Diezel Herbert blown fuses???

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VESmedic

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Hey guys, got my herbert today!!!! :D :D :rock: :rock:


Everything sounds great, nothing odd, however there are 2 blown fuses. The LED for tubes 1 and 6, as well ast 2 and 5 are both lit up. Now, The fuse for 2/5, is DEFINITELY blown, however 1 and 6 looks perfectly fine? Anyone have any ideas? doesn't seem to be that big of an issue I don't think? All the tubes look fine, there isn't any corky noises/microphonics, the amp is DEAD silent ( quietest amp I think I've ever owned)....Just wanted some input, thanks!!!
 
Hello,

are you saying that you are playing your Herbert with blown fuses? Tube fuses blow due to power tube problems. Since you just bought a used amp I would recommend a full retube (preamp and power amp), especially since the amp came with blown tube fuses. Of course you need to replace the tube fuses before continuing to play.

Kind regards,

Jens Kruse
 
Well, I didn't notice it right away. However, I haven't played the amp since. However, it DOES sound fine...Could it simply just be a bad fuse?
 
can someone shine some more light on this please? I could use the help......
 
The fuses blew because of faulty power tubes. There is always a good reason the fuses blow as they are a safety mechanism to protect the amp from damaging surges.
You can replace the fuses and hope for the best, but I would still recommend a retube, at least the power tubes.

Kind regards

Jens
 
Thanks jens. I guess I'm not much of a techy with this stuff....so the fuse couldn't have blown from a surge in power or something eh? Definitely a powertube issue? Why no tone loss? If the fuse is blown, does it shut down that set of tubes so that they are not functioning?

Thanks for the help, I'm quite the noob apparently.. I just thought if there was a power tube issue, it would be much more apparent...anyways, I ordered a quad of winged c 6550s...what should the amp be biased at for each set of 2?
 
The tube fuses blow when there is something going on with the power tubes. We are talking about a technical fault. The tone loss with power tubes occurs over time when they get old. They can still function perfectly, just with tone loss. These are 2 very different issues. You can install brand new tubes that sound perfect and they have technical faults, light up, get hot, blow fuses etc etc

I am sorry, I can not help you with the 6550s in a Herbert. We at Diezel do not support, nor recommend those tubes. They get very hot and can cause internal trouble. The bias trimmer might not even support the low quiescent current the 6550s need. Maybe you find some other source on the Internet or on this forum regarding this.

Good luck with everything.

Jens
 
What tubes does the herbert support then? I thought in the manual it says 6550s are fine, and I thought that was one of the big selling points of the herbert? The ability to mix and match tubes?
 
Can someone tell me alittle about the external bias on these amps? listed below is the only volt meter I have, and the only leads I have. They are kind of "small" and I've seen some videos of bigger connectors/leads that actually "plug" into the herberts external bias points. My question is though, since this is all I have right now, will these leads work? They stay in the bias pots, but I just wanted to make sure.
 

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Please read the thread below.

http://www.rig-talk.com/forum/viewtopic.php?f=14&t=87989

Big tubes like 6550s have lower efficiency than for example EL34s, so they need to operate at higher quiescent currents which results in higher temperature emitted from the glass. For EL34s the bias is set to about 70-75 mA per pair. For 6550s you would need about 90-100mA per Pair. This means the amp's transformer needs to draw much more current with 6550s and much more excess heat is generated. The transformers were optimized and designed by Diezel with EL34s in mind. Using the big tubes like KT88s or 6550s means risking much greater wear and tear inside the amp.

To run 6550s safely in a Diezel Amp you would need to bias them cold at 40-45 mA. In order to achieve that you might need a small mod as the bias trimmer will most likely not go low enough.

To find out what tube types the Herbert safely accomodates please contact Peter Diezel. In any event, Diezel recommends and installs EL34s only. The other tube types can be installed at the users' discretion.

Kind regards,

Jens
 
Question: When a tube failure LED is lit in the back indicating tube failure, does the amp automatically shut down that set of 2 tubes that the LED is pertaining to? What if the fuse is blown, do those tubes still function (if they are able to) or, again, are they shut down? I think I read that the VH4 will automatically shut down a set of 2 tubes if there is failure ( I believe Engls do this as well?) just curious if thats how the herbert functions...
 
When 1 tube fuse LED lights up it means that there was a surge from 1 of the tubes on the particular pair which caused the safety mechanism (the fuse) to blow, thus interrupting the current flow for that pair. When you replace that blown fuse and that tube pair is still mechanically working, this tube pair will be utilized again. When such a surge occurs once it is prone to occur again. Sometimes (only sometimes!) the tube that produced the surge might continue to work fine, but from my experience the problem will come back, much sooner than later.
It just happened to me this morning. I retubed a customer's Herbert when 1 tube lit up brightly and caused the fuse to blow. I replaced the fuse, turned the amp on again and after 1 min the same tube caused all 3 tube fuses to blow. So, I replaced that faulty tube and threw it in the trash.

Bottom line: when the fuse LED is lit up, the pertaining tube pair is not working. You CAN replace the fuse and hope the problem will never come back, but you should be prepared to throw the bad tube(s) out and replace them ASAP.

Kind regards,

Jens
 
Change your tubes man. The only time any of my fuses blew on my herbert was because of a faulty tube that was in my amp. The beauty of it's design is that it totally shuts the amp down preventing further damage. Check the fuse in your mains as well.
 
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