I’ve rebuilt most of this amp but can’t get anything out of the left channel.
During rebuild, some of the muting circuitry needed to be replaced as both of the 8099s and the 8599 transistors were bad. Replaced with same part numbers. Also several resistors especially r170, r171 , and r185 were burned up and now replaced.
New outputs across both channels. I’m not getting left audio on the base of the mpsa14. I tried swapping driver boards and same. Both driver cards work in the right channel.
All switches in this amp have been replaced. They are testing 100% functional with my dvm.
Tracing through, I observed both L and R audio up until the muting circuitry. This ones getting me scratching my head.
Is there perhaps a problem with the new r170,r185, and Q56? Where else can I look. Anything I might be obviously missing?
During rebuild, some of the muting circuitry needed to be replaced as both of the 8099s and the 8599 transistors were bad. Replaced with same part numbers. Also several resistors especially r170, r171 , and r185 were burned up and now replaced.
New outputs across both channels. I’m not getting left audio on the base of the mpsa14. I tried swapping driver boards and same. Both driver cards work in the right channel.
All switches in this amp have been replaced. They are testing 100% functional with my dvm.
Tracing through, I observed both L and R audio up until the muting circuitry. This ones getting me scratching my head.
Is there perhaps a problem with the new r170,r185, and Q56? Where else can I look. Anything I might be obviously missing?
Using the 700s diagram, Q56 is in the over-current circuit.
What are you referring to as the muting circuit?
What are you referring to as the muting circuit?
All fixed now. I realize the muting circuits are on the riser board near the speaker terminals. This amp was plagued with SMD cap leakage. I had to replace most of them. They’re leaking also caused a few bad connections also on those boards.
Thanks
Thanks
Correct me if this is wrong but, that muting is only for the RCA output terminals.
The only muting for the amplifier is the delay that's built into the driver board, in the differential amplifier's tail circuit.
The only muting for the amplifier is the delay that's built into the driver board, in the differential amplifier's tail circuit.
I believe you are right. The signal gets split off from the OpAmps to be internal and external. A few 10uf SMD caps were corroding off the little riser boards on both the pre-amp and the pre-out sides.
I high output bench testing this amp today.
First I testing mids/highs - Passed
Then I tested 2-ohm per channel subs - Passed
Then I tested 2-ohm bridged - Passed (Pulled 75 Amps DC)
The amp was in High Power mode for the above tests
Then I tested high-current/switching mode by putting more load across bridged; effectively at 1-ohm bridged which is 1/2ohm/channel. I figured it was OK to test this since the amp IS rated for 1-ohm bridged, and since the previous tests did not latch into high-current mode, this test would be OK.
Applied the second subwoofer and the amp then latched into High Current.
Within 4 seconds the amp pulled 200A from the bench and popped my 100A breaker.
Ended up burning up 2x TIP102 and 1x TIP107 outputs and opened up the emitters of those as well.
I removed all failed components.
Lightly bench testing again under low amperage; the amp has no issue latching into High Current when I intermittently short Q55 C-E.
Everything seems to be checking out ok. Rail voltage drops from 80v down to 60v between high power/current modes. Idles at 1.8Amps.
Any thoughts why this would have happened? Maybe I'm over-zealously thinking this amp is 1/2-ohm stable? It wasn't getting warm.
First I testing mids/highs - Passed
Then I tested 2-ohm per channel subs - Passed
Then I tested 2-ohm bridged - Passed (Pulled 75 Amps DC)
The amp was in High Power mode for the above tests
Then I tested high-current/switching mode by putting more load across bridged; effectively at 1-ohm bridged which is 1/2ohm/channel. I figured it was OK to test this since the amp IS rated for 1-ohm bridged, and since the previous tests did not latch into high-current mode, this test would be OK.
Applied the second subwoofer and the amp then latched into High Current.
Within 4 seconds the amp pulled 200A from the bench and popped my 100A breaker.
Ended up burning up 2x TIP102 and 1x TIP107 outputs and opened up the emitters of those as well.
I removed all failed components.
Lightly bench testing again under low amperage; the amp has no issue latching into High Current when I intermittently short Q55 C-E.
Everything seems to be checking out ok. Rail voltage drops from 80v down to 60v between high power/current modes. Idles at 1.8Amps.
Any thoughts why this would have happened? Maybe I'm over-zealously thinking this amp is 1/2-ohm stable? It wasn't getting warm.
Also, since I had to previously replace the high-current sensing transistors, wonder if I may have missed something?
Ouch. When I shorted q56 E-C, it actually blew Q55 dead shorted across all legs. And amp was stuck in high current. Hmmmm
I can see how that could damage the 8599. It's odd that there is no base resistor for the 8599 (I missed that) but if the 8099 transistors are ever driven fully on, it would do the same thing.
No issue; I replaced the Q55, MPS8599. I'm going to bench test this amp more tomorrow but I'll first try latching high current mode at lower impedance loads. I'll also have meters ready across various points.
I fixed my Fluke 10 btw. DeTox spray on the button contacts and connections and it seems to be working!
I fixed my Fluke 10 btw. DeTox spray on the button contacts and connections and it seems to be working!
Well I couldn’t get this amp to fail again so it’s likely fixed. No issue with auto switch. That said, what are your thoughts on disabling auto switch on this amp to avoid any future blow outs?
Actually I find it hard to believe Soundstreams auto switch is viable. I mean, if driving a signal through with only 5% headroom before clipping, the amp decides to auto switch. Now all of a sudden that signal w previous headroom hits a brick wall. And it’s not even a wall created by addition signal; it’s actually a wall created by dropping the voltage out from under the outputs. That’s got to be tough on tip10x darlingtons.
On other series with power/current switch is not something that can be switched while the amp is powered up.
While it may be necessary to run say 1/2ohm, who would do that anyway. What if the end solution is to force the amp to stay in high power mode, and then warn the user not to go below 1ohm per channel?
Actually I find it hard to believe Soundstreams auto switch is viable. I mean, if driving a signal through with only 5% headroom before clipping, the amp decides to auto switch. Now all of a sudden that signal w previous headroom hits a brick wall. And it’s not even a wall created by addition signal; it’s actually a wall created by dropping the voltage out from under the outputs. That’s got to be tough on tip10x darlingtons.
On other series with power/current switch is not something that can be switched while the amp is powered up.
While it may be necessary to run say 1/2ohm, who would do that anyway. What if the end solution is to force the amp to stay in high power mode, and then warn the user not to go below 1ohm per channel?
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Dropping the voltage on the outputs isn't going to do any harm.
I'd leave the circuit intact. Some people believe that an amp has to be run below the manufacturers lowest rated load.
I'd leave the circuit intact. Some people believe that an amp has to be run below the manufacturers lowest rated load.