Line 6 HD-147

[ricach]

No output to speakers however output to headphones. Requested schematic from Line 6 and received the expected "send to authorized service repair shop". I suspect the power PCBoard is fryed since this is apparently a problem with this amp, (but Line 6 is not going to sell me that board either). Can somebody help me out here with a schematic or avenue to purchase the power board? Thanks in advance.

[J M Fahey]

Ouch!! An *expensive* amp.
Don't have the schematic but if I had it on my bench, I'd first check power transistors and their drivers for shorts, replace them (plus any visibly cooked resistors and wirewound emitter ones, just in case) and plug the amp into a bulb limiter, no signal, no speaker connected.
It might be enough.
Living in Argentina no authorized service center available, so my second option would be to junk the dead power board and somehow mount one of my own 300W boards (or an aftermarket one) and feed it from the original PSU.
Remember that the Power Amp is not much more than an add-on controller hooked between the PSU and the speakers.
I bet your main rails are around +/-60 to +/-75V.
A third option and to avoid junking it, would be to use it as a preamp to drive an external Rack type Power amp.

And of course you always have the basic option: sending it to an authorized service center.

[Gtr_tech]

Line Sux.

[ricach]

Diving into this thing without schematics. What fun. This amp is stereo, with no output to either side means what? (good output to headphone jack). Where do I start? There are no visibly cooked parts. When it comes to ss amps I'm pretty new at this so how do I check if the power transistors are fried. There's several, maybe 6 or more.60

EDIT: Looking at the voltages going from the power supply to the power output board, there are 6 wires, one being ground, the others are reading 0.1mV, 50mV, 50mV, -150mV, and -150mV (all DC). This is under load. (With cable disconnected I'm getting about half those voltages from the supply) I would expect to see a lot higher voltages than that? Can someone tell me what I should expect to see. Keeping in mind the preamp sections works as it should, the power supply is not completely shot if that's the case. So where might the culprit be if it is the power supply?

[ricach]

I've got a schematic now thanks. to Sell Files Online: Affiliate Program, Software Downloads, Digital Downloads.
Here is the section of the power supply that supplies the power amp. The outputs as stated above are obviously too low, although the schematic does not give an expected value. Just +Hi, +Lo, -Hi, and -Lo. The transformer T5 is an ICA-0617, and the Inductor L2 is a ICA-0831. It's next to impossible to get reading on any of these components without further dismantling the power supply. Since all the outputs are so low, I think the problem must be in either those two components since they are the only components that could effective everything. At least thats how it appears to me.

[Jazz P Bass]

That image appears to be the secondary of a switch mode power supply.
Can you post the primary side.
That may be where the problem is.
There may also be a separate power supply branch for the preamp.
That is why the preamp is working but not the power amp.

[J M Fahey]

Agree and add: yes, it is a SMPS.
The power amp is probably class G or H , that's why it has separate Hi and Lo power rails.
Judging from the capacitor ratings (63V and 35V) It might be around +/-45V and +/- (extra) 25V or thereabouts.
Remember I had earlier estimated around +/-60 to 70V rails, in a conventional amp, because that's required for 300W into 4 ohms, which I think is the head rating.
That said, with a hand over my heart, I think this amp is unrepairable, as/is.
SMPS + complex power amp + lack of info + Line 6 being famous for bad Tech backup point to that.
Personally I would use it as a preamp and drive any regular good old school rack power amp (Peavey CS400/800 or something equivalent) which by the way will sound *much* better.
I would only try, as a last chance, to get the whole new SMPS from Line 6 (yes, they don't repair it either, just replace it, much cheaper for them), but I wouldn't hold my breath on it.
Or, as we say in Argentina: "mejor espero sentado" ("I'd rather sit to wait") or "te va a crecer la barba" ("your beard will grow waiting")
Sorry.

EDIT: this is what a user posted one year ago. Situation grows harder along time, not easier:
I bought the amp 2nd hand and it was broken slightly, there was a fault in the power board which had to be replaced for £150... Yay... But ever since Line 6 fixed it no problems. One thing I must say is that Line 6 customer service is s*** on the phone, I rang up MANY times and could never even get through! This was when I was trying to get it fixed. I ended up taking to the Neville Brothers in Derby who then managed to get in touch with line 6.

