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  1. #1
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    12.16.17 @ 06:41 PM
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    Default 5150 combo amp help

    Hey guys,
    total noob on amp mechanics, but I have a 5150 combo amp and I just turned it on to test out my new Malmsteen strat and the lights on the amp aren't turning on, but the tubes are glowing bright red. Pre amp tubes aren't lit. The fuse is still in tact. I can smell a faint burning smell but nothing is smoking or anything. Does anyone know what the deal is? Really thanks a lot, maybe it's time to buy a mini EVH head.
    Thanks

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    10.26.16 @ 03:37 PM
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    Quote Originally Posted by mrbond5150 View Post
    Hey guys,
    total noob on amp mechanics, but I have a 5150 combo amp and I just turned it on to test out my new Malmsteen strat and the lights on the amp aren't turning on, but the tubes are glowing bright red. Pre amp tubes aren't lit. The fuse is still in tact. I can smell a faint burning smell but nothing is smoking or anything. Does anyone know what the deal is? Really thanks a lot, maybe it's time to buy a mini EVH head.
    Thanks
    DO NOT TURN IT ON AGAIN UNTIL YOU TAKE IT TO A TECH.

    Are the tubes glowing a dark, cherry red color like this?:


    The yellow/orange glow is normal in most cases -- even if it's really bright. But if the metal guts of the tube are glowing red like lava (shown above), then there is likely something wrong that needs the attention of a tech. That's called "red-plating," and if left running in that condition, it's just a (very, very short) matter of time before the tubes burn out, possibly damaging other parts of the amp, and causing an expensive fix.

    I also don't like the fact that you mentioned the lights on the amp are NOT turning on, but the tubes are definitely getting current. That sounds to me like something is definitely wrong internally, and it's something serious enough that I can't diagnose it over the internet either.

    I would 100% recommend unplugging it immediately, and take it into a tube amp tech to have it troubleshooted before attempting to even power it on again.

    You'll likely need a new set of tubes, and the tech might find a few other minor issues that can be taken care of easily and cheaply (parts wise). HOPEFULLY, it's NOT your power transformer that is bad. You can still get them from Peavey (last time I checked about a year ago) but it's probably the single most expensive replacement part in the entire amp.

  3. #3
    Sinner's Swing! Rick S's Avatar
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    i concur with the above post.

    faulty tubes or a circuit in a 5150 combo is hardly a viable reason to purchase a new 50 watt amp head that still needs a 2x12 cabinet.
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    Quote Originally Posted by Rick S View Post

    faulty tubes or a circuit in a 5150 combo is hardly a viable reason to purchase a new 50 watt amp head that still needs a 2x12 cabinet.
    Exactly. There's a good chance it can be fixed by a tech.

    However, if you are just looking to just dump it "as is" and pick up something else to replace it, I might be interested in taking a chance and taking it off your hands. (I do tube amp design/building/repair)

  5. #5
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    alright thanks man! Yes they're glowing red like lava. I have it unplugged and sitting here. Any idea what the price range on a repair (not the most serious case)? I have never replaced tubes before and I have no idea how much they are. Thanks again man, I really appreciate it.

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    Quote Originally Posted by mrbond5150 View Post
    alright thanks man! Yes they're glowing red like lava. I have it unplugged and sitting here. Any idea what the price range on a repair (not the most serious case)? I have never replaced tubes before and I have no idea how much they are. Thanks again man, I really appreciate it.
    You might as well just replace all of the tubes -- since your power tubes are either already bad, or close to it, and it sounds like your preamp tubes are probably getting pretty old. A lot of guys on here like re-tubing 5150's with all JJ's. A full set from Eurotubes (highly recommended seller) can be found here: https://ssl.eurotubes.com/cart/index...category_id=39

    If you go that route, get the "Standard Retube Kit" which is $91.50.

    Personally, I like the JJ 6L6CG power tubes in 5150's (like Eurotubes sells), but not JJ preamp tubes as much (in the 5150). I'd recommend the cheapo Chinese preamp tubes -- like these: http://thetubestore.com/chinese12ax7.html . That is what the 5150 was originally designed for, and after trying many different brands of preamp tubes, that is what I've been using in my 5150(s).

    You could order whatever tubes you'd like, and have the tech install them after they fix whatever is wrong with your amp.

    As for that repair itself, it's hard to know. If it's just a cooked resistor that needs replacing, it could be a simple $30-50 repair (including labor). If the problem is harder to find, it could still be an easy fix, but take a few hours of labor to track down the problem, and thus cost more.

