Ampeg BA-115 help needed

[shooter]

anything when you plug in headphones?

[smackoj]

I am getting guitar thru it now but the signal is distorted. I guess maybe I need to go back and check all the transistors again?

[shooter]

getting guitar thru it

speaker?

if so, how does the loudness seem?
you got an old cd player, something you can jack into the CD in and make sure your issue is on page 2 of the schematic? Looks like if you can jack in you want the Master Vol at 0

[smackoj]

Yes, I'm running it thru a speaker. Loudness seems about right to me. I will see if I can find the stuff to do the CD test.

thsnks Shooter

[smackoj]

Ok Shooter; the CD test is done. It was playing so loud that it way over driving the speaker. None of the vol. controls lowered the vol. so the music was good and loud but distorted. therefore, I don't know if the distortion was in the signal or just from the high vol.? My best guess is that it was running all 100 watts thru my 6" car speaker and just well over what the spkr could handle?  What's next?

thanks, jack

[shooter]

just from the high vol.?

whatever input you use also needs it's own volume, sorry, shoulda mentioned that.  I can definitely over drive my amp with the CD on max. 

EDIT: You also have a line out to plug into, something?

you have a scope?

[smackoj]

my CD player is a real basic one (actually a DVD/CD) with no vol. control. And NO I don't have a scope.

jack

[shooter]

so is your guitar distorted at low volumes, or only when cranked?

[smackoj]

hi shooter; yes, distorted at low or high. I have a problem with the pcb. the solder pad has deteriorated under te N channel mosfet and I am uncertain how to proceed? I am sure that Loud Technologies probably skimped on the thickness on the pcb to make money off of a low cost amp. So, I'm going to take a few more hours and see if it's repairable? I have my doubts but I'm willing to try.

thanks, jack

[smackoj]

Well pardners I have to call the fight. Throw in the towel and let the fat lady sing. The flimsy pcb has proven too much for me. Ampeg aka Loud Technologies made this amp like all the other low end electronic gadgets on the market. If it breaks, throw it away and buy another one. The N-channel mosfet pads are shot and the mosfet won't make good contact anymore. So, I'm going to count my blessings and be glad that I learned a lot with all the attempts. Thanks everyone for your effort to help me. The learning experience has made me wiser if not smarter. 

[shooter]

I learned a lot

That's what I like best!, glad you didn't get frustrated and gain no knowledge.  If you're truly into pain, you can rtv the fet and use 24-26ga solid wire and probably get it, but sometimes as you said;

Throw in the towel and let the fat lady sing

[smackoj]

hey shooter; could you tell me where on the schematic would be a good place to take off the preamp signal? I still might try to use the preamp section to run a nice hefty Allen organ amp I picked up. I'm not sure how I would convert a plus and a minus signal into one wire for the input to the slave amp? This amp doesn't have a "preamp out" jack like most of the more expensive SS amps.

[shooter]

a good place to take off the preamp signal?

on sheet 2 there is a balanced line out, that is basically "preamp out" 

[smackoj]

yes, I see that on the schemo. That should be an easy test to see if the preamp has a nice clean signal.

thanks

[shooter]

You'll have to do a little surfin on balanced line out, there is no "DC" ground there, just AC ground, not sure if that's a problem.  I believe you have 2 inverted signals so you probably want to grab just one unless your PA have a balanced line in.

[smackoj]

senor shooter; hi. I spent another couple hours today making a signal jumper from the 'line out' xlr to the SS Allen amp. It had too much hum at working volume so I took some pictures and put it on ebay as "broken for parts or repair"  I thought about taking the signal off of R25 which is right before the 'line out' circuit, but I'll wait a few days and see if anyone else wants to give it a go. I really thought hard about trying to fix the traces and pads but I've spent so much time on this one that I'm leery of investing any more.

thanks,  jack










































r25