KAM RZ12A V3 Portable

[daba]

Hi all - Happy New Year ...

Has anyone got the KAM (or Evolution Audio) RZ12A V3 Portable PA speaker ?

I ask because the "12V DC Output" on mine doesn't have 12V on it, just 0.09V !!!

When I complained about this to JHS last year, I got the following reply, which astounded me.....

Hello Dave

The DC terminals on the back are for a 12v input like a car battery its not an output even though it is labelled so , so you will not get a reading from it voltage wise from the battery.

Kind regards

JHS Service Department

I wasn't too fussed at the time, but now I want to use it.

I'm convinced there should be 12V Output on there, you would not approach those spring terminals with the bare ends of a cable connected to a car battery, as suggested by JHS, and it would be highly dangerous if someone were to trip over any wires connected to it.

If I can confirm that it should be an output, I can raise the issue again, hopefully get a repair or a replacement....

TIA

[Excalibur]

I must be missing something, because on the manuals I've found, there's no mention of 12volts in or out? 240v only. I'm not at all familiar with this machine, perhaps someone who has knowledge of them may pop up.

[DJ Jules]

I must be missing something, because on the manuals I've found, there's no mention of 12volts in or out? 240v only. I'm not at all familiar with this machine, perhaps someone who has knowledge of them may pop up.

It looks like lots of online retailers are showing the non-portable manuals and images. From what I can tell the backplate on the portable version is totally different (it includes a MP3 player, bluetooth and built in radio mic for a start!)

Everything I've read suggests it should be an output (including the offcial manual which lists it under outputs). Could the fuse be blown? Does it only become live when the power switch is off (or on?) Is it only live when the mains is plugged in?

Unless you find it turns on with some weird combination of power switches/mains power, I'd tentatively suggest taking the back off and tracing back from the termainals to see what they're actually connected to?

Julian

[daba]

All fuses etc. are OK, and it doesn't matter whether the unit is switched ON or OFF, plugged in and running on mains, or running off the internal battery, the most volts I have seen on those spring-loaded terminals is 0.9V.

It is marked as an OUTPUT on the back panel, It is specified as an OUTPUT in the manual, and it is being sold, by the aforementioned company, the advert claiming it is an OUTPUT.

It would make NO sense to have a 12V DC INPUT to a machine that already has a 12V battery inside, and the use of spring-loaded terminals for an INPUT is a definite no-no, as far as I am concerned.

Everything points to it being an OUTPUT, which does make sense, so why did someone write that email response to me ?

I think I've just been fed total bu11cr@p by the aforementioned company's service department.

Just wanted someone to tell me it's definitely an OUTPUT on their speaker, and I'll be taking it further.

[DJ Jules]

Just wanted someone to tell me it's definitely an OUTPUT on their speaker, and I'll be taking it further.

Best of luck with that. I'd definitely be taking the panel off to see what it's actually connected to. But that's just me...

Julian

[daba]

Best of luck with that. I'd definitely be taking the panel off to see what it's actually connected to. But that's just me...

Julian

The terminals are soldered directly onto the power and amplifier PCB, so whatever the issue is, it ain't gonna be easy to trace. I've had a go, but it's too complex for me, as there are SMDs on the bottom side.

And that tiny black IC bolted to the heatsink at the back is the amplifier !!!

[daba]

.... into buying a new board, and to be honest it wasn't as expensive as I thought it was going to be.

Fitted it this morning, all working OK, but guess what.... still no 12V dc output on the aforementioned spring loaded terminals !!

So I'm guessing it's a design flaw ....

I'm going to resort to isolating those terminals from the PCB, and connecting them (via a fuse, of course) to the 12V battery. A Job for another day methinks ....

I've also discovered the unit has an infrared remote control receiver fitted in the front of the cabinet and wired to the function PCB. No mention of remote control anywhere in any documentation for the speaker. My guess is the CE (China Export) makers couldn't get that working either !!!

[daba]

It seems that there is total confusion over what the spring terminals are for, and it probably stems from the fact that it does not work as designed.

Clearly labelled as "12V DC OUTPUT"



In the sales documentation as a "12V DC OUTPUT"



In this video review https://www.youtube.com/watch?v=vz22zamGWoM at 3:11 the reviewer (Kam Lamba) says "Also on the back panel we've got the two, erm, hardwired speaker inputs, so you can connect this up to an amplifier".



I wonder if his hesitation was due to him knowing he was going to say some bull-crap.

Conclusion is this amp has a design fault that is just being glossed over ....

[DJ Jules]

It does sound like they're not designed to do what the label says. If the Amp IC is stereo, it could be an output for the other channel!

It ought to be fairly easy to trace them back using a multi-meter, they'll either go to 12v and 0v or be mapping to output pins on the IC, stick one lead from the meter into one of the output pins, set the meter to continuity and have a wander around the board and see what beeps

Julian

[daba]

It does sound like they're not designed to do what the label says. If the Amp IC is stereo, it could be an output for the other channel!

It ought to be fairly easy to trace them back using a multi-meter, they'll either go to 12v and 0v or be mapping to output pins on the IC, stick one lead from the meter into one of the output pins, set the meter to continuity and have a wander around the board and see what beeps

Julian

The amplifier IC is a TDA7377, and has 4 outputs, as it was designed for (according to the specifications) car stereo systems. The outputs can be "bridged" for higher power, but according to the specs, even in "bridged" connection the device output power doesn't match the stated power of the speaker !!






I've already tried tracing the circuit, and it's not as simple as it might sound.

The board is double-sided, has conventional through-hole AND surface mount-components. Tracing the circuit out is nigh-on impossible without removing some components which obscure the tracks. And you may know that removing components on a double-sided PTH board has its challenges, especially if you want to put it back, clearing the holes of the old solder is often difficult.

And, I discovered that one of the power diodes near to the spring-loaded terminals has a direct short across it. Removing one leg of it from the board to test it revealed that the short is on the board, the diode was fine. So I ordered the new board and swapped it, thinking the fault would go away - it hasn't.

I've spent many hours on this problem, and I'm not going to get a return on the investment in my time. I've just had enough, to be honest.

I think the answer will be to connect the spring terminals directly to the battery, fused of course. And that will give me a way to meter the battery voltage as well

I shall be looking to sending the replacement board back as well, no point replacing a "faulty" board with another one that has the same "fault" !!