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TAD 5881 grading

Discussion in 'Glowing Bottle Tube Amp Forum' started by NorthenLights, Mar 2, 2021.

  1. NorthenLights

    NorthenLights Tele-Meister

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    I've got a bunch of TAD selected 5881 tubes, that I was gonna put inside my Ceriatone OTS. Some of them have a sticker saying "1" on them, and some are marked "4". What does these classes signify?
    I'm assuming it means that 1s are matched and should go with other 1s, and 4s should be paired with 4s, but I thought I should ask first before putting them in.
     
  2. NorthenLights

    NorthenLights Tele-Meister

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    Ok, no immediate answers, so I meassured them myself.

    Out of five tubes marked 4, three matched well, one ran about 3mv colder (32mv while the others were set to 35), and one ran 6mv colder.
    Out of the tubes marked 1, one tube ran 10mv colder than the matching ones, two were microphonic, and one didn't work at all.

    I bought these second hand several years ago, although the seller assured they were new. TAD doesn't use these classifications anymore, so I guess they might be kinda old, or maybe some sort of b-stock.

    A shame about the unusable tubes. I had hoped to be able to sell the ones that got left over, but left with only two unmatched tubes, I guess it no use bothering with that.
     
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  3. uriah1

    uriah1 Telefied Gold Supporter

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    GT used a rating like that..some kind of hardness curve thing.
     
  4. Wally

    Wally Telefied Ad Free Member

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    NorthernLights, you figured out the answer to your question. In addition, that matching can be useless imho unless the tubes are burned in. Tubes’ operational parameters can drift in the first hours of usage. That drift can undo any matching. I have been buying ‘burned in’ tubes for decades now. When tubes are burned in..usually for 24 hours...they do not drift and the matching holds true through the life of the tubes, ime. if you have not realized it, those numerical ‘grades’ indicate the operational parameters...which tubes run hot or cool at any one certain bias setting. The matched ‘4’s ran at 32ma of current draw. I might guess that the matched ‘1’s ran at a slightly lower current draw???
     
  5. NorthenLights

    NorthenLights Tele-Meister

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    Really? This is the first time I have ever heard anyone say this. From what I've been told, you should only use new tubes, that are as closely matched as possible (I'm actually a bit worried about the one tube that is running cooler than the others, but I'm hoping it will only result in that it will age slightly slower, and cause any problems). But I'm definitively no expert, just another forum person.
     
  6. archetype

    archetype Fiend of Leo's

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    Nope. What @Wally says, above.

    Have the vendor burn them in for 24 hours. That allows them to change, as they might, with full power applied and the internal elements heated. They tend to stabilize that way, then you match them. At the vendor's, many won't match after burn-in and the vendor needs to try again with another tube.
     
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  7. Wally

    Wally Telefied Ad Free Member

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    The burn-in period does not render the tubes ‘not new’. It merely assures that once matched, the tubes do not drift. Rest assured that every new vehicle you have ever purchased was tested before it was shipped. When an engine is overhauled, a good mechanic will run that engine down the road in a controlled manner to assure that it is in proper running condition. Those two tubes that are 6ma and 10ma outside of the match for the grade indicated on the label were matched when they left the vendor. The first 24 or so hours of use in a full voltage, real life situation changed those two tubes. So, if one is going to be discriminating about ‘matched’ t7bes, one wants to have stable tubes when the match is done.
     
  8. NorthenLights

    NorthenLights Tele-Meister

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    Sigh... and when I pluged in, it started humming, blew a fuse and died. Times like this that makes me thinking about getting a kemper.
     
  9. Wally

    Wally Telefied Ad Free Member

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    what tubes were in the amp before you installed whatever TAD 5881s you chose to use? What was wrong with them? What were the voltages before the change? Do you have a light bulb limiter? Did you misorient a tube by mistake? That can happen with certain newer sockets and/or tubes, ime. Fwiw, TAD is just a rebrander. I have bought exactly one duet of TADs back when they first came out. I tend to stay away from any rebranders. Ommv.
     
  10. NorthenLights

    NorthenLights Tele-Meister

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    TAD 5881 aw well, probably from the same batch I had. I thought my tech told me he had switched tubes last time he looked it over, but I might have misheard, because they look awfully familiar.
    There's only one way to insert the tubes, so that's probably not it. I didn't measure the current the old ones were running at, I just put the new ones in. I actually didn't have to adjust the bias, as ceriatone recommends a voltage of 35-40 mV, and as mentioned, they were all at 35 except the one runing at 32.

    I tried switching tubes because the amp has a tendency to start making sizzing and popping noises from time to time. Two techs have been over it, without succeeding in eliminating the problem completely. After watching some videos on Youtube, I had the idea that it might be to microphonic tubes. Since I had these lying around, I thought I might as well give it a go and see if it would improve anything. What's the worst that could happen, right?

    This amp has been giving me so much trouble over the years. Always acting up, totally unreliable. Don't dare to bring it to gigs, don't want to sell a broken amp at a considerable loss. And for what it's worth, it is my favourite amp when it decides to work. Really love the tones I'm getting from it.
     
  11. archetype

    archetype Fiend of Leo's

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    Some tubes have a locator that's undersized. If you have a socket with a big tolerance on the pin hole, the tube can definitely be installed without being indexed correctly.

    Find out exactly what the tech did.

    If it makes sizzling and popping sounds "from time to time" it's not the tubes. If tubes are the problem, put in good tubes and the problem is solved. It doesn't come back from time to time.

    You're taking it to the rong two techs. Ask around and get advice from folks who've had amps successfully troubleshot and serviced. You might consider shipping the chassis to a tech or service center on Ceriatone's list. That's probably a sure way to put it right. Obviously, you really dig the amp and it would be a shame to have it in a less-than-stellar condition electronically.

    https://www.ceriatone.com/dealers-techs/
     
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  12. NorthenLights

    NorthenLights Tele-Meister

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    Thanks! Both techs are locally reknowned amp builders, but that doesn't mean they are the right guys for this amp. I don't think I will risk Ceriatones list of techs. Seems like any hobbyist can get on there just by sending a mail. But I do have a friend who has a well made OTS, so I'm gonna ask him who built it for him.

    One thing I noticed when swapping tubes was that when turning the amp off, while it was draining, putting my finger on the first power tube caused a hum. The other three was silent when touched. Might be some kind of grounding issue with that one?
     
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  13. Wally

    Wally Telefied Ad Free Member

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    Swap that tube that is making that noise with one of the other tubes...just trade places. Does the other tube exhibit the same problem in that socket or does the noise follow that tube?
     
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  14. NorthenLights

    NorthenLights Tele-Meister

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    Thanks! That's a good advice. Unfortunatly I can't test it as the fuse is blown, and I don't have a spare. Don't want to mess around with it anymore now anyway.
    I'm a bit of a tinkerer, and tries to get the hang of electronics, but I guess that a 100w, 1500 dollars tube amp is not ideal to start practicing on.
     
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  15. Wally

    Wally Telefied Ad Free Member

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    I forgot that a fuse blew....tech time.
     
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