Problems With Amp Overheating, Seems To Be Clipping?

[Jonboy84 0]

Hi guys, I'm new to the scene and just getting my gear together and learning how to use it all. The problem I'm having is that when I connect my studiomaster mixer to my leestar 1350 power amp and play music through it to my soundlab 500 w peak speakers, even at a very low output the amp goes into protection mode and all the fans start up. I was wandering if anyone could give me some advice on what I'm doing wrong? As I said I'm only learning so please be patient : ) I can provide photos of how I've got it set up on request. Thank you, Jon

[McCardle 1]

Sorry, i'm not familiar with that amplifier. Do you have a link to a website with it on? so I can check out the technical specification

 

 

 

even at a very low output the amp goes into protection mode and all the fans start up

 

Could be a number of possibilities. I guess prior to the amplifier cutting out, that you do get some sound from the speakers? and that they are both working?. Does the sound that you get prior to it cutting out, sound clear and ok or is there any distortion or cracking.

[Jonboy84 0]

Yes it powered up ok and both speakers were operating fine, then the sound seemed to fade out and come back in from both speakers at random, then this overheating kicked in very shortly after this. I'm just trying to figure out exactly what's going on

By the way the amp appears to be Chinese and there is precious little information available online

[McCardle 1]

I suspect the Amplifier has developed a fault. For two seperate speakers to develop the same fault, at exactly the same time is pushing coincidence.

 

How are you wiring the speakers from the amplifier and with what type of cables?.

 

They should each be wired with a single lead - with either Jack Plug or Speakon connectors fitted to each end. The left speaker should be connected to the left hand channel output of the amplifier, and the right hand speaker connected to the right hand channel output at the amplifier.

 

If your amplifier has a switch on the back marked 'Bridge' or 'Bridge Mode' then this switch should be moved to the 'Stereo' position.

This is a slightly different model, but does the back of your amplifier look like this?

 

http://i.ebayimg.com/t/Leestar-TS-1200-PA-disco-power-amplifier-/00/s/NzYxWDE2MDA=/z/V-AAAOxy2d9SUYdy/$T2eC16d,!)MFIbsDGw34BSUYd)8wJQ~~60_58.JPG

 

 

If it does, are you connecting the speakers using the Black and Red posts or the Speakon sockets?

Edited January 18, 2014 by McCardle

[Jonboy84 0]

They are the quarter inch jack types to the speakers and the positive and negative are wrapped around the terminals of the amp as they don't have speakon connections on them. It's worth pointing out that the amp didn't shut off, it's just that after a few minutes of running fairly silently the fan at the back speeds up to a very high rate and makes a bit of a row. (This could be made worse by the fact I'm testing it in a small room!) and yes there is a slide switch with "stereo" "parallel" and "bridged" on it and is slid to stereo. I may be panicking over nothing and the fan speeding up may be a normal operation, but it's worth pointing out that it does this even when not connected to any device and silent. I appreciate you explaining all this to me by the way, thanks. It's an old amp and bound to be a bit noisy, does this help enlighten you a bit more? As I'm reluctant to run it more until I have a better understanding

[McCardle 1]

On your opening post you mentioned that the Amp went into 'Protection Mode', normally when this happens the relays inside the amplifier disconnect the load (speakers) and the sound goes off. This can happen for a number of reasons, usually a short circuit or a failed speaker driver, internal overheating or a DC Voltage appearing at the speaker outputs.

 

If this isn't the case then its unlikely that the amplifier is detecting a fault, there may not even be a fault if the speakers don't disconnect.

 

A lot of amplifiers have two speed or even variable speed fans which react to the internal temperature inside the amplifier - usally from sensors on the metal heatsink, so the fans speeding up suddenly would be considered normal, although it would usually happen at venue sound levels rather than low levels.

 

If the fan grilles and ventilation slots on the amplifier are caked in dust, then it will be good advice to give them a good cleaning, as lack of ventilation especially on the fan air intakes can cause the amplifier to get hotter than usual even at idle, hence the fans speeding up at lower volumes.

