ADA Depot - A Forum To Support Users of ADA Amplification Gear
Let's Get Technical => Troubleshooting Problems => Topic started by: W.Laturno on January 27, 2014, 02:02:12 PM
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I've finished swapping out the R913 and capacitors - no more motorboating -
now it's like the clean voicings 1-6 are super overloaded - the RED LEDS light up like a Christmas tree.....
I started replacing the original caps back ( all the polarities were correct BTW ) and was about 95% done ( testing each time before moving on to the next one ) when C907 blew up !
:hair-out:
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Picture added ....for effect,,,
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Hi Will, it made a bit of a mess :-\
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Gents - If possible, please reply -
What is your drive setting on voicing number 1 Sparkly Clean ?
Right now, when I goto the preset channel 12, it is very very loud and distorts if I hit a full chord....
It is not quite so bad if I lower the DRIVE to about 0.....but this does not seem right
thanks -
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Hi Will, this is Patch 12 in my spare MP2 so the previous owner may have changed it from factory :dunno: , my other MP2 (which I know is factory as I never changed any of the default patches) is 2 hours away and I wont get to it for a few weeks. I'll do a factory restore later when I get some time and compare. BTW what are the EQ settings on your patch, The EQ can add/subtract a lot of gain.
Voice -> 1 Crystal clean
Drive -> 50
Master -> 50
Comp -> out
Lo: 0
Mid: 0
Hi: 0
Pres: 0
Graphic (all flat (0))
Wah -> out
Trem -> out
NR -> out
Ch -> out
Loop -> in (mix A 25% mix B25%)
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OK - Update ( 02-06-2014 ) - After (MANY) e-mails and such to MarshallJMP, I've come to the concluesion that when I did the noise mod I simply did not have both sides of the printed circut board (PCB) 2-layer solder 100% since when I pushed the caps all the way down there was no way for me to insure that the top layer was making great contact....sounds lame I know, but what can I say...the whole MP-2 is seems to be working very well now....after re-doing the mod with longer cap leads so I could solder both sides...
the clean issue I seem to be having is still strange....in order to keep the voicing one super clean, I have to lower the drive ( to about 0-15 ), I just don't remember it being that sensitive before....but I can get by for now.
:metal:
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Once again, MJMP saves the day
Thanks!
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the clean issue I seem to be having is still strange....in order to keep the voicing one super clean, I have to lower the drive ( to about 0-15 ), I just don't remember it being that sensitive before....but I can get by for now.
:metal:
Seems very strange, what are your MP2 eq settings (including graphic) ?
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Sorry for falling off the grid, rnolan- eq settings are all flat....I've been jsut trying to get as clean a sound a possible...So, since Feb I guess, the MP2 has been good - but at practice last night, , , , it went south again...
I'm going to have to plunge back into it and recheck if I used any of the original caps as well as check the voltages at the test points.....sigh.....makes me wonder....
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Bummer, I feel your pain/frustration. Are you using the compressor in the clean patch and if so what's it set to, it also can add quite a bit of gain ? drive 0-15 is very low, particularly when mine is 50 :???: for that patch, and my clean stage patch (see MP2 patches) is 37 but that's with compressor gain at 50. Also what's the input chain into the MP2 ? guit > MP2 ? and what pickups. Or are you running other gadgets before it as well ??
Cheers Richard
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What seems to be the problem?
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Seems ANY channels that had the compression ON - are now a complete waste ( 100% garble and muck sounds )....even the preset 12 which was suppose to be Compressed Clean. If I take and shut the compression off - - it cleans right up . . . amazingly too....
There (seems to me ) to be a lot of humm now.....
To appease, I'll go to a clean channel and keep the tone and eq at 0 ( flat ) - no chorus, no effects loop, no noise reduction, no wah, no compression - Voice 1 Crystal Clean, drive 15, master 79....nothing plugged into the unit ( no guitar cord) just one cable to my ADA microtube 200 and a single 30W celestion . . . audiable hummmmmm
Plug in my guitar ( Les Paul Shred stock pickups ) - and it's nice, clean and loud...but...hummming...
