserve power for any future op amp upgrades.

It’s winter in Minnesota, and Eddie is feverishly removing the wheels on his roller skates hoping to upgrade them to cross-country skis with some leftover lumber. Drop by www.tangible-technology.com and see if reindeer really know how to fly.

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