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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 344

post #5146 of 7549
Quote:
Originally Posted by i luvmusic 2 View Post
 

I'm wondering what will happen if i switch the jumper from EF95 to EF91/92 setting with 6SN7 Tube.fireworks maybe?

 

I do not know what your adapter looks like....  My adapter uses two 7-pin test sockets inserted into the LD. The 6SN7's two triodes are directly connected to pins 1, 2 and 5 on each test socket. As the EF91/92 setting connects pins 6 and 7, which are not used by my mod, nothing would happen.....

post #5147 of 7549
Like gibosi said, the 7 pin LD sockets have pins 5&6 shorted together permanently on the circuit board. When you move the jumper to EF92 it shorts pin 7 to 5&6.
post #5148 of 7549
Quote:
Originally Posted by gibosi View Post
 

 

I do not know what your adapter looks like....  My adapter uses two 7-pin test sockets inserted into the LD. The 6SN7's two triodes are directly connected to pins 1, 2 and 5 on each test socket. As the EF91/92 setting connects pins 6 and 7, which are not used by my mod, nothing would happen.....

OK Thanks no need for me to try switching.

post #5149 of 7549

on the 6sn7 tubes, which is the heater positive and negative? is 7 positive or 8?

 

also how do you adjust the output of the regulator? mine is stuck at 11.6 output and there's a little screw on it but it does nothing.

post #5150 of 7549
Quote:
Originally Posted by gibosi View Post
 

Two Japanese 8FQ7

 

Quote:
Originally Posted by mordy View Post

 

I have three different Japanese 8FQ7/6CG7 tubes.

 

I take it that you have checked the relevant parts of http://www.geocities.jp/radiomann/HomePageVT/TV_GPTT.html.

 

If not, please do.

post #5151 of 7549

Hi Oskari,

 

Thanks - the first time I checked I could not find them, but now I think that I have identified Hitachi and Toshiba tubes, with the nod going to Hitachi.

The Raytheon/Hitachi 8FQ7 is one of my favorite tubes at this point.

post #5152 of 7549
Quote:
Originally Posted by mab1376 View Post
 

on the 6sn7 tubes, which is the heater positive and negative? is 7 positive or 8?

 

also how do you adjust the output of the regulator? mine is stuck at 11.6 output and there's a little screw on it but it does nothing.

According to Gibosi it does not matter 7 or 8  on mine 8 is +.IMO on your Regulator maybe input and output are reverse or faulty Pot.

post #5153 of 7549

The component in red is also a little wobbly.

 

I probably have to request a replacement and wait another month...

post #5154 of 7549
Quote:
Originally Posted by mab1376 View Post
 

The component in red is also a little wobbly.

 

I probably have to request a replacement and wait another month...

Try resoldering those components or replaced the pot. in my area those pots are less than $1.

post #5155 of 7549
Quote:
Originally Posted by i luvmusic 2 View Post
 

Try resoldering those components or replaced the pot. in my area those pots are less than $1.

 

I found that if i twisted the pot to the left it eventually went down, strangely i can only set 6.19 or 6.35 with no in between?

post #5156 of 7549
Quote:
Originally Posted by Oskari View Post
 

I take it that you have checked the relevant parts of http://www.geocities.jp/radiomann/HomePageVT/TV_GPTT.html.

 

Yes, I have checked my tube against the pictures. Unfortunately, tall, flat, ladder plates can be seen on Toshiba and Hitachi, as well as other brands. Further, my tube has a disk getter and one of those mica-spring structures on the top mica, and ferrous grids, not copper. I don't see anything quite like it there.... :(

 

 


Edited by gibosi - 2/27/14 at 6:15pm
post #5157 of 7549
Quote:
Originally Posted by mab1376 View Post
 

 

I found that if i twisted the pot to the left it eventually went down, strangely i can only set 6.19 or 6.35 with no in between?

 

Our cheap voltage regulators, being digital and not analogue, are adjustable in discrete steps. It is not infinitely adjustable and you simply can't adjust it as precisely as you might want. Further, this is somewhat exacerbated by having LED displays with 2 decimal points. My display is only 1 decimal point so these discrete steps are not as noticeable. On the other hand, there is nothing to be gained by setting the voltage to exactly 6.3 volts. Either 6.19 or 6.35 is perfectly OK.

post #5158 of 7549
Quote:
Originally Posted by gibosi View Post
 

 

Our cheap voltage regulators, being digital and not analogue, are adjustable in discrete steps. It is not infinitely adjustable and you simply can't adjust it as precisely as you might want. Further, this is somewhat exacerbated by having LED displays with 2 decimal points. My display is only 1 decimal point so these discrete steps are not as noticeable. On the other hand, there is nothing to be gained by setting the voltage to exactly 6.3 volts. Either 6.19 or 6.35 is perfectly OK.

 

I used a multimeter on the output for exactly 6.3v which actually reads 6.19v

 

I would assume to much voltage would shorten the life by increased heat?

 

Its now dead silent while not playing music!! No background hiss/buzz!

 

:gs1000smile: 

 

Got a Tung-Sol JAN-CTL-6SU7GTY running right now!

 


Edited by mab1376 - 2/27/14 at 6:28pm
post #5159 of 7549

Glad to hear that everything is working well for you. And yes, it is great to be able to kill two birds with one stone. Now we can roll higher heater current tubes, like 6SN7, E80CC and ECC40, and our amps are quieter! Win-win!! :)

post #5160 of 7549
Quote:
Originally Posted by mab1376 View Post
 

 

I used a multimeter on the output for exactly 6.3v which actually reads 6.19v

 

I would assume to much voltage would shorten the life by increased heat?

 

Too much voltage will shorten tube life, but not 6.4 or 6.5 volts. If you were running at 7V or 8V, yes.  

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