Hey guys I'm new here and new to working on amps :)
I have a line 6 spider III 15watt amp which had a problem where it was extremely quiet even when cranked. I figured I would pull it apart check for anything obvious then put it back together.
Upon putting it back together I managed to release the smoke stored in the electronics. I found a fries diode and replaced it, I also checked the other diodes and all good.
Now I turn it on I get a hum from the speaker, checked and found I had 10V DC there.
I also checked the power amp which had a 13V DC supply and 11V DC output. Input was about 0.8V and volume was all the way down.
I studies electronics a long time ago so I am comfortable with replacing components but would appreciate if you guys can help to guide me through the trouble shooting process :)
I forget, is the power amp IC a TDA7293 or an LM3886? Either way, look up the data sheet for the part to see which pins are what. Then verify that both positive and negative power supplies are up to the same voltage and frree of ripple. Perhaps you are missing the negative supply?
If you have good power supplies, then most times any power amp failure is simply a bad power amp IC.
Hi frankfurts, Welcome!
DO NOT turn the amp on again. Only more damage will result.
DISCONNECT the loudspeaker and do not reconnect until the diagnostics tests show the repair is complete.
You will need to make up some form of Limiting Lamp (http://www.ssguitar.com/index.php?topic=2093.0) so that you can liven it up for testing without damage.
Even with a serious blow up this class of amp is normally quite repairable.
Thanks for the replies. I'll make myself a limiting lamp and do some more tests.
The poweramp is a TDA2030
I don't have a cro but I assume I can check for ripple of its bad enough by switching my meter to AC?
Yes, you should be able to measure ripple on the AC range, unless it is a real cheap meter that can't measure AC on DC. You can check by measuring a AA or 9V battery with the AC range, it should read 0V AC. If so, you should be able to measure ripple with it.
Quote from: Roly on March 11, 2015, 11:51:44 AM
Even with a serious blow up this class of amp is normally quite repairable.
If you mean the power amp, I agree ;). But there is still the original fault, which I don't think was power amp, and in this regard Line6 stuff can be non-repairable.
So there remains the possibility of going to all the trouble of repairing the power amp only to find you need a new "mainboard" :grr.
Well I just bought stuff to build my bulb limiter then I'll try some fault finding.
I'm not sure how I smoked the diode initially as once pulled apart everything just plugs/screws into place it physically won't fit any other way.
I'm thinking maybe a bit of ESD may have been the cause.
Now when I work on it I have the mains plugged in but switched off at the wall so that whilst I'm touching the frame I am earthed.
A TDA2030 is simpler still than the others.
If you remove the IC, you can fire up the amp without it and check the rest of the voltages. There should not be DC on either input pin.
OK tested the power amp pins 5 (+ve) and 3 (-ve) and I have about 21V on the +ve and 0.9V on the -ve.
Showing only about 10mv on AC so that parts good. Just trying to find the test points after the rectifier. I can see a row of 6 diodes and also a row of 2. I have no schematic though.
I thought a bridge would only be made of 4.
Appreciate the help by the way hopefully I can get this baby going again.
I also have +20V DC on the O/P pin (pin 4) the inputs all have less than 1 V
So find out where the negative supply went, nothing works without good power supply. If only +20 is applied to the IC, then all that can appear on its output is +20.
Quote from: Enzo on March 12, 2015, 05:03:48 PM
So find out where the negative supply went, nothing works without good power supply. If only +20 is applied to the IC, then all that can appear on its output is +20.
Thanks for the help, doesn't seem as terminal as I first thought when I saw smoke come out :)
Does anyone have a schematic for this amp? I can't find one. I'm confused with all the diodes as I thought you only need 4 for a full wave rectifier not 8. Or do they have 2 DC voltages? 1 from the center tap of the transformer?
Quote from: frankfurtsI'm thinking maybe a bit of ESD may have been the cause.
Don't spin your wheels - you don't even know what is actually wrong yet (and some random short is a more likely cause).
Quote from: frankfurtsOK tested the power amp pins 5 (+ve) and 3 (-ve) and I have about 21V on the +ve and 0.9V on the -ve.
You have the +ve supply but not the -ve supply. (Ripple is the least of your problems ATM)
I'll try and attach the circuit. On page 3 are the power supplies;
- main supply using four diodes in a bridge with a centre-tapped tranny to end up with a bi-polar supply for the power amp, +HI and -HI;
- these are regulated down to provide +VA and -VA which are around 9V;
- a mono-polar bridge rectified supply +VL of around 12-15V; and
- a 3.3V monopolar supply regulated down from +VL for the DSP/Fx board.
HTH
{it won't take the upload, helpfully telling me the file is already here, but unhelpfully not telling me where it is.}
What a pain. If I could look at the diagram it would be much easier to test the diodes as they are all numbered on the board. I'll give it a go though with my trusty pen and paper
As DeCastro said when writing about dBase-II, "Water is wet, rocks are hard, and software has bugs." You can sit and complain about the state of things, or you can try to find a work-around.
This forum software, good 'tho it is, isn't cutting it for our needs, so we try something different...
