Advertisement
Quick Links
Advertisement
Subscribe to Our Youtube Channel
Related Manuals for Gallien-Krueger ML Series
Summary of Contents for Gallien-Krueger ML Series
- Page 1 Service Manual ML Series...
- Page 2 Table of Contents Operating Instructions Troubleshooting Instructions Output Disabling Preamp Description Power Supply Start-up ML/E Turn-On Procedure ML/S Turn-On Procedure Schematics Engineering Change Orders (ECOs) ML/S Bill of Materials ML/E Bill of Materials...
- Page 8 Microamplifier Series- Lead Disassembly and Preliminary Troubleshooting Procedure GK Document # 426-0063-A Model #’s: ML260E, ML260S, ML120E, ML120S- all options 2/15/91 Rev. 9/10/99 SW Disassembly Procedure 1) Remove the bottom cover first by removing the six # 6 screws on the bottom and the three # 6 screws on each side. One side has an extra screw which may require a # 4 screwdriver.
- Page 9 Fuse Inspection Lightly blown- Very often an amp in service has a blown fuse, and is one of the first things a service tech checks. Sometimes, much can be determined from the condition of a blown fuse. With the amp series, it is possible that the amp is OK and the fuse is the only problem. a lightly blown fuse may indicate merely an overload condition that did not trip the overload protection circuit, or a weak Troubleshooting Procedure (contd.) fuse.
- Page 10 Microamplifier Series Circuit Description of Output Disable GK Document # 450-0062-01 A. Mihalka, 2-13-91, Rev. 9/10/99-SW Scope This document describes the shutoff feature of the microamplifier series. Some boards may be stereo, but all boards work on the same principle. There are 4 conditions whereby the output is disabled, each of which are described below (see Circuit Descriptions). Disable Modes Pop Elimination with Power Switch The first type of output disabling is for the elimination of speaker pops when the unit is either turned on or off.
- Page 11 Turn-Off Pop (contd.) it there. All this causes pin 7 to go high, disabling the outputs. This condition persists for many seconds until the rails can no longer power U605 through the zeners, at which time a very faint, low rumble is heard. Output Overload The overload circuit is developed around U604, another slow, quad LM324 op amp.
-
Page 12: Channel Switching
Introduction The following is a brief description of the operation of the circuits found in the ML Series amplifiers. It should provide enough information to get a basic understanding of the circuits in order to perform any repairs. When calling attention to a component with the use of a reference designator, the r.d. - Page 13 Compressor (ML-E only-contd.) input voltage- a higher voltage at this point corresponds to a lower compressor gain. C97, R98, and R99 are used to bias the output down to approx. 0Vdc. Diodes D105 and D107 limit the transient output to 2.8V. The 4.7K resistor, R100, sets the maximum gain of the compressor to about 2.
- Page 14 Chorus (ML-E only-contd.) through a 5-pole filter, around U17, that has a cutoff frequency (like the chorus input filter) of 3.6kHz. Finally, it reaches the output expander that ‘undoes’ what the input compressor did and expands the dynamic range back to that of the original input signal. The expander circuit is built around the other half of U14 and uses an external op amp, U13.
-
Page 15: Visual Check
Microamplifier Series Power Supply and Power Amp Assembly Line Start-Up Procedure GK# 420-0071 Power Supply Board #206-0071-C Power Amp Boards 206-0064-D, and 206-0074-D, -75-D, and –76-D 6/7/90 Rev. 9/10/99-SW Scope This procedure is for bringing up Rev. C power supplies and Rev. D power amps for the assembly line. ( It can also be used for troubleshooting and technical purposes.) This procedure is written with the board oriented in such a way so that the heat sink is on the bench and the rear panel is facing from the technician, so that the channel on the technician’s left is labeled the Right Channel. - Page 16 Adjust Reset Caution: The following procedure calls for increasing the variac from 25Vac to 117Vac in less than 5 seconds. The startup circuit is designed as such that Q518 turns on when line voltage is below 90V. This causes it to dissipate a large amount of power. Q518 will fail after about 10 seconds if line is set at 50Vac.
- Page 17 Open Circuit Test (contd.) (-6dB). See Fig. 3 for a distorted signal. (See note regarding waveforms above. –Ed.) For a power amp (ML/P), check that turning down the rear panel pot reduces the output to zero on each channel. Return the pot to fully on. Set the oscillator to be a –6dB, 1kHz signal. With both loads set to 8 ohms, adjust R688A so that the output voltage from the left jack (R Channel) is 14.5Vrms, as indicated by the VOM.
- Page 19 Microamplifier Series-Lead Standard Preamp Turn-On Procedure GK Document #420-0073-A Preamp Board # 206-0073-D- ML/S board Model #’s- ML120S, ML260S-All Options 5/18/90 Rev. 9/15/99-SW NOTE: Italics refer to stereo power units. SETUP Power switch off- Connect power cord. 1) Connect power 3-pin connector from power amp to P1 on board. Colors should read (L-R): Black, Violet, Brown. P1 is furthest to the back.
-
Page 20: Footswitch Test
B) Hi-mid to 10- Fig.4; hi-mid to 0- Fig.5. C) Lo-mid to 10- Fig.6; lo-mid to 0- Fig.7. D) Bass to 10- Fig.8; bass to 0- Fig.9. BOOST / SHAPE TEST 1) Engage Channel select switch to go to lead channel. 2) Change scope-B to 5V/cm @1ms/cm. - Page 21 Microamplifier Series-Lead Effects Preamp Turn-On Procedure GK Document # 420-0063 –A Model #’s: ML120E, ML260E- All options Board #: 206-0063-E (ML/E preamp) 5/18/90 Rev.9/15/99-SW NOTE: Italics refer to stereo power units. SETUP 1) Power switch off- Connect power cord. 2) Connect power 3-pin connector from power amp to P1 on board. The colors should read (bottom-top): Black, Violet, and Brown. P1 is closest to front.
- Page 22 5) One at a time, turn control knobs and compare outputs to figures below (resetting after finishing): A) Treble to 10 –Fig.2; treble to 0- Fig. 3. B) Hi-mid to 10- Fig.4; hi-mid to 0- Fig.5. C) Lo-mid to 10- Fig.6; lo-mid to 0- Fig.7 D) Bass to 10- Fig.8;...
- Page 23 RETURN AND STEREO AUX IN TEST 1) Set AC-VM to 10V scale. 2) Set oscillator to 100Hz sine wave @ -26dBV (50mV). 3) Insert plug from oscillator into return jack (J6). 4) Set output level to 10: R channel output = 5.5Vrms. 5) Insert plug from oscillator halfway into stereo aux in jack (J5).
Need help?
Do you have a question about the ML Series and is the answer not in the manual?
Questions and answers