Edited January 18, 2014 by McCardle

[Jonboy84 0]

No sorry I was wrong about that, it didn't go in to protection mode the fan simply started spinning extremely quickly even though the load was very low on the amp, there also seems to be something rattling inside when this occurs. It could be the fan bearings are knackered or simply very noisy. Another thing to point out is that when you flick the switch on the back to stereo a red light appears on the front of the amp, but when switched to parallel or bridged it's an orange light. I'm presuming this is normal! The strange thing the speakers were doing could just be the way I've got it rigged up to the mixer or the laptop. I work in an engineering workshop so I will take it in to work Monday and blast it out with compressed air, in the meantime should I send you some pics of the set up and how I've got it wired so you can spot if I've got something obviously wrong somewhere? Thanks

[McCardle 1]

 

 

in the meantime should I send you some pics of the set up and how I've got it wired so you can spot if I've got something obviously wrong somewhere

 

Sure. I'm not sure whether you are able to upload images directly to the forum being a new member. If not you can either link to images hosted from your own website or Flickr album, or use a free image upload site, such as

 

http://postimage.org/

 

http://tinypic.com/

 

http://hostmypicture.com/

[Jonboy84 0]

I will be back home tomorrow so I will take a few pics and explain how I've wired it all up, maybe I've cocked up somewhere. I will try the upload sites but alternatively I could email them to you directly?

[McCardle 1]

It will probably be better to upload them if you can, since somebody else may spot something which I miss.

 

However, if you have no option but to email them, my email address is below

 

 

joshmac@gmx.co.uk

Edited January 18, 2014 by McCardle

[Jonboy84 0]

 

 

 

. Please let me know if these links are ok as I've not used that site before. Here's what the score is. The amp seems to operate ok even when the noisy fan kicks in, so I'm going to blow the dust out of it and replace the old fan with a new one. The problem still remains with the speakers, in that they are fading in and out randomly but never at the same time. Then all of a sudden come back again. If you could have a look at my set up in the pictures and let me know if anything is wrong that would be great. The cables came with the amp and I've no idea of their quality

[McCardle 1]

The pictures are OK. It seems that the speaker cables use 6A Flymo mains lead you can't beat that bright orange colour for use in low light venues. I've seen this used many times before!.

 

Everything seems to be connected OK, I can't see any wiring related reason for the fading in / out problems, but it may be worth changing the cable you use to connect between the mixer and amp, just to rule out internal breaks and bad connections, shouldn't be more than a couple of quid and its useful to have a spare anyway.

 

Also turn up the volume on the amplifier to at least 1/2 to 3/4 travel on its front panel controls, and use the mixer master output controls to achieve your desired volume. Its always better to have the amp controls high, and use the source (mixer) controls to determine the actual overall output.

 

When the sound appears to fade in / out, try wiggling the input connectors on the amplifier, also wiggle the front panel volume controls on both the amplifier and master controls / faders on the mixer to see if this has any effect on the fading problem.

 

If you are only using one input source into the mixer (e.g laptop) then try also plugging it into another channel on the mixer, just to also rule out issues with a particular mixer channel.

 

I would certainly open the amplifier and give it all a good blast out with air, not only the fans but also the circuit boards inside the amp, as years of dust can stick to the bottom of circuit boards and accumulate to the point where it can cause glitches. Just be aware that compressed air in industrial compressors can contain tiny droplets of water from condensation in the airline, so make sure you give it time to dry before powering up after its blasting.

 

The one thing which does concern me, is given the rust present on the fan grille, that the amp has spent a lot of time in its past stored in a damp environment, and of course rust and corrosion on the outside metal, can be repeated inside the amp on other metal parts like solder joints and volume control tracks.

