No Power--Peavey Valveking 212

[SamX]

Hello ---I've been wanting to build an amp and thought it might be wise to try to resurrect a dead amp first . I just bought a Peavey ValveKing 2-12" that does absolutely nothing when flipping the power switch . The fuse looked good but I put in a new one just in case . I tried turning on the power with just the 2 outside power tubes installed and then with just the 2 inner tubes . Next, I will pull the chassis out and look for burn spots , bad parts, wiring or solder . I know to drain the filter caps before undertaking the next steps but I wanted to know how to check the O.T. to determine if it is blown or if anyone has any thoughts on how to proceed . I really want to get this amp going without taking it to a tech but I don't want to buy an expensive part only to find out that it's not the problem . I only paid $100 for it and it looks like a new amp . It also seems to have some cool features and could be a nice amp although 100 watts is more than I would ever need . There's a switch that allows me to select 2, 8 or 16 ohm and a "Texture" knob for half (class A)or full (class AB) power . I've read good reviews about it too so it might end up being a great amp for me . Can anybody give me some guidance please ?

[Chuck H]

It's kind of funny that you mention the OT in this first post. If you look around here you'll see that it's a sort of running gag with us that most novice amp enthusiasts go straight to the OT as the problem when it usually isn't. Case in point: You flip the switch and nothing happens. I assume this means that there's no pilot or hum (even a small amount of mechanical hum). In this case we're not even dealing with the OT yet and in fact the OT wouldn't be part of this particular problem. That doesn't mean your OT is good, but it does mean it's nothing to suspect yet. The first thing to do is take the amp out of the chassis, drain the filters (they may already be drained since most modern amps include a circuit that does it whenever the amp is shut down). Do always check for voltage on the power supply capacitors and drain as needed.

Next you'll need to look for any obviously burned up stuff (as noted). Probably best to just report back here if you find anything. If you don't, things get a little more hairy... You'll need to mak sure the amp is plugged into a load and plug it into the wall. Flip the power switch and use a meter to check for voltage going into the PT primaries and coming out of the PT secondaries. This means there will be voltage in play and the potential for electrocution. DO NOT TOUCH ANYTHING WITH AN UNINSULATED TOOL, not even the chassis. If there are no obvious signs of failure and you read correct voltage going into the PT primary but nothing at any PT secondary then you probably have an open PT primary wind (bad PT). If you don't read voltage going into the PT there is probably a fault in the AC mains circuit before the PT primary. Without a schematic I can't say what all it might be since Peavey is notorious for fusing things internally and occasionally uses unusual circuits. But following the AC mains circuit should be easy enough There's usually only a fuse and possibly a pilot light involved prior to the PT primary wind.

This is where we need to start. We can't diagnose further problems without power, so we fix that first.

If you electrocute yourself I refuse to help you further

[SamX]

Thanks for the reply Chuck--Oh, I'm a novice alright ! I thought I was being cool typing O.T. when I should have hit PT ! In the a.m. I'll start the carnage and post the results. The guy I bought the amp from said it just went dead in the middle of a practice . He also pointed to the transformers and said , "See, it's got a tube power section but a solid state pre-amp section like all of the Valvekings" so I guess I'm half a notch above HIM when it comes to amp guts ! I was able to download a schematic for it so I've got THAT going for me ! Thank you again for taking the time to assist .

[Jazz P Bass]

Check the internal fuses.

[Chuck H]

Yup. I just saw the schematic and as I thought, there are internal fuses. If the pilot doesn't light and there are no tubes glowing it could be the fuse on the filament supply. If it did blow there is a reason. You should probably plug in a set of known good power tubes or at least test the ones that are in there before firing it back up.

[Jag]

Further to Chucks last post; if you find a bad fuse replace it and fire it up without tubes first. If the pilot lights and stays lit, then proceed with further tests.

[vavlehead]

The guy I bought the amp from said it just went dead in the middle of a practice .

So refreshing!!! He actually didn't claim that a "friend" borrowed it and he got it back fried!!

[SamX]

Well, I took a look at the boards and it all looks like it just left the factory--no burns, no dirt, no obvious signs of malfunction and there are 3 internal fuses that seem to be good . I got a signal through them when I put my meter to them so my very limited knowledge make me believe they're good --also the inside wires are unbroken . Next, I put a known good set of of power tubes in, made sure the speakers were connected and plugged in a guitar too . I THINK that assures that a proper load was on the amp . I didn't find any loose connections or suspect solder joints either . I have a digital multimeter that measure all the regular stuff , capacitance ,Frequency, diodes,AC & DC voltage,&current,resistance, audible continuity and temperature . Still, I have no indicator light, no activity of any kind from the amp . There is a small board for the connections at the back of the amp where the power cord plugs into the amp, another (larger) board above the power tubes and one of the 12AX7's and then the main board is at the front where all the rest of the stuff is--2-AX7's, all the pots etc . I did NOT get shocked Chuck . I just had to take care of some things before I could devote time to my amp dilemma ! I took some photos of the boards too if that would be helpful . Thank you everybody who takes the time to reply to me ! If the next step involves testing the PT, I don't know how to do that so any advice is greatly appreciated .

[Jazz P Bass]

Take your ohm meter I place the leads on the power plug. L1 & L2. Not the middle ground lug.
Turn on the power switch.
You should now be reading the transformer primary winding.
If you do not get a reading, then there is a break somewhere between the power cord & the transformer.
If you can verify that there is indeed continuity from the plug to the transformer, then the transformer is open.

[SamX]

Hey J.P.Bass !-- I clipped on the leads as you instructed and in the Ohm setting with the amp switched "On", it reads14.82 k and nothing in the "Off" position . In the Volt setting , with the amp switched "On" it reads .oo4 and when I move the switch to "Off" it reads .685 then jumps to 1.2 when my gnarled fingers grasp the switch . When you say the transformer is "open" , do you mean there's a short and/or it's bad ? The small board has a couple of capacitors, a fuse (which I replaced although the original was good) , a hot and a neutral connection for the transformer (it reads "Xfmr") , wires coming from the power switch and the standby switch and the housing for the prongs that the power cord connects to and that's about all . Does this info narrow down the possible cause of my amp problem ?

[Jazz P Bass]

An ohm reading is what we want.
(A voltage reading is not going to "read" anything. The amp is unplugged.)
Anyway, if you read a resistance of 14K, the next step is to measure the actual primary.
P213 & P214.
If it also reads 14K then the tramsformer is bad.
Time to call Peavey.

[SamX]

By the beard of Zeus !!! It reads exactly 14.82k on both ! So the transformer is bad . Does this typically suggest that I buy a new transformer and I could be in business or does this mean it could be the tip of the iceberg ?