noise in power tubes?

This just in and am tired to boot. Can power tubes such as the Genalex KT-88, generate noise in a channel all by themselves? I have swapped out the preamp tubes to no avail and am left with some puzzlement. This is a Bob Latino ST-70 with all the cap upgrades and it has been a trouper.

Point is, that I am just too tired to get up and swap the power tubes from left to right and instead will willingly tickle the keyboard...

Any tube can generate noise- but what's most likely is poor pin to socket contact. Take the power tubes out and clean down in the sockets. I use a good old fashioned pipe cleaner (get 'em at the drug store) and some DeOxit D-5. Spray the end of the pipe cleaner and work it around in the socket - repeat until a new pipe cleaner comes out clean.

Spray the tube pins lightly and then wipe them down with a clean white paper towel.

That's likely to help your noise issue, and even if it doesn't it's cheap and very much worth the effort.

Keep in mind that just the act of removing and reinstalling a tube can scrape the contact enough to get contact back for a while. But tube sockets and pins are very unsophisticated connector contacts, they are not gas-tight so they tend to collect crud. Clean them regularly and you'll likely avoid trouble.

Caig also markets some real nice little fiber brushes that work well in tube sockets ...

http://store.caig.com/s.nl/sc.5/category.202/.f

Handy for all sorts of stuff ... I also use them extensively for refurbing old mechanical clocks.

If it's crackling sort of noise then it is most likely the preamp tube sockets. What kind of nose are you hearing?

I have the same hash problem with front driver tube on one of my M-125s, so it doesn't have to be a poor contact in the pre-amp to cause this. I haven't tried DeOxit yet but old-fashioned tuner cleaner seems to do the trick. One of these days I'll get around to replacing the socket, as it's the only one that ever acted up, even after a tube trade with the rear one.

Rather than replace it, you may be able to get away with just closing up the contacts a bit. Only tool needed is a smallish blade screwdriver, but a sharpened paper clip with a few wraps of black tape for a handle works too.

http://billmaudio.com/wp/?page_id=171

Goes without saying, you also need to know how to properly discharge the amp and protect yourself prior to doing this, but you'd have to do the same thing to physically replace the socket, right?

sKiZo wrote:Rather than replace it, you may be able to get away with just closing up the contacts a bit. Only tool needed is a smallish blade screwdriver, but a sharpened paper clip with a few wraps of black tape for a handle works too.

http://billmaudio.com/wp/?page_id=171

Goes without saying, you also need to know how to properly discharge the amp and protect yourself prior to doing this, but you'd have to do the same thing to physically replace the socket, right?

Yeah, I wrecked enough TV chassis when I was a kid to learn the hard way about discharging. How long do those big caps in the M-125 stay hot, anyway?
Thanks for the tip, though. That would be a lot easier than soldering-in a new socket.

Just turn it off warm - a tube amp will discharge itself. I forget whether the 125's have a standby switch, but I do know some amps get modded, so if ya got standby, turn that off first.

Couple or five minutes should bleed them down below lethal levels ... if you're not sure, rule of thumb, keep a hand in your pocket so you don't accidentally ground yourself.

Oft mentioned, and worth repeating, never never turn an amp on without less than at least a couple minutes of rest time. You can do some serious damage otherwise.

sKiZo wrote:Just turn it off warm - a tube amp will discharge itself. I forget whether the 125's have a standby switch, but I do know some amps get modded, so if ya got standby, turn that off first.

Couple or five minutes should bleed them down below lethal levels ... if you're not sure, rule of thumb, keep a hand in your pocket so you don't accidentally ground yourself.

Oft mentioned, and worth repeating, never never turn an amp on without less than at least a couple minutes of rest time. You can do some serious damage otherwise.

No standby switch on the stock M-125.
"Never never turn an amp on without less than at least a couple minutes of rest time. You can do some serious damage otherwise."
I know that, but try telling it to our local power utility. Not their fault, entirely; we get electrical storms in the summer and enough snow and black ice in the winter to ensure some drunk runs into a power pole on a fortnightly basis, so two-second power blips are the norm.
I'm running a spendy Furman to clamp voltage at 120, give or take a volt, and two 20-amp GFIs that need manual resets should they encounter a power failure. Fingers crossed, so far, so good.
Thanks
David

The manual reset GFI sounds like a good idea. Unfortunately I don't know what it is. Anybody got a link?

Rather than hard wiring, I went with one of these ...



http://www.trci.net/products/shock-shield/user-attachables/single-outlet-adapter

Here's the important bit ...

To prevent unmonitored equipment startup, manual reset is required after GFCI trip and power outage.


15 amps, so it should be able to handle anything you can throw at it. I got mine at Amazon for less than $20 ... seems a good investment.

NOTE > As with any circuit breaker, you'll want to occasionally cycle the switch to make sure it trips as intended. Lot of older breaker panels are accidents waiting to happen - if they've never tripped due to a fault, they may not when you need it as the contacts can freeze due to internal corrosion.

Thanks. I'll check down at Lowes' first and then go to Amazon.

Maybe we can get Bob to start putting those in the kits ... along with what we need for the diode mod.

And maybe some gummi bears ... Panel Express gives me gummi bears.  

sKiZo wrote:Rather than hard wiring, I went with one of these ...



http://www.trci.net/products/shock-shield/user-attachables/single-outlet-adapter

Here's the important bit ...

To prevent unmonitored equipment startup, manual reset is required after GFCI trip and power outage.


15 amps, so it should be able to handle anything you can throw at it. I got mine at Amazon for less than $20 ... seems a good investment.

NOTE > As with any circuit breaker, you'll want to occasionally cycle the switch to make sure it trips as intended. Lot of older breaker panels are accidents waiting to happen - if they've never tripped due to a fault, they may not when you need it as the contacts can freeze due to internal corrosion.

