Mute on BrianGT LM4780 PCB ?

[AmA]

i buy the BrianGT LM4780 PCB and i don't understand how work the mute and how to make it . please help me. thanx

[AmA]

Originally posted by AmA
i buy the BrianGT LM4780 PCB and i don't understand how work the mute and how to make it . please help me. thanx

does it work with or without the 10k resistor ? anybody ? please

[AmA]

anyone ??

[SpittinLLama]

Is there a schematic for this amp? I am new to these boards. If you read the datasheet for the LM4780 found on National's site (www.national.com) it explains that Mute is controlled by current. If no current is pulled from the Mute pin then the IC will be in MUTE mode. So you should have a resistor from the MUTE pins to the negative supply rail to put it in PLAY mode.

[lgreen]

The schematic is here, although its not very complete, doesn't include the power supply stuff for example, lacks pin numbers for the 4780, etc... Looking at it quickly, for example, I don't see an R8 and R9 (listed onmy board), and it has a RZ1 and RZ2 that are not indicated on my board. Maybe the R numbers correspond to the ones on the board, maybe not. They apparently have not had time to fully document this board, so it will require a little study, but you see that there is a 10K resistor from mute to the negative power supply. Put this in and good luck. Maybe reading the materials on the 3886 boards and 3875 boards will help.

Note- you need a 10K resistor or something close, because if you don't connect the mute pins to a negative voltage, you won't draw current from the mute pins, and this results in a mute condition.

[bike]

Brian sent me this picture because I had the same question. You need to put the mute resisitor at Rm. It is on the bottom of the PCB.

[AmA]

Thanx very much for your help

[SpittinLLama]

That's the schematic for the amp? That is just the schematic from the LM4780 datasheet with some value changes and some caps removed. Intereting. Thanks for the link.

SL

[kestrel200]

Originally posted by bike
Brian sent me this picture because I had the same question. You need to put the mute resisitor at Rm. It is on the bottom of the PCB.

Cr*p...I just ruined a board trying to put a resistor on these pads. I pulled the pad right off the board while I was trying position the resistor just a little bit better after soldering one side.

Now I'll have to get a whole new board try to remove all the components off the damaged board & try again. I might just forget the mute this time. Has anybody had problems without the mute?

[RCBandwidth]

If you pulled a pad off the board,you should be able to repair it without resorting to a rebuild.I would not be too concerned about it.If you need guidance let me know. Bob C.