[ricach]

That image appears to be the secondary of a switch mode power supply.
Can you post the primary side.
That may be where the problem is.
There may also be a separate power supply branch for the preamp.
That is why the preamp is working but not the power amp.

I'm going through the schematics and I can't find the primary side, or rather the circuit that references the primary side. I have figured it out that this is a 'switcher' because of the small size of the transformer. But, it doesn't appear they included that schematic. I need to reduce the size of the file (14MB) before posting it.

Voltages on the 'housekeeping side' of the power supply checks out with the schematic values.

[g-one]

Sometimes I forget to always check electrotanya , they have the schematic for free. LINE-6 HD147 SCH Service Manual free download, schematics, eeprom, repair info for electronics

[J M Fahey]

I'm going through the schematics and I can't find the primary side

I downloaded the Elektrotanya one, I guess it's the same as yours.
You posted the "secondary power section" on page 11.
Just to its left is "primary power section" which turns 120VAC into +/-170V rails for the switcher (Q3/4/5/6) which are transformer driven through T3b/c secondaries.
Find where T3a sits and who's driving it (I got tired searching).
Anyway I still find it a little too much for home repair.
Even official service shops find them tough .

[ricach]

I downloaded the Elektrotanya one, I guess it's the same as yours.
You posted the "secondary power section" on page 11.
Just to its left is "primary power section" which turns 120VAC into +/-170V rails for the switcher (Q3/4/5/6) which are transformer driven through T3b/c secondaries.
Find where T3a sits and who's driving it (I got tired searching).
Anyway I still find it a little too much for home repair.
Even official service shops find them tough .

Juan, I have looked at that Primary power section 20 times and never saw the 170V rails, and the T5 primary marked. Until now.
Thanks. Now to find T3 ............

As for it being too much for home repair - I can always chalk it up as a learning experience. I've never worked on a switcher, much less SS power amps.

[g-one]

Maybe I'm off base here, but doesn't the fact that the preamp is ok mean that at least part of the secondary is good? Does this not imply the primary is ok?
Ricach, can you check what DC voltages are running the preamp, and where they are coming from in the secondary of the power supply?

[ricach]

Maybe I'm off base here, but doesn't the fact that the preamp is ok mean that at least part of the secondary is good? Does this not imply the primary is ok?
Ricach, can you check what DC voltages are running the preamp, and where they are coming from in the secondary of the power supply?

What they call 'housekeeping section' in the power supply schematics is what drives the preamp section. all those voltages check out ok. as well as all functionality of the preamp section as heard through headphones.

[g-one]

Thanks! I'm on dial-up today so I was able to locate the schematics but have been unable to download them yet, was just going by the secondary drawing you posted. So now I know there is a separate supply for the power amp .

[Jazz P Bass]

As for it being too much for home repair - I can always chalk it up as a learning experience. I've never worked on a switcher, much less SS power amps.

Please do some research before you dive into the SMPS.
The Primary is HOT to line voltage.
The 'ground' reference is the -170 volts point when attempting any voltage measurements.(on the primary side)
The secondary is totally disconnected from the primary (sort of) so voltage readings there can be referenced to chassis ground.

[ricach]

Please do some research before you dive into the SMPS.
The Primary is HOT to line voltage.
The 'ground' reference is the -170 volts point when attempting any voltage measurements.(on the primary side)
The secondary is totally disconnected from the primary (sort of) so voltage readings there can be referenced to chassis ground.

What role does Q5 play? The line voltage hits that before the Primary side of the xformer. Feel free to explain switching technology to me.

BTW Juan: T3 primary is shown in the Primary Supply Diagram, at the very right of the diagram. Q5 &Q6 drive it.