Yep, that's the right stuff. I went with this one:
http://www.amazon.com/gp/product/B000XU7848/ref=oh_details_o09_s00_i00?ie=UTF8&psc=1#productDetails
Important thing, of course, is the manual reset. And good advice about cycling breakers etc. once in awhile.

Jim McShane wrote:Any tube can generate noise- but what's most likely is poor pin to socket contact. Take the power tubes out and clean down in the sockets. I use a good old fashioned pipe cleaner (get 'em at the drug store) and some DeOxit D-5. Spray the end of the pipe cleaner and work it around in the socket - repeat until a new pipe cleaner comes out clean.

Spray the tube pins lightly and then wipe them down with a clean white paper towel.

That's likely to help your noise issue, and even if it doesn't it's cheap and very much worth the effort.

Keep in mind that just the act of removing and reinstalling a tube can scrape the contact enough to get contact back for a while. But tube sockets and pins are very unsophisticated connector contacts, they are not gas-tight so they tend to collect crud. Clean them regularly and you'll likely avoid trouble.

Used the DeOxit on the socket cleaning and lightly used a small wire wheel on the pins with my Dremel.  Used DeOxit Gold on the pins and all is well.  This is the weakest link and I keep forgetting it. The sockets are cheap crap at best and oxidise if you look at them cross-eyed. I don't mind taking amps out of service for tweaking but I can well understand why most of the world abandoned tubed equipment when solid state came out with the promise of zero maintenance and never having to replace tubes again! The marketers never mentioned audio quality but so what...

Tested this using some very sensitive horns and it is silkily quiet now!

Still one of my favorite amps for sheer fun.  I do stress it as it is usually on for 12-16 hours per day and it is just a trouper.  It is the first amp turned on and the last turned off as it is hooked up to an iMac running PureMusic in my "lab" and is fed by the Toslink out of the Mac then to a Grant Fidelity Tube DAC-09 then to a Transcendent Grounded Grid preamp then the ST-70 makes an original pair of DCM Time Windows sing! Good to have it back on the line...

Anybody try using the Mr Clean Magic Erasers? I just took an old tube that was pretty grody and worked the pins a bit with one and they're nice and shiny now ... I imagine a quick brush with Deoxit Gold would make them good as new.

I just wiggled the pins into the pad then put a bit of side pressure in all directions as I worked it in and out a few times.

sKiZo wrote:I just wiggled the pins into the pad then put a bit of side pressure in all directions as I worked it in and out a few times.

For a minute there, I thought I was reading Penthouse!  

Bob Latino wrote:Nine pin noval tube sockets are more inclined to have non contact or partial contact issues than octal tubes simply because of the amount of contact area on the pins. The pins on those nine pin tubes are thin and have much less contact area with the socket than octal tubes do. If you experience a crackling noise or a static type noise on your amp, you should probably pull all the driver tubes and clean the pins as a first step in tracking down the noise. I may catch hell here but > years ago before Deoxit we just pulled the tubes and sprayed the pins with WD-40 and then wiped the pins dry and reinserted the tube. Many times this would cure the problem ...

Bob

Hee!

Bob, I'll forgive you!  

WD-40 - like almost all cleaner/lube/etc. type products has a carrier that is used with the active ingredients to allow the product to be carried into the device being cleaned. I'm sure it was the carrier in the WD-40 that was doing the work.

Caig DeOxit D-5 uses naptha as the carrier, which is a relatively slow evaporating (as compared to acetone and such) fluid. The naptha carries the active ingredients which have an affinity for copper based compounds like copper oxide or copper sulfide so they are an effective cleaner; the naptha also serves as a flushing agent. IF YOU FOLLOW THE INSTRUCTIONS DeOxit does a superb job of cleaning without leaving anything behind that would attract dirt (like WD-40 would have if you didn't wipe it off well when you used it back in the day).

If you want to see what gets left behind when you use DeOxit or any other spray cleaner/lube just spray a bit on a clean piece of glass plate. Then see what happens.

Note - the edits were to replace the word "acetone" with "naptha" where I mixed up the two - sorry!!

What do you use to clean out the mating pins on a noval tube socket?   I read somewhere that a cut off piece of a wound acoustic guitar G-string is about the right size.  Together with something like Deoxit the guitar string's windings are used to scrub the sides of the pin socket.  Be careful of what you read but sounds plausible.

And Jim McShane... which of the Deoxit extensive product line can be used on tube amps?   I also read to use Deoxit Gold as it has a higher temperature rating if some remains behind but may not be as effective in removing oxidation as the regular line.  So confusing.  Thanks, Scott

Hard to go wrong with the Caig cleaning brushes ...

http://store.caig.com/s.nl/sc.2/category.202/.f

Also, clean first with D5, then use the gold as a finish/enhancer/preservative. Put the pins halfway in, then wet brush them before seating them.  

And careful talking about G strings ... you'll wake up Captain Coconut ...

(Still hoping to hear some real world experience with the Magic Erasers ...)

The Caig brushes are all too large. The typical noval (small 9 pin) socket pin opening is a bit under .040" and the Caig brushes are .0625" or larger. The Caig brushes usually won't go down into the hole unless they are forced in which is not a good idea. They may fit some worn sockets, but the dental brushes are a better fit, they cost a lot less too.

There is no need to use the Pro-Gold or the newer "Gold" products on tube sockets or pins IMHO, but it won't do any harm if you do.

Just so everyone knows, I have cleaned 1000's of tube pins and sockets with D-5 with great results, so I'm speaking from real world experience. D-5 is good to 400F.

Edited to fix typo...

Thank you for the Deoxit clarification.   Sorry Capt. Coconut but that would be more like a light gauge D-string (32 mils) to fit the socket opening.