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Little Dot I+ Tube Rolling - Page 131

post #1951 of 1959
Quote:
Originally Posted by forestitalia View Post
 

I'm using cv138 setting for the first time, the right channell is much more loud than the left, even if I invert the valves.

Any suggestion? It could be balanced?

 

 

It could be that one of the jumpers is defective.

 

There is a way to check this. The EF91/92 jumper for each socket simply connects pin 7 to pin 5. That is, it connects Grid 3 (pin7) to the Plate (pin 5).

 

To test this, you can easily make this connection in the socket. Put your LD back into EF95 mode. (I am assuming that EF95 has been working fine). Looking down on your sockets, the pinholes are counted counter-clockwise, starting with the pinhole to the right of the gap. Therefore, pinhole 7 is the last pinhole to the left of the gap. Cut two small pieces of 26 (or smaller) gauge stranded wire just long enough to allow one end to be inserted into pinhole 7 and the other into pinhole 5. Strip the ends of the insulation off both ends and then carefully insert these wires into the pinholes in both sockets. Next, carefully insert the tubes. Having done this, you have tied pin 7 to pin 5 in the socket which is exactly what the EF91/92 jumper was designed to do.

 

If you feel comfortable doing this, I suggest you give it a try and see what happens.

 

Good luck

post #1952 of 1959

Thanks a lot, I going to try.

 

Meanwhile I investigate and found that last owner used cv131 with the 6JI settings! (thats why was not happy thought)

could have damaged the amp?

post #1953 of 1959
Quote:
Originally Posted by forestitalia View Post
 

Thanks a lot, I going to try.

 

Meanwhile I investigate and found that last owner used cv131 with the 6JI settings! (thats why was not happy thought)

could have damaged the amp?

 

No, running EF91/92 tubes in the EF95 setting should not cause any damage to the amp. But the tubes might not sound very good.

post #1954 of 1959
Quote:
Originally Posted by gibosi View Post
 

 

It could be that one of the jumpers is defective.

 

There is a way to check this. The EF91/92 jumper for each socket simply connects pin 7 to pin 5. That is, it connects Grid 3 (pin7) to the Plate (pin 5).

 

To test this, you can easily make this connection in the socket. Put your LD back into EF95 mode. (I am assuming that EF95 has been working fine). Looking down on your sockets, the pinholes are counted counter-clockwise, starting with the pinhole to the right of the gap. Therefore, pinhole 7 is the last pinhole to the left of the gap. Cut two small pieces of 26 (or smaller) gauge stranded wire just long enough to allow one end to be inserted into pinhole 7 and the other into pinhole 5. Strip the ends of the insulation off both ends and then carefully insert these wires into the pinholes in both sockets. Next, carefully insert the tubes. Having done this, you have tied pin 7 to pin 5 in the socket which is exactly what the EF91/92 jumper was designed to do.

 

If you feel comfortable doing this, I suggest you give it a try and see what happens.

 

Good luck

You're right, it works! And is very good with these Telefunken, without connection there is noise too.

Do you think it could be fixed?

post #1955 of 1959
Quote:
Originally Posted by forestitalia View Post
 

You're right, it works! And is very good with these Telefunken, without connection there is noise too.

Do you think it could be fixed?

 

I was pretty sure this would work. :)

 

And I would think that it could be fixed. First, I suggest that you try another set of computer jumpers. Perhaps your jumpers are corroded and/or defective. And while you are at it, check and clean the jumper pins on the circuit board, perhaps they are corroded. If this doesn't solve the problem, then I suspect it will be necessary to resolder connections on the circuit board. (At this point, I should say that I have no experience soldering connections on circuit boards, so the best I can do is suggest how one might do this...)

 

Using an ohmmeter, check to make sure there is a good connection between the jumper pins on the circuit board and pinholes 5 and 7. (Remember that you will be looking at the underside of the socket, a mirror image if you will, so the pinholes are numbered clockwise, not counter-clockwise.) If the connection is poor, it may be necessary to resolder the connections. If you are not comfortable doing this, perhaps you have a friend who can help you.

 

If not, there is no reason why you cannot continue to tie these pins together in the socket with the wire jumpers you made. Just make sure you use 26 gauge or smaller stranded wire. For example, do not use solid-core 30 gauge wrapping wire. Solid-core wire, even 30 gauge, is simply too fat. And a wire too fat can stretch-out your sockets. I have used these wire jumpers extensively to run tubes that would otherwise be incompatible with the LD, such as 6AU6, with no problems.

 

Edit: And very frankly, it is a pain to open the amp up to switch between EF91/92 and EF95. so I often used these wire jumpers instead. :)

 

Cheers


Edited by gibosi - Yesterday at 10:16 am
post #1956 of 1959

Changing tubes is so funny, you have a complete different amp in 20 second and 10 quids, I found the right  punch and back listen Metallica's One after ages.

 

I'm thinking how install an external tube selector, no one tried?

post #1957 of 1959

An external tube selector? Something like a "jukebox" of tubes? lol I'm sure it is possible...  But as you say, it takes only 20 seconds to roll a pair of tubes, so maybe it's more trouble than it is worth?

post #1958 of 1959

No, I mean only a switch to pass from ef91 to ef95 without open it.

post #1959 of 1959

Well, until you get around to installing such a switch, the wire jumpers you made are a lot easier than opening the case, IMO.

 

Cheers

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