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I have a Mk4 Boogie which I have had from new (1996) and which I love to pieces and use for at least 50+ gigs a year. On my last couple of gigs it has been very slow to come up to volume. i usually leave it on standby for about 30mins before the 1st set. It starts quiet and thin (very worrying) but gradually come up to normal volume after about 10minutes. The tubes are a couple of years old but don't seem to be malfunctioning. Any ideas?
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Boogie doesn't like their schematics being posted on the internet so I don't have anything to look at and wouldn't know of it's accuracy if I did find one. Beyond that, I would check that each tube is getting it's heater voltage. One or two of the preamp tubes may be run on DC and that could be the problem. Dirty tube pins or a bad tube socket could also cause a slow warm up.
Check the glow inside the tubes. Do any of them seem dim when you first turn the amp on?
Does the amp have any kind of effects loop or power amp input? Try running a guitar through there (cold and hot) to see if the problem is in the power amp or the preamp.
A problem like this can drive you crazy. You take the amp to a tech and he can't reproduce the problem. Try to gather as much information as you can. Verify that it's not anything on the guitar side, stomp box, cable etc, and nothing on the speaker side.WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
REMEMBER: Everybody knows that smokin' ain't allowed in school ! -
Thanks loudthud. I sent for a new set of tubes and the tech guy there also suggested dirty pins/sockets so before I installed the new tubes i sprayed swich cleaner on the pins of the old ones and waggled them around a bit. Seems to have done the job - complaints all round on Saturday night about the volume!!Comment
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If you will need in the futur, the schematic is in the link below:
http://www.schematicheaven.com/boogi...oogie_mkiv.pdfComment
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