Help fixing Onkyo M-5000 power amp

Sheddingskin

Sheddingskin

Active Member
I have an Onkyo M-5000 power amp that I just started experiencing problems with. When the volume gets to about 10 o'clock on the preamp the Onkyo protection will kick on. If I back the volume down the protection shuts off and the music will play again. Everything sounds good at low volumes, no distortion that I can tell.

This all started one night when I had my subwoofer taken out of this system (it was connected via high level inputs) and had the speaker wire connected and taped together where the subwoofer would normally be. The volume was turned up fairly high and went into protect. Ever since then it has consistently happened at the same volume.

My preamp is an NAD 1020B and I am using the regular outputs. My speakers are a pair of Design Acoustics PS-10a's.

The specs for the Onkyo M-5000 are as follows:

Power Output: 105 wpc RMS at 8 ohms, both channels driven, 20Hz to 20kHz
THD: 0.09% at 105 watts
IM Distortion: 0.09% at 105 watts
Damping factor: 40 at 8 ohms
Frequency Response: 5-100kHz +- 1dB
Signal to Noise Ratio: 100dB (IHFA-202 1 watt output)

I checked the DC offset of the amp and got 7.5 mV for the right channel and 12.7mV for the left. What else should I look for to try to fix this? I do have the service manual for it and plan on using this as a learning experience. I ordered a Dayton DTA-100a to use in the meantime :banana: Any help would be greatly appreciated!
 
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That amp should be able to drive just about any set of speakers. Why it's going into protection mode is a mystery. First thing I'd do is to remove the speaker wires off the amp, then turn it up. No damage running it without speakers (for a short test). This will give you a clue as to if the problem lies with the speakers or wires. If it doesn't go into protection, a bad wire or speaker(s) x-over may be the problem. If it does, something internal is bad, and I would refrain from using it until the problem is resolved. More damage = MORE MONEY in repairs.

Too bad. That's a real nice amp.

It might be the pre also. Dirty controls could trigger the protection circuit. Maybe a cleaning is in order on the pots with contact cleaner.

Better to cover all the bases.

Good Luck.
 
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Greetings;

The SM at the very beginning shows the protection circuit and aside from current detect etc. the protection extends between the amp out to speakers. Most mfr's recommend checking spkrs. and wires regarding protection issues as well as recommended above. one or both of your speakers could be unstable and the amp is sensing that, the amp needs a load.

You did note that you removed the sub. I'm not sure if this amp has the circuitry to remember your last settings as other onkyo models but most of the time the same precautions are recommended. I.e. if your amp goes into protect you're supposed to shut it down and let it cool off. I could go further to say unplug it for a few hours or longer.

Aside from speakers, heat and cooling is always an issue. Your amp uses stk output and they get hot and the associated circuitry nearby gets hot and heat can create unstable circuits. This can trigger the current detect and put it in protect, too.
 
Binkman said:
Greetings;

The SM at the very beginning shows the protection circuit and aside from current detect etc. the protection extends between the amp out to speakers. Most mfr's recommend checking spkrs. and wires regarding protection issues as well as recommended above. one or both of your speakers could be unstable and the amp is sensing that, the amp needs a load.

You did note that you removed the sub. I'm not sure if this amp has the circuitry to remember your last settings as other onkyo models but most of the time the same precautions are recommended. I.e. if your amp goes into protect you're supposed to shut it down and let it cool off. I could go further to say unplug it for a few hours or longer.

Aside from speakers, heat and cooling is always an issue. Your amp uses stk output and they get hot and the associated circuitry nearby gets hot and heat can create unstable circuits. This can trigger the current detect and put it in protect, too.
Click to expand...

Ah Jees. :twak: :bash:

Totally forgot about the possibility this might have a memory.

Thanks Binkman for stepping in.

I'm gettin' tired of these "Senior Moments". :D
 
Ok, I unhooked the speakers, turned the volume up and the protection did not kick on. I tried with a different set of speaker cables and the protection did kick on. I have not noticed this amp getting particularly hot. As far as the pre goes, I have cleaned the pots and all contacts within the last few months.

So does it sound like my speakers are the culprit? What should I look for to diagnose them?

EDIT: I forgot to mention that I tried using my DAC as a preamp and got the same results, so the preamp is ruled out as the problem.
 
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OK. you've done the steps to narrow the problem. Now, on to more testing.

