I’ve starteed working on the Laney amp as mentioned in an earlier post found here. I had it recapped and with no tubes, slowly brought it up to main voltage. Here’s a picure of them new caps.
Here’s the preamp section.
As it has fixed bias but not adjustable I added a bias pot and measure points accessible from the outside on the back of the amp as seen closer in this image. I’ve also installed new 1K screen resistors instead of the 470R :s.
Here’s the back panel with the bias pot and the measure points.
Time to power it up with tubes, I had the bias voltage set to -54VDC as in it’s original state. Checked with dummy load and scope and all voltages are in specs. Also changed a few resistors and the master volume pot installed before I recieved it.
Checked the switch for D.TIME due to the problem of changing from 200mS to 800mS of delay. Found it’s not the cause. Had the wiring from the switch resoldered and it’s hey, it’s back in normal operation! Also fixed the knob for E.LEVEL wich was glued in place.
Found these vintage OA5 germanium diodes in the box of vintage stuff. Beutiful diodes indeed. Got to make something with them, just don’t know what? Anyone care for a custom built pedal with these beuties under the hood and in what circuit?