Blew a kt88 in a mesa four 88......

[D Rock 247]

Put in a 25 amp fuse, problem solved

Or a piece of copper!!! Hell i Had an old kalamazoo combo amp with one in it and im sure it was in there for a many of years. And on a two prong cord.....it actually sounded killer. Wide open, maybe 5 to 10w all tube power.

 

[Old Garage-Bander]

Cause u cant pump your volume at about 125w on only two kt88s? I dunno. I know the tube is gone. U could shake the tube, and it was tinging. Rest wernet as hot. Hell u could see it through the amp dude. Blue led quickly turn bright ass orange with a nice pop from a sli blo. Read the manual and they said theyve had a problem when creating the bass prod amps that hard low end bass notes make em start poping tubes at half power. I prob leave it on 250w from now on since its only on 4 power tubes as supposed to a 6x6550s in a 300w svt. But so far it whoops tail in tone but gonna fender it up with some 12at7s to get rid of some of that extra fuzz i dont like. I squeeze all the grunt i need through banging the crap out of those bass strings. Ill just do it myself, easy to bias, blow another one and send it back to mesa....lol

Your superior command of technical language tells me you know exactly what you were doing.

 

[Old Garage-Bander]

Or a piece of copper!!! Hell i Had an old kalamazoo combo amp with one in it and im sure it was in there for a many of years. And on a two prong cord.....it actually sounded killer. Wide open, maybe 5 to 10w all tube power.

I rest my case.

 

[D Rock 247]

I rest my case.

Dude, relax man. It was a given to me with that copper in it......and yes im pretty familiar with pcbs. And ive already checked the guts out inside the amp. Everything is fine. Just needs a tube and a fuse. If u look at the new prodigy amps chassis on the top side, it makes it even easier for a dummie like me to bias the amp since u think im not qualified to work and diagnose my own problems. Thanks for the confidence!!!

 

[Old Garage-Bander]

Dude, relax man. It was a given to me with that copper in it......and yes im pretty familiar with pcbs. And ive already checked the guts out inside the amp. Everything is fine. Just needs a tube and a fuse. If u look at the new prodigy amps chassis on the top side, it makes it even easier for a dummie like me to bias the amp since u think im not qualified to work and diagnose my own problems. Thanks for the confidence!!!

If you had taken out the copper slug and put in a proper fuse, I could let the rest slide.

I can't figure out if you are intentionally making a mockery of electronics technicians or you just don't know how you come across to others.

Your presentation, my perception.
You imply, I infer.
Tomaaato Tomahato, let's call the whole thing off.
But good luck with your amps.

 

[agedhorse]

I repeat... the voltages are VERY high inside that amp (higher than a typical tube amp) which requires additional precautions (beyond what are normally employed) when servicing. Do not get in so deep that we are unable to help you resolve this in the event that you are "unsuccessful" with your attempt.

 

[BassmanPaul]

Mazda Octal, back in the day, issued application notes on using the new KT88 in various amplifier designs. IIRC one was for a 1KW amplifier with ten output tubes. The B+ rail was typically in the 650 to 700V range. I still have the notes so maybe I’ll search them out.

 

[D Rock 247]

If you had taken out the copper slug and put in a proper fuse, I could let the rest slide.

I can't figure out if you are intentionally making a mockery of electronics technicians or you just don't know how you come across to others.

Your presentation, my perception.
You imply, I infer.
Tomaaato Tomahato, let's call the whole thing off.
But good luck with your amps.

Thanks. Ive been pretty successful at doing my own amp mods, cap changes, etc. I just dont go around on forums flexing muscles on how or what ive done an can do to a vacuum amplifier. Basically i posted just warning others with a bass prodigy, to not try to peak out the amp only on half power. Ive tried to explain to others who seem to be gurus on power tube amps that I believe mesa may have should have put an extra or two power tube in the four 88. If u look at almsot any other older, very reliable bass tube amp, youll see that even the 100 watters have atleast 4 6550s etc.... basically, i see that so far, that the four 88 is a cute, small footprint all tube bass head that cant take a round house punch from a bass string at 125w (probably was peaking close to 150) on two kt88s. Now it may be a problem with too high of a bias, cap issue, on and on. And when or if i blow another tube, off to mesa it goes. I dont plan on trying to blow another tube, but just in case. I just cant see a all tube 250w all tube head, get man handled (volume wise) and actually played like it should be, only housed with only 4 kt88s.
And of course i removed the copper and installed another fuse with a new cap lock, and , wired a 3 prong plug to it. (Then sold it for $300 lol) but sorry if it seemed like i was slinging poo on you electrical techs, i just dont have a degree in industrial electronics and dont know most of the terminology. Hell how hard is it to drain the caps and watch you tube vedios on how to build a diy amplifier......j/k.

