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FOR THOSE THAT ARE INTERESTED...


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8/13/1999 3:18 AM
Trace
FOR THOSE THAT ARE INTERESTED...
Hey gang;  
 
 
 
Well, the pots that fit this aren't the easiest thing t track down or go out and buy at the local electronic store but for those that are interested you can use a Fender PCB mount pot and it's the same thing but only a bit more sturdy.  
 
 
 
MODS:  
 
 
 
Nothing really drastic but here's the basic scoop.  
 
 
 
First 12AX7:  
 
 
 
Plate resistors: 100K's instead of the 150K's  
 
Cathodes: pin#3 is 2.7K/.68uF in place of the 1.5K  
 
Pin#8 is 4.7K/22uF in place of the 1.5K/22uF  
 
Plate Cap for #1 is .1uF instead of the .047uF  
 
Plate Cap for #6 is .022uF instead of .047uF  
 
 
 
Second 12AX7:  
 
 
 
Plate Resistors: 100K's in place of the 150K's  
 
Plate Cap for #1 is .022 instead of the .047uF (same with #6) I also put a 330pF cap (connected to a switch) across the treble cap of the EQ section.  
 
Cathodes: Pin#3 is 820ohm/22uF in place of the 1.5K/.047uF  
 
 
 
That's pretty much it and I'll hopefully have a JPG schematic ready soon if anyone wants it.  
 
 
 
For what it's worth;  
 
Trace
 
8/16/1999 8:18 AM
Steve Ahola

Trace:  
 
 
 
    I finally got around to screwing around in my studio and making some sound samples of my amp mods and guitars. This one here is my Peavey Classic 50 with the Tweed Bassman mod (my strat has Lindy Fralin pickups, mainly the neck on this tune). I made up a stupid 60-ish garage band instrumental just to illustrate the smooth channel switching on this amp (well, the button did keep getting stuck in the treads of my work boots...)  
 
 
 
http://www.techaccessinc.com/blueguitar/noodlin.mp3  
 
 
 
Steve Ahola  
 
 
 
P.S. There are more sound samples on my site [the Hot Rod Tweed ones came out sounding a lot better than the Peavey... 8-( ]:  
 
 
 
http://www.techaccessinc.com/blueguitar/snappy.mp3
 
8/15/1999 12:38 AM
Ed/SS
Re: LOOKING FOR SCHEMATIC
You must be kidding, Steve. Using laser technology to perform that feat? You know if you hurry thru something, you can easily goof it up.  
 
You're telling me you:  
 
you pull the chassis out of the cab (I can't remember if you can unplug the reverb cable from the chassis or if you have to pull them out of the tank like the 30 or not), remove the tube doors, the tubes, the socket PCBs, the knobs, jack & pot nuts, unplug all those headers, unscrew the PCB mounting bolts, then finally flip over the main PCB all in 15 minutes? Perhaps so.  
 
What if you want to experiment? You put it partially back together, then try it out, then take that apart again, then try another thing, then put that back together again, then try another thing, then take that apart again...it goes on & on. Are you telling me you only charge a half hour labor for disassembly/reassembly plus the troubleshooting/repair charge?  
 
Sorry, I'd prefer to spend more time being thorough with troubleshooting than disassembly/reassembly.  
 
 
 
Hope it works,  
 
Ed
 
8/15/1999 4:22 AM
Steve A.

Ed:  
 
 
 
You know if you hurry thru something, you can easily goof it up.  
 
 
 
    How true! I tried to save time last year by pulling out just the preamp tube board when I was trying out different resistors and caps in the contour network between V2A and V2B. But the added strain on the soldered-in ribbon cable broke off one of the wires, and when I tried to repair that one wire I ended up breaking the one next to it... So I now take the whole amp apart everytime I need to work on any of the boards to not cause any further damage to the cabling.  
 
 
 
Are you telling me you only charge a half hour labor for disassembly/reassembly plus the troubleshooting/repair charge?  
 
