The 300bs should be going all the way down to the socket no matter which 300b tubes you're using. If they're not all the way in, that could be the source of your issue. And just because the old tubes work not being in all the way, doesn't mean they're working correctly. Be firm, but don't over force them when inserting into the socket.
I'll mention that you have to be careful with the different-sized pins. Make sure the tube is aligned correctly. And yes, the tube's pins should go all the way into the socket.
Yes, I'll echo Strat Mangler. 300b tubes have two different sets of pins at the base. Two are larger and two are smaller. Make sure you're lining them up to the corresponding holes.
That's strange, I've never had that issue with a bias meter before. Usually faulty tubes will be completely dead or will red plate. Do the ACME's light up at all in both positions? Echoing what was suggested that prior to installing new tubes, bias should be adjusted to the minimum voltage possible (at least closest to minimum), and adjustment should be done after 2o-30 minutes and checked periodically to see if the tubes have settled and bias holds.
Nope, checked the seatment it is seated all the way. Same thing happens. I am using the stock tubes currently. Exhausted at the moment troubleshooting it.
Depends on many factors ranging from its architecture to how it was used (cranked VS babied). Impossible to predict but tubes in general will last hundreds of hours at least. Some will last thousands of hours. And you might run into a defective tube or one who'll prematurely die or start to misbehave. Again, next to impossible to predict.
Seeing lots of rave reviews for the PSvane ACME 805 tubes in this thread. Has any fellow LM owner upgraded from Cossor to the ACME? It’s more than 3x the money, but how big is the jump in sound quality? Is it as large a jump as going from stock to Cossor?
There should be some 'wobble' as the sockets are spring loaded. Is there 'a lot' more wobble with the problem tubes in place? I own several brands of 300b's, I can tell you that there is no standard for the diameter of the pins... just that 2 are fat and 2 are slim. It is possible to orient a 300b the wrong way, all it takes is a socket with wider than normal holes (even though 2 are bigger than the others) mated with a tube that has smaller than normal pins (even though 2 are bigger than the others)... in that case, the big pins could fit in the small holes. Always double check before seating. A more likely issue might be that the sockets have lost some tension and while making contact with your original tubes, they may not be making good contact with the different brand. Try re-tensioning the sockets and see if that helps. BE CAREFUL, know what your doing. At the top of the list is: Amp off and unplugged, even let it sit for awhile. Anecdotal experience on the above... I had an amp with 4 el34 tubes that I could check the bias of each tube easily. When I would check it, one of the tubes would always be a little low. I reset it then the next time same tube was a little high. I cleaned pins and sockets to no avail. One day I found that if I touched the top of the tube (while in bias mode) and moved it as little of 1/16 of an inch, the bias would jump back up to perfect. Re-tensioned the socket and it's been fine ever since. I bet if I had bought another tube 'that happened to have fatter pins' it would have solved the problem also. One way was free. I like free. Good luck.
I had a similar issue when I introduced Acme 805 tubes to my system. On the 8 Ohm taps, bias would rocket all the way right after about 20 seconds of use, and the 805 tube would glow very bright. This issue didn't follow the 805 tube based on the channel I put it in, so I suspected other tubes were the cause, and I nailed it down to the 300b. Switching speaker cables to a lower impedance terminal, 4 Ohm taps rather than 8, prevented this sudden bias swing and tube glow. And, as an addict, I believed the issues were behind me. You are being redirected... However, over time, that channel couldn't maintain bias, and dialing the bias pot all the way to the right would no longer hit the 140 recommended mark, and this value kept creeping down. Solution was to eventually replace the Elrog 300b on that channel. This was a painful replacement since the Elrog was out of its 1 year warranty period. After replacing that single tube, I have been able to switch speaker terminals with no issues, had no biasing issues, and all seems well with the world. I would surmise that it is best to replace those 300Bs while you can. Their stability is what influences maintaining bias, IMO. What is weird is that I had no issues with my 300bs until I introduced the Acme 805s. It appears they require the driver tubes to work harder that their predecessor Psvane 805-ATs. Best of luck!
Thanks for the reply. To clarify, are you referring to the delta from going stock to ACME or the delta going from Cossor to ACME?
I had upgraded from Cossor to Acme and keep Cossor 805 just in case. I think it is worth it. Cossor is not bad but Acme is more transparent and refined every way. But it is a value judgement. Thus it is up to your budget.
Good evening. Has any of the gentlemen obtained a schematic of the LM-508IA? Neither my dealer nore Line Magnetic are willing to disclose it. If not, can you tell me for the time being where coupling caps are and what values they have? Thank you very much and regards from Germany
Hello guys Im a happy owner of a LM-508IA and I've just read your posts about the caps failure and I've got worried. Can you please give us more information about how do you use yours LM-508IA? I mean, average hours per listening section, average volume levels, how many months it took to fail, ventilation of the rack holding the amp, and any other information you consider important. Thank you! PS: sorry for the late reply, but I didnt follow the thread in a long time.
I recommend you to read the thread dedicated to the failure so you can see the outcome. Design flaw for Line Magnetic's LM-508IA.
Welcome to Lm 508 clubs. You will have lot of fun in tube rolling with 508. On the safe side, I turn off the amp after playing it for 2 hours and have a break of 30 minutes before turning it on again. Acme 805 and 300B work wonder for LM508 amp. Some Acme tubes seems to have QC problems. I had issue with mine too. But good news is that I have not had any problem with my Acme 805 and 300B for 1.000 hours during last 10 months.
Looks are the last thing that'd concern me with tube purchases. At that price, I'd suggest buying a matched pair of Sylvania Chrome Tops which will inevitably sound better.
Have you tried and compared the treasure globes to the chrome tops? Just curious since you mentioned it is inevitably better sounding. I do have the chrome tops btw.
