My friend made some speaker cable changing, Thule amp was in standby mode. He made short circuit + and - on right side and amp is not working now.
Can you help me, where to start finding? Schematic I have...
Thank you very much for help!
Franta
Can you help me, where to start finding? Schematic I have...
Thank you very much for help!
Franta
There is DC voltage -8,65V on both +, - speaker terminal, measured against the ground on right side. Left side is clear, without any voltage...
Thanks for the schematic, Franta2.
Be sure to check fuse S4; the problem is probably not that simple, but worth checking.
This is an interesting amp. Each channel uses bridged drive to the speakers, i.e. single phase drive re ground isn't even an option because there's no high current path to ground. The power amp appears to operate without any negative feedback at audio frequencies; however, each power stage does use a low bandwidth servo loop to set the bias to each power stage, eg. U100 A,B and U101 A,B.
Your 2nd post indicated both speaker terminals presented a voltage of -8.65V. Assuming the S4 fuse is intact, take a series of voltage measurements across the right channel to determine why the bias is defective. For example, the emitter follower power stages (eg. Q117--Q122) should all have about the same base voltages aside from a series of base-emitter drops. Similarly for Q127--- Q132. Insightful measurements re ground would include:
base of Q117
emitter of Q121
base of Q118
base of Q127
emitter of Q131
base of Q128
collector, base, emitter of Q103
collector, base, emitter of Q104
opamp pins 1,2,3,7,6,5
With any luck, these readings will lead us toward the defect.
Be sure to check fuse S4; the problem is probably not that simple, but worth checking.
This is an interesting amp. Each channel uses bridged drive to the speakers, i.e. single phase drive re ground isn't even an option because there's no high current path to ground. The power amp appears to operate without any negative feedback at audio frequencies; however, each power stage does use a low bandwidth servo loop to set the bias to each power stage, eg. U100 A,B and U101 A,B.
Your 2nd post indicated both speaker terminals presented a voltage of -8.65V. Assuming the S4 fuse is intact, take a series of voltage measurements across the right channel to determine why the bias is defective. For example, the emitter follower power stages (eg. Q117--Q122) should all have about the same base voltages aside from a series of base-emitter drops. Similarly for Q127--- Q132. Insightful measurements re ground would include:
base of Q117
emitter of Q121
base of Q118
base of Q127
emitter of Q131
base of Q128
collector, base, emitter of Q103
collector, base, emitter of Q104
opamp pins 1,2,3,7,6,5
With any luck, these readings will lead us toward the defect.
0V on collector of Q201 sounds very strange. If Q201 isn't conducting, it should pull up to +24V; I can't spot any path that would yield 0V. Make sure there's positive volts at K11 pins 5 and 4--- maybe there's an open trace. Check volts at collector of Q200. If you find -24V, it's probable that the relay is in shutdown state. i.e. Q201 failure diagnosis may be wrong.
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