Do you have a multimeter? If you don't, buy one. RadioShack has them. PartsExpress, Amazon, and others also carry them. If you have an interest in getting other audio equipment, this tool is invaluable.

If you do, test each speaker from its terminal plate. Set your meter to (low) ohms, and record what the reading is. They (your speakers) are listed as 8ohms.

Both should be the same or VERY close. If 1 is way off, that might be the problem. It could also be a bad driver, x-over (cap or coil), terminal plate, ect.

Let's start there. Measure off the boxes and post back.
 
OOPS. Forgot to ask. Do you have another set of speakers?

You might want to swap them in (if you have) to see if the same problem occurs.
 
Ok wow I think I found the problem now. I checked each speaker at the terminal plate and got 6.3 ohms for one, but 1.8 for the other.

I opened up the back and was able to measure tweeter and midrange and got around 6 or 7 for each of them. The leads that connect to the give me a value of about 1.3 ohms. When I measured all of these I just measured them off the solder point on the crossover board, I don't know if that would change what this means.
 
Ah. Now we're getting somewhere. :banana:

On the speaker with the low ohms reading, you need to do a more detailed test.

1 - Take out and disconnect all drivers. Leads from the x-over need to be removed from the driver to be accurate.

2 - Test each driver. What are the ohm readings?

3 - Remove the drivers from the "good" speaker. Compare the readings from (the same driver) to the "bad" speaker drivers. Are they the same?

Post back when you get the results. This will point to what the problem is.
 
Sheddingskin. Sorry. I read your post, but it didn't sink into my pea-brain. :D

You DON'T NEED to remove the drivers, just remove the x-over leads to them. Do 1 at a time, so you don't get a tangle of wires, and can't remember where they go.

If all the matching drivers have the same readings (woofer>woofer, mid>mid, tweet>tweet), then there's a problem in the x-over.

Again, sorry for the mis-information. This should make things easier. Post back the results.

Phil
 
I think my problem is solved! I'm pretty sure the woofer on that speaker was blown. The woofer on the good speaker gave a reading of 6.8 ohms. The bad speaker gave a reading of 0.8.

So buying a replacement woofer should solve this, correct?
 
If that's the reading on the woofer, the VC got cooked. That would definately stress any amp. Sometimes this happens with too much power. VC wire coating melts, and the windings short out. That amp has a lot of available current, so be careful.

Yes. Replacing the woofer with a good one should solve the "protection mode" problem. I would also look over the x-over in that speaker. See if anything looks discolored from heat (over-powered) on the board. I doubt there's anything wrong, but better to be on the safe side.

It's good that you found the problem. With a replacement woofer, you can get back to enjoying music.

Have Fun. Enjoy your system.
 
I remember reading about replacement woofers for your speakers. It was right here on AK. http://www.audiokarma.org/forums/showthread.php?t=426088

This might help if you can't find an OEM replacement. I also read about this one as an upgrade to the stock one. http://www.parts-express.com/dayton-audio-dc250-8-10-classic-woofer--295-315

This one might work also. http://www.parts-express.com/goldwood-gw-1038-10-butyl-surround-woofer-8-ohm--290-360

You have to measure the height of the old one. On the first link, someone mentioned the magnet hitting the mid enclosure. Each woofer link has the height in the specs, so compare yours to them.

Any other questions, post back.
 
I looked over the rest of the crossover and compared the values with the good speaker, and everything matches up. There doesn't seem to be any discoloration anywhere.

Thanks for all of your help! I learned a lot about diagnosing problems.

I'm pretty sure that this woofer was cooked with my Crown XLS-402 last spring. I had thought that I had only blown the tweeters, and actually just replaced both tweeters about a month ago. They were just powered by the Onkyo for the first time then, which is why I thought it was the amp.

So now I'm just trying to decide if I want to go with that Dayton woofer or the original DA woofer that I found on ebay. I think I also am going to replace the polyester batting inside them with some spare acoustic foam I have laying around.
 
Sheddingskin said:
I looked over the rest of the crossover and compared the values with the good speaker, and everything matches up. There doesn't seem to be any discoloration anywhere.

Thanks for all of your help! I learned a lot about diagnosing problems.

I'm pretty sure that this woofer was cooked with my Crown XLS-402 last spring. I had thought that I had only blown the tweeters, and actually just replaced both tweeters about a month ago. They were just powered by the Onkyo for the first time then, which is why I thought it was the amp.

