HELP!! (amp problems)

[Low_fidelity2100]

A few weeks back my Vibrochamp Blew its fuse, I thought I'de narrowed it down to the rectifier tube. So I bought a new rectifier (Jan-Phillips 5Y3WGT) and it arrived in the mail today. So I Put it in, and It Hummed LOUDLY all the tubes lit up, and then The fuse blew again. So I guess it wasn't the rectifier afterall. (which is fine cause I'de been meaning to get a new rectifier anyways)

So I found the R.G. keen/GeoFX Tube amp Debugging page back when It first blew the fuse. I did a test given on the site to deterimine if its blowing fuses because of the rectifier. Basically it says to Take the rectifier tube out, replace the fuse, and See if it still burns the fuse out. It says if it DOESN'T then the rectifier is the problem. So I did that (didn't leave the amp on Long though, maybe a minute, probably less) and the Fuse didn't Burn out, But the amp did Hum LOUDLY (hum uneffected by volume control). So I Figured that meant that the rectifier was the problem. But I was wrong apperently.
So after the fuse blew even after replaceing the rectifier, I looked on that site again. An it said it might also be a shorted Output tube. So he gives instructions to see if thats the problem. Basically same deal as the rectifier tube test thing. Pull the power tube, replace the fuse, turn the amp on, If it doesn't blow the fuse then Its probably the power tube.
So I did that, and the fuse Doesn't blow (Left it on for a few minutes Just to make sure this time). And It also didn't hum this time. But, I haven't an extra 6V6 To test in it....

So here's my question. Before I go to the trouble of Ordering a replacement 6V6 (the suspected broken rectifier is a Very old RCA), Does this sound like Its just a tube problem? Like if I just get a replacement, that'll be that? Or Does this sound like something else? Like a blown transformer? or Something? I have no problem ordering new tubes, I just don't wanna wait a week for new tubes to come in the mail, only to Find out That wasn't the problem in the first place. I also really don't wanna just take it to a tech (being as theres no techs around here I trust), if I don't have to.

So heres the symptoms...

1. Blows Fuses (only with The power tube in though now)
2. Before it blows Fuses it produces a Loud hum that is uneffected by the volume control.
3. When it initially stopped working, it didn't act strange at all. Just Totally fine one minute, then nothing but a loud hum the next.

Any Help would be REALLY appreciated. I'm starting to worry.

Thanks for any help/info anyone can provide.

[ginormous]

Re: HELP!! (amp problems)

If it was an x-former prob, then the head wouldn't power up, and you'd have that "fried electric" smell. Hum most likely means there's a short-circuit to ground, and if the volume doesn't affect the hum level, then it's occurring after the preamp section. The new 6V6 may ease your worries.

[Low_fidelity2100]

Re: HELP!! (amp problems)

If it was an x-former prob, then the head wouldn't power up, and you'd have that "fried electric" smell. Hum most likely means there's a short-circuit to ground, and if the volume doesn't affect the hum level, then it's occurring after the preamp section. The new 6V6 may ease your worries.

Thanks for the response man. Knowing its at least not a transformer makes me feel a little better, haha.

Anyone else have any ideas of possible causes for this?

[Low_fidelity2100]

Re: HELP!! (amp problems)

Anyone else? Gearjoneser? Lew? Bruce? Scott_F? anyone else? I'd really like a second opinion, Or a conformation of what Ginormus said. Its not that I don't believe him or anything, haha. I'd just really like the opinion of a few more people if at all possible. I know theres alot of knowledgeable people on here, so please share your knowledge if you would? Thanks for any further responses guys!

[kmcguitars]

Re: HELP!! (amp problems)

If your having a loud hum. This generally means you have a open ground some where? (Like the sound your cable make when it's not fully plugged into your guitar jack) When troubleshooting it's a ruling out process. You've already ruled out the rec. tube. So the power tube in the next obvious place to look. The tube may have shorted internally? Your tube socket could need retentioning?(i.e.) Not making good contact with the tube pins. It could be a number of things? Go with the simple things 1st . Change that 6V6 and see what ya got? 90% of tube amp problems are the tubes. So the odds are in your favor. Good Luck

[Low_fidelity2100]

Re: HELP!! (amp problems)

If your having a loud hum. This generally means you have a open ground some where? (Like the sound your cable make when it's not fully plugged into your guitar jack) When troubleshooting it's a ruling out process. You've already ruled out the rec. tube. So the power tube in the next obvious place to look. The tube may have shorted internally? Your tube socket could need retentioning?(i.e.) Not making good contact with the tube pins. It could be a number of things? Go with the simple things 1st . Change that 6V6 and see what ya got? 90% of tube amp problems are the tubes. So the odds are in your favor. Good Luck

Yeah, I've been trying to Check all possible simple things I can think of. Looked inside and checked for any loose solder joints (no visually messed up ones), Checked the continuity of all the grounds By placeing one probe of a meter in a screw hole on the chassis and useing the other meter to touch every spot where it should lead to ground (The wire leading to ground, Not the actual solder joint to the chassis, cause obviously the chassis is grounded to itself, haha). No open grounds from what I can tell.
Also checked the resistance of basically ever resistor, with a meter. Most all of them tested close to what the schematic says they should be. A few tested a little far off from the value indicated on the schematic, But every single resistor did Give a reading. So that makes me think none of them are dead (although I could be assumeing wrong).
I cleaned out all the contacts on the Rectifier tube, and power tube socket. Tested all of the pins for continuity, and all checked out. Even used a tiny little pair of tweezers to bend the connections inside the socket to make sure they were makeing firm contact with the pins of the tubes.
I know the speakers not blown. Not only does it still produce a hum (for the few seconds before the fuse pops), But I also ran my valve jr. through it for a minute or two, just to be sure it worked.

I decided to recheck the tubes. Pulled the rectifier and left the 6v6 in place, fuse didn't pop (there was also no hum). Pulled the 6V6 and put the rectifier back, fuse didn't pop (although it did hum loudly). But when I put in both the 6V6 and the Rectifier at the same time, the amp Hums loudly, and then the fuse pops, every time. I'm useing preamp tubes that I KNOW are good (tested them in another amp). So I'm not sure whats going on.

I don't know how to go about checking the OT, or the PT to see if they're working. Which I assume they are considering the amp is getting power (tubes light up, and pilot light lits, up until the fuse pops), and obviously sending signal to the speaker in the form of a HUM. They are the Original OT and PT though, So I dunno if that means anything.

I also dunno how to check the filter caps to see if they're working. (although I'm fairly sure they are considering when I discharge the caps each time I open the amp up they spark. So that makes me think they're doing what they're suppoused to do, although I might be wrong. Not to mention that when I bought the amp in april it had Just had the caps replaced. So I doubt they've gone bad this quickly)

So I'm really confused as to whats happening and why. If only the Rectifier, or ONLY the 6V6 are in the amp, it doesn't pop the fuse (but does hum loudly when the 6V6 is in). But when they're both in together the fuse blows. Does that say anything? I mean does that give any sort of indication as to what the deal is? It seems really weird to me that the fuse Pops when they're BOTH in the amp. But if just one is in, its totally fine. Which seems Odd to me.

I'm really starting to think that the tubes aren't the problem, but that something else has some how gotten seriously messed up.

[Low_fidelity2100]

Re: HELP!! (amp problems)

Com'on Someone's gotta know SOMETHING that can help me figure this out. I really don't got the money to take this into a tech, so seriously if anyone knows (or even has a pretty good idea) what could be wrong given the info I've posted, I would REALLY appreciate some help.