Lab Gruppen FP14000 clone amplifiers - Page 74

What is the email address for Johnson Tang ??

Does the clicking occur with no signal to the amp (nothing playing)? Yes, with nothing connected but the power cable

Does the clicking occur when you turn the amp on, but stop after the amp has been on for a while (hour or more)? Accurs right at startup. Used to just turn on (click once) now it clicks three or four times with amp going on and off then it stays on. Looks like the front power switch is wired to this relay. Same thing happens when turning switch on or connecting power cable with switch on. Amp turns on and off normal after initial power up. If it sits for around 10 minutes or more powered off same startup behavior. It is like a capacitor needs to charge up enough to hold the power relay in. first post, 14th pic down you can see the board with the relay.

Did you say BOTH fuses on the amp board (one channel) blew, but your transistors are all OK (not shorted)? You shouldn't have to disconnect them to read a short. Both fuses on one board blew. The element was not just severed, it was splattered all over inside the glass tube fuses. I am a bit confused with this, I need to unsolder the ground and power wires to the boards and check them. Both boards transistors are showing a path to ground. ie chassis, heat sinks. Will check out more in the next couple of days

You say the scene in HTTYD was played before at 0dBRL with no problem, does that mean the clip lights (since you've effectively disabled the VCL by setting them to 195V) didn't flash? Have they ever? At the 0db setting they did flash, That was really loud I usually play movies somewhere between -10 to -20 depending on the content. Had watched Prometheus earlier that evening at -12 NP. Was doing a 3D demo of HTTYD about an hour after we finished. Was playing some music after that and noticed the inactive sub.

Just random Qs at this point, if you don't mind.NP appreciate the input
Edited by RDKing2 - 11/11/12 at 11:20pm

Think it is in the first post. If not, second or third page.

So I found a post on another board with someone having the same clicking problem I have. Seems he had two bad capacitors in the power supply section. Will have to pull them to check individually as they are all in parallel. Up to late again messing with this stuff again, off to bed now.

If the clones can't replicate the real ones(Lab Gruppen), ie produce 2 ohms, how can these manuals actually provide any useful information on them? I don't see how someone can just ignore the 2 ohm column and expect the other columns in the PDF to provide accurate info? I suppose I am just cynical, but I have no delusions that my clone can even hold a candle to the real ones.

Hi King,

Thanks for the answers. The clicking you describe indicates a short circuit, IMO. The clicking is the amp detecting a short and shutting down PWM, then trying again after 1 second or so. That should repeat until the short is repaired or removed or fuses blow, or worst case, a cascading failure.

The other possible problem is running the amp in stereo while playing extremely low frequency content. I've touched on this in the past, but no one seemed to want to further the discussion. In stereo mode, bus pumping is a possible result of very low freqs source, the bi-directional nature of class d amps and the power supply not being able to absorb the feedback. So, yes, that would lead to checking the capacitors. If they cheated (I've seen these amps with caps ranging from 2200 to 3300 mf) or if any of them are not operating properly, then the failure would occur most likely during a ULF moment like HTTYD gladly provides.

I've always run the Sanway amps I have in bridged mode which eliminates bus pumping, so I've not encountered the problem with those amps. Although I suspect the topology of the amps is such that a bus pumping problem has been eliminated in stereo mode as well in the real Lab amps because I believe it's possible to do that and the real Labs don't encounter this problem that I'm aware of. I believe this is why other D amps roll off much higher than the Lab amps and may be an area for investigation of the Asian D amps being used in this thread.

Remember, I posted the only test of one of these amps I'm aware of done in England a few years back. It met its rated output nearly exactly until the stereo 2 ohm test at the lowest frequency of the test, where it was said to have "buggered out". It would have been nice if the guy gathered more data, like what caps and their values and exactly what failed during the test, etc.

If you mentioned it, I missed it, but can you post the voltage/farads values of your amp?

Amp is 220v. Caps are 3300mfd 200v I think. Will be pulling them this evening.

Pulled all the caps and all are working. Over half are more than 10% out of spec. Out of the 12 3300mfd 7 or 8 were under 3000mfd. There are 4 1800mfd caps that read in the 1600-1650 range. Though out of spec probably not the problem. Most of the low caps were on the channel that went out so that may have caused increased current? Anyway all the transistors on the bad channel board show short to ground at all three legs. The good board shows continuity on only the center leg of most of the transistors. The board is toast. I have not started pulling components yet to find what has failed. Have an email to Sanway about getting replacement board. Waiting to see at this point. If I can get a new board I may source some better quality caps and replace them all. Thanks for the help.

the tolerence is correct most caps are 10-20%. if u would take a knife and cut the tops off all the capacitors to see if they are using salvaged components in the amps which i assume they are.

@ FP 14000 Clone Bosses . A very basic configuration is bothering me. How do I adjust this amp in parallel mono .?? that I only feed the amp with one signal jack to feed both A and B channel. Also I noticed specs on clone manual shows different numbers to original . ???? , Tang said specs are same as original . ?????

In retrospect to earlier discussions on fan noise . In my experience , if fan blades pass too close to grills with high resistance , the drag creates an unnecessary noise. So it may not be the fans after all but that coarse grid grill holding the fans in place. ( less resistance - less drag - less noise ).

If the less resistance grill theory proves successful, then go on to install those thin amplifier air filter across the front vents for long term reliability .

