Glockenklang Soul

[gbono]

Soul head that will not power up - doesn't blow fuses. The front panel red LED that indicates some type of fault has occured flashes briefly before relay trips power.

Power supply rectifiers check out, all caps check out and all output devices pass simple check with DVM. The PCB is a mix of SMT and through hole (might also be a lead-free assembly).

Anyone ever work on one of these? Don't have a schematic for the power supply section...

Soul0105.pdf

[Enzo]

Well, the 15v supplies are on that page. Is ther both + and - 15v being made?

[gbono]

I can't keep this thing on long enough to test supply voltages - not sure I even see the relay that is shuting down power in the schematic.

I tried de-soldering some of the transformer leads on the PCB and there must be lead-free solder on this board since I have to really turn up my iron to get reflow.

Anyone have any experience with this design and its fault circuit logic?

[Jazz P Bass]

Soul 0105

This thing must look like a christmas tree!
LED city. I saw an LED 10.
Can you identify which LED is lighting when the amp goes into protect.
The LED may have a marking on the board.

[gbono]

Okay - the only LED lighting is the red one on the front panel which (see attached manual) trips when one of the fault circuits engages. The yellow LED does not come on so I am ruling out the temp sensors on the OT heatsink.

I have to "assume" that the fault is in one of the power supply circuits but the components check out there. No burned discolored/parts on the board.

soul-manual-en.pdf

[Enzo]

Check the power amp - are there shorted power transistors?

Disconnect the power amp, does the power supply wake up and run the mixer part?

[gbono]

Already checked active (discrete) components and all electrolytics and found no issues. The amp has ONE PCB so you can not disconnect the pre/power amp without trace cutting.

I believe that I may have found the problem with what appears to be a PTC thermistor in the torrid wiring??? at least I believe that what's happening - do not know the value of this thermistor so I will have to do some guesstimation regarding testing and replacement.....any suggestions??

[gbono]

Bump....okay his is an early version of the design with no thermistor in the primary of the PT. When I power up the amp there is a relay that trips and the red fault LED blinks for a second and the amp is shut off.

I measure 120VAC on the primary in the above fault mode but I also measure 120VAC on the +-30V supply bridge????? I'm assuming the toroid is damaged. Best way to verify by a second test method?

[gbono]

bumping this back up....

On power up the amp will briefly light the red fault LED and then shut down except the fans come on at low rpm?

I checked out the transformer (torroid) and all secondary winding/voltages are correct - out of circuit. When I re-solder the secondaries back on the PCB and power up the amp I do not see correct voltages at the +-15v and +-5 supplies. I'm assuming that the issue is with the pre-amp and PA driver sections of the amp.

Checked limiter transistors Q5/6 and they appear to be okay.

I'm having a problem tracing the fault protection (what lights the red fault LED on the front panel). It looks like the SCR (Q3) is part of the protection scheme but what's disabling the low voltage supplies?