 

When you open the amplifier to clean it, look for obvious signs like rust or corrosion on metal parts and on the circuit board underside solder joints. Also look for any bulging or leaking capacitors, which may look like the ones on images shown below

 

http://www.markdigital.com/wp-content/uploads/2011/02/bulging_capacitors.jpg

 

http://www.tnpcnewsletter.com/dan/Bulging_Capacitors/close-up.jpg

Edited January 19, 2014 by McCardle

[Jonboy84 0]

Your a star, thanks for taking the time to go through all that. I'm taking it in to work tomorrow to blast it out and will change the fan and check out the circuitry later in the week and let you know when I get to the bottom of the problem! Thanks again, Jon

[Jonboy84 0]

Hi guys, as it turns out it appears to be the studiomaster club 2000 mixing desk that is causing the unusual fading in and out of the speakers at random. Connecting a newer behringer mixer to the amp proved this. The problem with the amp overheating was solved by blasting years of nicotine and dust from it, so thanks go out to mc cardle for that tip : ) as for this problem with the mixer, we are still trying to get to the bottom of it unfortunately. So any advice on what to check would be great. Thanks again : )

[DJTREV 0]

Nice one Josh.Thanks for taking the time to help JonBoy

[McCardle 1]

Does the fading in / out happen across all of the channels?. If you haven't done so already, try to plug your music source into one of the other channels.

 

PA Mixers have inputs for a wide range of equipment to its channels, make sure that you are connecting to the mixer using the line level option, as opposed to a mic, instrument or phono input (This may appear obvious but you would be surprised how often it gets accidentally overlooked smile icon )

Edited January 23, 2014 by McCardle

[Jonboy84 0]

Yes sadly it appears to do it on all channels, leading me to believe the fault has to be somewhere on the master volume. I am connecting via the 6.3mm jacks located on the top of the mixer, and ignoring channels 1 and 2 as these are labelled mic. We have stripped it down and wiggled various cables and connections around, none of which made the fault occur when I wanted it to, instead it continues to annoyingly do it when It feels like it. There is a ribbon cable running from all channels to the master volume, I'm not ruling out this as the culprit but its undisturbed so doubtful. I've tested all internal capacitors and all seem fine. This is driving me nuts, but it would be a good little mixer and a shame to not to bring it back to life : (

[McCardle 1]

Depends on how upfront and personal you want to get with the circuitry and what test equipment you have available to you for indepth fault finding. If its happening across all channels, then yes the master output is one possible suspect but if the fading happens on both L & R channels, then it would be more than a coincidence for both sections to fail with the same fault, as I would think that there would be two amplifier IC's driving the master outputs - one ic and associated circuitry for the left output and one for the right output, even if they share the same pcb. In these types of mixers the ic's handling the audio are standard NE series, usually NE5532

 

Schematics used to be available freely for Studiomaster stuff, then they became obsolete but there was a pay per download studiomaster archive site, which now seems to be offline. There doesn't seem to be any dedicated circuit diagram solely for the Club mixer anywhere. However the Club series did share a lot of common parts with the Diamond & Powerpack series.

 

I've attached a PDF Schematic for the Studiomaster Diamond / Powerpack to this post which you can download, which does reference the Club 2000 in its diagrams, so I would imagine that a lot of the circuitry, especially the channels, is exactly the same across all of the models.

 

Personally, I would also be checking the main power supply unit, making sure that both + / - supply rails are present and stable, and then checking the main smoothing caps for these rails. On this mixer is the PSU built in internally, or do you have an external 'brick' which connects via a multicore cable to the mixer?.

studiomaster powerpack 400.pdf

Edited January 23, 2014 by McCardle

[Jonboy84 0]

The PSU is internal, located on the bottom right I believe. I will have a look at the diagrams also. When the fault occurs it can be randomly either the left or right speaker, but you can still faintly hear the sound through the affected speaker, it just drastically reduces output to an extremely low level and then all of a sudden will come back again.

[McCardle 1]

Well for what they cost, if might be worth replacing both amp IC's on the master output pcb. Have you tried gently flexing and tapping the master pcb to check for dry joints and track breaks?, these can cause intermittent faults.

