• 33 Ball Pond Road, Danbury, CT 06811-2828
  • 203-733-2110
Series PB3 RF Power System FAQs

It is assumed that the product is connected to a live AC mains outlet rated at the proper voltage level, turned on and front panel meters and fans are operational. If not, troubleshoot the AC mains circuit, AC mains cord and fuses first. See the serial number label on the unit for confirmation of it’s required input voltage. Two AC mains fuses are located inside of the entry module located on the outside lower left side on the rear of the unit.

It is also assumed that the Analog Interface Shorting Plug is properly wired and connected to the rear of the unit. Click here for a download of the shorting plug schematic and connection information – you may also consult the product manual for additional information.

See the product manual for installation and operational information. Clicking here will start a download.

The Interlock LED (green) will not light 
External Interface plug: Is the DB25 interface plug properly connected to the rear of the unit? This plug is shipped with each PB3, pre-wired for front panel control operation and also has the external interlock connections jumpered.

If the external interlock wires are connected to the user’s process system and not closed, the interlock LED will be unlit and the RF output will be inhibited. See Section 3.2 in the owner’s manual for details.

The RF ON LED (red) will not light
External Interface plug: Is the DB25 interface plug properly connected to the rear of the unit? (See description above).

Proper wiring: If this plug has been re-wired to accept an external contact closure to turn the system ON & OFF, these wires need to be closed and the front panel switch depressed to enable the RF to turn ON.

The fan, LED indicators and (digital meters -MD models only) are properly functioning however, there is no indicated RF output

Proper AC Mains voltage: Is the unit connected to the proper AC mains voltage ? A 220VAC unit improperly connected to a 110VAC outlet will turn on and appear normal but the RF power section may be inhibited from operating.

Proper wiring: Has the External Interface connector plug has been rewired to accept an external 5VDC control signal? Is this signal present?

The Forward RF power output is limited
Check is the AC mains voltage: Make sure that you read the tag on the unit to verify the required operating voltage and then measure the AC mains with a voltmeter to ensure it is compliant. The PB3 may operate on lower input voltages with less than full rated output power level.

Plasma load conditions: The Forward power will also limit if the Reflected power is too high. This is caused by un un-lit plasma and/or a broken coax cable between the plasma and the PB3 match output. With a lit plasma discharge, properly tune the Reflected power towards zero by adjusting the Load & Tune matching controls.

The Reflected power is at maximum and the Match controls have no effect
RF generator coax: Verify that the miniature coax cable + BNC connector is properly connected to the match input on the rear of the unit. This coax “dongle” transfers the RF power from the RF generator section to the match section.

The plasma will not ignite
Coax cable connecting the matching network output to the plasma load: If the plasma discharge does not ignite and adjusting the match controls has no effect on the reflected power you may have a problem with the connection between the “match” output and the plasma electrode. Assuming the plasma load is a parallel plate, capacitive load or magnetron sputtering source, a simple test is to disconnect the (type HN female) connector from the match output and test for a short between the center pin and the shield (outer conductor) – the correct result is an “open circuit”. If you measured a short circuit, then isolate the problem to a shorted coax cable or a shorted electrode and correct the problem.

Now test the continuity between the center pin and the powered electrode by connecting the ohmmeter between the connector center pin and the electrode (with the vacuum chamber open) –  the correct result is a short circuit. If you measure an open circuit or infinite resistance, then the problem is a broken wire in the coax cable, burned center pin in a connector or a broken wire connecting the electrode to the vacuum feed through and/or connector. Try to visually locate the problem and repair it.

Heating the coax cable: If the plasma discharge does not ignite and the reflected power is able to be lowered by adjusting the match controls, you may be coupling the RF power to the plasma output coaxial cable. You may need to adjust the length of this cable (make it shorter). The suggested maximum length cable is 5′.

Adjusting the process: To help ignite the plasma you may raise the gas flow or throttle the pump line initially (to increase the background pressure inside the vacuum chamber).

Sputtering cathode shutter position: Verify that the shutter (if used) is positioned to allow the process gas to get to the target surface. Open the shutter momentarily during the plasma ignition process and/or increase the gap between the shutter and the target surface.

The Reflected power cannot be tuned down to 1% of the forward power
Plasma discharge: Is the plasma discharge actually lit? It needs to be lit before proceeding – see “The plasma will not ignite” description above.

Set the inductor tap: Is the correct series inductor tap (inside the match compartment) selected? It is preset at the factory however this tap may not operate with your particular plasma load. An incorrect tap setting is usually verified by the following conditions: a lit plasma, the Load control dips the reflected power within its 0 to 100% range however, the Tune control is at one extreme or the other. Try another tap setting.

Add fixed Load capacitance: The plasma is ignited and the match tuned for lowest reflected power however the Load control is at it’s maximum. This condition is caused by the load capacitor value being too small. An optional fixed load capacitor kit is available from the factory and will solve this problem. You may also add your own capacitor – see the Technical bulletin link below for information on adding fixed load capacitors.

Add series inductance: Additional series inductance may be required when powering small cathodes (1″ & 2″ diameter) or small capacitive electrodes. We offer a kit for this purpose so please contact the factory. You may also “roll” your own inductor on a 3/8″ rod using #10 or #12 AWG solid copper magnet or electrical wire. Simply connect this inductor in series with the existing tap wire and inductor. See the application note download below for more information.

Extend length of RF generator cable: Another condition may exist when powering small cathodes (1″ & 2″ diameter) or small capacitive electrodes. The condition manifests itself as a high reflected power indication even though the matching network controls are adjusted for  “lowest” reflected power (both Load & Tune controls positioned between 10% & 90% of range). Experience has shown that the small diameter (high impedance) plasma load creates harmonic energy that fools the reflected power meter and limits. This condition can be resolved by simply adding additional (type RG58 or RG316) coaxial cable in between the RF generator output and the matching network input (this is the “dongle” cable located in the middle of the rear side. Manitou can supply this cable assembly or you can make your own. We suggest starting with a 2′ to 3′ length however, up to ¼ wavelength or 12′ can safely be added. Ignite the plasma, re-tune and verify that the measured reflected power can be reduced.

If you have a problem and wish to contact the factory for assistance, please have the following information available:

·       How old is the PB3 system? (What is the purchase date or was it included in an OEM plasma system?

·      Who is the OEM manufacturer of the plasma system?

·       Can you advise us of the serial number? (located on the rear of the unit).

·        Is the powered electrode a parallel plate (capacitive) type? or another type?

·         Was the plasma system ever operational ?

·         What has changed since the time is was operational?

– PB3 Owner’s manual
– PB3 shorting plug schematic
– Adding additional fixed shunt capacitance
– Adding additional series inductance