And the troubleshooting begins

[rhubarb9999]

So I started with the chassis and iron from an Earth Sounds Super Bass 100 ... essentially a Twin without the reverb.  Schematic is almost an exact match.  I had the Super Bass running before I gutted it.


I installed a Revolver built Hoffman Twin AB763 board.  I removed the first channel bits.  So I finally fired it up tonight.  Heaters look good, bias looks good.


When I take it out of standby, there is a slight hum in the speaker.  I can hear a faint click when I touch the input jacks .. but that's it.  I hear no difference when I turn any of the pots.  The reverb tank is not installed.


So I noticed a few things.  First, the B+ off the 6 diodes is only 318v.  Seems low.  The diodes took a lot of heat from the soldering tip.  Could one or more have been baked?


Second, even though the power transformer has a tap to ground for the heaters, I still ran them to the 100 ohm resistors to ground.  I get 3.2v from each heater wire to ground .. 6.4v between the heater sides.  Is this correct?


Any other ideas on a good place to start trying to make this thing work?


Thanks

[Willabe]

Welcome!

Look in here for a great way to double check the wiring on a new build;

http://el34world.com/Forum/index.php?topic=17701.0

[John]

The diodes took a lot of heat from the soldering tip.  Could one or more have been baked?

I think they're pretty sensitive to that, yes. I always clip a heat sink one when I'm soldering those. However, even 318 should be enough for making sound.


re: your heater CT. You don't have that grounded *and* have your artificial tap, correct? But yeah, 6'ish volts is right on the money.


As far as no sound, there's a mis-wire somewhere. I know for a fact it sure feels good when you find it!