 

If you have a digital multimeter I would attach it to the PSU and monitor the supply rails to see if there is any sudden voltage drop or fluctuation across one or both rails whenever the fault occurs.

Edited January 23, 2014 by McCardle

[DJTREV 0]

I am not quite sure why I just read those last few posts.You might just as well be talking Swahili.Thank heavens someone knows what he's talking about

[Jonboy84 0]

Hi Mccardle, I'm pleased to tell you that having looked more closely at the PCUs for both master volume channels, as well as wiggling the circuitry back and forth, I was able to make the fault occur at will rather than when it felt like it! Having discovered that the fault was being caused by bad joints around several components i have resoldered all components on both boards and the fault has not re occurred! Sadly upon reconnecting back to the amp and speakers (rather than in my dads workshop to a small hifi) there is a lot of background noise through the speakers even with no volume and no source connected : (. I fear static or the soldering of delicate areas could have damaged the preamps on the master volume boards. Would you concur??? If I can get hold of the preamps I was going to change them, considering I can't see them being very expensive. Still at least we have solved one issue, let's try to forget I've caused another haha.

[McCardle 1]

Its possible to cause static damage through soldering, but more likely to occur if handling components prior to fitting them to the PCB. In most cases soldering iron elements and tips are grounded through the electrical earth connection. Its probably more likely that you have overlooked a ground connection somewhere, did any of the screws holding the PCB have a crimped terminal with a wire connected, under the screw?, or washers which made a physical connection to any metal PCB stand off pillars?.

 

Is it possible when re-soldering, that you accidentally bridged two joints together with a solder blob, which were not physically connected via the pcb tracks?, i've done this before when remaking fine pitch joints, such as i.c legs, and it can be really easy for a tiny splash or whisker of solder to bridge across two pins or tracks which isn't immediately obvious.

 

Assuming that a mixer of this era uses through hole components, if you do want to replace the Op-Amps, it seems that the ones used throughout these mixers are either

 

RC4560 - http://uk.mouser.com/ProductDetail/Texas-Instruments/RC4560IP/?qs=sGAEpiMZZMtxdzBvM0rKcXOd7KQa2ueJY7SCMr%252brDp4%3d

 

Or

 

NE5532 - http://uk.mouser.com/ProductDetail/Texas-Instruments/NE5532P/?qs=sGAEpiMZZMtCHixnSjNA6Araa3jp4DVBKprmLw7OjBo%3d

 

Check on the actual IC's though before committing to an order.

 

However, before, randomly replacing components, I would double check the joints which you soldered, and also make sure that any screws holding the PCB(s) to the stand-offs are tightened correctly and any washers under the screws are all present and in place. Its not unknown for ground connections to be made to the metal case, panel or chassis via the metal stand offs holding the PCB

Edited January 28, 2014 by McCardle

[Jonboy84 0]

Sorry about the delayed reply. Yes it's quite likely that by not being careful enough with handling the delicate preamps when working on the master volume boards we inadvertently caused static damage. In answer to your question they do use through board soldering and seem to have 3 legs per side. I actually found someone selling them relatively cheaply on eBay, (around £4 for 3 of them) so I am going to give these a go and wear an anti static wrist band while working. As it's hard to envisage what else could have caused the terrible background noise... Naturally I will get back to you in the next few days when the parts arrive and let you know the results!

Oh yes, and as per your advice we did check all relevant earths and all seem ok, as far as the naked eye can see anyway!

[McCardle 1]

Always be cautious about buying components from Ebay, a lot of Chinese Counterfeits and blacktopped components find their way onto there. Sometimes its worth paying a little bit more and getting spares from a Franchised catalogue distributor, just for peace of mind. There is nothing worse than carefully de-soldering components and refitting new ones only to find that the 'new' component fitted is a fake or a blacktopped version of something completely different, and having to go through the process again.