Any ideas?

(I would have put this as a comment, but needed more words. I would have edited my original post, but couldn't upload pics on an edit.) Every once in a long while, the lights on the front of the power amp will light briefly and then die, but 98 percent of the time, nothing. I have opened it up, and here is the power path:

There is the plug/fuse combo:

As you can see, there is a green/yellow ground. There is a black wire that goes straight into the heart (massive heavy cylinder of wires) of the amp. There is another black wire with a capacitor (I think?) directly after the plug. This wire goes to the switch in the front, which is a simple push button. There is a blue wire coming out of the switch back into the heart of the amp, completing the circuit.

The rest of the components (led board, input boards, output boards, volume knobs) seem irrelevant because it's not getting power at tall (but I could be wrong). Here's a pic of the entire setup:

Any ideas? I am not an electrician, so please use small words :)

⟐ Commented February 20, 2021 at 15:16 MST

⟐ Commented February 14, 2021 at 9:32 MST

Gow i can fix it

I have CONNECT a pair of tower speaker that never used or test BEFORE,

Do you think that speaker can blow a power transistor and display now protect on display

Any ideas

⟐ Answered February 01, 2026 at 7:39 MST

I wanted to use this old amplifier, a Kenwood KA-56.

But unfortunately for both outputs (speakers A and B) only the left connector receives a signal.

Somewhere the signal to the right terminal is lost.

I know i is not expensive to buy a new one, but I wanted to have an idea first about the option to fix this myself.

what do you think?

Thanks,

⟐ Answered September 02, 2020 at 5:07 MST

It is stuck in protect e01.

The repair manual says that it could the main amp board or the power supply. Here is the description: "The overcurrent condition to MOSFET occurs by a defect of MOSFET or defect of PS output line."

So I want to check the power supply first. Since I cannot power up the amp as it disconnects on boot, I can unplug it as it is modular and it boots fine. The test procedure doesn't require high-end testing equipment just a multimeter. The readings on the pins that come from the power supply are all good with the exception of the 1 st pin. It shows -22V when it should be 16V~23V. The actual power supply schematic says "pin1: V3+ (DC+16V~23V) _ (ref-V1)".

My question is what is V3 and ref-V1 from the above formula? Am I testing this correctly?

⟐ Answered July 22, 2018 at 11:09 MST

⟐ Comment deleted July 28, 2017 at 18:38 MST

⟐ Commented October 19, 2010 at 21:32 MST

⟐ Answered October 13, 2025 at 8:50 MST

⟐ Answered April 27, 2021 at 16:33 MST

⟐ Answered September 02, 2020 at 5:11 MST

We’ve checked the speaker wires. Receiver turns on. Amp shorts out after a crackle-hum sound.

any advice for repairing this?

⟐ Commented September 16, 2025 at 3:48 MST

⟐ Commented August 08, 2025 at 8:12 MST

I read somewhere that when the fets blow, the IC that regulates the switching of the fets gets taken out as well. I’ve taken out the 2 blown up fets and was thinking of powering up the SMPS with a light bulb limiter to see if I could measure the voltage coming into the IC, but I read somewhere that you should replace both the IC and fet, because if you don’t, then whichever part you leave in will cause the other part to blow again. That is, if I replace the fets only and if the IC is blown, the IC will cause the new fets to blow.

So my question is, should I replace the IC and fets together? Can I try powering up the board without the fets and see if I’m getting voltage to the IC, or is it likely I’ll blow something else up? The schematic is for a B215D which is very close to the B212D I have. The main difference is it has a 15” speaker, where mine has a 12” speaker. Unfortunately the schematic came out blurry where the original is not. I’ll see what I can do to get it clearer. Thank you!

Behringer B215D Schematics

⟐ Commented February 18, 2023 at 12:44 MST

⟐ Answered November 22, 2022 at 13:04 MST

⟐ Commented August 06, 2022 at 5:42 MST

I dont understand much of the internals of my technical devices, unfortunately. Its getting power and I can turn it on, LED's are shining from inside and from the power button. Also you can connect other devices t the AC-Power Outlet. But there is no sound output on the speakers anymore. I tried every input channel, different cables and every output speaker channel. All dead output.

And diffrent speakers of course

Im affraid I damaged it when I, in my stupidity, coneccted a battery powered fary lights to the music output (speakers) adapter/ports. I know, I shouldnt have done that. But im not sure its realy the reasen for it to be dead and I never would understand whats damaged exactely.

Thanks for your interest! Havent expected that :)

PS: I also checked the boards inside for any burned stuff. But with my untrained eyes I coulnd find any obvious damaged components

Update (11/06/2021) ===

ok I got the multimeter now and watched some youtube videos to get an expert.

I would set it like on the photo to measure the 2.2V:

But then… Where do I have to touch the black and red stick of the multimeter? One of them to the 7th pin of CI 401 (photo), but which one? And the second to…?

And I’ll do all this while the amplifire is pluged in and powered on right? Little afraid of that :)

⟐ Commented January 24, 2022 at 10:41 MST

⟐ Commented December 04, 2021 at 4:58 MST

Now, regardless whether I am playing CD's, radio or tapes, it powers down after about 20 mins from starting. I can then power up immediately again and it will operate for a shorter time before powering down again and so forth.

Any thoughts on what may be causing this?

⟐ Commented June 28, 2021 at 19:58 MST

no lights come on with either phantom power or a proven 9 volt AC power source

can this be a symptom of a bad tube?

thanks!

⟐ Answer edited May 13, 2018 at 13:01 MST