You said the voltages checked out, does that include the + and - 15V at the IC's, and +15 at IR18 in the power amp?
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Peavey Mace VT Problems
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Originally posted by g-one View PostYou said the voltages checked out, does that include the + and - 15V at the IC's, and +15 at IR18 in the power amp?
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Well, good to hear you haven't checked those yet, as the +15 is common to preamp and power amp and could explain why you seem to have problems with both.
Look for an IC labelled TL072, like U2 or U4. Check DC volts at pin4 and at pin8 (black probe grounded). See attached pic for pin numbering.
In the power amp section, look for a resistor called IR18. One side of it should measure +15V.
Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by g-one View PostWell, good to hear you haven't checked those yet, as the +15 is common to preamp and power amp and could explain why you seem to have problems with both.
Look for an IC labelled TL072, like U2 or U4. Check DC volts at pin4 and at pin8 (black probe grounded). See attached pic for pin numbering.
In the power amp section, look for a resistor called IR18. One side of it should measure +15V.
[ATTACH=CONFIG]30899[/ATTACH]
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Originally posted by Jazz P Bass View PostYou may want to recheck the IC power pins.
Looking at the IC pinout diagram, it is clearly stated that pin 8 is +(plus)VCC & pin 4 in -(minus) VCC.
So, unless there was a reading error on pin 4, you do not have the -VCC supply working.
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Originally posted by Jazz P Bass View PostWell that's good to know.
I forgot what we are trying to fix though.Last edited by ric44; 10-10-2014, 03:54 PM.
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One other fault you didn't mention, when you plug your guitar straight into Power amp In jack, you don't hear any audible sound.
Maybe double check this, hit the guitar hard and see if you can make out a slight sound from speaker.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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^^^^^^^^^^^^^^^^ what g-one said! MUST fix power amp first - no point in checking anything else until you know signal will reach speakers!
Is it entirely possible there's more than one problem? I have a Deuce VT here, working fine... let me know if I can verify anything for you. Not identical, but pretty damn close...
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -
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Just double checked.....no sound at all coming from speakers with guitar plugged in to power amp in jack. Just to be sure here and make for certain someone hasnt juggled the plugs ? The power amp jack has a bakelite covering on back and has a thin black , a thin light green, and a bare (ground I guess ) wire connected to it .
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On mine, looking down into the chassis at the in/out jacks:
Top lug (closest to me): bare wire connected to both other jacks' top lugs.
Right lug: green wire
Bottom lug: black wire
Left lug: no connection.
Looks fine to me...
I tried my guitar into Power Amp In - quiet, but definitely there and clean.
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -
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Originally posted by ric44 View PostJust double checked.....no sound at all coming from speakers with guitar plugged in to power amp in jack. Just to be sure here and make for certain someone hasnt juggled the plugs ? The power amp jack has a bakelite covering on back and has a thin black , a thin light green, and a bare (ground I guess ) wire connected to it .
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Originally posted by Jazz P Bass View PostMy only guess (seeing that a preamp signal does pass through the jack) is that you have a missing connection to ground.
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