2061 w/ low volume on bass channel

[Birk]

I've got a 2061 ('73 JMP Lead & Bass 20 watt head), and some time ago I noticed that the bass channel had much lower volume than the Lead channel.
To compere the channels: when lead is on "2", bass has to be on "6" to follow the output.
When I bought the amp, they seemed to be equal in volume/output.
Any idea what's wrong?
Could it be dried out capacitators?

One stupid thing I've done once is to run two 8 ohms cabs at the same time.
The amp has two 8 ohm outputs, but they are run in parallel, so my guess is that I've overloaded it by running on 4 ohms. Am I correct?
(I only did that one time, and with the volumes on 12 o'clock)

Thankfull for any help.

 

[Birk]

No one? Please?

 

[PaoloJM]

Can't seem to find a schematic for that amp.
Often, multi channel amp have different preamp valves per channel.
Have you tried swapping preamp positions?
The could be other causes but this is the best place to start.

 

[Birk]

Thanx, I will try that.
BTW: the amp is the orginial to the 2061x HW, if that makes it easier to find schematics.

 

[tone_master]

Have the same amp a Handwired. the bass channel volume is lower than the other one, isn't this the way they come?? (not sure since I bought mine used)

 

[manktelow]

The lead channel inputs and the bass channel inputs.
The top input is 'high sensitivity' and the bottom input is 'low sensitivity'
The bottom input being 6dB lower in volume than the top input with a darker sound.

 

[Birk]

What I ment was that I discovered that the bass channel had much lower volume than it used to have....