    I should also mention, if they quote you something that seems a bit high on labor, or they end up charging you for what seems like a lot of labor, it very well might be legitimate. 5150 Combos are a particularly hard amp to work on and troubleshoot, mostly because of the odd geometry used in their circuit board construction. It's definitely not a "tech friendly" amp.
    Last edited by mrjstudios; 07.27.12 at 06:17 PM.

  7. #7
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    Thanks, I really appreciate it man! I'll check back soon on how much and whats wrong. Thanks a million!!!

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    hey guys, I hope you guys could get back to me before I pull the trigger.
    I was quoted by an outstandingly well spoken amp repair service close by that a full repair and retube will cost around $300. I was just wondering if you thought that would be worth it!
    Thanks guy!
    It could be less, thats the highest estimate they have. Its an 8 day turn around. I just wanted to know what you guys thought at it being a 100lb amp, for me to lug it all the way down to the shop haha.

  9. #9
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    02.24.16 @ 07:27 AM
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    Quote Originally Posted by mrbond5150 View Post
    hey guys, I hope you guys could get back to me before I pull the trigger.
    I was quoted by an outstandingly well spoken amp repair service close by that a full repair and retube will cost around $300. I was just wondering if you thought that would be worth it!
    Thanks guy!
    It could be less, thats the highest estimate they have. Its an 8 day turn around. I just wanted to know what you guys thought at it being a 100lb amp, for me to lug it all the way down to the shop haha.
    Whoa, I would put in new tubes myself and save the 200 bucks. The problem is if you don't know what else is wrong and the dude can "invent" a problem...not saying he will or that he is dishonest but how would you know if he were?

    Synthetic oil change in Hollywood Florida is 65bucks...except if you are my better half and tell them you had regular oil in it...then it's 125 bucks because they have to "switch over the oil, you just can't mix them and it's more labor intensive"...

    Never let them know you don't know...

    Replace the tubes and get some pic online, honest helpful forum members are abound!

  10. #10
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    I hear nothing but the best from these guys, ever heard of them out on LI? Davidson?

    I just don't think it's just the tubes though. Does guitar center have the tubes I need?

  11. #11
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    The lights on the amp aren't even turning on, correct? This would indicate a more serious problem than just tubes that needs to be checked out by a tech -- because tubes are farther 'downstream' in the circuit than than the power lights. Even a 5150 with bad tubes (or no tubes) should have the lights come on (unless/until something blows completely).

    Looking at the 5150 schematics that I have:

    The 5150 has the power and standby LED's running off of the bias control voltage supply, which is right off of one of the power transformer windings. It is protected by Fuses 3 and 4, which I believe are internal fuses (not accessible from outside the chassis).

    If one or both of those fuses has blown, it would kill both indicator lights, as well as the bias control voltage being supplied to the power tubes (WHICH IS VERY BAD, and would cause the red-plating you saw on the power tubes).

    I'm pretty sure that's what is wrong with your amp. A tech could likely replace the fuse(s), and the tubes, and it could be good to go.

    However, what caused those bias supply voltage fuses to blow? Shorted power transformer winding? Shorted bias voltage supply circuit? Shorted relay switching circuit (which appears to also be running off of that particular power transformer 2ndary winding)? Nothing at all?

    I can't answer those questions without going through the amp in person, which is why you need a tech to look at it. There is about as good a chance that he pops in new tubes and those fuses, and it fires right back up as there is the chance that you get new tubes and fuses, but after replacing them yourself, the bias supply turns out to be shorted, and a set of new tubes and fuses will just immediately blow again and you're back to square one that you are now.

    As for the $300 estimate, ask him how much it would be if you supplied the tubes for him to install. If he quotes you around $150 for the repair and re-tube if you supply the tubes, that's probably fair. He's gonna have to put in a good hour or 2 in labor to check everything over even in the best case repair scenario (and believe me, it could take about an hour labor to carefully disassemble the 5150 combo chassis and circuit boards alone!).

    I'd highly recommend Eurotubes to order the tubes from -- I posted a link above. Or if you want to go with the more "EVH-1990's-sound-'correct'" chinese preamp tubes, you can order a matched pair of JJ 6L6's still from Eurotubes, and just order the 5 preamp tubes from the other link I posted above.

  12. #12
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    Again, you don't disappoint. Thank you so so much for your help. I'll call them up now to ask how much that would be if I supplied the tubes. They promise a whole rework on the amp so it'll sound better than ever before. I don't want to screw with the internal fuses, but that sounds pretty likely the case. I'll drop it off by them today and hopefully I can get back to rockin' in the coming week! Thanks again. I'll sure to buy that tube package.
    And thanks to all involved!

 

 

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