Peavey Classic 400 schematic ?

[nsubulysses]

Anyone have Peavey Classic 400 schematic I could peruse? the one that does 400W with 8 6550s

Yes, I did ask peavey.

It's 5:08 and I missed the boat. Got the answering machine

Please post if you have it or if not I'll just contact them tomorrow

WOuld like to try to work on this tonight

[The Dude]

The Classic 400 all tube bass head

Schematics towards bottom of page.

I hope you're feeling strong today.

[nsubulysses]

I just took a nap so this dead lift will wake me up.

Maybe I am not good enough at using a computer but when I clicked those schematics I got a blank page

Edit: AH, duh. it is a pdf so I must open it in photoshop or some other program that can do PDF.

thanks for making me give it another try

[The Dude]

Hmmmmm,...They load fine on my computer. Maybe they're large enough that it takes more time. Try waiting it out.

Or maybe try this. Here are the direct links.


http://www.hartsafire.com/classic400/Peavey_Classic_400_service-1.pdf

http://www.hartsafire.com/classic400..._service-2.pdf

[nsubulysses]

Out of curiosity, can you open it by clikcing the link and viewing in your web browser? I get blank page that way and also blank page when I view it with Preview even though it is supposed to support PDF.

If I open in photoshop there is no issue other than annoying toggling between page #s rather than scrolling up and down like I would in the other scenarios. Maybe there is a way to scroll pages in photoshop as well, hmmm

[The Dude]

Most people have Adobe Acrobat Reader installed on their PC. PDF files will then automatically open if configured normally. Do you have that installed or another .pdf reader?

FWIW: I use Foxit Reader instead. It does everything Adobe does and is also free. The advantage it has over Adobe is that it also allows you to do some editing of .pdf files. You can fill out forms, add signatures, etc., etc.

[nsubulysses]

I can use Preview to read many books and whatnot I have in PDF. Not sure why it won't open some schematics. Maybe I gotta check out Foxit. Thanks Dude

I have the same problem with these 5150 schematics. 5150 combo can be opened in seemingly anything, but I must open Peavey 5150 II schematic in photoshop or I get blank pages. I must be missing something. they are both PDF. I'm not a good tech geek in the computer realm

[vintagekiki]

... ...

http://www.oldapps.com/adobe_reader.php

http://schems.com/bmampscom/peavey/

https://elektrotanya.com/peavey_classic_400_sch.jpg/download.html

https://www.electronica-pt.com/esquema/audio/amplificadores-audio/peavey/peavey-classic-400-28139/

http://www.eserviceinfo.com/downloadsm/41034/Peavey_Bass%20400.html

[nsubulysses]

Does this amp really do 400W? I would believe it does, and it even lists itself as doing 56.5V into 8 ohms for 400W, but I only get this one to do 280-290W at clipping. Tubes are strong and good, even replacing 6 of the 8 power tubes with new ones it still does same power output.

B+ is 670V and sags to about 590V at clipping. No screen grid resistors are open. The amp had a shorted 12AT7 phase inverter but I found no shorted/open resistors in the gain stage. Also I guess it doesn't really matter because when you plug into the power amp in the amp does the exact same, 34V into 4 ohms. DDT button has been pushed in and out so I'm not overlooking that. Anything come to mind that might be worth looking into? I have never gotten one of these for repair before so hoping I might be missing something simple

[glebert]

Did you go through the bias procedure?

[nsubulysses]

Is it anything more than setting the bias to -53 to -53.5V?

[J M Fahey]

I never expect tube amps strictly meet rated power if **clean** , zero clipping.
real "Hi Fi" almost 300W RMS looks acceptable to me.

Just for peace of mind, do it the other way: rise output until you have rated 56.5V "RMS" out (actually whatever you have, but read on rthe "V RMS scale), then look at the screen, if possible take a pic and upload it hgere.

I bet weŽll have the classic power tube output waveform, sort of skewed similar-to-crossover type mixed with top clipping (but not a full squarewave either) and to boot: horizontal parallel line tops which actually show ripple .

Funny thing is, such waveforms do not "sound distorted" to the average Rock player, but "just a little grungy" or "with character" or some other colourful description.

[Enzo]

In my view, the power rating of a guitar amp is about how much power the amp can put into a speaker. Distortion? So be it. My 100 watt speakers will not turn away 150 watts of signal just because it gets distorted after 50 watts.

[g1]

Not to disagree with anyone, but I seem to recall generally being able to get that kind of power from SVT's, with 2 less power tubes.
You said the screen resistors were all good, but how about the screen supply voltage?
Otherwise, maybe that amount of sag in the B+ is more than the SVT's sag. Or maybe it's running out of drive to the outputs? (12AX7 driver vs. 12BH7 in the SVT)

[nsubulysses]

G1 is correct. Or as far as I know.

power supply voltages are the same as SVT plus two power tubes so yes, i think this amp should do more power than an SVT

I'll be at the shop again tmrw and can give it another look

Thanks for the insights so far

Tomorrow I will post the scope image. 34V at clipping into 4 ohm load with a nasty crossover look. Plugging into input jack on front panel or plugging into power amp in, the output looks the same. It has to be some sort of power supply problem.

If the amp is hitting clipping too early isn't that basically controlled by how high the B+ and screen voltages are? It seems the only other thing that could drag this down are weak power tubes