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3/1/2000 9:44 PM
Could somebody please help me find the schematics  
for the head of the EVH 5150, or  
the head of the Marshall JCM800...please?!  
See, i don´t have the money to buy a new one  
so i'll try to make one....i'm sure it'll  
be way cheaper.  
Please help me.  
3/1/2000 9:56 PM
Don Symes

...i'm sure it'll be way cheaper.  
Cheaper? No. Educational, fun, satisfying? YES!
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3/1/2000 10:15 PM
Reid Kneeland

"Cheaper? No."
I'd qualify that as "probably no". It  
*can* turn out cheaper if you can get a  
deal on used or surplus parts (especially  
transformers), and if you already have all  
the tools you need, and if you don't care too  
much about appearances. (And if you  
don't exfumigate (Latin: "let the smoke out  
of") too many parts in the debugging process!  
3/1/2000 11:11 PM
Your Friend JP
Here's a link to the 5150 schematic on Steve Ahola's site.  
Good luck finding power and output transformers, chassis, cabinet, sockets, tubes, caps, pots, resistors, diodes, switches, jacks, knobs, wire, power cord, screws, and other miscellaneous hardware for less than Peavey can buy with their massive quantities buying power.  
Knock 50% off the retail price and that is probably very close to what it actually costs Peavey to make it.  
Knock 40% off the retail price and your local music store will probably sell it to you.  
The transformers each will probably run from $80 - $120  
A chassis will likely be around $60 - $100 depending on if you need to have one made or if you can find one you can hack up.  
A cabinet could run over a bill if you had a really nice one made. I guess you make one out of scrap.  
Tubes alone could be in the neighborhood of $100 - $150  
Pots and good jacks are few bucks a piece so count all those and add it up.  
And there are still the wire, resistors, caps, electrolytics, leds, switching transistors, diodes, blah, blah, blah which even at maybe a few cents apiece still add up very quickly.  
Not to mention the fact that building a clone of a commercial amp doesn't necessarily mean you will get an amp that sounds, performs, or behaves the same as the commercial version. 5150s are built using PC boards, so if you wanted to be authentic you would have to somehow get a 5150 pc board or make one. You probably won't be able to get the same transformers they use unless they use off the shelf Hammonds or other common replacement types.  
The schematics don't come with step-by-step assembly instructions either, and unless you are experienced at building amps or know a lot of electronics (and valve) theory, saying you are going to build an amp from looking a the schematic is a lot like saying your going to marry Britanny Spears because you've got her picture on your wall. It's not impossible; it'll just take ALOT of time, work, luck, and proper alignment of the cosmos.  
Ultimately, by the time you finish you'll probably have a job making enough money to buy the darn thing.  
Don't get me wrong though. Like Don says, do it for the learning experience, the challenge, the desire to make something that you can be proud of. If you like tinkering, building things, playing with electronics, go for it, absolutely! But you will quickly be sorry if you think making your own will be cheaper. Not a chance.  
You'll also be sorry thinking that you could stop after doing just one! This stuff is more addictive than crack, sex, and heroin combined and provides waaay less immediate gratification. Maybe its the high voltage and risk of imminent death that makes it all so appealing.  
Check out Torres Engineering, London Power, Hoffman Amps, or Anglea Instruments for kits that will provide some good guidance for building a Fender Champ-like starter.  
Your Pal,  
Jackie Paper  
3/2/2000 1:27 AM
Don Symes

Don't forget the AX84 site!  
3/2/2000 1:53 AM
Your Friend JP
Oops! Thanks. I haven't been over there in awhile, but yes you are absolutely right. This is probably superior to some of these other options since AX84 has an entire community of folks willing to lend a hand all at your disposal.  
There's also Rocket Amps:  
Your Pal  
Jackie Paper
3/2/2000 7:56 PM

I want to thank you for providing the link for the 5150 schematic. I have one in for service, and it blows the HV fuse violently upon startup, with standby switch open. I had no schematic, so after checking power supply rectifiers for shorts, and finding no visible burnt or failed components on the board, I was temporarily stumped.  
According to the schematic, the HV feeds the plates even with open standby. There are also flyback diodes fitted. So there are a few more things to check that could be causing severe overcurrent. (It could even be a shorted tube, since everything but the screen grid is always in the circuit.)  
And thank you, Steve, for posting it.  
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