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Topics - paelgin

Howdy all.  I bought a broken Peavey PV215D (powered speaker system with two 15" speakers and a quasi-3-way output) ("does not pass signal", but found it really out blows fuse) and searched for an electrical schematic for it.  Peavey had not responded to my request in a week, so I went deep-diving in the Internet.

Attached is the schematic I found and downloaded (for free, although it says "Buy it").  If there is a problem with posting this here, please let me know.

In troubleshooting the powered speaker amplifier, I found so far that the power supply is the initial problem.  I found the -VCC side had a shorted FMG22R (dual "fast-acting" diode with common anode in TO220 type package).  I have one on order so I can see what else is wrong, if anything.  One of the two diodes in that package is a total short, and with that device removed from the board, the power supply caps both build up resistance (where the one on the -VCC was always 0 ohms with the device in the circuit).

The amp uses what they call class D amplification, and for the 700 watt rated output, doesn't seem too robust, so it must be very efficient.  (I hope the Peavey watts are as loud as the Fender watts, lol).

I post this in case anyone else needs this and to give back to this forum for the help I've gotten.

Phil in gorgeous Young Harris, Georgia, USA
Howdy all.  I need a schematic for the USB version of the Xenyx X1832 mixer.

I bought a broken Behringer Xenyx X1832USB mixer on Ebay and am cleaning and repairing it.  I have the schematic for the non-USB version, which I was hoping would be close enough.  That schematic is attached.

Alas, it is not sufficient and I need a schematic for the USB model.  In addition to gummed up pots and blown resistors (on the power for the Op Amps for the headphone for some reason), I discovered that the USB is sending left and right, but sadly both from the left channel.

The non-USB schematic that I have looks close enough (so far) to be usable in my repair of the headphone circuit. 

In my testing, I found that the headphone circuit was bad, but everything else worked, at least after spraying some of the pots and switches with Deoxit Fader lube.  [side note: I had heard about the loss of intentional weighted "drag" in the slide pots and that is true].

Once I get it off my phone, I will post a picture of the circuit board after removing two surface mount resistors (47 ohm). They were in line with the plus/minus rails going to the two preamps outputing to the headphone jack.  Something pulled a lot of current through them and I suspect that the two Op Amps (4580) are also toast (three on order now, along with several resistors and parts to make a "5th Gear Overdrive" pedal).

Phil in gorgeous Young Harris, Georgia

ps, the schematic of a different model of Behringer USB mixer might also work for my purposes.  I just need to see how the USB is driven.
Howdy all.  Attached is the PDF schematic of the Peavey PV6-USB mixer.  I am posting this as well as my journey, struggles and questions as I work to repair a broken mixer.

I have seen online comments regarding power supply for these older mixers: it is critical to note that the non-USB models require a 16 volt AC adapter, while the USB models require a 15 volt DC supply.  I will also post a picture showing the input requirements shown on the back of the mixers.

The mixer I am trying to fix had a serious power problem which blew the NCP3063 boost/buck/inverting converter surface mounted chip apart.  It was so bad that it burned the top layer of the board down to the fiberglass matting below (I think I have a picture; if so I will include it too).

My questions will start in my next post as I work with my meter to see why the mixer works but the USB does not.

Phil in gorgeous Young Harris, Georgia, USA

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
Anybody know anything about a Kustom powered mixer, K8320?  It appears to be fairly old, has 8 inputs (XLR and 1/4") with 160W x 2 out, but it has a unique 1/4" patchbay on the front panel.

I am following an ebay auction for a broken ("Unit does not function, sold AS IS, for repair or parts") powered mixer. It is incorrectly identified as a KB320, but appears to be a K8320 (8 inputs, 160W x 2 = 320).  I tried to attach picture saved from auction.

I cannot find any information about that model anywhere: not on Kustom website, not in Google searches, not even a picture in Google images. 

I might be interested in buying and fixing, but maybe not if I can't find a schematic. Depending on what's wrong, I could probably fix it anyway but easier with schematic.