Change to voice 2 Spanky Clean - - same thing, with a bit, less hummm, but still there...
Voice 3 Fat Clean - nice - ....with hummmmmm
Voice 4 Vintage Brown and 5 - I hear no humm a lot less volume though...a lot . .
Voice 6 hummm is faint...
Voice 7 brings in the OD - I played with it . . even at 0 and the drive at 0 ( Master at 79 ) - it's garbage....worse sound ever...
8 - same . . .not even playing any notes, nothing plunged into the input, the green light stays lite on the Graphic EQ and Chorus . . . hummmmmmm
I can probaly re-work all my patches and live with this - I'll have to use the Noise Reduction for sure.....
but by no means can I turn on the Compression anymore....it just is a loud obnoxious bunch of garbled feedback...ughhh
So - having been schooled a bit by M_JMP - the first thing I did was measure the test point - 193.9 vdc ( a hair high...)
then I started to check my caps since I did the noise mod in March. .. I swapped out a few, but no real difference....
I am going to probably try some new tubes just to rule that out....it would surprise me ( though I haven't a lot of experience) if the new caps I installed a few months ago were to already be shot....
VCC1 = 5.09vdc
VCC2 = 15.24vdc
VCC3 = -15.49vdc
uh-oh.....suppose to 24vdc at pin three of U 906 (LM317T) . . .I measure 38.2vdc
U 901 (LM337T) @ pin three is suppose to be -24vdc I measure -38vdc
Filliment U 904 should be 12vdc - I get 11.8
sooooo - something is messing up the 24 vdc . . . feedback ( no pun intended ) . . . .
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U906 (LM317) pin 3 is the input and pin 2 is the output,so it's normall you measure +38V,measure on pin 2 what's the voltage there?
U901 (LM337) here is pin 3 the output and pin 2 the input,what voltages you have here?
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Across U 901 ( LM337T ) pin three I was getting -38vdc
I'll check back tonight when I am able to get a level on pin 2 ( input )
as well as re-check U 906 (LM317T) . . I had not paid attention to the schematic and noticed pin three was input...grrrrr :crazy:
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Hey Will, you'll get it sorted, new tubes can't hurt but your issues seem a bit more than that unfortunately. Between you and MJMP I'm confident you'll get it sorted.
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Anyway that 38V doesn't look good,could be that the LM337 is busted.This could be the reason of the hum.My guess is also that U205 and U207 are busted (OPA2604A),one of these is used by the compressor.Now i suggest not using the mp-2 until this problem is fixed.It also could blow up your input section.
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Ok - here we go:
U901 (LM337T) Pin 2 input measures -38.9vdc and pin 3 output measure -38.6vdc
U906 (LM317T) pin 3 input measures 38.7vdc and pin 2 output measures 23.7vdc
I seem to remember we discussed these U205 and U207 before.....
here is what I measure now:
U205 pin 4 -38.2vdc pin 8 +23.6vdc
U207 pin 4 -38.3vdc pin 8 +23.6vdc
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Ok seems like the LM337 is busted so replace it,also replace those 2 OPA2604A's just to make sure.
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So, last night I installed a new U901 (LM337 ) . . . had some trouble fitting my iron in the top side to insure the joint was soldered there ( it’s a tight fit )
I also believe C916 was loose so I took it out and re-did it . .
I had not received the new OPA2064A’s . . but I wanted to see if indeed now I would get -38vdc into U901 and -24vdc out, but it is still -38vdc out…
Perhaps I had too much heat on my iron and destroyed it while installing….(?) it is an adjustable temperature iron and I believe I have the dial set to around 350°C….
I am just wondering if maybe D901 ( across the in/out pins 2/3) of U901 is bad or something…..it just seems that the adjusting part of that circuit is not pulling the voltage down….or it is quite possible that during the noise mod, a certain cap has a bad connection (C903,4,or 5 ??)….this is possible, but I am grasping at options here…
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Hang in there Will, you'll get it done :thumb-up: , I get what your saying regarding the adjusting part of the circuit not pulling it down, that's where my thoughts would go in the circumstances also, I'm sure MJMP will throw some light on it..