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What did I just buy? 6DJ8/6AS7 Headphone amp on ebay... - Page 3  

post #31 of 96
Thread Starter 

The seller responds with the following model number:

 

04-07-8512 on MCI

 

 

Any help here is really appreciated! 

post #32 of 96
Thread Starter 

Trying to get the best pics possible of the hookups there

 

IMG_1454.JPG

IMG_1455.JPG

IMG_1456.JPG

IMG_1453.JPG

post #33 of 96

Seriously, I'd return this Amp. It doesn't matter how good it sounds if it ends up burning your house down. Thats my advice

post #34 of 96

Truly horrific, its one thing messing around with circuits, but you shouldn't be selling them unless you can back up the product with some degree of quality engineering.

 

post #35 of 96

Poor design, VERY poorly wired, wooden chassis, be very afraid. Look dude, I'm not trying to bust your chops, but you should ask this so called amplifier builder for a refund. If he refuses, file a complaint with paypal, or your credit card company. Better to be safe than sorry.

post #36 of 96
Thread Starter 

No, I don't feel offended by anyone here.  I'm honest when I say I know enough about this and am asking for help here.  I'm going to have a friend of mine that builds custom tube guitar amps look at this thread and give me his opinion as well.  Its not that I don't trust you guys, I just need to know for sure because sending it back and getting a refund is likely easier said than done.  I need to make damn sure I understand the issues here and not go off all half-cocked because of a couple posts on a forum.

Does that make sense?

So far I've got one guy making what sounds like an educated statement on the technical safety of the way the transformer is wired, based upon experience in a similar design.  Everyone else just seems to be developing opinions about it's worth on the way it looks, expecting to see a bread board or something?  I understand that ideas don't always make their way through the internets the way intended so I understand that I may be misinterpreting....which is exactly why I'm trying to be thorough and clear and damn sure.

 

So please bear with me and if possible help me understand more by giving me verifiable, empirical information.

 

EDIT:

The sellers reply when I asked him about the apparent misuse of the transformer, please refer to the scematic linked at the beginning of this thread if needed:

 


IN5400 it 5A 500V diode, its hot but no problem, any item will hot but save, except the Transformer, if the transformers hot, the item will be problem, like the tube, always hot. if dont like that, ship back and must before Monday.
 
Also, if you scare IN5400 hot and not save, you can take it out and just use AC filament, I like AC Filament, AC filament will be more musical but just little bit hum. But, if you return it back to me, dont going to modify, I will not accept money back if you modily.


Edited by levlhed - 5/15/10 at 7:18pm
post #37 of 96

From this page

http://www.mcitransformer.com/i_4-06_2.html

its clear that the design uses one of the primaries as

the secondary. Clearly against all the UL rules and regulations

for safety on dual bobbin transformers.

 

A 35 watt transformer running at half power.

6.3 volts @ 2.5 amps is 15.75 watts

plus another 9 watts or so for the output

tube plate current. Plus the input tube power.

Absolutely running 20 to 30% over the ratings.

Not as bad as singlepower, but still...

 

half wave rectification of the filament, and a cap

way to small.

 

Definitely has singlepower written all over it.

 

I would monitor the temperature of the transformer carefully

while listening to it, and never EVER leave it turned on unattended.

 

Edit: there are some things about the new forum software that don't

make any sense. like you can't delete your own post or edit it

some of the time.

 

The problem with that 5 amp diode wired like it is, is the fact that

the current peaks are in the 12 amp range. Same problem with

other singlepower amps, go and find those threads.

 

This is not the way to do DC filaments.


Edited by kevin gilmore - 5/15/10 at 8:20pm
post #38 of 96

LevlHed, if Dr. Gilmore and Spritzer say the amp is dangerous, then I'd highly recommend listening to them.  Return it.

post #39 of 96
Thread Starter 

I am leaning in that direction for sure.

 

Is there any reasonable way to change the thing to make it safe?  Or is that akin to building an entirely new amp from used parts....

post #40 of 96
Quote:
Originally Posted by Skylab View Post

LevlHed, if Dr. Gilmore and Spritzer say the amp is dangerous, then I'd highly recommend listening to them.  Return it.


X 2.

 

To the OP : Dr G is an expert in the field. I'd trust his advice/analysis without question.

 

To answer your question about the parts quality used...none of the parts that I can make out are high quality....the entire amp uses low grade caps and resistors (sorry to say). Maybe 20 bucks worth of parts (if that) excluding the transformer, vol pot. This thing would require a complete rebuild that would end up costing you more than you paid for it IMO. The best course of action is to return it and re-order that Bottlehead kit rather than risk using this amp any further.

 

Peete.


Edited by Pricklely Peete - 5/16/10 at 12:08am
post #41 of 96

You're hardly going to get better advice than that from Dr. Gilmore.

post #42 of 96
Thread Starter 

Alright, I'm convinced.  I will be trying to send it back for a refund on Monday. Wish me luck!

 

Thank you all for the help.

post #43 of 96

Look at this positively: you can have the same problems as with a Singlepower amp, for a fraction of the Singlepower price! Quite a bargain if you ask me.

post #44 of 96


would be funny if peoples safety wasnt at stake...  Man poor guy... trying to get a deal on a tube amp and ends up with something that could kill him or his house... or both..

Quote:
Originally Posted by Sebhelyesfarku View Post

Look at this positively: you can have the same problems as with a Singlepower amp, for a fraction of the Singlepower price! Quite a bargain if you ask me.

post #45 of 96
Quote:
Originally Posted by levlhed View Post

Alright, I'm convinced.  I will be trying to send it back for a refund on Monday. Wish me luck!

 

Thank you all for the help.


Good luck! After you get your money back you should consider Bottlehead's Crack if you're willing to build a kit. Looks really nice

 

http://www.bottlehead.com/store.php

 

P.S. How did you pay or your amp? If it's paypal or your credit card, you can always file a complaint if this guy give you a hard time refunding your money

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