Solid State Amplifiers > The Newcomer's Forum
Gallien Krueger ML250 output issue
pmarchione:
it has a 4 volt ac setting, I bought the one you posted from radio shack. ill return it and get a different one from lowes. I get no reading from playing a guitar chord. ill retest the u18 u19 ic in the am after work and getting a better multimeter.
ill try this multimeter
http://www.lowes.com/pd_136122-12704-61-340_0__?productId=3127727&Ntt=mulitmeter&Ns=p_product_price|1
J M Fahey:
Incredible.
The user manual states it does have a 400mV scale, I attach part of it.
Please post the link to the Lowe one.
EDIT: I am re-reading the user manual, now I guess your multimeter *does* have a 400mV AC scale, but it has to be manually selected.
Otherwise it gets autoset in the "up to 600V" scale, which obviously is deaf to a 200 mV guitar signal.
Look at my corrected picture and try the following:
1) set the rotary selector to ~mV
2) push the Select button once so a nš "2" appears (I guess) indicating it will measure AC (or the letters "AC" or a "~"symbol) Hate this stupid manual.
3) press the "Range" button once so the "Auto" label dissappears, then push it again 1 or 2 times until the screen looks like the one I show.
You should see the decimal point as "---.-" and the "mV" little sign should appear.
Hate this stupid manual and meters that think they are helping me. They don't.
So now you should have succeeded in setting:
400 - mV - AC
*Now* it should indicate the output of your guitar (which obviously has a pickup selected, and volume/tone on 10).
The bar graph display on top should show the output of your guitar, like a Vu Meter.
With the meter so set, touch the output pins I suggested earlier, which had around 7.5V DC on them.
The meter (specially the bar graph) should show a pulse, while you touch the 7.5V, and then drop to almost zero, if it really can differentiate between DC and AC.
All this without injecting any AC in J9? (the aux in).
As you see, I hate automatic stuff (meters and software) which auto set, "to help me", to what I don't need or want.
Post results before sending it back, It *might* do, after all.
Also post the link to the other multimeter.
Oh well.
pmarchione:
I tried that it didnt work. so i returned it. I sent the link to the lowes one in the post above. I think one of these should be ok. It states that it does 400.0m ac voltage. its only 15 bucks or so more than the radio shack one.
heres a link to the site from the company.:
http://www.idealindustries.com/products/test_measurement/multimeters/test-pro_340_series.jsp.
or this one.
http://www.extech.com/instruments/product.asp?catid=48&prodid=277
ill pick one up in the am and retest all of those voltages and repost.
pmarchione:
ok here are the results with a good meter.
U18 pin 5 = 7.56dc
u19pin 5 = 7.09dc
u18 pin 6 = 15.09dc
u19 pin 6 = 15.1dc
u18 pin 5 = .1m ac
u19 pin 5 = .1m ac
I went with the Ideal meter from Lowes for 58$ works great and sturdy, well worth the extra 20$
J M Fahey:
Good.
This Lowe one is the real thing.
As you see, even when touching Pin 5 and its 7 V DC present, it shows 0.1 mV AC (please always shows it's "V"olts or whatever you are measuring) which probably is noise.
Now to useful measurements:
Inject your 1KHz tone into J9 , measure the AC voltage there, I guess you will find around 200mV (most MP3 players put out about that) , and then measure on Pin 5 .
*Maybe* you have over 400mV there, in which case you should rise the measuring scale to 4.0V AC (maybe the multimeter does so in Auto).
If value on each channel is about the same, fine, these LM386 are working as intended, then the next suspect is the Power Amp itself.
So far I suspect these LM386 because they are used as headphone outputs, have direct connection to the "outside world" and a bad connection might have killed one of them.
Good luck.
And congratulations on buying a good multimeter.
Which, by the way, should be able to measure your MP3 and guitar output .
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