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Projects => Tech Help - Projects Page => Topic started by: destro on August 06, 2016, 11:52:41 PM

Title: Peavey Classic 30 debug - need suggestions
Post by: destro on August 06, 2016, 11:52:41 PM
I know this is an amp and not a pedal, but debugging principles apply.

Well, I really did something stupid. Swapped out all my tubes but installed them backwards s in tubes 1-7 were put in 7-1. I know, I know.... Turned on saw a bright flash. Immediately turned it off. Realized what a dummy I was. Replaced the blown 1a fuse. Other checked out fine. Powered it back up and still no luck. Power amp tubes are glowing. Pres are out. Checked voltages and I am getting 130 volts at the fuse and around 370v for b+ and b++. Should be notably lower at these spots. Wondering if a diode or cap has gone out, but dont want to blindly start replacing stuff. Nothing looks screwed visually of course.

Any advice on what to check or swap out would be greatly appreciated. Thanks!

http://www.bustedgear.com/images/sch...classic-30.pdf
Title: Re: Peavey Classic 30 debug - need suggestions
Post by: galaxiex on August 07, 2016, 01:26:04 AM
Link for schematic doesn't work.

You say the Power amp tubes are glowing, but not the pre-amp tubes.
Does the amp have a separate fuse for the pre-amp tube heaters?

Check pre-amp heater circuit. Voltage?
Title: Re: Peavey Classic 30 debug - need suggestions
Post by: HamSandwich on August 07, 2016, 05:44:00 AM
There are two other fuses on the PCB on the secondaries of the power transformer. F2 1AFB for the B+ and F3 1AFB for the heaters.
Title: Re: Peavey Classic 30 debug - need suggestions
Post by: destro on August 07, 2016, 01:47:48 PM
That's weird. Here's the schem. It got abbreviated for some reason. It only has two fuses. Both check fine, the 1a was replaced cause it blew. I am getting -41.5 on pin 5 of v3

3
1 - 373v
2 - -15mv
3 - -16mv
4 - 7mv
5 - -41.5v
6 - 373v
7 - 7mv
8 -0
9 - 190mv

http://www.bustedgear.com/images/schematics/Peavey_classic-30.pdf
Title: Re: Peavey Classic 30 debug - need suggestions
Post by: galaxiex on August 07, 2016, 03:07:10 PM
Very likely some tubes got damaged being in the wrong sockets.

Reinstall original tubes and test.

Do you have a light bulb limiter? 
Strongly urge you to build and use one to prevent more damage.

http://www.antiqueradio.org/dimbulb.htm (http://www.antiqueradio.org/dimbulb.htm)

Edit; If you google search "light bulb limiter" and come across Uncle Doug's video on you tube, do NOT follow his advice.
He says to use a high wattage bulb, the higher the better. He is WRONG!

Use a bulb that is appropriate for your amp, in this case I'd start with about a 75W bulb.
Title: Re: Peavey Classic 30 debug - need suggestions
Post by: destro on August 07, 2016, 03:12:00 PM
Yeah it was a tube issue. Two blown and a backup I was using was bad. Litterally blew $30! Ha!