Sorry i typed it wrong.  I have selective dyslexia lol.  It was supposed to be EBC on some when looking at the flat side, and others CBE on the same side.

I don't know what NTE parts are.  But i replaced the MPSA56 and MPSA06 (Q3 and   One was shorted and the other lost a leg in removal.  But the new ones were just the reverse of the originals.  ECB instead of BCE.  so they basically just had the flat side of the case on the opposite side.

Should i measure them in circuit or life one end and measure them that way?

P.S. i used new transistors the second time.  I ordered 15 of each so i had plenty to spare.  So i wouldn't think the new transistors would be the problem.

Enzo, you have any other ideas here?  I can't find anything else wrong with the dang thing.

One thing i forgot to mention.  I originally installed the new transistors backwards. The pinout is reversed from the original transistors.  The first time i powered it up( with the transistors backward, it oscillated like this, and nothing changed when i put the transistors in the correct way. 

So i guess this is not as fixed as i thought.  It worked fine with the transistors removed, but with the replacement transistors installed, i've generated a new problem.  There is now some sort of oscillation that starts a few seconds after powering up, and slowly works its way up in pitch.  I'v double checked all my soldering and everything seems to be clean and installed correctly.  I get sound throught the amp  but now the oscillation is there as well.  Any thoughts on what i might have bumped, touched, changed, screwed up, etc?  The original distortion prblem is gone at least.

If you want high volume and clean...your kind of using the wrong kind of speakers to start with.

-I never said i was going for clean.  but power amp distortion sounds like absolute crap.  Not quite the distortion i want.


Those are guitar speakers designed TO start breaking up long before getting to their power rating. Although adding MORE of the same speakers will give you higher volume at the same power level.

-I would love to add more speakers, but unfortunately all my money is currently being pooled towards a new classical guitar.


A power meter to me is not a solution...I've spent several thousand hours watching meters and indicators. They are good for telling you what just broke, not often preventing it.

-I don't really see it as protection.  I just want to use it to find out how much volume i can safely get out of my current setup






Additionally if you're using the Line 6 processing amp models cabinet models etc you probably SHOULD be using PA type speakers as guitar type speakers don't work that well with modeling...they are meant to change the sound (breakup etc)
-this i disagree on.  I have always gotten a much better sound out of the amp models by leaving the speaker simulations turned off and running through these speakers. But thats a whole other thread on its own. lol.


-Part of the reason i do not want to rewire my cabinet for a 32 ohm load is that i often use only one speaker (they are connected to separate inputs on the back) especially when i am recording.  I will only plug the amp into the one i am currently tracking so that i can hear what is going on more accurately, and so the mic only picks up that one speaker.  So i would love to keep it wired the way it is now. 

So aside from all the advantages/disadvanteages of a power meter, back to the original question.  Does any company currently produce one or should i just shop used?

They are 16 ohm version, which according to tech 21 would make the amp have a max output of 90 watts.  But it would clip at that, and don't clipping amplifiers kill speakers faster than anything?

http://www.tech21nyc.com/archive/powerengine400.html  - i have the 300 watt mono version of this

I have one of each of these in my 212 cabinet
http://professional.celestion.com/guitar/products/classic/spec.asp?ID=2  - rated 60 watts
http://www.hempcone.com/pro/store.html - its the 12"  ceramic tone tubby.  rated 50 watts

I would be using the meter to set the max output power somewhere around 90 to 100 watts (hopefully less, but i can't tell without a meter) so that most of my playing will be below the rating of the speakers, but can never exceed it.    I understand your point about the big swing in power, but i want to make sure my MAX volume does not exceed 100 watts at any time.

I'm looking for something to monitor the wattage that my amp is sending to my speakers.  Its very hard to find anything that's suitable, and doesn't have a bunch of extra features.  I play a digital Line 6 preamp into a 300 watt tech 21 amp, which powers 90 watts of speakers.  So i would really like to be able to tell how much power the speakers are getting.  I would love to be able to turn up more, but i'm afraid to blow my speakers.  Tone tubby's aren't cheap, and neither are celestion century's.  I've seen a few units like the radio shack APM units from the 70's, but is there anything in current production that does the same thing?  I prefer buying new rather than used for stuff like this.

ohms sorry i don't know why i didn't mention that.  And i wasn't sure about powering it up without that transistor, but i just checked it and no it doesn't work yet.  I checked the datasheet for that transistor too.  Its only supposed to read about 50 ohms between source and drain anyway so i guess thats probably within range.  Q1 appears to be functioning normally.

And there's the problem. It was either Q3 or 8.  I removed both and the amp works.  One of them reads as being shorted.  So i guess i'll just order those.  Is there anything else i might need to check that might have been the root cause of the transistor shorting?  or was it probably just a bad transistor?

q12 measures 1100 and infinite between gate and drain, and about 40 both ways between drain and source and 1090 and infinite between gate and source.  Sounds like a shorted transistor to me.  Am i right?

Should those zeners really be getting hot enough to make it smell like they're burning?  That really doesn't seem normal and the board is kinda charred underneath 'em.

Its tough to describe, but its not extreme.  About like a blown speaker probably would, but that's obviously not the problem.  And no i don't have a scope.  I have a scope program on my computer but i don't think i should plug the speaker out into the line in on my computer.  I'll try messing with those other transistors and get back to you.

All the voltages that i can find coming off of the power supply section (all 6) and voltages on the power transistors are right where they should be.  I can't leave it powered up for long because the same two diodes start heating up majorly.  I just can't figure out why.  There is no DC on the speaker terminals though.  

One thing that might be a hint is the two transistors just before the power transistors.  The base and emmiter appear to be shorted, unless something else in the circuit is throwing the reading off.  they are mje15030 and mje15031 tansistors.  One read 70 both directions between B and E in the diode test setting on my meter, the other read 120 both ways.  possible short?