 

[D Rock 247]

Mazda Octal, back in the day, issued application notes on using the new KT88 in various amplifier designs. IIRC one was for a 1KW amplifier with ten output tubes. The B+ rail was typically in the 650 to 700V range. I still have the notes so maybe I’ll search them out.

I thought they quit making kt88s a while back and now most of them considered new are re glassed, rebadged?

 

[D Rock 247]

I repeat... the voltages are VERY high inside that amp (higher than a typical tube amp) which requires additional precautions (beyond what are normally employed) when servicing. Do not get in so deep that we are unable to help you resolve this in the event that you are "unsuccessful" with your attempt.

I know i know, drain the caps.......

 

[agedhorse]

I thought they quit making kt88s a while back and now most of them considered new are re glassed, rebadged?

Completely incorrect. The KT-88 is a very different tube which is why it is capable of ~125 watts per pair with proper plate load. If you understood what the tube's spec's actually mean, you wouldn't be so puzzled about what the tube's capabilities are.

If the AC primary fuse has failed, this may mean that other damage has occurred, you should NOT just power it up with a new tube installed without following the factory servicing protocols. Really. It's a lot more than just discharging the power supply caps, which is why I are trying to discourage you from attempting this. The possibility of causing greater damage (and a lot more expensive) is very real whenever there is a catastrophic tube failure, no matter what the cause. This is not an amp a hobbyist or DIY'er should be messing with.

 

[D Rock 247]

Completely incorrect. The KT-88 is a very different tube which is why it is capable of ~125 watts per pair with proper plate load. If you understood what the tube's spec's actually mean, you wouldn't be so puzzled about what the tube's capabilities are.

If the AC primary fuse has failed, this may mean that other damage has occurred, you should NOT just power it up with a new tube installed without following the factory servicing protocols. Really. It's a lot more than just discharging the power supply caps, which is why I are trying to discourage you from attempting this. The possibility of causing greater damage (and a lot more expensive) is very real whenever there is a catastrophic tube failure, no matter what the cause. This is not an amp a hobbyist or DIY'er should be messing with.

Completely incorrect. The KT-88 is a very different tube which is why it is capable of ~125 watts per pair with proper plate load. If you understood what the tube's spec's actually mean, you wouldn't be so puzzled about what the tube's capabilities are.

If the AC primary fuse has failed, this may mean that other damage has occurred, you should NOT just power it up with a new tube installed without following the factory servicing protocols. Really. It's a lot more than just discharging the power supply caps, which is why I are trying to discourage you from attempting this. The possibility of causing greater damage (and a lot more expensive) is very real whenever there is a catastrophic tube failure, no matter what the cause. This is not an amp a hobbyist or DIY'er should be messing with.

Understood. If youd like, you can call or em

Completely incorrect. The KT-88 is a very different tube which is why it is capable of ~125 watts per pair with proper plate load. If you understood what the tube's spec's actually mean, you wouldn't be so puzzled about what the tube's capabilities are.

If the AC primary fuse has failed, this may mean that other damage has occurred, you should NOT just power it up with a new tube installed without following the factory servicing protocols. Really. It's a lot more than just discharging the power supply caps, which is why I are trying to discourage you from attempting this. The possibility of causing greater damage (and a lot more expensive) is very real whenever there is a catastrophic tube failure, no matter what the cause. This is not an amp a hobbyist or DIY'er should be messing with.