 
 
    Actually I don't charge myself anything when I work on my own amps... < g > As I mentioned in another current thread on the Peavey Classic amps, I think that coming up with good sounding mods for these amps has to be a "labor of love" more suited to the DIY-er with too much time on his hands than for a commercial amp repair shop. So you finally get it back together for maybe the 5th time and you think it sounds really great, but the customer doesn't like it and wants you to put it back the way it was when he brought it in... Argh!!! I would really recommend not trying to redesign those amps unless it for yourself or for a close friend. (Just my own very non-professional opinion as a chronic DIY hack'n'slasher...)  
 
 
 
    Thanks!  
 
 
 
Steve Ahola  
 
 
 
P.S. If you were to repair a lot of the Classic 50's (like if you were the local authorized repair station) you'd probably want to devise some sort of test rig to be able to run the amp with the circuit boards out of the chassis. I never felt that was worth the extra time and expense because I'd want to put the amp back together so that I could playtest it for a day or a week (however long it took me to decide that additional work was needed).  
 
 
 
P.S.S. There is one quick'n'dirty mod that does not require the chassis to be removed from the cabinet: replace the SPST channel select toggle switch with a center-off DPDT switch and use the extra pole to add in a mid-boost cap across the terminals of the existing 270pF treble cap. Although I was using a 750pF boost cap when I came up with that mod last year I have since migrated to a more subtle boost (I've been using a 390pF cap across a 330pF treble cap, with a 56k slope resistor). I find that with those values, both channels sound pretty good boosted or unboosted, for 4 usable positions. (So how do you get 4 positions from a 3-position switch? By using the footswitch you can access the Normal channel with the mid-boost activated...)
 
8/18/1999 1:18 AM
Ed/SS

Oh yeah, you DO have to take those amps entirely apart just to work on them, and I don't have the time, inclination, or customer's bucks to pursue modding the Classic 50, OR 30! It's enough of a pain just to repair one!  
 
 
 
I refuse to work on those amps anymore, unless it's for a friend. But usually I tell my friends to dump those amps.  
 
 
 
To me, they're not even worth modding, unless one converts the amp to a hardwired Vox or Hiwatt, like getting rid of the PCB pots, PCB jacks & PCB sockets, and the PCB itself!  
 
 
 
 
8/18/1999 5:01 AM
Steve A.

Ed:  
 
 
 
    I think that we both agree that commercial shops should avoid trying to mod a customer's Peavey Classic 50 or 30 amp- and unless you are a factory service center you'd probably want to pass on any repairs to them, too. (Without the schematics and layout drawings you can spend a lot of time just figuring out what is going on...)  
 
 
 
    But if a friend brings in a Classic 50-410, for the hell of it you ought to try out the "30 minute mod" I described in my last post. (You just need to remove the 5 screws holding the back panel, replace the channel select switch, solder leads to the tubular treble cap (it looks like a FP resistor, only it is green instead of blue) and then run them to a mid-boost cap (~360pF to 750pF or even 1000pF) on the new center-off DPDT toggle switch.) That should only take 20 minutes tops, but I added in an extra 10 minutes in case you decide to try out different valued boost caps before soldering it up. < g >  
 
 
 
Steve Ahola
 
8/19/1999 1:00 AM
Ed/SS

Thanks Steve, but I'll pass on that mod. Again, I either have to get them working or simply refuse to work on them.  
 
 
 
I have the schematic & layouts for the 50 & the 30 - modding those disposable units are simply a waste of time to me. They eat up the EL84s every 6 months too.  
 
 
 
Those 2 amps are one of the main reasons I never applied to Peavey to do warranty work for them.  
 
 
 
I actually bought a Classic 30 off a customer SO I WOULDN'T HAVE TO WORK ON IT AGAIN! At least now I have a fairly good cab for a 12". The original (I'm sure you know) is 16 ohms, the chassis is cheesy but I'll use it anyway, the transformers are lame, but I will eventually get around to hardwiring a cool circuit into it with CHASSIS mount pots, jacks & sockets.  
 
 
 
Have fun, I hope it works,  
 
Ed Blum  
 
Sonic Surgery  
 
 
 
 

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