Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: simonallaway on April 04, 2011, 11:17:33 am
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Some of you fine forum members might recall my persistent posting about problems with my AX84 P1ex. It would cut out occasionally, had a dry joint on the preamp cathode cap and at one point had a blown rectifier. After all that it *still* cut out occasionally, but not as often. Other projects kept me from playing that amp quite as often, but I had the opportunity to do so yesterday. And of course it cut out on me again. Frustration led me to make a concerted effort to diagnose it once and for all.
Then a lightbulb turned on above my head. What about the speaker cable? Sure enough, there was a loose connection. As my iron was on for something else I had it fixed it 30 seconds flat! How stupid do I feel now?
:cry:
So, lesson learned....verify the simple stuff...i.e. get the fundamentals right first.
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That's thinking outside the box, literally. Glad you found the problem.
I followed those posts and I always take away something from this place everyday.
Rob
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Yes, that's really the hardest kind of problem to diagnose for me. My son's amp is on the bench right now. I'm just going down to check the speaker cable!
Thanks,
Dave
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Anytime anyone calls with a problem with their guitar electronics, my first question is ALWAYS, "Have you tried it with different cables?" Cables are the single most common electronic fault.
Gabriel
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Anytime anyone calls with a problem with their guitar electronics, my first question is ALWAYS, "Have you tried it with different cables?" Cables are the single most common electronic fault.
Gabriel
Or the knew neato gadget switch they wedged in there.
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I always check cables , power cords all the simple stuff first then dive into it. Glad you where able to locate the problem .
Rock On
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Thanks for the encouragement everyone. You're all right...check the simple stuff like cables, batteries, power cables, fuses etc. And especially blame the last thing that changed. I've been writing software for almost 20 years..I should know better.
A further question:
We all know that since the speaker is integral to the circuit, we cannot operate a tube amp without one. But in this case where I basically had an intermittent speaker connection, how much damage could it have done by not being connected for as long as 10 seconds? Or is the amp protected in any way by the 220R/5W that goes from the 8 Ohm tap to ground? See R5 on this part of the schematic:
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A bass player friend of mine(it figures a bass player.. :laugh:) was having trouble with his amp. It sounded terrible, distorted and low power. The first thing I looked at was his guitar cable. It was the one I had given him 10 years before. I pulled some POS thing out of my sound system van and OMG fixed!!!!!!
I got him some high end cables made for bass players. Who knows if it's was any better then anything else but I got a good price on them. That was 10 years ago and as far as I know he is still using those, but those should still be good.
I learned the hard way, especially doing the sound systems. Check to make sure you have a signal, make sure it's plugged in and getting power and make sure the cables are working and not intermittently. Same for building an amp, I always made sure all the bolts were tight, especially the input jack, speaker jack, transformer connections(some weird things can happen to an amp with a loose PT) and grounding lugs.
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A further question:
We all know that since the speaker is integral to the circuit, we cannot operate a tube amp without one. But in this case where I basically had an intermittent speaker connection, how much damage could it have done by not being connected for as long as 10 seconds? Or is the amp protected in any way by the 220R/5W that goes from the 8 Ohm tap to ground? See R5 on this part of the schematic:
Yes, it definitely helped you. But, tranny's aren't the most sensitive things like how a fuse can blow quickly but a factor can also be overall volume, power, and heat.