SWR SM400 not working in bridged mono mode

[nsubulysses]

thanks for the info everyone. I will scope this properly tomorrow and confirm what I believe is just user error. by me and the bass player

[Dave H]

I will scope this properly tomorrow

If you have a two channel scope you can scope it in bridge mode by using the scope in A+B mode with one channel inverted. Connect channel A to one bridge output and channel B to the other. Keep the channels set to the same sensitivity.

[Mick Bailey]

Sometimes there's a misunderstanding of bridging doubling the volume. I've had a few customers who thought the bridging wasn't working properly because of this.

[nsubulysses]

Hmmm in bridge mode if I probe one banana jack at a time with my scope probe but leave ground clip unclipped I get a signal on one banana jack but not the other. If I use two channels of the scope and put one positive probe of each channel to each banana plug I only get signal in one channel

If I probe with amp in stereo mode both channels work fine.

I know this is not exactly the same way Dave h, Enzo and g1 described testing in bridged mode, but I dont see why it would mess up my results. I'm either doing something wrong or one poweramp doesn't work in bridge mode.

[Enzo]

Your scope is grounded to the amp through the power cords. You can clip the scope probe ground to chassis to probe either post if you like, what you CAN'T do is ground clip to one of the red posts.

If in bridge mode on side stops producing signal, then I suspect the switch itself first.

Put the amp in bridge mode. Now connect a speaker to the quarter inch jacks of one side, then the other side. Do both side produce signal. They will be out of phase, but you won;t hear that when listening to one channel at a time.

[nsubulysses]

Hmmm in bridge mode if I probe one banana jack at a time with my scope probe but leave ground clip unclipped I get a signal on one banana jack but not the other. If I use two channels of the scope and put one positive probe of each channel to each banana plug I only get signal in one channel

If I probe with amp in stereo mode both channels work fine.

I know this is not exactly the same way Dave h, Enzo and g1 described testing in bridged mode, but I dont see why it would mess up my results. I'm either doing something wrong or one poweramp doesn't work in bridge mode.

[The Dude]

I'm not saying it's not worth testing, but I don't recall ever seeing an amp "kind of work" in bridge mode. Generally, there will either be sound out of the banana jacks or not. If you can hear sound out of a speaker connected to the banana jacks in bridge mode, it's more than likely fine.

[Enzo]

I'm either doing something wrong or one poweramp doesn't work in bridge mode.

And that is exactly why I suggested the test I did. Put the amp in bridge mode, feed it signal and use a 1/4" cord to connect each channel to a speaker one at a time. It works in stereo mode, but do both channels work in bridge?

[nsubulysses]

The switch was the issue. It was soldered but had no continuity because of a junky solder connection. Thanks for all the info on how these bridged mode amps work