Hello everybody.
Integrated amplifier TECHNICS SU 7600.
Protect relay not click.
If I activate the relay manually right channel ok,but -33.5v on left channel.
I desoldered 2 power transistors,drivers no problems,all parts are ok,no blown fuses or resistors.
Thanks.
SM
TECHNICS SU-7600 SERVICE Service Manual download, schematics, eeprom, repair info for electronics experts
Integrated amplifier TECHNICS SU 7600.
Protect relay not click.
If I activate the relay manually right channel ok,but -33.5v on left channel.
I desoldered 2 power transistors,drivers no problems,all parts are ok,no blown fuses or resistors.
Thanks.
SM
TECHNICS SU-7600 SERVICE Service Manual download, schematics, eeprom, repair info for electronics experts
Sometimes the components need a few more volts/amps than your test equipment can supply, before the part fails. So simple testing may not show up the issue, however -33.5V is about rails voltage so probably a shorted transistor.
Problem could be driver transistors. Measuring b.c.e voltages to GND for each of TR207, 209, 211, 213 may help identify.
Problem could be driver transistors. Measuring b.c.e voltages to GND for each of TR207, 209, 211, 213 may help identify.
Measuring.
TR 207
C......+35.6V
B......-31.5V
E......-32.2V
TR 209
C.....-35.5V
B.....-33.9V
E.....-33.2V
TR 211
E .....+36V
B......+33.2V
C.....+35.6V
TR 213
E.....-36V
B......-36V
C.....-35.5V
TR 207
C......+35.6V
B......-31.5V
E......-32.2V
TR 209
C.....-35.5V
B.....-33.9V
E.....-33.2V
TR 211
E .....+36V
B......+33.2V
C.....+35.6V
TR 213
E.....-36V
B......-36V
C.....-35.5V
Voltages in Red MUST be the same, why not?
They are electrically connected.
Measure continuity between those points, you have a brocken/cracked track/pad/solder or if some connector/wire is involved, poor/open contact somewhere in the path.
Fuzzy picture in manual seems to show TO3 transistors in separate heatsink, how are they connectd to rest of circuit at PCB?
Good suggestion by MBZ: most people waste time by searching for "bad parts" or simply replace everything, but OFTEN it´s not a "bad part" problem at all, a wiring/connections one instead.
A voltage measurement with parts still unmolested is a better/faster tool.
Please check that.
With TR207b at -31.5V suggests amp is "flooded" with negative voltage, possibly something on the negative rail has failed short. TR209,213 kinda look ok. Check b/c/e voltages to GND for TR203
Correction on TR209, 213, would expect these voltages to be negative. Maybe recheck voltages, +/- sign is very important. If sign is ok then check the emitter resistors R239,241 0.33ohms. Measure incircuit is fine, expect one to be open/OL.