[Amps] QRO 2500 MARK lll

[Bob Gibson]

I have a problem that just came up with my QRO amp..First I blew a 1/2a fuse on the bias board..I replaced it turned it back on then a 1/2a fuse blew on the LV and bias board again but not the same fuse..Screen voltage is OK and HV is OK. When I hit with 10 watts the fault light comes on and kicks the amp off and I see the grid current meter go all the way over..I see no burnt parts or smell parts...could this be a grid short in one of the tubes? I have pulled the tubes and nothing looks bad below..I think I will send the tubes down and have them check just to make sure it is not a problem with one of them..Bob W5RG