[J M Fahey]

Dear Ricach:
no, that is secondary T3c and it drives Q5/6 , the same way as secondary T3b drives Q3/4.
I'd love to find T3a which I guess is the primary.
I find real stupid spreading the PSU over several pages, real STUPID.
It should be all together on a single page.
If they need to make that page tabloid newspaper size, so be it.
Worst is the PSU designer must be thinking "hey"" , it's EASY !!!! "
Not only that, the amp itself is also a nightmare to me.
Funny thing is, *my* 300W amp also uses 4 x IRFP250 , has 1/4 the parts count and works like a charm ... and can be repaired
As of the switcher: thge 120VAC gets rectified into 170V DC, so C36/37 get 85V each.
Q3/4 and Q5/6 form a "half bridge inverter" providing a 170Vpp squarewave to T5 primary.
It has a lot of secondaries which get rectified by high speed dual diodes, seen on the secondary side.
I guess (too tired/bored/angry to check) that there is another smaller PSU which feeds the "logic/control" part of this PSU and also powers the preamp.
I also guess that *maybe* the main PSU is fine, but the power amp is dead and some sensing circuit is shitting its power off.
As you see, way too many unknown variables.
I'd unhook the power amp and check whether those "Low" and "High" rails reappear.
You *might* get lucky.

[ricach]

Juan, if you see one of my early threads I did check the voltages with it disconnected from the power amp. It was about half. half of about nothing is pretty much nothing. lol.

[ricach]

I think my logical next move is to take voltage readings from the primary side first.
After the first full-bridge rectifier, should I see AC anywhere on the Primary side?
What do I use for a ground reference? -170V rail?
Should I see 340V from hi to lo rail?
Where should my scope pick up a squarewave?
What other expected results should I see?

If this all checks out, then next logical place is the secondary. But I already know coming off the half-wave rectifiers on the secondary side I have little to no voltage. These half-wave rectifiers are seperate from each other - they all can't be bad. But the secondary sides of the xformer is (obviously) one component, as well as the 4 inductors being one component. If primary side checks out ok, then it HAS to be a faulty xformer or inductor. Correct?

[J M Fahey]

Consider *nothing* on the primary side is Ground.
*Everything* there is hot, so you can't connect a scope there or any other instrument.
You can only use a multimeter , very carefully, as if you were checking a live appliance, which is exactly the case.
You can only check that you have 170V from the top of C37 to the bottom of C36.
You will not be able to check for oscillation on the transformer primary (20KHz to 100 KHz possible) but you already know that indirectly because you heve not DC on the secondary.
Anyway, supposing you have the primary 170V, my real suspect is that those MosFets are not being driven, simple as that.
Why?
Either the driver stage has failed or more probable, has auto shut down because of some other problem it detected.
With amp unplugged, check all diodes on secondary side.
Even one of them shorted should turn the PSU off.

[ricach]

Anyway, supposing you have the primary 170V, my real suspect is that those MosFets are not being driven, simple as that.
Why?
Either the driver stage has failed or more probable, has auto shut down because of some other problem it detected.

This is what needs further explanation for me. What driver stage? What has auto shut down? Is all the switching done on the primary side? Do I assume the secondary follows all the normal rules? Are is there logic elsewhere still making the decisions for the secondary side as well?

[J M Fahey]

Yes, of course.
A conventional PSU has a very simple primary side because the transformer works with the power line AC voltage and a simple secondary stage with diodes and capacitors.
A SMPS is very complex.
It first rectifies wall voltage, then switches it at high frequency then a special transformer and rectifiers, *but* the switches are driven by a circuit which not only does that, but also controls and regulates ouitput voltage, and adds safetry featuresm such as soft turn on and short protection.
I have not found this 3rd stage, although it obviously is there.
What I *hate* is that the SMPS is split and spread over many pages.

This is a very simple SMPS:

Look at the grey rectangle labelled Control Drive SMPS IC

[ricach]

Now I'm beginning to understand why you are preaching 'doom and gloom' in regards to this SMPS.

[Jazz P Bass]

Here is a previous post to help with the SMPS theory.
The Principles Of SMPS
As to the Line 6 schematic, page 10 is the SMPS 'hardware' & page 12 shows the 'drive logic'.
You can see many points on the drive logic schematic that can 'shut down' the main switcher.
So not only does the main switcher have to be sound but also the drive logic.
I have removed the main switcher mosfets already when trying to track down a drive problem.
Less chance of going poof.
I have noted an 'Enzo trick' where you mearly pass the scope probe over the primary transformer to see if it is doing anything at all.
By the way, we are talking somewhere around a 50K switching frequency when all is working.

