[Shane D]

On my first day with my MKIII, I was getting noise out of my 6HM5 Yugoslavia tubes. When.i was talking to the seller, he mentioned that they were new to him and he hadn't tried them.
So I decided to run them last night while watching TV. Maybe they just needed breaking in. After a few hours of being on, with all four tubes in and no mysic playing I started to hear noises. It was like a hiss and a crackling. It seemed to be coming from the power bar and not the amp. As soon as I turned the amp off, it was gone. Bad tubes? Lustening today with the Voshkods in and it sounds great.

Are these defective tubes? Could they be the wrong tubes?
Pics:

 

[triod750]

I carefully clean the pins on all tubes - new or used - before I use them. Before I made this a habit I once had the same problem as you describe. Other people have described the same problem and solution. I use fine emery board. Some use a dull small knife. I then use contact spray on a 'cotton pin'. 'PRF 6-68' is a contact spray for electronics that leaves no residue. There must be plenty of others that work as well.

Your tubes look the same as mine.

 

[TrollDragon]

Do you use de-oxit? Now that I have three tube amps I should probably splurge on a can.

I've never used Deoxit but do have a can of LPS Contact cleaner around to clean electronics.

I clean the pins of tubes with a Dremel 4mm bullet point polishing burr, it makes fast work of cleaning pins.

I'd definitely give those pins a good cleaning either with a similar Dremel bit, an emery board like Triod750 mentioned, a strip of fine emery cloth or something.

 

[TrollDragon]

It's really too bad that thousands of pictures from this thread and others were lost when they changed forum software...

 

[Shane D]

It's really too bad that thousands of pictures from this thread and others were lost when they changed forum software...

I noticed that when I was researching. Too bad.

 

[Jolterrrr]

Hello

I am new to tube Rolling can i use 6AS7G's power tubes in My Ld mk2? Or is it only for mk3? (With that strange cut pin thing) ??

 

[lupoal]

@Shane D
... if you don't have Deoxid then just put them inside Coca Cola... don't leave them inside too long (start with a couple of hours and then inspect them with magnifier... the app Lente d'ingrandimento for android works really well) otherwise you loose your pins, then whasm them with warm water and then, if you like, the pins with a toohbrush and some alcool

 

[TrollDragon]

Hello

I am new to tube Rolling can i use 6AS7G's power tubes in My Ld mk2? Or is it only for mk3? (With that strange cut pin thing) ??

6AS7G draw 2.5A each on the heaters, you must use an external heater power supply to use them in your MK II.

 

[Jolterrrr]

http://www.ebay.com/itm/NEW-DC-DC-S...037?pt=LH_DefaultDomain_0&hash=item3a901724dd

http://www.ebay.com/itm/1pc-6SN7-6SL7-TO-12AU7

6AS7G draw 2.5A each on the heaters, you must use an external heater power suppl

6AS7G draw 2.5A each on the heaters, you must use an external heater power supply to use them in your MK II.

Aha! Can i use this device ???

https://www.ebay.com/itm/XL4015-5A-...-/132816365155?_trksid=p2349624.m46890.l49292

And to what pins do i solder ? 4 and 5 ?

 

[Jolterrrr]

6AS7G draw 2.5A each on the heaters, you must use an external heater power supply to use them in your MK II.

And what adapter/s is it enough to buy 2 of these 6SN7-6SL7-TO-12AU7? Cut pin 4-5 and solder Them to an external heater? It Will fit in My mk2 ?

 

[TrollDragon]

Aha! Can i use this device ???

https://www.ebay.com/itm/XL4015-5A-...-/132816365155?_trksid=p2349624.m46890.l49292

And to what pins do i solder ? 4 and 5 ?

Too bad all the old information (pictures) on this mod was lost when Head-Fi updated the forum software.

You will need a pair of adapters to convert the 6AS7G tubs to 6CG7 compatible pinout.
https://www.ebay.com/itm/1PC-Tube-D...O-6CG7-for-Vacuum-tube-amplifier/303542012598

A pair of B9G socket savers so you can cut off pins 4 & 5 and attach the external power supply wires.
https://www.ebay.com/itm/NEW-9-PIN-...7-5751-12AT7-etc-FAST-USA-SELLER/254612574139

Finally I'd go with at least a 8A DC converter as the one you linked has a maximum output rating of 5A and will require cooling if you are running both tubes from it. If you use one for each tube that would be better and probably not require cooling. You will also need a decent power supply to provide enough source power for the DC converter board, a lot of the members here used old laptop power supplies.

Note that this will make your MKII run hotter, the biasing of the circuit is all wrong since the amp was never designed to run those tubes.

I've never bothered to play with any octal tubes as outputs, many others have and YMMV with results.

 

[Jolterrrr]

Too bad all the old information (pictures) on this mod was lost when Head-Fi updated the forum software.

You will need a pair of adapters to convert the 6AS7G tubs to 6CG7 compatible pinout.
https://www.ebay.com/itm/1PC-Tube-D...O-6CG7-for-Vacuum-tube-amplifier/303542012598

A pair of B9G socket savers so you can cut off pins 4 & 5 and attach the external power supply wires.
https://www.ebay.com/itm/NEW-9-PIN-...7-5751-12AT7-etc-FAST-USA-SELLER/254612574139

Finally I'd go with at least a 8A DC converter as the one you linked has a maximum output rating of 5A and will require cooling if you are running both tubes from it. If you use one for each tube that would be better and probably not require cooling. You will also need a decent power supply to provide enough source power for the DC converter board, a lot of the members here used old laptop power supplies.

Note that this will make your MKII run hotter, the biasing of the circuit is all wrong since the amp was never designed to run those tubes.

I've never bothered to play with any octal tubes as outputs, many others have and YMMV with results.

Thank you soo much !

 

[triod750]

Thank you soo much !

Jag har skickat ett PM på ditt eget språk .

 

[lupoal]

.... just received my new couple of C3g NOS NIB, comparing with the others I have there are some small differences... here are some pictures, as you can see there are mechanical diffences in pins shape... the total tube length.... and others... what do you think about?

 

[gibosi]

.... just received my new couple of C3g NOS NIB, comparing with the others I have there are some small differences... here are some pictures, as you can see there are mechanical diffences in pins shape... the total tube length.... and others... what do you think about?

Tubes made in the same factory at different times are often different due to new processes, new technologies, new materials and feedback from the field. So in my opinion, perfectly normal.