I'm looking at a Rockford Fosgate BD10001 that I took in as "working" but needing the remote turn-on tab repaired (torn off trace & vias, etc). It had typical broken RCA shield leads, so I repaired those. When I pulled the board I also found C39 had shorted to the heatsink at some point as well.
The amp powers up and produces audio, but I only have small bookshelf speakers currently available so I can't test to full potential. That said, I was wondering if these are normal for this amp:
Idle current: 1.9A
Speaker terminal DC offset: 0.182V
84.3V between twisted red & black wires
R44 gets hot, transformer gets warm
Speaker crackle/pop with remote connect/disconnect
Constant light speaker hiss/noise regardless of gain position or RCA connection
The amp powers up and produces audio, but I only have small bookshelf speakers currently available so I can't test to full potential. That said, I was wondering if these are normal for this amp:
Idle current: 1.9A
Speaker terminal DC offset: 0.182V
84.3V between twisted red & black wires
R44 gets hot, transformer gets warm
Speaker crackle/pop with remote connect/disconnect
Constant light speaker hiss/noise regardless of gain position or RCA connection
Attachments
The high-frequency noise probably won't be audible with the speakers that the amp was designed to drive.
R44 is large because it's going to have to dissipate significant power. Check C67 but the heating is likely normal.
The cap doesn't look like it was trimmed to the correct length. Cut it. If you're still concerned, install a spacer to keep the board away from the heatsink.
Does pin 7 of U21 switch immediately when remote is disconnected?
R44 is large because it's going to have to dissipate significant power. Check C67 but the heating is likely normal.
The cap doesn't look like it was trimmed to the correct length. Cut it. If you're still concerned, install a spacer to keep the board away from the heatsink.
Does pin 7 of U21 switch immediately when remote is disconnected?
C67 appears good out of circuit (9nF on Fluke 117 and 8.8xxnF on Peak LCR45).
U21 Pin 7 reads
-0.179 immediately at remote connection, jumps to -0.199, settles around -0.191, and drops off immediately at remote disconnect.
If I discharge the caps I get a high pitched squelch/squeal upon first remote connect, then afterwards just the click/pop upon subsequent connections.
U21 Pin 7 reads
-0.179 immediately at remote connection, jumps to -0.199, settles around -0.191, and drops off immediately at remote disconnect.
If I discharge the caps I get a high pitched squelch/squeal upon first remote connect, then afterwards just the click/pop upon subsequent connections.
U21 or a component connected to it is likely defective.
Confirm that pin 5 is at 5v and that pin 6 charges from 0v to over 5v just after remote is applied. As pin 6 passes 5v, the output should go to approximately -9v.
Confirm that pin 5 is at 5v and that pin 6 charges from 0v to over 5v just after remote is applied. As pin 6 passes 5v, the output should go to approximately -9v.
I'm sorry, I was mistakingly reading U11. Here is what I get from U21:
U21 Pin 7 reads
-0.225v without remote connected
8.56v immediately at remote connection, then drops to -8.44v, and returns immediately to -0.225v at remote disconnect.
U21 powered up reads:
Pin 1: -8.39
Pin 2: 0.053
Pin 3: -8.72
Pin 4: -9.69
Pin 5: 5.043
Pin 6: 7.64
Pin 7: -8.47
Pin 8: 9.93
Pin 6 charges from 0 to 7.64v.
U21 Pin 7 reads
-0.225v without remote connected
8.56v immediately at remote connection, then drops to -8.44v, and returns immediately to -0.225v at remote disconnect.
U21 powered up reads:
Pin 1: -8.39
Pin 2: 0.053
Pin 3: -8.72
Pin 4: -9.69
Pin 5: 5.043
Pin 6: 7.64
Pin 7: -8.47
Pin 8: 9.93
Pin 6 charges from 0 to 7.64v.
Does the output on the emitter of Q120 (also lighitn of protect LED) follow the output of pins 1 and 7 of U21?
I'll have to check this evening. Protect is not on, amp works other than my concerns/questions about normal operation for this amp model.
Q120 emitter starts at 7.23v and then switches to -8.14v. Pin 1 is always -8.40v and pin 7 switches from positive to negative 8.XXv. These values all vary a little around these numbers depending on how long the amp remains powered.
Does the voltage on pin 2 of both U5 and U8 go to about 8v on start then to about 0v when pin 7 of U21 goes to -8v?
They go to about 6.5v, meter set manually so it's not trying to auto-range
U5 Pin 2: 6.49v ---> 0.06v
U8 Pin 2: 6.52v ---> 0.04v
U5 Pin 2: 6.49v ---> 0.06v
U8 Pin 2: 6.52v ---> 0.04v
It should be muting on turn-on/off.
If you bridge the terminals of C51, it shouldn't be able to make any sound unless there is a defective component. That's probably the next step if you want to troubleshoot further.
If you bridge the terminals of C51, it shouldn't be able to make any sound unless there is a defective component. That's probably the next step if you want to troubleshoot further.
Ok, that does mute, and if I pull the bridge/short it un-mutes after short delay. That seems to be working at normal startup as well, but either way I still get speaker pop/crackle when making the remote connection.