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Messages - EDWARDEFFECT1

#121
I WANT TO BE ABLE TO TAKE THE CIRCUIT BOARD OUT OF AMPS WHEN I WORK ON THEM AND BE ABLE TO POWER THEM UP FOR SIGNAL TRACING WITH AN OSCILLOSCPE AND NORMAL MULTIMETER TESTING WITH THE BOARD OUT OF THE CHASSIS SO THINGS ARE EASIER TO MINIPULATE.WHAT  EQUIPMENT DO I NEED TO ACCOMPLISH THIS.THANKS!
#122
anyone have any ideas what is wrong with my hartke gt60.it plays perfectly and is dead quiet till you turn up the reverb knob.when the knob is turned up any amount at all the amp gets a loud hum in it which gets louder as you turn the reverb knob up louder.i tried putting a shorted 1/4" jack in the input and foot switchable reverb jack and it didn't help. i also reflowed any solder joints that looked like they might be bad.i also noticed now that the amp is not switching channels since i took it apart for the second time(bad switching transistor?)amp stays in dirty channel.does anyone have a schematic for this amp or know where to get one as it would probably help me alot....thanks...ed
#123
Tubes and Hybrids / Re: OP Amp question
August 27, 2010, 01:44:07 AM
hi sounds like this thread is right up my alley for a question that is simular. i was fixing a dead channel on an 808s mackie pa.i replace one op amp and it still didn't work so i replaced a second one in the signal chain and the channel now works, but you can't turn up the channel volume much because the channel is extremely hot now.you probably would blow out the speakers with distortion as it is really a mess.is this a feedback problem???...thanks!!
#124
thanks cool!!............ed!!!
#125
found the power plug wired wrong! i now have voltage going to the ics.replaced the output chip ,but haven't tested the amp yet...still wish i could find a schematic.anyone have any ideas?...thanks..ed
#126
hi enzo could you be more specific what you use for test equipment for these tests.example.ripple(oscilloscope??)bypass capacitor passing dc.coupling cap (multimeter???)also if using an oscilloscope do you put it on ac or dc.just wondering if you could give me the lowdown.thanks! enzo and all others on this site for being able to help us all out with our troubleshooting.i see there are alot of others looking at this post and i think they have the same question ,but are afraid to ask...thanks for all your help everyone.....this is the best site on solid state amps on the net!!! love it.....ed!!!
#127
The Newcomer's Forum / johnson jt50 mirage schematic
August 12, 2010, 02:00:59 AM
does anyone know where i can get a copy of a schematic for this amp.i am getting about 86 volts on the power plug connections?120 volts at the plug.not getting any voltage on the ic v+....thanks...ed!!
#128
i fixed one with the same problem.it is a very common problem with this amp. the resistor burns out due to bad solder joints on the heavy heatsink next to the resistor.the heatsink lets the resistor take all of the current instead of sharing.....good luck....ed!!
#129
anyone steer me in the best way to check electrolytic capacitors in circuit?esr meter,oscilloscope,capacitance meter,voltage readings,ect.what type of pattern would you look for with an oscilloscope?bypass caps,filter caps,coupling caps.any help appreciated.what is a better capacitor meter the sprague to6a or the sencore c55..what do you reccomend for a meter or testing?or should i say what do you do and use??...thanks....ed!!
#130
thanks everyone for the help. i followed jm fahey's advice and signal traced the circuit with my oscilloscope and got the static fixed. it had a bad 10uf capacitor. nasty little bugger.alot ceaper than a $300.00 plus board.the unit works like new now.i new i had it fixed when i got a square wave pattern out the output that was uniform....thanks again!!!...ed!!
#131
Quote from: EDWARDEFFECT1 on July 21, 2010, 06:15:51 PM
here is a tough one . i know this is an amp forum,but i am having a problem with static crackling noise in a gr20 roland guitar synth.you can't get a shematic from roland for it.i'm not sure where to send a signal into the midi connnection so i can signal trace with an oscilloscope.anybody had a simular problem or have any ideas.the unit works great in all other areas. it just has alot of noise.the guitar and pickup works perfectly with another unit.the midi chord is good and there is a new input board in it and it didn't make any difference. don't see any cold solder joints.....any help appreciated.i thought this would be my best place to get a fix for this unit.as i have delt with this site in the past and rate this site as the #1 elcectronics knowledge base on the net!!!....keep rocking....thanks...ed!!
#132
here is a tough one . i know this is an amp forum,but i am having a problem with static crackling noise in a gr20 roland guitar synth.you can't get a shematic from roland for it.i'm not sure where to send a signal into the midi connnection so i can signal trace with an oscilloscope.anybody had a simular problem or have any ideas.the unit works great in all other areas. it just has alot of noise.the guitar and pickup works perfectly with another unit.the midi chord is good and there is a new input board in it and it didn't make any difference. don't see any cold solder joints.....any help appreciated.i thought this would be my best place to get a fix for this unit.as i have delt with this site in the past and rate this site as the #1 elcectronics knowledge base on the net!!!....keep rocking....thanks...ed!!
#133
got the amp working. it had a cold solder somewhere on the board.i measured the temperature with a infared temperature gun and got 170 degrees on q11 transistor.when i touched it with my hand there is no way it was that hot. played it 4 1/2 hours with no quit, so i put it back together and it is ready to rock....thanks for your help again.....just thought i'd let everone know what was up...latter....thanks....ed!!
#134
any ideas! i have a fender fm65-r amp that plays for about an hour then it turns off for about 10-15 seconds.then it starts up playing normally for a bit then cycle off and back on again.like a computor loop.when it starts up after quitting it starts low in volume and gets louder as it comes back to normal playing volume.just like an amp that is initially turned on.i replace 2 transistors as they were getting hot to the touch. i thought they might be leaking,but guess that wasn't it.do you think it might be an output chip?anyone had this problem with this model?how do i test for a bad chip.i have a signal tracer ,scope ect.i replaced a 1013 and c 2383 which are larger in size than the other chips on the board.thanks...ed!!!
#135
these chips are in a kustom L1 amp.i have jrc4558 chips ,but seem to have a problem getting the right chip for a 739 ic.i get signal to the chip ,but nothing is coming thru it.....any help appreciated.i bought a new chip for it. mouser gave me a nec 7411 chip to replace it. i don't think it is working right....thanks...ed!   again sory for the caps....ed!