Do I need to replace all my tubes?
Hi,
I have a Laney Cub 10 that sounds great, but some time ago I would lose volume after about 15 minutes of playing. The sound would come back after the amp was switched off for a few minutes. Now the amp won't produce any sound at all. I have tried playing through another amp with the same setup and I get sound. I'm pretty sure the problem is with the amp.
I live in Sumatra and there doesn't seem to be any tube amp specialists in my area. I got the technician from the shop where I purchased the amp to look at it. They said that all the tubes need to be replaced, and then they stopped communicating much and it seemed like they weren't making a lot of effort to find replacements. So I've brought the amp home to attempt the replacement myself. But I have a few questions.
I wonder if I need to replace all the tubes in one go, or if it could just be one that needs replacement. The manual says the amp needs 2 x ECC83 preamp tubes and 2 x 6V6GT power tubes. The preamp tubes that I pulled out are Ruby 12AX7AC5HG type. I have sourced some Sovtek 12AX7 preamp tubes that are in the same city as me. Do I need to match the rest of the nubmers in the model number or is this sufficient? The seller has these variations: 12AX7WA (7025), 12AX7WC, or 12AX7LPS. The seller also asked if I wanted light or dark tone. I wasn't sure what to answer. Any thoughts on which I should get? Here is the link to the online posting for these preamp tubes https://www.tokopedia.com/martwonderful/sovtek-12ax7wa-12ax7wc-12ax7lps-twin-triode-tube-12ax7-ecc83-7025?extParam=whid%3D12800657%26src%3Dchat.
I understand that power tubes need to be replaced together at the same time. The tubes I pulled out are Ruby 6V6GTSTR. I've sourced some Electro-harmonix 6V6GT tubes but they'll take about 5 weeks to get here. It seems like I've got the code matched up so I think I am find with these. Here is the online posting https://www.tokopedia.com/langsungjadi/6v6gt-electro-harmonix-pentode-power-tube-amp-guitar-fender-6v6-eh.
So is it likely that all the tubes need to be replaced at once, or should I start by buying just one or two tubes to start testing? I'm wondering if I should just buy one preamp tube and try that first. Or two power tubes, or should I just get the whole replacement set and hope that works? Does anyone think I've matched the tubes up wrong? Is there some other tests I should do before trying a tube replacement? (The indicator light comes on and all the connections appear clean and solid)
I would appreciate any ideas as I'm kind of working my way through this alone and am interested in other people's thoughts.
Thanks for the help and have a great day.
Greg McGuire
Hello Greg- Thanks for writing. Well, you have a tough question to answer!
It's certainly possible that you have a bad tube, but it's nearly impossible that you need ALL new tubes.
It's also very possible that you could replace all the tubes and the amp still won't work.
If you decide to buy tubes, any 12AX7 and 6V6 tubes work. The suffix used at the end doesn't matter in this case.
I suggest taking a look inside the amp. You may see some additional fuse(s) in there that could be checked with an ohmmeter. If you find a blown fuse you need to replace it. You could learn more about trouble-shooting over time but at this point checking the fuses and changing the tubes is about all you can do.
530-771-7345
www.skipsimmonsamps.com
Thanks David and Skip,
While looking for a fuse that I could check I started rexamining my tubes. I tried shaking them and noticed that one of the 6V6s produced a small metal on glass sound. The glass is painted black everywhere except the top. I got that tube under a brighter light and noticed scorching inside of the clear glass section. I'm starting to think that I've found the problem. I'm going to try and order a pair of 6V6s and try that out. I'm feeling that I should have noticed this before (and the tech before me too), but I guess I've learned something (if I'm right). I'll keep you posted on what I find.
I appreciate you both for taking the time to consider my situation and give me a hand. I hope you all have a great day.
Greg
Hello Greg. Skip will answer soon, but I just wanted to put you at ease, at least in regards to tubes. Tubes are pretty resilient... I've been playing tube amps since I was 16 years old and have not had one die on me yet.
They do die of course, so that could be the issue, but no way should you change all of them.
All the tube types you mentioned will work, and the local Sovtek 12AX7 is a perfect solution. I would definitely do one tube at a time, starting with the 12AX7.
With this said, it may not be a tube issue in your case. Can you go to the local source and try the tube before buying it? Pull out the first preamp tube and put the new one in... fixed?... no?... then try the next tube. This will save you money.
Don't buy anything until Skip gets back at you.