A) try this;
http://www.schematicsunlimited.com/l/line-6/line6-spider-15w-ii3012-1508-amplifier-schematic (http://www.schematicsunlimited.com/l/line-6/line6-spider-15w-ii3012-1508-amplifier-schematic)
B) failing that, try Googling <line6-spider-15w-ii3012-1508-amplifier-schematic.pdf>
Cheers mate I have the spider 3 but I think the basics supply should be near identical. I'll have a look.
OK done some testing and I've found.
+3.3V
+HI
+9
Are all good.
-HI and -9 are missing
Can't find yes points for +VL yet.
OK VL is not there as its for a foot pedal. My model isn't compatible with one.
OK the problem is with the diode I replaced I think I destroyed the solder pad a little any tips on how to repair it?
I definitely have something else that's shorted. I didn't realize the diode I replaced was on a dual layer part of the PCB so I fixed the connection on the top and as soon as my bridge rectifier was intacted I powered it up ( with the bul limiter) and straight away burnt out the two diodes on the negative side of the bridge.
If it's not triple layer pcb, consider yourself lucky. :o
Attached is the very extensive service manual for the III:
Quote from: g1 on March 13, 2015, 12:03:57 PM
If it's not triple layer pcb, consider yourself lucky. :o
Attached is the very extensive service manual for the III:
Haha it may well be. I failed to notice the 2 layers. The must be a short on the negative somewhere.
Probably my only concern when I pulled it apart was the way the power amp bolts to the chassis. And I think it's probably what's causing tho problem now I think of it.
The top tab is also connected to pin 3 of the amp which is the negative supply. However there it is booked to the chassis. I did notice the bolt has a plastic washer. Is this supposed to go inside the whole in the tab to insulate it from the chassis? In just using it as a regular washer.
YEEEEP datz ya problem,,, No *Insulation washer* yikes. Which means you have created a dead short.
And before you power on again do a continuity test and make darn sure the washer is actually insulating.
Also depending on the type of washer you may need some thermal paste. (the white grease stuff)
Phil
Well the whole amp is mounted onto a sort of insulation tape so when I get a chance tomorrow. I'll replace the diodes and fix the washer. Then I'll probably be back to my original problem.
In that spider 3 manual, look at page 4 of the pdf.
It shows how the output IC is mounted. If it has a grey silpad like that (no rips or damage) you don't need heatsink grease. The silpad insulates the back of the IC from the chassis.
Now the tab of the output IC needs to be insulated from the mounting screw. This is what the plastic shoulder washer does. The narrower part of the shoulder washer fits into the hole in the tab of the output IC.
After the shoulder washer, there should be a flat washer, split washer, and nut.
After it is all mounted, check that there is no low resistance between tab of output IC and chassis.
Rectifier and Poweramp all fixed now. I can listen to music from my phone through the mp3 input perfect but when I plugged a guitar in I get little or no sound.
Sometimes by playing around with the pots etc I can get it to work for a bit, however much quieter than it should be. Also it doesn't seem to be 1 consistent setting that makes it work.
I measured the pots and they are all 10K and adjustment is working.
Have a real good look at the solder connections on the pots and jacks. Maybe just resolder them anyway.
I checked all the pot connection continuity and they are all sweet.
I think I may have found a problem with the input jack. I'll start browsing the prints you guys sent me to work it out.
Are input and output jacks wired the same way? I done some tests comparing the two and on both I get a circuit across each pair of connections with no jack in.
However when I plug the guitar in I get open circuit across the pairs on the output jack but on the input I get a circuit of 4k on one 300k on another and open circuit on the third. I also have a circuit between the top and bottom pairs on input jack only.
Sounds suss to me. Like I said I'll look the prints up and confirm but I figured you guys would probably be able to tell me straight up.
Thanks for helping, I really appreciate it.
So I found my problem. My 1M grounding resistor (R1) is short circuited. It's a tiny little black one that I can't even read the writing on it let alone replace it.
Anyone know of an easier position for me to put another resistor as looking at it I very much doubt I can replace this.
They got it in there, therefore you can get it out.
Quote from: frankfurts
I think I may have found a problem with the input jack.
...
I found my problem. My 1M grounding resistor (R1) is short circuited.
Now hold on a minute here.I assume we are talking about R1/1Meg across the input socket?
A) you are aware that this socket has a shorting contact in parallel with R1, and that if an open lead is not plugged in to the socket the input is
shorted?
B) Shorted 1Meg resistor is quite unusual in itself, and cause for a few moment pause. Is it burned up? If so, how much voltage would it take coming in the input to fry a resistor of this wattage like this?
If this is not a mistake but a real failure, then it has profound implications for the components surrounding, not least the first op-amp.
But this now seems to be working okay now you say?
My intuition is that this diagnosis needs to be revisited in more detail. 8|
If this socket solders directly onto the PCB, have you carefully gone over its solder connections with a lens and a bright light? With modern gear this is a primary fault zone.
Ok cheers didn't realise about the shorting resistor I only read about the 1meg grounding one so that makes sense I'll go over the solder and might just touch it up anyway.
Well it's fixed :) I resoldered all the connections and put it back together and it's sounding perfect.
Really appreciate the help you guys and being patient with an idiot like me.
Cheers