Gallien-krueger_700RB,_1001RB_Turn-Off_Thump_Modification电路图.pdf

SM700-1001-02.doc 12/12/01 2240 Paragon Drive, San Jose, CA 95131 Phone: (408) 441-7970, Fax: (408) 441-8085 www.Gallien-K Gallien-Krueger Service Center Memo Model 700RB and 1001RB heads and combos Subject Turn-off thump Date 12-12-01 Memo ID Sm700-1001-02 Description of Service Issue: It has been brought to our attention that some 700RB and 1001RB heads and combos may exhibit an excessively loud “turn-off thump”. The problem has occurred under these conditions: 1. Speaker cabinet connected to the 700RB or 1001RB head (none if its a combo) 2. Boost at 12 oclock and the Master volume at 2 oclock. No bass guitar is needed. 3. Amplifier is turned on by indication of green power light. 4. Amp is switched off and an excessively loud turn-off thump occurs through the speakers. This unacceptable turn-off thump is extremely loud and sounds like a “thump-discharge-snap” sound. A normal turn-off thump should sound like a slight “bump” or “bump-click” and should barely be noticeable. We have notified our dealers about this possibility with these amps and have instructed them to send any defective units to their respective GK authorized service center for an update. Update procedure: 1001RB: Unplug the power cord from the amplifier. Remove head from the combo or top cover if its a head unit. Remove the preamp board. Two parts have to change. R28 has to be replaced with a 1N4148 diode, with the Cathode (striped end) oriented closest to the rear of the board (pointed away from the control pots). Replace C14 with a 470uf 25V cap. 700RB: Same disassembly procedure as 1001RB. This process is fairly simple and should take about fifteen minutes. Retest steps 1-4 to make sure the amp is quiet. If parts or schematics are needed, contact us at: . Part #: 031-1477-0 470 uf 25V cap 020-1000-0 1N4148 diode RadioFans.CN 收音机爱 好者资料库