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.

[g1]

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.

[g1]

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.

[g1]

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.