[J M Fahey]

Thanks JPBass (and thanks to Enzo for his invaluable capacitive test Enzo trick of the day).
Different to most (99.9%) modern SMPS which rely on a dedicated Controller IC (which, worst case , can be swapped) ; Line 6 chose to make a discrete Controller which only they understand.
This one has over 40 (forty !!!) Test Points (TP1/2/3 .../42 and counting) which obviously are needed to check some aspect or another.
Clearly indicated are a Current Sense and 2 DC fault sense , one per channel, which will turn this amp off if they don't like something, but I'm sure there are other internal watchdogs doing their job.
Of course, it *is* repairable, and there are guys who make a living out of this, but they have learned along time a very specific set of skills.
Is it worth learning them yourself?
Just as an example: imagine a $1000 thingie is broken, and you have a service manual ... in Korean ... and it can't be machine translated because it's a .jpg or something ... will you learn Korean for that one repair?.
Worst of all is that I'm sure Line 6 provides (or used to) a full board replacement, and not even the official service technician repairs it at component level.

[Enzo]

On that secondary side, I see four dual diodes. Are ANY of them shorted anode to cathode on either side?

Your SMPS is not running. One of the most common reasons for that is a shorted rectifier.

And I just have to chime in that the SMPS is EXTREMELY dangerous to work on. On the primary side, there is no "ground." A schematic might use a ground symbol, but it refers to the -170v rail. These things rectify and filter the mains DIRECTLY. That means either 170 or 340vDC at all the current the wall outlet has to give. You cannot connecty your scope ground to it. You really need to use an isolation transformer to work on it.

[ricach]

First of all I'd like to thank all of you for taking the time to help, and/or dissuade, me. My hope/intent was more to learn about SMPS in general, and not this apparent 'mandarin chinese' version that only LINE 6 can understand. lol.

Enzo, I have not had time to check those diodes.

Is it normal to still see voltages (however small) at the outputs even if the logic has 'shut down' the power? And remember that those voltages are different (by 50%) depending on whether its connected to the power amp or not.

LINE 6 will not sell me a SMPS. Only to an authorized service place. I plan to contact one and ask (nicely) if they would mind purchasing one for me. Does anybody have a good working relationship with one of these?

[Jazz P Bass]

Well it has not been determined if the SMPS is at fault. (or the only fault)
There may be a problem with the power amp itself.
I realize that the power amp header was disconnected but this in itself does not 'prove' that it is the smps that is at fault.
There may be a signal that is required 'from' the power amp to the smps.
Just a thought that I had when I saw you that were looking at purchasing a new smps.

[J M Fahey]

Just *suppose* Line 6 sells you a brand new SMPS for U$ 200 .
You hook it up and it shuts off ... because the (unrepairable) power amp is dead (the original failure).
Another $200.
The amp can be bought on EBay (working) for about $400.
Tough decision, huh?
This is something I posted in another Forum, where I'm trying to help a guy with a dead Line Spider IV, 120W 2x10" combo:

Personal opinion: I'm seeing it more and more all over the place: wonderful programmable amps which because of any, often minor problem, have to be junked, because, of course, info is unavailable and even if you get it, it's too complex to be used.
I'm getting into the mindset that the sensible option is to get a multi emulator *pedal* or POD and plug it into a regular amp.
Failure of one does not kill the other, separate parts tend to be more robust and worst case, one dead means you can still play with the other and save the night.
POD dead?: plug straight into the amp and play somewhat simpler, less effects.
I bet the *music* won't suffer that much.
Amp dead?: plug the POD straight into the PA.

While in the full digital combo amp, any problem means very frustrating not playing at all.

[Enzo]

Forget this 50% stuff. If a 40v supply is sitting at 5mv or 10mv is irrelevant, it is not at 40. SOme tiny residual voltage doesn't matter if it changes by "50%."

If a SMPS tries to start but can't, there is often a small spike, which is enough to put a few millivolts or whatever into the filter caps.

