Gallien-Krueger 400RB series User manual

Service Manual
400RB

Table of Contents
Operating Instructions 3
Turn On / Calibration Procedure
Schematics 9
Engineering Change Orders (ECOs) 1
Bill of Materials 20

400RB-200W Bass Amp
Turn on Procedure
Board#’s: 206-0047-C(preamp),206-0041-A(poweramp)
Model# 400RB all options 8-19-91
Setup
1) Variaconzero,powerswitchoff-connectpowercord.
2) Connecteitheroutputtoloadbox(loadA).
3) Resistanceloadsopen ( switchincenter).
4) Speaker on.
5) Load box to scope-B and AC-VM.
6) Set scope switch on load box to look at load A (down).
7) Setoscillatoron200Hz sine wave @ 5mVrms(-46dBV).
8) DVMon20mV(DC)range.
9) ACVoltmeteron 30V range.
10) Scope-Bon10V/cm.
11) Scope sweep on 1ms/cm, scope trigger on B on RB Front panel, set:
12) Tones,masterandboost to 10, switches out.
13) Volumeon0.
Power Supply and Power Amp Test
1) Withpowerswitch on,graduallyturnup variacto50V,whilelisteningtospeaker
andwatchingscopeandammeter.Outputshouldgonegativethen snap back to 0.
2) Check regulated supplies: (+ or -)14.5V, + or – 1V.
3) Adjustvariacto120Vand turn speaker off.
4) Set Bias. Adjust R14( on ’41 board) for 5mV across R26, R27.
5) PowerLEDand boost LED should be lit.
6) Connect oscillator to input. ( 200Hz @ -46 dBV).
7) Turnon4ohm load.
8) Adjustvolumefor slight clipping(2-3o’clock).Output =28Vrms.
9) Engage - 10dB switch- Output becomes5.7Vrms. Disengage switch.
10) Turn boost to 0. Output becomes3Vrms.
11) Turnmasterto0.Outputbecomes0V.
12) Turnloadoff.
Tones and Filter Test
1) Setallknobstocenter(12o’clock),switchesout.
2) Set scope-B to 5V/cm and 1ms/cm.
3) Setoscillatorto200Hzsquarewaveat–46dBV.
4) Lookatoutput,compareto figure 1.
5) Oneata time,turntonecontrol knobsandcompareoutput tofigures(resettingtocenter afterfinishing):
A) Treble to 10- Fig.2; Trebleto 0-Fig.3
B) Hi-midto10-Fig.4;Hi-midto 0-Fig.5
C) Lo-mid to 10-Fig.6;Lo-mid to0-Fig.7
D) Bass to 10-Fig.8; Bass to 0- Fig.9.
6) Engagelow-cutswitch, comparetoFig.10.Disengage.
7) Engagecontourswitch, comparetoFig.11. Disengage.

2) Turn frontpanelknobsto10,switches out.
3) Connectfrontspeaker to output andlistentonoise.Itshouldbe smooth, not crackling.
4) ChangeACvoltage range to 1V.
5) Noiseshouldmeasure lessthan400mV.
6) Engagelow-cut,contour,and hi-boost. Noise < 400mVrms.
7) Volumeto0.Noise<100mVrms.
8) Boost to 0. Noise <10 mVrms.
Returnknobstozero,switchesout-readyforburn-in.