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Author Topic: Peavey Mixer: PV8USB Schematic and Repair  (Read 557 times)

paelgin

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Peavey Mixer: PV8USB Schematic and Repair
« on: March 28, 2020, 10:34:43 AM »
Howdy all.  Hope you are all doing well during this shelter-in-place time (Covid-19).

Several years ago (2014), I bought a broken Peavey PV8USB mixer on Ebay hoping to repair it with my amateur skills and tools.   After diagnosing that the NCP3063 boost/buck/inverting converter would not function with the corner blown clean off (reminds me of Dirty Harry), I set about attempting to repair it.  Mouser got my order for several NCP3063s, a Zehner that I thought might be bad, and a couple replacement LM317s. 

I took my soldering iron to the NCP3063 which is surface mount.  I got it off, but also accidentally took one trace up from the board.  So in frustration, the mixer went into a drawer for future consideration.

It is now the future (compared to 2014).  In February, I bought two broken PV6USB mixers off of Ebay to practice on (since I really want the PV8USB).  I spent several weeks watching YouTube videos about soldering SMD (surface mount devices) and discovered a new product that I had never heard about before: "Chipquik" SMD removal solder.  It has a lower melting temperature and stays liquid longer: add flux, then melt onto the leads on both sides of the chip, keep it hot and the chip floats off.  Works AWESOME!

So I worked on the PV6USB (similar problems: I discovered that a common fatal error made by users is to try the power supply for the PV6 non-USB, which is 16VAC, with the PV6USB which uses 15VDC 500ma and that blows the power regulator[side note: seems like a weak design when adding a diode might avoid issues]).  One PV6USB works almost as expected (the USB receives but doesn't send) and one PV6USB works with no USB. 

So here is the schematic from Peavey. I could not find it online (and still cannot), so I had emailed Peavey who then sent it to me. This PDF has been indispensable, but I wish the part numbers were searchable on the layout page as well as the schematic to make locating parts easier. Maybe the PDF has layers that my Adobe Reader cannot see.

More later (have to replace all seven 4565 dual preamp SMD chips connected to the inputs, and more).  Thanks for allowing me to share.

Phil in gorgeous Young Harris, Georgia, USA

paelgin

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Re: Peavey Mixer: PV8USB Schematic and Repair
« Reply #1 on: March 28, 2020, 05:51:56 PM »
Here is a picture from the repair in process.  I have removed the seven known-bad preamps using ChipQuik.  Here is a picture after removing one of the chips and cleaning with solder wick to remove the excess solder.  The chip is a 4565 in SMD form (square, 5mm per side) apparently (hopefully!) and I've got 10 on order (at less than the unit cost of $0.39 each at Mouser).

I will try to keep this thread updated as I progress.  The PV6USB models that I repaired were only broken in the power supply, so this is way out there for me.

Phil in gorgeous Young Harris, Georgia, USA

paelgin

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Re: Peavey Mixer: PV8USB Schematic and Repair
« Reply #2 on: April 02, 2020, 11:18:47 PM »
I have replaced the one open zero ohm SMD chip (jumper), three bad SMD resistors and seven of the SMD ICs (parts removed and locations circled in attached picture). 

I found two more ICs bad (circled in black, in the headphone and control room outputs).  I also found three more out-of-spec SMD resistors (4.7ohm, reading over 8 ohms each).  Two of the three 4.7 ohm resistors are spec'd for 1% tolerance, so I will get them all like that.

I expect parts to be delivered tomorrow and will try to get it done and working.

Phil in gorgeous Young Harris, Georgia, USA

paelgin

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Re: Peavey Mixer: PV8USB Schematic and Repair
« Reply #3 on: April 09, 2020, 11:54:49 AM »
Got the parts, installed them in the PV8-USB and then tested the mixer.  Everything works as expected.

I did find that the USB operation had fooled me, since when I started testing, I did not see any signal going into my DAW from the mixer, but HP on the mixer allowed me to hear music playing from my DAW.  It turns out that the traffic is one-way at a time. Although it seems obvious now, if I set the switch to feed the Tape/USB into the mix or set the switch to feed the Tape/USB into the Ctrl/HP, I got the USB signal from the PC into the mixer, but no return signal. Once I unset those two switches, I got signal into my PC from the mixer.  In the schematic, I have not found any switching but it works.  I also tested one of my previously repaired PV6-USB, and the USB does work on the one that I thought was only one way.     

I went back into the board on the PV6-USB that has no USB function to see if I can repair that too.  I had to replace the +16vdc transistor (Q21) with a different model (spec'd model is obsolete) and I am not getting the +16 VDC rail to where I think it should be.  I think I will start a new thread and post the Schematic for the PV6-USB and ask questions there.

Thanks for letting me share, and for sharing so much on here. 

Phil in gorgeous Young Harris, Georgia, USA

willpirkle

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Re: Peavey Mixer: PV8USB Schematic and Repair
« Reply #4 on: April 09, 2020, 09:17:16 PM »
Thanks for your posts! - this is a great forum (I’m relatively new) and a wealth of information here.