[Buggins]

I have an energy s8.3 plate amplifier (100 watts rms).

Long story short - used a 4ohm sub, the amp turned out to be 8ohm stable - fuse blew.

Replaced the fuse, and as soon as I plugged it in, fuse immediately blew again (with no signal going to the amp). Same thing happened once more (third time's the charm, right?). Replaced with a fuse double the strength to try and determine where the short was happening...

This time, fuse didn't blow, but smoke started coming out near one of the large capacitors. Upon further inspection, the ceramic resistor near the cap was glowing RED hot, and smouldering that yellow glue stuff near the cap.

I would like to repair this amp as I can use it to build a budget subwoofer for my office, but I have no idea what the problem is. Could it be that I fried the cap, and the resistor is getting too much voltage? I have some experience with soldering on new caps, and I have a multimeter, but that's as far as my knowledge goes.

Any ideas what I can do to test this amp and figure out what to replace?

The image attached shows the resistor that is smoking right next to the left cap. You can see where the glue has been burned black.

Thanks folks.

 

[Stroh]

Can you see the black "circuits" that are bolted to the heat sink? If so do any of the look burnt, they should be connected to the circuit board by three terminals.

 

[Buggins]

If these are what you are talking about, as far as I can tell they look fine. No sign of anything out of the ordinary.

 

[Stroh]

Yes that is what I meant, from my experience they don't like the extra current flow from the lower resistance. This can really be a needle in haystack hunt if you don't have a schematic and a descent understanding of the circuitry. Do you have access to a schematic and can you follow it?

 

[Buggins]

No schematic that I could find anywhere.

 

[Stroh]

Ok you have several options, wait for someone more knowledgeable than me to chime in, you can make a partial schematic yourself if it is a two layer board (if it has more than two layers it will be a nightmare), you could contact Energy either for repair cost or possibly a schematic, find a local repair shop, or you can play the trial and error method.

 

[lcaillo]

The output devices attached to the heat sink need to be tested. Visual observation often tells you little.

 

[Buggins]

It looks like this is beyond my scope, guess ill have to eat this one.

thanks for the advice fellas

 

[Gregr]

I zoomed in 300% to look at the boards posted (great pics by the way) and in the very first board pic are you not seeing the burnt resistor. located to the right of the left lg black cap there is a buff rose colored lg resistor soldered standing on end. This one is definitely burnt/blown. The Pic with the arrow and exactly what you think is burnt.

It is definitely a power prob. not an amplification prob. every thing looks good on the heat sinks. It is not going to be on any of the features boards (anything w/inputs/outputs buttons or controls). It does not sound like a diode issue usually if a diode goes one or another feature simply will not work and you will not blow fuses.

In any case I am not an expert, not an electrical engineer, I am not a licensed electrician and not a journeyman. I have many years of interest in electronics and lots of fun with DIY projects similar to what you have. When I decide to take on a task I am successful, sometimes success is knowing when to stop and bring it in for a professional to complete.

I begin by first narrowing the search area. Your fuses issue tells me pretty clearly "power supply". The power supply is the first board that the AC line-in goes to (possibly one maybe two boards etc).

It may be that the resistor I described in the first (paragraph) is acting alone in this issue but I/we don't know that. I would assume there is cause for the resistor to blow. If it was loud and long playing then the resistor may have burnt and is simply arcing to ground.

With good light and magnifying glass take a close look at the power supply board. If the resistor does in fact look bad to you and it is not an optical illusion I am seeing, I would then begin to clear the area of glue so you can actually look for the rest of the story.

In this case, after pulling the glue slowly/carefully making sure not to pull anything up with the glue, I would look for any obvious red flags or reason for the problem/issue. If it looks like nothing else has suffered I would cut the high looping lead wire then unsolder both pieces "CAREFULLY" (see below)

When you pull the resistor wires "DO NOT PULL HARD" make sure the solder is soft enough to free the resistor leads. Anytime you are removing parts from a board especially on double/triple sided boards there is a thru ferrule attached to the board and Integrated circuit. The ferrule could easily detach from the opposite side and at that point you will begin pulling the IC lead up from the board.