Parallel mono feature has become standard in the industry that I almost forgot that . Back in the days I used Y plugs . It looks more tidy and trouble free using less jacks.

If anyone is selling or thinking of selling there 14000 or one of the other models. Please let me know, I'm interested.

If not using speakon, how do you bridge the FP14k? Also would I be able to keep the output level the same for channel 1 as it is currently in stereo operation?

Channel A+, Channel B-, change the switch to bridge mode. Not sure what you are asking here? By bridging the amp you only have a single channel. If you are connecting two speakers they will be in series or parallel, both will play at the same level.

After pulling the legs on all the transistors I found the channel B board has 5 bad transistors. Looks like one of the transistors was attached with a small wire where the board connection spot was damaged. Mr. Tang replied to me and I am ordering a new board. I may get some transistors as well to see if I can repair the original board just for fun. I have only checked a couple of places for caps and am having no luck finding caps that are the same physical size and honestly I would not know what the better quality caps are. My friend has been with an electronics place that does board stuffing. They do small runs for niche high end audio companys quite a bit. I may stop by and see him to see what he says. Probably just going to stuff the old caps back in.

for most of the caps, they're power reservoirs to clean the voltage and/or to provide power storage. it's quite easy to trace what function the caps are doing using a multimeter and the internet. for power reservoir caps, you could swap them out using similar voltage rating or higher voltage rating. if you could confirm the working voltage, you could even swap them out to a lower voltage and higher capacitance.

Thx, confirming the hook up was the most important. I was just curios if the trim level would remain the same for output 1 for bridged operation as it was for stereo.

Has anyone managed still to test definitively if going from 4 ohm stereo to 8ohm bridged actually helps with output? It was being discussed and tested earlier, just never followed up on??

Hmmm for me I was just trying to increase efficiency 3db. I saw the clip lights for the first time ever when the Hulk hits (the very last hit) Abomination with the cop car. Am I right in assuming that at 98DB bridged vs 95DB stereo the amp will work half as hard driving the subs?

Why would the output change at all? To the amp 4 ohm stereo=8 ohm bridged. When bridged the amp is still seeing a 4 ohm load on each channel so output will be theoretically identical.

Yes this is correct for sure, and as gpmbc stated, doing the bridging increases the efficiency of the amp, not the output. I will go back and rephrase. To answer the previous post tho, I dont think it would come close to a full doubling of efficiency.

Thanks RD. I suspected there had to be blown transistors on that board. While you have it out, can you check the triac I mentioned earlier? Here's a pic of it. It's on the underside and the one in this pic is only attached with solder, leaving the other side of the board with an empty hole:



We're still left with why the short occurred and where. I've been trying to narrow the causes down so that we might prevent it in the future or find a DIY fix for those who are interested. I appreciate your input.

I did not pull it from the board yet. No longer reads short to ground on any legs with bad transistors lifted, was showing short to ground at all legs. About 57ohm across outer legs, open from center to either outer leg.
Have been feeling a bit weird posting in the thread about my (amplifier) woes. Was hoping some may be interested in fixing their own. Thanks for letting me know.
BTW, late last night as I was drifting off it popped into my head as to why I purchased the 14k. I originally was running one EPX4000 on each of my LMS Ultra's. One stopped working. Cannot remember if it was the same sub. I did ohm out the subs today and both are just above 4ohm. Do you think it is worth the trouble to pull the one that was on the bad channel, disasemble the driver and do a visual?

When you say the trim level are talking about the the low level output? There is only one speaker output when bridged. With the limited experience I have with pro amps, I believe the gain on channel A would be the only one used when bridged.

The two small knobs on the front that control gain for channel 1 and 2. I know only 1 will adjust the level once bridged. I'll just find out re the level when I run audyssey again. Thx

There are 2 things I think about when an amp fails as yours did:

1) Heat, especially if the fans were modded to give 1/2 the air flow or if the amp is in an enclosed space, etc.

2) Bus pumping when the amp has been operated in 2 channel mode. This is probably not a problem for a real Lab-type amplifier, but certainly something to consider using a lesser cost option, especially considering the application, which includes single digit signal at high levels.

Bus pumping occurs with low frequencies and specially so with ultra low frequencies. I've had several big iron amps cry uncle with WOTW at reference level. It can also cause components to heat to a destructive point in a heartbeat.

Another cause is very low impedance. I'm not convinced that impedance is a simple thing to measure and that includes impedance sweeps done with DATS or REW. So, yes, if it were me, I'd certainly have a look at the driver in question. I would not want to get a new board and repair the amp and have the same thing happen again.

Finally, a problem I've been looking at is the PS caps not having enough sink capacity, which would definitely be a problem with bus pumping, especially since I was given the following heads up regarding low cost amplifiers...



Amazing. I'm not saying this amp has that problem but the picture shows that the problem exists.

I don't know how to measure the values of a cap. If anyone can help out here, I'd appreciate it. I do know that the Asian amp build houses buy the lowest price, most readily available caps when the need them. From amp to amp, the cap brand has never been the same twice. If the amps were tested before leaving the factory, a problem like crap caps would show up and be dealt with before it got to you, but I pretty much bet it ain't happenin and won't happen. So, I'd prefer to check them myself, I just don't know the proper procedure and the best tool to use?