So i recently just inherited an Ampeg SVT-CL head from a friend of mine and it needs a little bit of work. He told me the power supply needs to have a few resistors replaced and that it will need to be re-tubed. When i turned it on to try it i noticed that one of the 6 tubes was arcing. When i opened up the back to look at the tubes i noticed that 5 of the tubes were Genalex Gold Lion KT88's and that the one tube that was arcing was a Tung-Sol 6550. Is this an issue that all of the tubes are not identical? I know that the back of it says it has 6 6550's, but apparently this isnt the case here. Please help, this is my first tube amp so i am new to this!