If you do not have a 25watt soldering iron, desolder wick, clip on heat sink, extra flux etc "DO NOT PROCEED FURTHER"

A hotter soldering iron will spit and sputter hot solder all around. One little droplet of solder could your next issue.

Be careful, take whatever time is needed, do not move until you are sure. Good hunting..., don't forget to enjoy it. :innocent:

Greg

 

[Buggins]

Thanks Greg, and yes, I assumed the resistor has something to do with the problem - its the only thing that looks out of sorts (that's why I pointed it out with the arrow) everything else looks perfectly fine. I'm just not sure why the resistor would cook like this.

Wouldn't the burnt resistor simply be a symptom of some other problem?

 

[Buggins]

and the resistor isn't shorting, it's just getting ridiculously hot. I put a higher amp fuse in to try and figure out the problem, and the resistor started getting RED hot, and the glue sitting next to it started to burn, that's where the blackness is coming from.

 

[Gregr]

Exactly,

It could be a result of a line problem, but if there is an associated cause why did that go wrong? And since the resistor blew what unseen problem did this potentially create. It is certain that moving parts fail and that repair need is obvious and usually straight-forward. With electronics you can play the guessing game all day long.

In this case the resistor could have been micro arcing inside (faulty from the start) until the lead separation with resistor temperature etc forced the arc thru the resistive material. If you look at comparisons between "Ohno Continuous Cast Copper Wire (OCC copper)" and OFC or even 101 Copper (Lab Quality) you will find much opp for micro arching in the OFC and 101 copper wire.

I would deal with the obvious first. Then if all of your best efforts fail you can take it in for repair with a pro. It obviously is of great benefit to you if you have schematics but they can be difficult to translate but the test points are absolutely necessary to work efficiently/effectively. Power up testing is a hard way to go and you do not want to jolt the system any more than necessary.

What I would do...,

1. find the wholesaler/dealer - go online to the Energy factory they will have a list of regional dealers etc and find one that will work with you. In any case they will let you know what you need to do. What they suggest may not be your first choice but still helpful info.

On this first call ask for "Parts and Service" do not speak with the secretary...,
A. when you get a Tech on the line ask about emailing schematics (eSchematics)
B. ask about the price of a power supply board approx 20-30% of total prod. cost
C. Talk with the Tech about your problem and ask if this is a common problem and if there is a known cause or other issues you should be aware of in deciding if this repair is worth your time and $$$.

Search out all of your options with an open mind. Things may not go as expected they could end even better then you imagined.

"If you answer your questions with, I THINK..., you do not have the answer yet.

Take your time and do not forget to have some fun with the people you talk with and meet.

Everything I write are suggestions. The real work can become much more involved or complicated even if you decide to simply swap-out the PSBoard. With whatever procedure you follow please be careful. This is your project not mine and not my responsibility in any way.

Keep us up to date please.

Greg

 

[Gregr]

Most important: wear protective gear and take precautions associated with safe practice. Wear safety glasses, avoid inhaling vapors, etc..., If you are not sure what I am referring to here. Then, you probably should have a pro do the work.

Greg

 

[Gregr]

Please read this completely before attempting anything I suggest. For my convenience some important information is written at the very end. Other pieces where important info should be written in each situation needed I didn't, but I hope what I write is obvious to you and there is no need to repeat myself. If you have a question please feel free to ask..., even who I am.?!

I have read your posts and everything I have written applies weather the resistor is blown or going to. If you go any further with power up testing such as you have done you risk loosing something maybe everything.

This is what I would try "only" in a situation where I have no schematics (with test points) and the alternative is buying new. If you decide to go ahead with this repair..., please, stay in touch. Well please let me know either way..., thanks. Have you found out how much a PSBoard will cost?

