| Author |
Topic: Tube Amp Issues |
Craig Bailey
|
Posted 16 Mar 2018 1:29 pm |
|
| I wanted to see if I could get some suggestions/advice on a tube amp issue I am having. I have an amp I bought brand new a few months ago that is continually giving me problems. When turning the amp on and off it intermittently pops very loudly and I always use the standby to turn on/off. It does this regardless of location and I always use a surge protector. Also, the amp will go from beautiful sounding to sounding terrible. Not sue what is causing the changes in tone. Its weird. I sent the amp back to the builder and he changed a tube but said everything else tested out fine. I got the amp back. It did fine for a few days and the same problems started back. I have checked the tubes and they seem fine. I am afraid to gig with the amp because of the issues and find myself using other older amps because of the unreliable intermittent issues. I would love to be able to solve the problem and finally use the amp like I bought it for. I would appreciate any thoughts and/or trouble shooting ideas. |
|
|
|
Len Amaral
From:
Rehoboth,MA 02769
|
Posted 16 Mar 2018 2:10 pm
|
|
| Does it pop loudly with the volume completely off when you flip the standby switch and nothing plugged in the input jack? |
|
|
|
Craig Bailey
|
Posted 16 Mar 2018 4:25 pm
|
|
| Yes it seems to do it intermittently whether or not anything is plugged into the input jack. |
|
|
|
Len Amaral
From:
Rehoboth,MA 02769
|
Posted 16 Mar 2018 4:38 pm
|
|
| What type of power tubes and how many? Also, same question with preamp tubes. |
|
|
|
Craig Bailey
|
Posted 16 Mar 2018 5:19 pm
|
|
| looks like 4 6L6 JJ power tubes and has a 12AX7 preamp tube, a 12AX7 mid-amp tube and a 12AX7 phase inverter tube and Power rectification is handled by a GZ34. |
|
|
|
Len Amaral
From:
Rehoboth,MA 02769
|
Posted 16 Mar 2018 6:04 pm
|
|
Sounds like a tube issue. See if all the 6L6 tubes are glowing the same color.
V1 preamp tub is usually closest to the transformer or input jacks. Since all the Preamp tubes are 12 AX7, try switching them around.
Better yet, get a new 12AX7 preamp tube and swap that out one at a time starting at V1 and test the amp after every change. Process of elimination with the Preamp tube will help to narrow the search if it’s a Preamp tube.
Look at the back of the amp while turning on the standby switch on and off and see if the power tube react to the popping noise. Tube amps can be finicky and one bad tube can be a gremlin. |
|
|
|
Dave Meis
From:
Olympic Peninsula, Washington, USA
|
Posted 17 Mar 2018 12:52 am
|
|
| Pulling out the PI tube will isolate the power section for troubleshooting. Then it's just the power tubes and speakers. With the PI tube in, tap ALL the tubes with a pencil or chopstick and see if you can replicate the sound. Good luck! |
|
|
|
Tony Prior
From:
Charlotte NC
|
Posted 17 Mar 2018 1:14 am
|
|
It would help if you told us which amp you are having issues with. Leaving it generic doesn't help the cause.
A loud pop ( on/off) can be common or it could be a defect in the Power Supply. Many solid state amps POP normally. Regarding tone, this could also be a diminishing Power Supply issue, especially with a tube amp.
Probably the first thing you want to learn is, do the other AMPS ( same amp) from this same builder/supplier, POP when you turn them on/off ?
start there.
_________________
Emmons L-II , Fender Telecasters, B-Benders
Pro Tools 12 on WIN 7 !
jobless- but not homeless- now retired 9 years
CURRENT MUSIC TRACKS AT > https://tprior2241.wixsite.com/website |
|
|
|
Donny Hinson
From:
Glen Burnie, Md. U.S.A.
|
Posted 17 Mar 2018 5:10 am
|
|
| While your amp is operating, tap each tube with your finger. Any electrical noise will tell you if the problem is a tube with a loose element, or maybe a socket that needs to be re-tensioned. Next, try rapping the amp sharply with the heel of your hand, and see if there's any electrical noise as a result. These tests will usually identify a simple mechanical issue. If they reveal nothing, then you'll have to get a tech to check for purely electrical issues, like a bad resistors, capacitors, etc. |
|
|
|
Brian Hollands
From:
Geneva, FL USA
|
Posted 17 Mar 2018 5:40 am
|
|
Having built a couple of amps I can tell you Dave M's advice is sound. Separate the preamp from the power section to diagnose which end has the issue. Also contact the builder again as he can likely help you trouble shoot better than we can.
If you're not comfortable opening up the chassis to get voltage readings (which is dangerous) you'll likely have to send it back to the builder. Don't open it up if you don't know basic safety rules (one hand in pocket, chopstick use, etc) as even unplugged there are dangerous voltages present. Start with Daves advice |
|
|
|
Tony Prior
From:
Charlotte NC
|
Posted 17 Mar 2018 6:49 am
|
|
we really don't have enough information to answer any questions. For all we know this amp POPS normally . We don't know what brand , what model or how old it is.