However, I am absolutely _fascinated_ that this mixer is so obscure that no information is floating out there.  I might want it anyway...

Phil, in beautiful Talking Rock, Georgia, USA.
Schematics and Layouts / Fender GDEC Junior Schematic
December 31, 2014, 08:36:32 PM
I thought I'd share this schematic (didn't find it on here when I searched).

Several years ago, I bought a couple of broken Fender GDEC Junior amps on ebay, and fixed some.  Attached is the schematic that I got from Fender (great folks to work with).

I still have one that is in my 2-year-or-so queue for repair (was repaired and working, then I went to put it in a cab with speaker, it failed, so it went on the shelf).

Phil in beautiful Talking Rock, Georgia, USA.
I bought a broken Bogen GS-150.  No output from the power amp, although the pre-amp seems fine (seemingly proper signal on pre-amp output).

In the power amp section, I have +/- 43 volts (closer to 50) rails and no obvious shorts or burns. In diode checking with a Fluke diode voltage-drop tester, almost nothing jumps out.

Except D300. It shows 0 volts drop across either direction (in-circuit testing only), and has only about .2 ohms of DC resistance, which takes the power amp output straight to ground.

What is D300?  I do not have any other manual, and cannot tell what D300 is. In reviewing the schematic, I thought that it looked like a back-to-back zehner to protect the transformer from over-voltage on the output of the power amp. I'm tempted to remove it to see if I can get output (since I have not broken out my scope).

Any thoughts would be appreciated.

Phil in beautiful Talking Rock, Georgia, USA.
If I can attach the PDF file, here is the Service Manual for the Hughes & Kettner "Club Reverb" combo guitar amplifier.  (Follow-up before posting: Nope, had to make ZIP file...)

I almost got that amp (that darned Ebay), and when I thought I was going to get it (broken, unfortunately), I emailed H&K, and they sent me this. 

I didn't win the auction, and subsequently communicated with the actual winner and emailed him this booklet (which includes schematic). I also gave him some suggestions on what I was going to look at and test once I received the amp (which I never did, boo hoo).
Yesterday I picked up a Traynor YVM-10L mixer with 240 watt internal power amp. It's a 10 channel mixer made by Traynor in 1976.  I was told the power amp doesn't work, but the mixer is dirty but OK. Yep, that's what I found.

As I opened it up, an envelope fell out which contained 10 pages of hand-drawn schematics for the mixer section.  Here are some of the photos I took of those pages.  The others in subsequent posts. (Had to reduce the size to get them to fit.)

I wish I had the schematics for the power amp though, but searches on Google proved fruitless.  I also couldn't find anything like these anywhere either, and want to make them available

Output uses 4 TO-3 MJ802 power transistors, and while testing, I found that 1 is shorted E-C.  I hope that's all that's wrong.  My wife thinks I should replace all 4, but for crying out loud, they are $4.60 each! ::) Well, she said I could if I wait until after Feb 1 (finances being what they are).

So, is my wife right? Is it worthwhile replacing all 4?

Also, should I replace the power supply caps?  I say one guy comment that he was "recapping" his PS.

Oh, by the way, what's the best way to clean the zillion dirty pots on the mixer?

Thanks for any advice.  Phil

Oops, typo: YVM-10L, not YVN-10L as originally posted...sorry.
Here is a schematic emailed to me from Fender for a Fender 1270P powered monitor.  This is not DIY, but it is solid state...Interesting to see what they did.  So, I hope it's OK to post this here. 

I got this because I bid on Ebay (USA) and won a broken one.  (I should get the shipment tomorrow.)   I will be trouble-shooting and seeing if it is salvageable (and usable). 

I found this forum Googling while looking for schematics, and have had fun looking through what is here.  I downloaded the book from Teemu, but haven't had a chance to look yet (thanks for sharing!).

Not sure what I can add to the Forum, but can try to help with questions or trouble-shooting, and may post what happens with my monitor project.

Thanks for everyone who has been helping make and keep this Forum going.