I would replace the resistor, find the resistor value before touching the old resistor($.25, you have a color pic of the color coded resistor value)
with the volume down to 0% and
no connections made except for power supply,
I would replace the "fuse" w/low amperage down to as little as .1 of the original amperage.
De-solder the old and re-solder in the new resistor as previously described

With the new resistor in place a light amperage fuse should hold if the issue was the old resistor.
"Keep in mind, with everything unplugged you risk overheating transistors/op amp etc so be brief."

A brief run in the on position should tell you if plugging in source media and speakers is safe (not all but enough to try again). Although there may be several even 6-8 fuses there are still usually one or two primary fuses. Keep these w/low amperage as low as possible, volume level off and no source material streaming until you are sure or beyond a doubt ready for a full trial.

Remember, with everything unplugged you risk overheating transistors/op amp etc so be brief. You know how long it took to overheat the last resistor. In this case with a new resistor in place it is possible to take a little longer to overheat. If the problem "is not" the old resistor it will not take long to reproduce the old result. If your problem was the old resistor you must remain cautious about the old resistors overheating and causing new problems.

Before plugging anything back in, maybe even before attempting any repair..., I would check each wire with your volt/ohm meter and a complete visual and hand check of everything as well. Taking your time to look over and feel speaker cables, power lines, interconnects and switches etc. This is also an opportunity for a thorough cleaning/dusting in and out. As you do a visual inspection..., your hands need to go over everything possible as well. Your touch inspection could reveal a swelling in a speaker wire where oxidation has become so extreme that the speaker wire insulation has split and the wires short circuited to ground. This is a time to reinspect old repairs and look for damage everywhere. Also check that wires were/are attached correctly. Be sure that nobody has done anything to the system without telling you. Well you get the idea here. Rule out human error and accidents and misuse/abuse. :innocent:

I hope you do the repair. It could potentially be that simple. Be very de-soldering and taking out the old resistor leads, as I have mentioned.

Greg :whistling:

 

[lcaillo]

Resistors do not overheat because they are defective. Something else is causing too much current through that resistor. Likely a shorted component.

 

[Gregr]

Hi,
Thank you and I agree nearly completely. I spoke too quick. In reality the electrical issue is probably a very obvious one and is a simple fix if given a little time to search out a cause.

Greg

 

[BIG'EN]

I am no expert but if you run a speaker that was 4 ohm instead of 8 ohm you prolly smoke one of your output power transistors. Output transistors typically put off heat and are usually connected to the heat sink in some manner. Remove the heat sink and write down the numbers for each piece that is connect to the heat sink. If you can post the part number I can prolly find a replacement at Digi-Key or Mouser. The resistor simply helps the transistor with power dissipation so if the resistor is smoking you more than likely hurt something in the circuit it is connected to. Without the board in front of me or a schematic it will be all or nothing deal. I usually shotgun (replace everything in the circuit) this type problem. Let me know if you need more info.




BIG'EN


Here is a look a one of my problems. No numbers to read !!!

http://s541.photobucket.com/albums/gg367/HT-EXT/Dayton SA100/

 

[Buggins]

Well I started working on the amp and just threw in the towel.

For some reason my soldering iron wouldn't even melt the solder at it's highest heat setting (and it's 40 watt) so I couldn't change any of the components if I wanted to. Not sure why it wouldn't work, it's worked for all the other circuit boards I've repaired.

Seems like this amp is destined for the garbage can.

Thanks for the help guys!

 

[Gregr]

Check to see if the tip is in tight; clean the tip when hot and tin the clean tip. rolling the hot tip in tinning paste and then brush off the excess is how I do it (don't tell my Dad). You don't want to use the very tip anyway..., try just to the side of the of the very tip, that's the hottest spot. You might try cleaning the tip threads also (both male and female). Copper oxides are not very conductive that 40 amp is probably acting like a 10 if the threads and the tip are not shinning.

Don't toss the sub put it up on ebay as an "as is", first dollar takes it, plus the cost of shipping. I know it is easier to toss it.

Greg

 

[Buggins]

Thanks, I'll give that a shot. And you're right, I shouldn't toss it. I'll stick her up on ebay as-is. Someone with a little skill could have themselves a nice little 100watt rms plate amp for cheap.