Being a schooled repair guy ( RCA TUBE Book ) tapping tubes may find an issue but may not. Seems to me someone has already told him the tubes check out ok, that would be the manufacturer whoever that was.
Opening up an amp, especially a tube amp , can be very dangerous to the unaware person. Tube amps can run a VERY HIGH +DC , many seriously above 400 VDC.
It's time for a legit tech to take a look and see whats up. Power Supply, screen/ grid resisters, tube socket, bad solder joint... all sorts of things can exhibit this same type of issue.
_________________
Emmons L-II , Fender Telecasters, B-Benders
Pro Tools 12 on WIN 7 !
jobless- but not homeless- now retired 9 years
CURRENT MUSIC TRACKS AT > https://tprior2241.wixsite.com/website |
|
|
|
Jim Sliff
From:
Lawndale California, USA
|
Posted 17 Mar 2018 4:31 pm
|
|
As already mentioned there's not enough info.
There is still no answer to one tech detail - does it do this with the volume control completely off?
And to repeat another previous question, what is the make/model? If it's a small maker were you given a schematic? If so, take a picture or scan and post it (if not - get one).
But I don't understand the reason for thread. The amp is only a few months old - DO NOT accept "it's working fine" when it's not. And if he's already checked it out for you it's not a "tube issue" - it's an amp issue.
Since you apparently are not a tech (as previously mentioned) DO NOT open the chassis - it's not safe. Tell the builder to 1) fix it or 2) you'll take it to a qualified tech and have him pay the bill.
It's a WARRANTY issue. There is NOTHING for you to deal with but have the builder fix it or pay to have it fixed. And if that has to happen - yikes.
And FWIW the standby switch is only used when turning the amp on - it does nothing when turning it off. Just shut both switches off.
Many techs - I'm one - think standby switches only serve the original purpose - to put the amp on "standby". They were never installed for powering the amp up and early installers like Fender and Marshall never intended them (nor used them) for "power up" reasons. Many amp makers don't include them - their "take" is to just roll off the volume control during breaks.
IMO you can just turn both switches on, or just leave the standby switch "on" unless you want to silence it at a gig. I haven't had a problem related to that ever, and neither have any of those I work with (including other techs in the area).
_________________
No chops, but great tone
1930's/40's Rickenbacher/Rickenbacker 6&8 string lap steels
1921 Weissenborn Style 2; Hilo&Schireson hollownecks
Appalachian, Regal & Dobro squarenecks
1959 Fender 400 9+2 B6;1960's Fender 800 3+3+2; 1948 Fender Dual-8 Professional |
|
|
|
Craig Bailey
|
Posted 18 Mar 2018 4:42 am
|
|
Thanks for all the input. The amp is a Little Walter 89 watt. Yes it pops with volume completely off. I don't have a schematic. The tubes have checked out fine. This amp has an issue somewhere and it is being a gremlin.
Last edited by Craig Bailey on 25 Mar 2018 4:31 am; edited 1 time in total |
|
|
|
Mark Fowler
From:
Minnesota, USA
|
Posted 22 Mar 2018 1:36 am
|
|
The standby switch could be bad/failing. The rectifier tube is bad.
To stop the pop sound a 100k or greater resistor across the switch. |
|
|
|
Stephen Cowell
From:
Round Rock, Texas, USA
|
|
|
|
Carl Mesrobian
From:
Salem, Massachusetts, USA
|
Posted 24 Mar 2018 12:41 pm
|
|
Save time - contact the builder. Keep bugging him until he gets it right. You paid a lot of money for it.
Also if it was shipped back to you, who knows what might get knocked loose - it doesn't take much to open a failing solder joint, short/open a component, etc., etc.
Was it tested complete (head/speaker), or just the head tested?
_________________
--carl
"The better it gets, the fewer of us know it." Ray Brown |
|
|
|
Craig Bailey
|
Posted 28 Mar 2018 3:47 am
|
|
| Thanks for all the suggestions |
|
|
|
Don Brown, Sr.
From:
New Jersey
|
Posted 28 Mar 2018 7:41 pm Amp Popping
|
|
Craig,
You wouldn't by any chance, be the Craig Bailey from NJ who had the Bar on Rt 40?
And to get back to the Amp, try using it Without the surge surpressor and see if it still does it.
Next (if the above didn't help) try turning each of the controls back and forth from 0 to wide open one at a time and see if you can get it to duplicate the pop.
Then finally check for a bad input, wiring, and Cold solder joints. That's what it sounds like to me And/or a Broken Circuit Trace Most likely would be a Bad Solder Connection.
Hope that helps.
Don Brown,
NJ |
|
|
|
