I have a B15T with several burned resistors on the output board. Anyone know if Loud Technologies has schematics for this amp? I tried Schematic Heaven and they only had the BT-15 series.

http://i284.photobucket.com/albums/ll33/bonosurf/470Lamp.jpg

I am working on a 470 and have run across a simple lamp driver circuit issue which is driving me mad. The B channel lamp will not operate when the switch is put in the B channel mode. I have checked both bulbs, replaced Q211/210, resoldered every possible node.

It looks like the drive transistors get the correct base bias voltages but the collector on Q210 reads 26V instead of 33 in the B channel mode and Q211 collector is at .7V instead of .3V in the B channel mode. I'm stumped by this very simple circuit.

Hello,

  I am repairing a ACC model 150 amplifier for a struggling student who is a very good guitarist and drummer but he is very short on funds (I'm sure we can all relate ). The amplifier is one of the later versions (>1973) and after rebuilding the power supply, new power cord, replacing the output transistors, bypass capacitors, etc I have run into a problem with the tremolo circuit.

The tremolo will work for about 5 min.s and then stop. I have replaced the FET (2N4360) which ACC replaced the LDR with on this later version of the amplifier. This portion of the circuit also has a trimmer pot which appears to adjust the mix of the tremolo output t on the output stage of the pre-amp (17-11E). Is there a procedure for adjusting this level?

I have also noticed that there is a transistor across this trimmer (2N2926) which is shown to have its emitter and collector connected across the trimmer in the schematic with the base floating. This makes no sense to me and I assume it's a typo in the schematic.

Well thanks in advance for any help or comments.   

Hello,

   Anybody want to volenteer their favorite thermal compound for use at the heatsink/package interface? I like Thermalloy non-silicon based product - though it's no fun to apply

THX

gb

Hello,

   First time poster - very interesting site.

  I have an Acoustic 150 which develops a loss of output and starts to distort after the amp warms up. The problem tracks both pre-amp boards so I believe that the issue is with the output board. I have replaced the output coupling capacitor, checked the thermistors, bias resistors and still have the issue. Any help appreciated.


   Also, why did many of the designs of this vintage use a transformer on the input of the output transistors? Was this for impedance matching?

THX
gb