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Ebay Tube Amps - Page 3

post #31 of 89
1/28/07 at 4:29pm
Thread Starter 
I have spoken to the seller and he is going to send me a replacement for the noisy tube. He also says the smell is caused by the oils on the transformer burning off. So I've got it back on.

Issues aside, this really does seem a very capable amp for the money. Its putting a lot more weight behind my AMT than the Amp1 at the expense of a little low bass extension I get a lot more general bass presence. The headphones also just seem to be "singing" better.
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post #32 of 89
1/28/07 at 11:35pm
Duggeh, what makes you think that you had a noisy tube?

I would be very interested if a different tube solved your hum!!! I've had this thing apart more than once now and have done some small surgery but with out fixing the hum!

Thing is, the sound through the headphones is fantastic! very very good. If I could just solve that bloody hum hten I'd be very happy. Anyway the tube gurus are still looking at it so maybe we might solve it yet. The other thing is that I have a schematic drawn for it, but I need to check it over a few more times before its ready for posting!

Fran
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post #33 of 89
1/29/07 at 8:09am
I've been thinking about this hum, and possibly it being a ground loop. How about trying a portable source through it, instead of your mains powered ones. That way you won;t get the best sound, but you will have gone a step forward towards isolating it.

I am still over-excited, and yet to recieve my amp...
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post #34 of 89
1/29/07 at 6:01pm
Mine arrived and I am having the same problem as Duggeh had. One crackling tube. One tube appears to be glowing slightly brighter than the others as well.

I have turned the amplifier off.

Is this normal? Will it explode?

EDIT: it's not glowing brighter, just glowing lower down, the hot bit seems to be lower on this tube than the others. Still the crackle in one channel though. I am monitoring the situation closely.
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post #35 of 89
1/29/07 at 6:15pm
Okay, it looks as if my tubes are faulty as well. Which tubes do you reccomend swapping to check if it's a tube fault? Are 1-4 all equivalent.

My tubes 2 and 3 both have burn marks on the top, do you think I should get a replacement for both of those?
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post #36 of 89
1/29/07 at 6:26pm
Hmmm bummer, but I suspect it is a tube problem. Talk to them and see if you can get a whole new compliment of tubes, it can't hurt to ask.
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post #37 of 89
1/29/07 at 6:39pm
Okay, new weirdness. I just was swapping the tubes to see which one was busted, and couldn't get the channel to move. I am now unsure it is the tubes. I will keep you informed.....
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post #38 of 89
1/29/07 at 6:59pm
OKay, so I swap around tubes 1-4. The positions move a lot. I have almost lost track of which is which. The crackle never changes position or character.

Then I swap tubes 5 and 6. The crackle moves side and is distinctly quieter. There is nothing cosmetically wrong with either tube 5 or 6.

Any clues?
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post #39 of 89
1/29/07 at 7:15pm
Thread Starter 
The smaller tubes 5 and 6 are the input tubes, if the crackling moves channel when they are swapped then one of them is probably at fault. My faulty tube was one of the 4 output tubes.


Dodgy chinese input tubes can and do explode. I would speak to the seller about a replacement set of input tubes. Its cheaper to send him back the tubes than the whole amp and he was very reasonable about sending me a new output tube.

Shame abotu these teething difficulties, but I had expected some niggles given what it is we are dealign with here.

My own faulty tube doesn texibit any problem until it gets hot, then the crackling becomes worse and worse. The amp is usable without this in stints of say 20 minutes. The problem is definately the tube though. The other artifact that has been noted, the group loop hum, I suspect isnt a ground loop issue. I suspect its just the cheap tubes. Its not a bother once the volume is turned on anyway.
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post #40 of 89
1/29/07 at 7:27pm
Quote:
Originally Posted by Duggeh View Post
The smaller tubes 5 and 6 are the input tubes, if the crackling moves channel when they are swapped then one of them is probably at fault. My faulty tube was one of the 4 output tubes.


Dodgy chinese input tubes can and do explode. I would speak to the seller about a replacement set of input tubes. Its cheaper to send him back the tubes than the whole amp and he was very reasonable about sending me a new output tube.

Shame abotu these teething difficulties, but I had expected some niggles given what it is we are dealign with here.

My own faulty tube doesn texibit any problem until it gets hot, then the crackling becomes worse and worse. The amp is usable without this in stints of say 20 minutes. The problem is definately the tube though. The other artifact that has been noted, the group loop hum, I suspect isnt a ground loop issue. I suspect its just the cheap tubes. Its not a bother once the volume is turned on anyway.
He seemed fairly unfriendly when I asked him about my tubes crackling. (Maybe he gets a lot of it). I have emailed him with the new situation and await reply.

My tube crackling occurs about 10-20 seconds after switch-on when they start glowing orange. The crackling doesn't really change much. There is also some hiss on one channel which increases with volume. Do you think this could be the input tubes as well? Do you think it would be wise to just get an entirely new set of tubes?

Fran was talking about the input tubes being equivalent to the russian 6P1P's, do you recon it would be sensible to just spring for a pair of better russian tubes? Couldn't be more than a tenner could it?
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post #41 of 89
1/29/07 at 7:40pm
Thread Starter 
The russian ones have 7 pins, the chinese 9 pins iirc.
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post #42 of 89
1/29/07 at 7:52pm
I found some russian tubes, (job lot of 10, so I will have some spare). Which are definitely 9-pin, and I think from what Fran said earlier, a direct equivalent.

I think I'll wait until I hear back from the seller first before I spring for them.

And I have been looking for the output tubes too, but best price I can find them is £23 for a pair. If I were looking for a replacement set, it's pretty much a whole new amp.

I also emailed the guy who supplied me my millett tubes, to see what he could do me.

Ah, the joys of retro audio.
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post #43 of 89
1/29/07 at 7:58pm
No Duggeh you have that wrong.


Chinese 6P1 = Russian 6P1P = Russian 6P1P-EV (mil-spec tube)

Chinese 6N1 = Russian 6N1P = Russian 6N1P-EV (mil-spec tube)


The waters are muddied however because although it says it right there on the amp, the 6P1 IS NOT THE SAME AS A 6AQ5! Electrically they are very similar, but the 6AQ5 is 7 pin. Likewise although some of these amps are sold as having 6N3 tubes, you should realise that the 6N1 and 6N3 are not the same tube and have different pin-outs.



Have a search on ebay and you will find plenty of them for small bucks. Chances are if a seller is selling the 6P1P, then he may well have the 6N1P as well. All of these tubes on ebay are Russian.

BTW I know someone with one of these amps and he doesn't have the hum, so it can't really be a design of PCB problem.

Also, seller has been AOk with me...

Lastly (!) the pins on my tubes were pretty dirty when I got them - you'd want to clean up the pins a bit with a bit of sandpaper or similar and insert/remove a few times to make sure you have good contact.


Fran
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post #44 of 89
1/29/07 at 8:00pm
We posted at teh same time!!! I found plenty of the 6P1P tubes on ebay for small money eg 8 tubes for $22 plus $10 post from the Ukraine. Search for 6P1P and you'll most likely turn them up


EDIT: have a look for the military spec ones (EV) they should last longer and be better made too.


Fran
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post #45 of 89
1/29/07 at 8:03pm
Yup I think I found the same guy from the ukraine. Do you recon to just go for a new pair of those then? What about the (was it 6n3 or 6n1?) tubes 1-4? Any links for easy places to buy a replacement quartet of those? Tempting to just ignore the cheap chinese tubes completely.

EDIT: oh, and I have cleaned up all of the pins with contact cleaner thoroughly.
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