low level hum caused by faulty/dying 5AR4?

OK, here's what I've noticed.
Can a faulty/dying 5AR4 create hum/noise? The reason I am asking is that the last few times I turned the ST70 on, once the TDR kicked in, there is a bright flash at the top, just for a second, as well, this morning, a small glowing object seemed to fall from the top area down to the bottom of the tube, perhaps the filament coating coming off?
It might not be a bad idea for me to get a couple of 5AR4's, is there a beefier replacement for it, I might also get a copper top, thanks.

ps I do have the diode mod

The GZ68 copper cap is handy to have available for testing and backup. Lotsa folk are happy with them for daily use also.

You know me ... I like BIG BOTTLES and I don't know why! They're just so BIG and they catch my eye!

(The previous Sir Mix-A-Lot moment brought to you by Mullard)   

I've also got a couple of the Chinese 5AR4's from Bob when I got the amp - good backup for the backup ... I like redundancy ... I like redundancy ...

PS ... I'd expect if it's a short in the rectifier, the hum would be equal in all channels. That's where an extra tube comes in handy for a quickie check. My first instinct would to try slight pressure side to side to eliminate a loose socket as the problem. As far as things falling from the top - some leftover sacrificial metal from the getter?

Also, not aware of any direct tube substitute for the 5AR4 other than the GZ33 or GZ37. Both pricey, but very reliable and amazing longevity. The Mullard GZ34's have the same characteristics and power handling of the newer 5AR4's but also have greater reliability. It's all those exotic metals they used to use that are either no longer available or prohibitively expensive to use. There's also the 5R4 family, but those have a larger voltage drop that may - or may not - work with our amps. Some folk here have had luck with them, me, not so much. I tried one of the Philips 5R4GYS that sell for half the price of the GZ37, but mine failed within a month. Maybe just luck of the draw ...

plug is good, thats the first thing I checked. The hum is the same out of both speakers, which makes me think that it is a common denominator.
I have ordered another 5AR4 as well as a Copper Top WZ34.

Were are you ordering the Copper top from?
I tried to order direct a few Months ago and could never contact anyone so I gave up.
Thanks

To make sure it's your amp, short the inputs of your amp and see if it still hums.

Maintarget wrote:Were are you ordering the Copper top from?
I tried to order direct a few Months ago and could never contact anyone so I gave up.
Thanks

I ordered it directly from Weber's site, http://www.webervst.com/ccap.html, below the 'models' table on the main page, you'll see an "Order" icon, click on that and it will take you to the order page.

corndog71 wrote:To make sure it's your amp, short the inputs of your amp and see if it still hums.

Pretty sure it's my amp, unless someone built another one just like it and snuck it in when I wasn't looking ...

Oh, wait ... you're talking to Montana ... my bad ... never mind ...   

***

PS ... does the WZ34 work well in the ST120? I do know the 5AR4 is getting pushed pretty hard in these things, so common practice is to go with the WZ68 ... twice the current handling, same price.

Oh. In the interest of being somewhat useful for a change, previous link to the copper cap website doesn't work ... try this one.

http://www.webervst.com/ccap.html

Thanks I was able to order two copper cap WZ68 as back up for my VTA ST-120, been thinking about those M-125s hard to justify when the ST-120 sounds so awesome at 350 hours and I haven't turned it up past 12 o'clock yet

Maintarget wrote:Thanks I was able to order two copper cap WZ68 as back up for my VTA ST-120, been thinking about those M-125s hard to justify when the ST-120 sounds so awesome at 350 hours and I haven't turned it up past 12 o'clock yet

I've been running WZ68 copper caps for about 6 months now in my M-125s and no grief with them. I have a more stable speaker load now than when I started with this business and the copper caps failed fairly regularly back then.  I guess 2 ohm speaker array is hard on everything. With 4-8 ohms, everything's stable. Troy Madden repaired and modded a couple of the WZ68s for me and they're working fine.
I have a pair of ancient GZ-33 Mullards that are just about bullet-proof, but they are hard to find and are expensive, so don't use them except for visiting royalty. The copper caps are built to order so expect a week or two to get them.

well I solved my low level hum problem. It was a combination of a bad VTA ground solder joint and I am also sure a bad 5AR4, it used to sparkle and crackle and finally gave up a couple of days ago.
A new production Mullard GZ34 is now the new rectifier, no sparkles or crackles, all is good!
A slight noise issue with my custom SP9 has also been solved, turns out that I had to ground every aluminum panel, not just the top one. I am using a wooden chassis, that is why.
Learned a lot about audio ground in the process, so all is good!   

Good to hear, Montana! Our learning curves get less horizontal as we enter our dotage.

deepee99 wrote:Good to hear, Montana! Our learning curves get less horizontal as we enter our dotage.

learning curve???....what learning curve.....  

MontanaWay wrote:

deepee99 wrote:Good to hear, Montana! Our learning curves get less horizontal as we enter our dotage.

learning curve???....what learning curve.....  

Kinda like learning how to fly-fish when you're 50.... Or do you Montanans use them bait rods. To spin is to sin.

deepee99 wrote:

MontanaWay wrote:

deepee99 wrote:Good to hear, Montana! Our learning curves get less horizontal as we enter our dotage.

learning curve???....what learning curve.....  

Kinda like learning how to fly-fish when you're 50.... Or do you Montanans use them bait rods. To spin is to sin.

SACRILEGE!!!....I spit on spin fishing!!   

MontanaWay wrote:

deepee99 wrote:

MontanaWay wrote:

deepee99 wrote:Good to hear, Montana! Our learning curves get less horizontal as we enter our dotage.

learning curve???....what learning curve.....  

Kinda like learning how to fly-fish when you're 50.... Or do you Montanans use them bait rods. To spin is to sin.

SACRILEGE!!!....I spit on spin fishing!!   

And a River Runs Through It. Story o' my life, complete with the newspapering and whoring etc. Bet if Norman Maclean were still alive he'd be running VTA gear.

we fished some of the areas on the Gallatin they used in the film.......yeah, that movie let some of the riff raff into Montana.....oh well......

MontanaWay wrote:we fished some of the areas on the Gallatin they used in the film.......yeah, that movie let some of the riff raff into Montana.....oh well......

Better they go to Montana than stop in Idaho. My mother gave me that book maybe 3 decades ago,when it first came out. So we hide in our little potato state, where you can't even grow a rock up in this part of it. You're welcome to the Hollywood honyaks.
We'll keep our rivers, rifles and rights to blow the neighborhood loose with good tunes, thank-you. Robert Redford is your problem.

The sign in your avatar should say will Fly Fish for food .   But the line would probably just get caught in your beard .

pigface wrote:The sign in your avatar should say will Fly Fish for food .   But the line would probably just get caught in your beard .

If I had to live on my fly-fishing skills I'd be skinnier than the guy in my avatar. But when the .45-70 comes out, game better keep their heads down. Gawd, I love that rifle, it's a Ruger No. 1, best long-gun I've ever owned.