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Tube guitar amp blowing fuses - suggestions?

unSane — Mon, 13 Aug 2012 18:51:16 -0800

My Egnater Tweaker 40w head is blowing fuses. Possibly lightning-related, or possibly not, but I need to fix it. More details inside. My fairly new Egnater Tweaker 40w head was accidentally left on in my outbuilding rehearsal room during a thunderstorm. We had a lightning related power outage during it.

When power came back the amp was dead, although it was at least 24 hours before I noticed so it may be unrelated to the storm.

I tracked this down to a blown 3A fuse in the mains socket, which I replaced. I powered it back on with all the tubes out to rule out a dead tube, and the fuse instantly blew again.

I live a couple of hours from anyone I trust to service amps, which is also how far I am from an Egnater service dealer, so if I can solve this myself so much the better. I'm happy working on tube amps and I know how not to kill myself.

Presumably this has to be a problem in the power section. Any clues? There's a surge protection cap which looks fine but is my main suspect at this point.

Help me fix a crackling guitar amp.

unSane — Sun, 24 Oct 2010 08:00:43 -0800

Help me diagnose my (probably user-induced) intermittently crackling tube guitar amp! Okay, here are the data points:

-- Brand new Blackheart BH15H head, worked fine out of the box

-- I installed the Bitmo Triple Bypass mod myself (which involves soldering in a three-way switch and couple of capacitors and resistors).

-- After the mod the amp works as expected -- overall tone much improved -- but produces a 'bacon frying' crackling and noisy volume pot when I first turn it on. After about 15 mins to half an hour, the noise goes away and it works silently.

-- I have checked all my solder joints and they seem solid

-- I have swapped out both the tubes and it makes no difference

-- I have cleaned the volume pot, no difference

At this point I'm suspecting either (1) a dry joint that I can't find which is closing once the innards of the amp warm up or (2) some DC across the pots from a leaky cap, but can't understand why this would clear up once the amp gets warm.

Any suggestions?

I can hear the ocean

uncleozzy — Thu, 05 Nov 2009 06:48:01 -0800

You are not my amp tech, but maybe you can help me diagnose the source of a strange noise on a brand new guitar amp. Yesterday, I got a tiny tube amp in the mail. After letting it come up to room temperature, I plugged it into a cab (yes, with the right impedance) and played away. No problems at all; made some really nice sounds, by the way.

The next time I turned it on (an hour or two later), there was an awful static noise--sort of like rushing water, or waves crashing--even with the volume all the way down and no guitar attached. Playing through it produced pops and crackles and unpredictable volume changes, and the static continued.

It's got 2 12AX7 tubes (and a funky setup--V1 and one triode of V2 are the preamp, and the other triode on V2 is the power tube). Best I can tell (which is not saying much), they both look normal, glow a healthy orange, aren't microphonic.

Now, the head is brand new, so there's a really good chance it's going back to the vendor as defective, but out of curiosity (and future diagnostic needs), what could the problem be?

Why, oh why, now and this way..

tmcw — Sun, 28 Oct 2007 12:15:12 -0800

Cursing bad luck: One of the preamp tubes in my Peavey Classic 30 seemed to peter out during practice yesterday. Two hours before my first concert of the year. An awesome friend came in in the clutch, but now I'm puzzled as to what to do. (and have another show on Thursday) So, playing. It was turned fairly high up (Pre at 6-7, Post at 6-7) (note that the scale is 1 to 12). I'm playing fairly loud (with a drummer, and a loop being sent to it), and within a few seconds I lose volume. We all stop, I look at the back of the amp, and one of the three preamp tubes is not showing its beautiful glow. Playing yields a barely audible, really sad sounding chime.

So, I live with it. The weird part is that today, I remembered that perhaps the other channel on the amp is usable (I think I'm incorrect in thinking this, because it isn't a 'true' two-channel amp) Anyway, the amp seems to work, although that tube still isn't glowing. I'm afraid to test it thoroughly, because I keep reading horror stories of this sort of thing (and I've seem some scary stuff happen with vacuum tubes in a photography setting).

So, wtf do I do? I'm thinking I should retube it, and Eurotubes is insanely hyped. At $61 for a retube of 7 tubes (my amp has 4 post, 3 pre), average price seems to be pretty good relative to other shops. And they can deliver in three days.

Or should I just buy one tube? Or am I set to go with this weirdly-working setup?

I'm disregarding bias for the time being because the C30 uses EL84s which supposedly don't need to be biased. But the thing is, I only have had the amp for about 6 months, and it was brand new. So, WTF? Tubes are supposedly usable for years on end, and these only lasted a half. Am I running the preamp too high? is there anything else that could have caused this (fuses?) that I'm not looking at?

Thanks for any guidance.

'cause I sleep with 'lectric guitars...

tmcw — Thu, 21 Jun 2007 17:06:52 -0800

Is a Fender Hot Rod (1x12) the best (tube) amp I can get for the amount of money I want to spend (~$400) and the power I want (>15 watts)? Right now I have a Princeton 112+, which is 'all right,' but has a few problems, especially with the input jacks (which are, thanks to modern technology, very tough to fix), and the sound isn't really much to talk about. I've really liked the sound of a Blues Jr. (which I had in my dorm room almost all the time this year, but I didn't own), and would like something really solid. I have an American Tele which I will never part with, and I'd like sort of the same thing, as far as quality.

Oh, and it's for 'indie rock,' and will also probably be used for my other instruments (ukulele, synth, 'laptop')

I've heard good things about the Peavey Classic series? I could go a bit above 400 if I love something, but that's the artificial price limit I've set in my mind.

Guitar Amp- Tube Change

InfidelZombie — Fri, 26 Jan 2007 15:33:36 -0800

Replacing power tubes in a guitar amp I’ve been considering swapping out the power tubes in my amp. I have a 100 watt Carvin 3212 2x12 combo with Groove Tube 5881s, and I’m wondering if I could get a more Marshall-like sound by using EL34s instead. Spent some time on Google but the information I’m getting is pretty technical; I really need some more straightforward answers to the following:

1. Has anyone here done a similar change? Did it make a significant difference in the sound you got from your amp? Any unforeseen problems?

2. The amp has a bias switch to go from 6L6s or 5881s to the EL34s. A lot of what I have read talks about bias adjustments that would need to be done by a professional, but I’m not sure whether the switch would take care of that or if further adjustments would be needed. Can I just flip the switch and install the tubes myself, or should I take it to a pro? What’s a normal price for that service?

3. The amp is switchable down to 50 watts, which is how I usually play. Right now the switch is broken and I’m locked in at 100. Can I just pull out two of the tubes to get to 50, or should I get that switch fixed? What do you think it would cost?

4. Does anyone know a reliable amp repair shop in the LA area, preferably somewhere between Redlands/San Bernardino (where I live) and Whittier (where we practice)?