Selmer 100watt PA/4

[blindboybenton]

Hi.. Ive got a British built Selmer PA/4 100watt PA Head.. I brought it from Ebay.. Did a full service 2 x Gz34 and 4 x EL34 JJ's and all new electrolics all the correct values..I aint changed the ecc83 for new ones but i have swapped them around from stock.. I used it for the first time at a gig ( Spare on standby) it started to make sounds like what i think you call Motorboating. I turned it off and on it was ok.. Than after a few times.. pop went the fuse.... New fuse, its ok mostly But if you connect the bass up last when its on, motorboating may start again.. But if you do the other way around its good as gold.. Mostly.. may motorboat with doing anything.. Im new to valve amp repair,, Brought up on transistor stuff.. Ive only got a test meter.. Can anyone help ?

[nickb]

Does it still happen if all four input gains are a minimum. Try bringing up one at a time. I'd look at C34, C33, then, depending on the channel C8, C16, C24 and C2. It didn't happen before you changed the caps, right?

[blindboybenton]

Hi
I didn't really use it when i brought it.. went straight for service.. all the pre amp caps changed.. ill have to check if it happens with all gains down.. i know it happen on any channel.. thanks for the info
John