Help On 82/83 Mark IIC 60/100 Reverb No Eq

[gem12]

I'm not sure but I think that there's something wrong with my Lead Master Volume control.
Setting the volume on Lead Master from 0 - 10 doesn't do anything. Right now I'm using
the Lead Drive to control the volume on the Lead Channel. Is my Lead Master Pot open?
Can someone with same amp help me troubleshoot this prob.?..............Thanks.

 

[Shep]

how old are your tube's? I would have ago at cleaning out the pot. It might be stuffed.

Are you comfortable with handling 483 volts? if you are open it up and have a look for burnt spot's.

Tom

 

[gem12]

how old are your tube's? I would have ago at cleaning out the pot. It might be stuffed.

Are you comfortable with handling 483 volts? if you are open it up and have a look for burnt spot's.

Tom

Tubes are all B-New (Pre/Power Amp)
Yes, I can handle it.
Will open it up and take a look inside which I haven't done yet.
I'll let you know.

Thnx

 

[chipaudette]

Hi,

When in lead mode, does the regular master volume (not the lead master) still work? If it does, I would suspect one of these two problems...

1) The Lead Master pot lost its connection to ground. The wire from the ground side of the pot could be broken. Also, on the Mark IIC, there is an LDR element on the circuit board between the pot and ground. When the lead mode is activated, the LDR activates, which allows the pot to go to ground. So, you may need to check both the wiring from the pot and you may need to check the health of the LDR.

2) The wire to the wiper of the pot is broken. On my MK IIC, there is actually a wire that connects the wiper of the lead master pot to the wiper of the (regular) master pot. Check to make sure that the wire is fully connected on both ends.

If you need a schematic or pictures of the inside of the chassis for my Mark IIC, you can check out this thread:

http://forum.grailtone.com/viewtopic.php?f=27&t=37463

Chip

 

[gem12]

Hi,

When in lead mode, does the regular master volume (not the lead master) still work. If it does, I would suspect one of these two problems...

1) The Lead Master pot lost its connection to ground. The wire from the ground side of the pot could be broken. Also, on the Mark IIC, there is an LDR element on the circuit board between the pot and ground. When the lead mode is activated, the LDR activates, which allows the pot to go to ground. So, you may need to check both the wiring from the pot and you may need to check the health of the LDR.

2) The wire to the wiper of the pot is broken. On my MK IIC, there is actually a wire that connects the wiper of the lead master pot to the wiper of the (regular) master pot. Check to make sure that the wire is fully connected on both ends.

If you need a schematic or pictures of the inside of the chassis for my Mark IIC, you can check out this thread:

http://forum.grailtone.com/viewtopic.php?f=27&t=37463

Chip

As long as the

Hey,

Thanks and yes the Master Volume is working fine.
I will check all the connections when I finally get to open it up.
For the meantime are there any risk of damaging anything while in this status?
I have been using the amp for almost 3 weeks now since it was given to me and seems ok so far
except for this one. And also disconnected the fan to cut the noise while playing inside my room.

Thanks for the tips.