Imagine you all come out to your car, and the tire is flat. Really flat. Now the rest of your family goes ahead and gets into the car. Your flat tire is now even 50% flatter. The important fact is that there is no air in the tire, not the dimension of the squished rubber.

[Enzo]

Forget this 50% stuff. If a 40v supply is sitting at 5mv or 10mv is irrelevant, it is not at 40. SOme tiny residual voltage doesn't matter if it changes by "50%."

If a SMPS tries to start but can't, there is often a small spike, which is enough to put a few millivolts or whatever into the filter caps.

Imagine you all come out to your car, and the tire is flat. Really flat. Now the rest of your family goes ahead and gets into the car. Your flat tire is now even 50% flatter. The important fact is that there is no air in the tire, not the dimension of the squished rubber.

[ricach]

Forget this 50% stuff. If a 40v supply is sitting at 5mv or 10mv is irrelevant, it is not at 40. SOme tiny residual voltage doesn't matter if it changes by "50%."

If a SMPS tries to start but can't, there is often a small spike, which is enough to put a few millivolts or whatever into the filter caps.

Imagine you all come out to your car, and the tire is flat. Really flat. Now the rest of your family goes ahead and gets into the car. Your flat tire is now even 50% flatter. The important fact is that there is no air in the tire, not the dimension of the squished rubber.

Enzo, I'm sure you'll agree that there are many circumstances where such 'little' things can help indicate where the problem might lie.

Patient: Doctor, it hurts worse when I do this....
Doctor: Then don't do that.

[Enzo]

Yes, of course, there are many times when tiny details matter. Not faulting you for being thorough. Just urging to put the data into the larger context.

[km6xz]

I am not happy working on Line 6 since I usually can't get parts and they are so flimsy that mechanical parts are often needed. I am not familiar with this amp because it was built soon after we stopped working on Line 6, being the first outside warranty station for them when the company started.
This is a case where many of the symptoms are good signs or bad, but telling the difference takes studying the schematic a bit. This amp has 2 independent power supplies as has been discussed. The high current power supply is either shut down, or not starting but the low level supply is working fine. When first turning it on, is there a pulsing in mains current, a small regular peak and drop of current draw?
For the complex fault detection circuit to run, it needs at least a short duration presence of supply voltage before it decides to shut down the power supply or shut off the gate drive to the output section. If there is a short in the secondary of T5 there will be a pulsing but a bit higher current. You should be able to see that with the scope on any point in on the secondary of T5. If there is no spike in current from cold start or pulsing while on, the inverter is not firing up at all so the problem is early in the primary of the larger power supply. There are shut down lines that give the signal to stop the power supply, pin 6 of Header 3. There is also a Sense pair coming from the Secondary of T6 going to Header 3 pins 1 and 2 that samples current through the primary of T5. readings of those points will tell you a lot, if it is trying to fire up or if the primary of T5 is just dead. If if it is just dead, there are only a few things that would prevent any current flow and those can checked with it unplugged from the wall and an ohm meter such as the primary of T5 being open, the power MOSFet driver bad etc. If you are seeing activity on pin6 of the header connector, the supply is being shut down for safety reasons. The power supply control circuit monitors all sorts of parameters and any one of them can trigger a fault: high temp, DC offset, high current in several different circuits, excess voltage in the secondary....
Try those listed first steps, all on the secondary side of T5 so you can measure with your scope ground clip on ground without blowing it up.

If it appears that the main supply is being shut down, it is not terribly difficult to figure out the sense trigger that is disliking what it sees.
If it is simply a shorted diode as Enzo pointed out, on the secondary of T5(very common, they lead a hard life) expect to see some pulsing of primary current.
Good luck.
By the way....did I mention that I HATE Line 6? When you buy one of their systems that connects to a computer, anything, they remotely control when and if you can use it, how many items at a time you can use, on which computer it can be used etc. I recommend everyone avoid Line 6 and buy real equipment.

[ricach]

Thanks for the suggestions. Unfortunately I have other pressing problems but will get back to this Line 6 soon. I really appreciate the time and thought that has been put into this issue by all. Thanks again.