So now I'm just trying to decide if I want to go with that Dayton woofer or the original DA woofer that I found on ebay. I think I also am going to replace the polyester batting inside them with some spare acoustic foam I have laying around.
Click to expand...

Help is what AK is all about.

Good that the x-overs look intact. Once the driver(s) are replaced, everything will be back to normal.

I don't know how much the e-pray replacement woofer is, but be careful. Sometimes it's a crap-shoot when buying from there. You never know if the sellers description is accurate or not. If the price w/shipping is close to the Daytons, it might make more sense to go for (2) new than used. The Daytons also have a rubber surround, and will last a lot longer than foam. Of course, it's up to you.

The poly fill is just fine. You really don't need to replace it, but if you want to, go ahead. A word of caution tho, it might change the response of the woofer. Try it. Worst case, you'll have to change it back.

Have you thought about doing a cap refresh on those x-overs? With the age of the speakers, it might not be a bad idea. Once the driver(s) are out, it should be an easy job. If you need help with the parts, I can look them up and give you a list. Not a problem.

Later.
 
Cablephil,

Thats why I love this place, everyone is so friendly and helpful.

Well I went ahead and ordered the used woofer. The guy has perfect feedback and seemed pretty knowledgable. He provided his measured DC resistance, all of the dimensions, many pictures, and just reformed them. It looks like he did a very professional job. I refoamed my woofers myself a year or two ago.

Hmm I wondered if it would effect the response much. Maybe I'll only secure the foam well enough to try them out until I come to a conclusion on what to do.

As to recapping the crossovers, I have been thinking about doing that. I've been having so much fun diagnosing this problem that I don't want to stop working on them. Will I be able to use the same board? Also, does hot glue work for securing the capacitors, or is that stuff something more advanced?

If you happen to have a parts list or anything I would greatly appreciate it.
 
Hey. This is what the hobby is all about. Having Fun.

Don't let me talk you out of changing out to the foam. It really doesn't have to be attached to the box. As long as it's placed abound the walls, that'll be good enough for the test.

The x-over should be a piece of cake. Yes, you'll use the board over, and yes, hot-glue is perfect to secure the new caps.

I don't know what's in them. The values are on the old caps, and I have no idea what they are. I've looked online, but came up empty. List the values here, and I'll look for caps that'll work. Inductors and resistors usually don't go bad, so those can be left in and not replaced.

Whenever you get a chance, give me a list. Then you can order whenever you want.

Get your glue gun ready, the fun's about to start.

Phil
 
It turns out that I actually don't like the way it sounds with the foam. It made everything sound too punchy.

Ok, I opened up the crossover and these are the caps per speaker. They were all Culver branded.

(Qty) (Capacitor)
2 165 µF ±20% 100 VDC
1 14 µF ±20% 100 VDC
1 10 µF ±20% 50 VDC 63 SV

Should I replace the hook up wire while I'm inside? The only problem is that the leads going to the mid are two pieces connected by a spade terminal, with the one side fed into the mid enclosure through a very small hole. And the mid seems near impossible to get out.
 
Hey Brad. Thanks for the values.

I'll give you the caps list in a bit. I've gotta look to see who has the sizes at a reasonable cost.

Are you ready for the snow? Here on Long Island we're looking at 10+ inches. I gotta move. :yes: I'm tired of shoveling.

Alright, I'll get it to you tonight.
 
OK. Here we go.

First thing to note, NO 165uf cap. So, we're gonna use 2 in parallel. 150+15=165. These will be regular NPE caps. Poly's would cost a fortune, and would be about Beer Can size. :yikes:

4 - http://www.parts-express.com/15uf-100v-electrolytic-non-polarized-crossover-capacitor--027-344

4 - http://www.parts-express.com/150uf-100v-electrolytic-non-polarized-crossover-capacitor--027-364

4 - http://www.parts-express.com/dayton-audio-dmpc-10-10uf-250v-polypropylene-capacitor--027-428.

2 - http://www.parts-express.com/dayton-audio-dmpc-40-40uf-250v-polypropylene-capacitor--027-421

So, just to recap (:D) the combinations by part #'s:

#027-344 + #027-364. This will be the 165uf cap replacement.

#027-428 + #027-421. This will replace the 14uf cap.

#027-428 will be the tweeter cap.

These will give you the best bang for your buck, and not empty your wallet. The poly's are 5% (NPE's are 10%), so this will give you a good balance between the two speakers. Closer tolerances = better, matched sound.

Let me know if you need more explanation on anything.

Phil
 
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