Undersood about the kt88. But if youd like to dicuss your concerns with my amp tech for the past 10 years (hes got 40 years exp with tube amps) hell be happy to explain to you what he directed me to do with the amp. I realize electronic components can be critical, but blowing a tube and a fuse is not rocket science. Im a player. Not so much of a tech (as youve gathered already). But like i say, if my amp is such a concern and unsafe for me to to replace a fuse, and a tube and careully watch my power up while rebiasing my amp, call my tech and tell him to call me. His website is ampworks.org heres his number: (864) 313-5647. As far as my concern with two kt88s getting 125w of power, (or however many volts) thats just my opoinion. All im saying about that is ,there are amps that have been running for ages, with more than only 4 power tubes at 250 watts. Or only 2 at 125 watts. Theres been proof that these newer designed amplifiers with a smaller footprint, sometimes dont work out. Look at the orange terror bass. One of the most bad ass lunchbox bass amps ever made, now discontinued.....why? If they were smarter, they wouldnt have just discontinued the amp and actually fix the problem and then be able to charge out the ying yang for such a great amp brand new. Im not in your ballpark when it comes to electronics, but u kinda see where im comming from? I may have a bad amp, or it could be several of them with the same problem, who knows. (Mesa) thats why i came here to post to make sure any other prodigy owners havent encountered the same problem. If youd also like, call mesa and see what kind of excuse they give. Ive read the manual, ive took all the precautionary instructions to make sure the ohm load is correct. Mistreated the amp with a crazy volume level? Hell yeah! Thats who i am and what i do. If a mesa boogie prodigy cant do that at half power on 2 kt's without problems i understand. But if they cant handle that at full power on 4 kt's at 250 watts. Thats not my problem. Never had a ampeg power tube fail on me! Or any other amp.

 

[Korladis]

Or a piece of copper!!! Hell i Had an old kalamazoo combo amp with one in it and im sure it was in there for a many of years. And on a two prong cord.....it actually sounded killer. Wide open, maybe 5 to 10w all tube power.

But the whole point of the fuse is to be an intentional weak link so that nothing more important gets damaged.

 

[D Rock 247]

But the whole point of the fuse is to be an intentional weak link so that nothing more important gets damaged.

I know that already?

 

[agedhorse]

Man, you are completely not getting it.

The reason I am recommending having a tech evaluate the replacement and followup testing is because the type of failure you described is common to an internal flash-over which is different than other types of failures. This can cause damage that an FACTORY AUTHORIZED tech would be aware of prior to powering up and would take the additional precautions. Being that your tech is not a Mesa authorized service center, and that the KT-88 tube is not all that common, he may not be aware of these issues. You do not have the proper tools to do this safely.

Regarding your "opinion" that the KT-88 can't do the 125 watts per pair, clearly you do not understand the performance data that this tube offers compared with say a 6550. The KT-88 has about 25% MORE anode current, about 20% more plate dissipation and 25% higher anode voltage capabilities than even the 6550, and about double that of say a 6L6. This is what makes the KT-88 a VERY different tube, and WHY I have suggested caution. If you really understood what you say you do, you wouldn't be saying what you have been saying because every pro tech that is familiar with tube is shaking their head at your cavalier approach.

 

[Dave W]

Do you understand that agedhorse is an engineer at Mesa?

 

[D Rock 247]

Do you understand that agedhorse is an engineer at Mesa?

Well gd why didnt he just say so himself?

 

[agedhorse]

Well gd why didnt he just say so himself?

If you are on a mobile device then the company affiliations may not show up, but most folks coming to a site for the first time are advised to learn how the site works and the folks involved before arguing about anything.

 

[D Rock 247]

Man, you are completely not getting it.

The reason I am recommending having a tech evaluate the replacement and followup testing is because the type of failure you described is common to an internal flash-over which is different than other types of failures. This can cause damage that an FACTORY AUTHORIZED tech would be aware of prior to powering up and would take the additional precautions. Being that your tech is not a Mesa authorized service center, and that the KT-88 tube is not all that common, he may not be aware of these issues. You do not have the proper tools to do this safely.

Regarding your "opinion" that the KT-88 can't do the 125 watts per pair, clearly you do not understand the performance data that this tube offers compared with say a 6550. The KT-88 has about 25% MORE anode current, about 20% more plate dissipation and 25% higher anode voltage capabilities than even the 6550, and about double that of say a 6L6. This is what makes the KT-88 a VERY different tube, and WHY I have suggested caution. If you really understood what you say you do, you wouldn't be saying what you have been saying because every pro tech that is familiar with tube is shaking their head at your cavalier approach.

Ok so now that ive heard from another member that ur a mesa tech yourself? Why in the hell didnt u just say that in the first place? And your right once again, not a tech, just a player. How bout next time, try explaining to me where i come from first, and how much you know about these prodigy heads before just saying: man, dont do it, u dont know what your doing. And more like, hey im a mesa tech, i would encourage you to call an authorized mesa boogie dealer with what problems you have concerning with your amplifier.........encouragement goes alot further with someone more than.......shag it nevermind.

 

[D Rock 247]

If you are on a mobile device then the company affiliations may not show up, but most folks coming to a site for the first time are advised to learn how the site works and the folks involved before arguing about anything.

I never started an aregument. Just a fyi-warning.