Line 6 Flextone help

[pchilson]

Today I was given what I believe to be an original Line 6 Flextone amp. It says made in USA.
The guy that gave it to me said it "screeches", you'll see.
I have had it fired for only a short time and when first turned on it seemed to be working normally, no screeching and nothing abnormal about the sound.
After it was on for a time and warmed up some the sound started to deteriorate. Hard to describe it but kinda like out of phase or something, like if your G and B strings are out of tune kinda crappy sounding. It did not screech on me but I've not had it on more than about 5 minutes so it may still do that.
I don't know the age of the amp. I don't have any pics at this time. I don't have a schematic of it.

Can anyone give me a starting point?

Thanks

[Enzo]

Does it have an FX loop? Or maybe preamp out and power amp in jacks? If so, then send the preamp out or FX send signal over to some other amp to listen how it sounds. Does it have the p[roblem over there?

Also, plug your guitar into the FX return or powr amp in jack. Does it sound clean or does it have hte problem.

We are trying to isolate the problem to either the preamp of the powr amp.

[pchilson]

Enzo,

Is there a schematic available for these amps?

Plugging the guitar straight into the Return jack of the FX loop I hear the same "bad" sound.

Running from the Send jack of the FX loop into another amp it sounds "as it should" from the other amp.

That is pointing to the power amp side of things then I guess.

[Enzo]

They don't give out schematics, I have none. Maybe someone else does.

OK, so it is the power amp. What does the PA look like? Is is a multileg IC like a LM3886 or a TDA7293? If so change it. OH I suppose we could scope the input leg to see what it is getting, but my lunch money is bet on a bad output IC.

Did Line 6 ever build discrete power amps?

[pchilson]

They don't give out schematics, I have none. Maybe someone else does.

OK, so it is the power amp. What does the PA look like? Is is a multileg IC like a LM3886 or a TDA7293? If so change it. OH I suppose we could scope the input leg to see what it is getting, but my lunch money is bet on a bad output IC.

Did Line 6 ever build discrete power amps?

Here is whats in this one.





Last time I bought ICs online I got the wrong package type. Don't want to do that again.

At Allied they show the LM3886TF as "non-stock" but the LM3886T as in stock but that isn't the same name. Will this one work or do I need to find the LM3886TF version?


Mouser shows the LM3886 as a cross reference to the NTE7197.

Neither site shows a picture of the IC. Can someone point me to the correct part to order?

Anything else I should consider replaceing while I'm ordering? Electrolytics?

Thanks

[pchilson]

Ok, nevermind on the link to a LM3886TF. I've found plenty.

[Enzo]

LM3886 and LM3886TF are electricaly the same thing. The TF version has the all plastic tab and is isolated - you don't need an insulator with it. You could replpace the LM3886TF with a plain LM3886, as long as you added a mica or silicone insulating washer and a plastic shoulder washer around the mounting screw. I take the trouble to get the right part.

Stay away from that NTE junk. If you got the LM3886 cross and the LM3886TF cross from NTE, you'd find the same part number, and it wouldn;t be insulated.

But mainly, Mouser shows $14 for the NTE thing, while Digikey has plenty of stock on the actual LM3886TF for $7.

Verify that your LM3886 has power supply getting to it. COnnect a speaker and touch the 3886 input pin with a meter probe or a small screwdriver. if hum comes out the speaker, then it is working. if silence, then it is not.

And on the off chance, look on the 3886 data sheeet for its mute or standby pins and verify the thing is not being muted.

[pchilson]

Ok, got the LM3886TF part ordered from DigiKey. Will see in a week what the outcome is.

[pchilson]

Have had a lot going on and haven't gotten back around to this one. Will be awhile before I can get time to work on it.

[doctor]

Enzo,

Is there a schematic available for these amps?

.

i happen to have seen this only now.

hope it helps even though it's a month late.

[pchilson]

doctor, thanks for that.

[gmichalak1]

Line 6 Flextone 3 Schematic Request

I downloaded the schematic, from this site, however, it is not correct for the unit I have. Does anyone have a Flextone 3 schematic for the units that use the TDA7293 audio amp chip? I had one burn up, and replaced it, but I also have a transistor the burned up, and I believe it is used to mute the chip, during power-up.

Here is all the specific P/N info:

Flextone III P/N 41-00-1028 Rev. E

(21) FT31A5321000248

614252013710

Gary

[Jazz P Bass]

Tda 7293

Here is the TDA 7293 datsheet.
The basic hookup is shown real well.

[gmichalak1]

Thanks. I already replaced the TDA 7293. I need the schematic, because when the 7293 blew, it took out Q4 and possibly Q3. Actually, if I just find the part numbers, for these transistors, that would probably do the trick. I'm in the business of repairing guitar amps, but sometimes the manufacturers of the amps make it very difficult to obtain schematics.
Gary

[gmichalak1]

I forgot to mention that Q3 and Q4 are on the main board, and control the mute function of the 7293 during power up/down.
Gary