UralTone Bias Tool Deluxe DIY noval probe build guide

This is instructions to build the Bias Tool Deluxe Noval probe pair. The assembly guide can be used for fixing the probes too. Fixing the probe is challenging so we recommend to build new pair to replace damaged one.

UralTone Bias Tool Deluxe noval probe BOM

Check all the parts

Always check first that all parts are included in the delivery. If you find any problems please contact us by email or through the "contact us" form on the pages. Note that the components may look slightly different than in the photos. Also, note that the voltage specs of the parts may be higher than what is listed. Read all the notes at BOM (bill of material) carefully.

Building the Noval probe pair

Follow the order in which the images below are assembled. We try to keep component manufacturers and types the same, but sometimes we have to change the manufacturer or model of a part due to poor availability. So if a part is a slightly different color or higher voltage rating, all is good, each component has the required values marked on the side of the part.

Nov Probe has high amount of parts fitted in relatively small space used on high voltages. Some of the resistors are SMD parts due space requirements. Follow the pictures precisely, don't leave the connecting wires too long and be sure the wires insulation won't melt when soldering close by. Doing checks with multimeter while building the probe is highly recommended.

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Bias Tool Deluxe Noval probe PCB kit. Kit contains two pcbs, one to solder the parts and one as bottom plate / protector towards the socket being inserted. It also supports the pins of the probe.

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Measure all 4.7Mohm resistors supplied with the kit. Mark the value of the resistor. On picture only the decimals are written.

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Pick two resistors of same or most close the same value. On the picture two of 4.680Mohm resistors are selected.

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Solder the selected resistors. Note the way how the resistor is fitted on PCB. It leaves some space for pin 5 not to touch the resistor body.

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Set the PCB aside. Cut the wire came with the kit on two equally long pieces. On jack end the cloth thread is cut short and the protective shield is twisted as single wire. White wire is cut shorter than red. Presolder the wire ends.

Solder the wire on PCB. Follow the markings R = Red, G = Ground, W = White.

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Route the wire through two holes on pcb.
Remember to set the plug shell and shrink sleeve before soldering the plug.

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Solder the red wire first.

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Then fix the ground and white wire on their places. Solder both wires.

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Heat up the shrink sleeve and tighten the tabs on plug. The idea of the shrink sleeve to recognise which probe is plugged on each channel.

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Screw open the socket saver as in picture. This circuit uses only the socket on right.

Press the socket to PCB pads. Make sure the contacts of the tube socket doesn't touch the 4,7Mohm resistor on pads on the PCB. However press the socket as deep it's possible to fit. When rules above are met, solder all nine pins.

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Cut off section of the pin 3.

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Solder jumper wire from pad SC to socket pin 3 where the piece of pin was cut off.

Note: On the picture the pin 3 has extruded from it's place after cut. If needed press in the contact before soldering the jumper wire from pad SC.

Measure the all pins on bottom and meeting sockets on top for zero resistance / conductivity. Exception is pin 3 with 11ohm resistance. Measure pins next each other as pairs (1-2, 2-3 ... 7-8, 8-9) for open circuit / infinite resistance. (Some quality multimeters may display resistance on tens of megaohms)

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When all measures are done and passed, solder the bottom. Pins should have approx 7mm length.

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Heat up two layers of heat shrink for side protection.

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Probe is ready!