hey guys..ive been having issues with my 1990 mark 4a.im getting a nasty 60 cycle hum.ive tried various things and had a buddy of mine look at it who knows his stuff.he said it could be filter caps.he checked all the grounds etc..and didnt see anything wrong.he said physically the caps looked good..but could be on the verge of going.what i need is a good tech that knows the boogie in the louisville,ky area.any good suggestions?thanks in advance.
mark 4 user needs service help..
- Thread starter billyg121
- Start date
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Boogiebabies
Well-known member
All Mark series Boogie's can suffer from a malady of 60 cycle hum when a power tube blows and take out
the two 100 Ohm Hum Balance resistors. It's the first thing I check.
Here is where they are and what they look like on a MK IVA.
the two 100 Ohm Hum Balance resistors. It's the first thing I check.
Here is where they are and what they look like on a MK IVA.
Boogiebabies
Well-known member
billyg121 said:
No, you can just snip the old ones out and solder the new ones in. This keeps buddies or friends from lifting the pads.
Boogiebabies
Well-known member
1/2W or .5W and 100 Ohm. They don't really see more than 6.3V unless a tube failure spikes them
with a huge surge, then they blow or get imbalanced. The should read 50 Ohm in parallel.
with a huge surge, then they blow or get imbalanced. The should read 50 Ohm in parallel.
