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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Tube amps blowing fuses posted by Sturmey on August 28, 2006 at 10:10:33:
Jeff,Did a quick google search but the only Jolida schemo I could come up with seemed to incorporate only one fuse - if we could identify where the fuse that blows is in circuit the advise would be better. If you know what this fuse does - B+ supply, heater, etc., please provide it. Also the sizes - in amps - for the fuses would help.
It sounds like there is a strong correlation between the popping noises and the blown fuses? That is, did they start "at once" or has the popping been going on for while? Do your output tubes seem unusually warm and can you observe them when you first fire the amps up or when the noises start to occur?
Someone suggested a tube tester but I'm not sure that this is the best use of your funds unless you are testing and selecting large quantities of tubes. In the early 70s when I worked in a "we fix everything" electronics shop (as opposed to audio only which has been my focus for the last few decades) we "tested" tubes by substituting a known good tube for one suspected of being problematic - we kept a specific set on hand. If the problem - noises, lack of oscillation in RF circuits, the presence of oscillation in audio circuits, etc., - went away when the suspect tube was replaced by a known good one then the suspect tube "test" was done.
Unfortunately most tube testers don't test tubes in conditions that closely enough match those in actual circuits - and the few that do are expensive and do require calibration periodically. You are also purchasing test capability that you will probably never use (such as thyratrons, etc.).
My "tube tester" is a small two/three stage SE audio amp with three preamp sockets (7 & 9 pin and octal) and four octal sockets (the same as the preamp with two differently wired octals). With a few switches and a bit of measurement (multiple tip pin jacks) I can determine current and gain and balance for the tubes under test up to 500VDC (and can extrapolate other factors but a constant current source would be nice). While definitely being limited I can still test most of the tubes I work with (no DHTS but I rarely use 'em) and I determine "noise" with my ears and a 'scope and a few taps with a pencil.So, since any tester requires calibration you might consider purchasing a "calibration set" of each tube that your amp uses - buying them from someone who will individually test each tube and determine that they are "average" in characteristics for the type - and sticking these in careful storage for use when you suspect a bad tube in your amps. With a tube tester you'll need a calibration set anyway so you've already started your investment should you decide to go the tube tester route.
Hopes this helps,
Rob
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Follow Ups
- Re: Tube amps blowing fuses - longish - Rob Mercure 05:17:29 08/29/06 (0)
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