Salad Days

Thanks again for the quick response but it seems my amp wont go into standby at all without blowing a fuse now. It even blew one without the amp being switched on at all. (I suppose it hadnt cooled down yet.) I'm at 7 blown T500mA fuses now just from trial and error in trying to get the thing to work. Funnily enough i'd just tried turning the bias pot the the extreme clockwise and anti-clockwise positions just before reading your reply but got the same result in both positions. Something is definetly up with it. I think its possibly time to take it to a tech but im open to suggestions. Thanks very much for your help myles. Its much appreciated.

Hi myles, thanks for the response. I tried to measure the bias on my amp but the fuses are blowing the second i hit standby off now. I might try setting the bias really low and turning it on but im reluctant as last time there was a blue flash in each power tube and im concerned about them becoming damaged (if they arent already that is). Last time I set the bias I set it to 32mA, that was when the tubes were brand new. I'm using 6L6CHP groove tubes. Does the bias change as the tubes break in or anything?

Hi again Myles, I'v got a problem with my 1987x marshall (again). This time I keep blowing the t500 fuses after about 20 mins of play. I seem to come into trouble when i'v got the respective volumes at around 2 and 6 with the channels linked via patch cable and I run an overdrive/fuzz pedal into the amp's front end. After a while the signal dims and breaks up quite quickly until nothing comes out the speakers. I check the fuse and its kaput. This is the second time its happened in 2 days. I ran into this problem a few months ago also but I thought it was because of the bad valves problem I was having at the time. I'm running the amp set to 4 ohms into an attenuator (tube cube) also set to 4 ohms and into a 4 ohm cabinet. The problems only really cropped up since I started using the attenuator so im begining to suspect its the cause as im not running the amp any harder than i have done previously. Any thoughts? Cheers, Rich

Ugh, its one thing after another just now... I'll try and take it up with the place that sold me them although I expect they'll pass it off on the post office. I wish now i'd gone through a shop rather than ebay. If i cant get this resolved I think i'll just shell out that little bit more for the winged C's this time round. Thanks again for the advice myles. Really. Its much appreciated. Rich W.

Its the marshall 1987x. I set the bias to around 32. One at 30, one at 34. If i measured the plate voltage correctly I got around 470.

Hi again Myles. I have another question. I hope you dont mind. So I got a set of matched JJ 6l6gc's. I looked around for the ones you mentioned but they were a fair bit more expensive than the JJ's so I just opted to go for them. So they arrived this morning and after trying them out I'v noticed something... Whenever I play a note at decent volume they give a high pitched rattle sound that sort of squeaks. The more I push the amp the worse it gets. This only happens for a second as soon as the note is played but after all the trouble i'v been through with my amp its got me concerned. I did wonder if it was perhaps that the valves were not broken in yet or perhaps i'v biased them too hot but I thought it best to ask a trusted opinion before i do anything else, just incase. I am running the amp with an attenuator (tube cube) if that matters. Thanks again! Rich

Looks like i'll go with the 6L6CHP's then! Thanks myles. I appreciate the advice.

Thanks myles! Sorry to keep bugging you but do you think i'd be able to use kt88's?

Yeah the tech told me it had the marshall mods to run 5881's and that the e34l's i was using were going to be problematic. I probably didnt give bob enough information when i discussed it with him. But I didnt want to harass the guy with emails about specifics i'd perhaps neglected. He's always been on the ball previously. Can you reccomend me a set of valves to use in my situation?

Hi Myles, Hoping you can help me. I have a 1993 Marshall 1987x reissue that originally came with 5881 valves. I'v been using a set of JJ e34L's for around a year now at the reccomendation of bob@eurotubes and its been great until recently when my amp went down while playing it cranked. So I took it to a tech who says I shouldn't be using el34 types in my amp as it has different value screen resistors (among other things) to accomodate the 5881's and i was lucky my amp wasnt fried. I emailed the Bob@eurotubes again who reassured me It should be fine with the e34l's. I trust bob's judgement generally but that sound control tech has me paranoid so I wanted to gather a third opinion. Cheers, Rich