Red Bear MKE60 mod too 12ax7

[Curran Murphy]

HEY HEY noob here with a rare and very cool red bear MKE60. this had the original russian tubes in it so I popped in a new set of 5881 short bottles and 12ax7's. the output became SUPER SUPER low but was still there(whisper quiet). there is a mod online for switching this amp to work properly with 12ax7's you pull the Heater leads from pins 4 and 5. run the heater lead from pin 4 to jumper between pin 4 and 5 and run the pin 5 heater too pin 9. you also remove the ground wire from pin 9 that was part of the original wiring scheme. This layour was on each tube socket. HOWEVER now that I have done this the amp just makes a very loud HUMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. until I kick it over from play too standby THEN you hear the amp start to work. do I need to "re-ground" the sockets or what and if so where do I ground them from. I am assuming that the little ground lugs next too the tube sockets that pin 9 was grounded too will work fine for grounding if this is what I am supposed too do.
thanks in advance for any help you can provide!!!

Love Curran

[mesherm]

The amp must have originally used a 6 volt tube in that socket. Pin 9 on the tube is a ceter tap between the two filaments inside. Common practice was to ground that pin. So right now you have one heater lead connected to a jumpered pin 4 and 5 aand the other heater lead connected at pin 9?
Try this. Make sure that any ground wires going to pin 9 are lifted. You should only have the other heater lead connected there. Now take two 100 ohm 1 watt resistors and wire one end of each to a ground lug. Then wire the end of one resistor to the jumpered pins 4 and 5. Wire the other end of the other resistor to pin 9. that should re-establish that tube's ground reference.

[Curran Murphy]

okay so on one socket put the 100ohm on the ground lug and the 9 pin and on another socket the 100 ohm to the ground and the 4 and 5 pin jumper? or do I only need to do this to ONE tube socket in its entirety? sorry for not getting it 100% out of the gate. but thanks for the Help!!!!

Love Curran

[mesherm]

okay so on one socket put the 100ohm on the ground lug and the 9 pin and on another socket the 100 ohm to the ground and the 4 and 5 pin jumper? or do I only need to do this to ONE tube socket in its entirety? sorry for not getting it 100% out of the gate. but thanks for the Help!!!!

If both/all the 12ax7s are powered from the same filament source you should only need to do it to one tube. Both resistors should be connected to the same tube socket preferably the last tube in the filament string.
One resistor from ground to the 4,5 pins and the other from the same ground to the 9 pin.

[Curran Murphy]

thank you so much Sir I will try it this after-noon after some studio session work I must attend too!!!!
Love Curran

[Curran Murphy]

hey do I need to remove ALL grounding wires from the 9 pin? there are (2) lead/ground wires one a couple of the sockets that I think feed the FX loop. the hot part of the lead runs into pin 3 of the 12axy socket and the ground part is still connected to the 9 pin. I think I should move it too the ground lugs attached too the chassis next too the tube sockets. the reason I ask is that I did the 100ohm 1watt mod to ground the two filament heaters and there is still just HUMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. I am gonna go for it and if the answer is no I cna always undo the work!!!

Love Curran

[Curran Murphy]

DAMN IT!!!!!!!!!!!!!!!!!!!!!!!! same F**King thing!!! man I wish i was better at this. anyway any more help would be wonderful!!!

[mesherm]

http://www.triodeel.com/images/rb6n2pcv.gif

In looking at the schematic, your wiring mod should have work.
The hum must be coming from elsewhere. Was the amp working correctly BEFORE the change to 12AX7s?

[Curran Murphy]

okay so that was the mod I was working off of BUT I had a friend of mine with the 120mke who had the mod done as well. after ghosting the mod I find that the FX loop and tube socket 3 where causing the hum. after rewiring that action I got the tones happening HOWEVER!!!!! the volume pot and Volume II pot(gain) are intermittent and BEYOND scratchy!! which makes the volume very low and non existent. sooooooooooooo I have the schematic and what not and i am gonna replace them because the radio shack TUNER cleaner did not help the problem as was adviced on the amp page forum. the only thing about this is do I use Linear or Audio taper for the 250k gain and the 1 Meg master volume?

Love Curran Yellow_Light_Colorz_PDT_01

[EWBrown]

The volume controls should be logarithmic or "audio" taper, and not linear taper.

Linear taper is best used for bias setting pots, if the amp has any.

The TV tuner / contact cleaner doesn't always work, and at best, it is only a temporary fix.

HTH

/ed B

[Curran Murphy]

okay okay! the mod worked and I popped in the new pots BUT the volume is not nearly where it should be and it sounds a bit "BLATTY" like a distortion pedal that is not getting the proper power to the IC Chip or something. I did put 5881 power tubes in the amp as per the recommendations from the redbear web site/fan site. any ideas or should I just breakdown and bring too a shop?