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[SeaOfEnergy]

Are there any amp techs in aberdeen? im changing the power tubes in my amp and need someone to bias it.

[skuzzlebutt]

what kind of amp is it....?

[SeaOfEnergy]

its a Rivera. Im changing from the stock el34s it came with and i hear you have to bias the amp after changing power tubes, does anybody here know their stuff about how to do this or know someone who does?

[Strat Harry]

Originally Posted by CRANIAL_MIND

its a Rivera. Im changing from the stock el34s it came with and i hear you have to bias the amp after changing power tubes, does anybody here know their stuff about how to do this or know someone who does?

i've never used an amp tech for a power valve change, i've always done it myself, and subsequently done a bit of bias adjustement here and there.. i've never done a rivera before. if you get nowhere with your search let me know... if i can help, i will...

[SeaOfEnergy]

Yea i really need to find someone to bias it, ive put in my new tubes but the amps not working properly, 2 of the tubes are heating up alot(too much) when i turn it on...

[skuzzlebutt]

Originally Posted by CRANIAL_MIND

Yea i really need to find someone to bias it, ive put in my new tubes but the amps not working properly, 2 of the tubes are heating up alot(too much) when i turn it on...

bias current way too high... different amps have different methods of adjusting bias, some have none at all, ie use these specific valves or nothing...

nice side of too hot is a quite warm and non brittle sound, down side, and it sounds like your amp is biased way too high, is that you can bugger your output transformer (expensive) and shorten the life of the output valves (a lot). i wouldnt turn your amp on again until you get it seen to.

does your amp come with a schematic diagram? any word in the manual regarding bias? what valves were in (ie stock) and what did you replace them with? (full part number of both) what is the model number of the amp?

[triggs]

i think bruce millers have an amp tech at the moment, or the only other thing i can suggest is Dennis Marshall he lives in fife but he's very good. heres a link to his company


Emerson Williams - Contact

[Lame Guitarist]

if the amp (and i can prob bet rivera don't) has an external bias point your ok, but if it doesnt dont go poking about in there. lethal voltages can kill in that thing and it doesnt even have to be switched on for that to happen. inside you will usually have your bias pot but you would need to measure the plate voltage with a multimeter and find out what reading your tubes need to be set at. even putting in the same valves as were stock you will need to re-bias.
i revalved and re-biased dan atoms VH-4 recently and had to do it while the amp was on. had to be veeeeerrrrryyyy careful i didnt touch anything else other than the bias pot.
find as much out about the amp as possible, maybe even send an email to rivera support asking what they recommend as the bias reading per pair of tubes.

[SeaOfEnergy]

Thanks for the help guys, im going to take it up to bruce miller at the moment, all the talk of lethal voltages and electrical know-how has put me off of d.i.ying it!

[Scotland]

Ron Macaskall in Balmedie. Excellent amp tech.