This is odd but ive noticed that the tubes on one of my ST70's vibrate while the other amps' don't. By vibrating i mean when you put your finger on the top of the 7199s, for example, you can feel them shaking. This happens with the EL-34s also but obviously they are slightly hotter to touch than the 7199's. Is there a reason for this vibrating and should i be worried? Thanks everyone!
2 posters
Vibrating Tubes
scsidude2- Posts : 21
Join date : 2010-03-19
Age : 38
Location : Dekalb, IL
Bob Latino- Admin
- Posts : 3277
Join date : 2008-11-26
Location : Massachusetts
scsidude2 wrote:This is odd but ive noticed that the tubes on one of my ST70's vibrate while the other amps' don't. By vibrating i mean when you put your finger on the top of the 7199s, for example, you can feel them shaking. This happens with the EL-34s also but obviously they are slightly hotter to touch than the 7199's. Is there a reason for this vibrating and should i be worried? Thanks everyone!
Sometimes tubes will vibrate because of induced vibration from the power transformer. The power transformer is the source of the vibrations and can set off the tubes vibrating. Other times the internal plates, screens filaments etc. of the tubes will vibrate on their own from current passing through the tube. Small signal tubes like the 7199, 12A*7 and especially the 6DJ8/6922 tubes are more likely to vibrate because the mass of the internal parts is smaller and more easily set into vibration. When the internal parts of a tube vibrates, the effect of the vibration may or may not be audible. There are a variety of tube damper devices out there designed to reduce or eliminate the vibrations ... Check out a few below ...
Cool damper
Herbies Tube Dampers
Vacuum Tube Dampers
Bob
scsidude2- Posts : 21
Join date : 2010-03-19
Age : 38
Location : Dekalb, IL
Thanks Bob, i had figured as much but its good to have clarification. Is it likely that the transformer will get worse over time? Thanks!
Bob Latino- Admin
- Posts : 3277
Join date : 2008-11-26
Location : Massachusetts
scsidude2 wrote:Thanks Bob, i had figured as much but its good to have clarification. Is it likely that the transformer will get worse over time? Thanks!
Sorry to say that yes - the POWER transformer will probably get worse in time. Most of the parts in the ST-70 except the OUTPUT transformers and the Mullard tubes were really of mediocre quality and were put in there so that the amp could be sold at a price point. That power transformer was never made to last 50 years. Many of the original PA-060 power transformers that are still in use hum, buzz, vibrate etc. They only had a 1 1/2 to 1 5/8 inch stack and without much iron in there to absorb the heat most of them run pretty hot also ...
Bob