Hammond Concorde Distorted

[mason357]

I also have a Hammond Concorde. The sound that comes out of the speaker is low volume and very distorted. When I plug in headphones it's a little better but still low and distorted. The Leslie does nothing. I cleaned the contacts and were all the circuit boards plug in same problem. I was wondering could it be the power amp and preamp maybe bad caps in these. I want to get it fixed to were it plays good clear sounds before seeing what else is wrong.

And yes I know the concorde isn't the best but I still want to repair it.

[KC9UDX]

There's nothing wrong with the Concorde. The fears of repairs are overrated. It's a marvelous design.

Did you clean the connectors on the bottom of the power amp?

[mason357]

All amp connections cleaned. I took all the circuit boards out cleaned and reseated all cables that could be disconnected were cleaned and reseated. I used CRC electric contact cleaner similar to DeOxit. For the low volume and distortion makes me think the pre/power amp section. It does sound better when I plug in headphones but not much. I keep seeing thing about caps going bad but I want to cover all bases before I send out the amp assembly or tear into it myself.

[KC9UDX]

Did you remove the power amp and turn it upside down? There are connectors under there that are easy to miss which could cause your problem.

[mason357]

All power amp cables were cleaned and reseated.

[mason357]

Anyone else with ideas?

[W4KSR]

Which series is your Concorde? 2100, or 2300? Also, the low volume/distortion is noted on everything, rhythm, percussion, drawbars?

[mason357]

I think it's a 2100. The distortion is on everything.

[KC9UDX]

I wonder if the power supply voltage is correct.

[Jyvoipabo]

Hello,

I understand that with the headphones the sound is better than with internal speaker.
Distortion increases as the requested power increases. This may indicate that the problem comes from the amp.

If true, this narrow the researches to the amplifier.

Without a schematic it may be a little bit complicated. I suppose the amplifier is solid state.
Look for a bad soldier overheat component (especially power transistors), burns of the PCB or capacitor leakage.

No need a schematic to do that.

Then, you have to identify the design of this amplifier.
Could you send a picture of it showing the whole Pcb and the P/N of the power transistors.

Regards.

JP

[W4KSR]

The amps are solid state. There are two identical 35 Watt amplifiers located underneath the power supply unit. I'm leaning towards a bad power supply power transistor. Without the service manual, it will be difficult to trace out, unless you have the patience. There are steps that are listed there to check for proper readings with a VTVM. If it was one side that had the problem, you could swap the amp boards around.
The easiest way to differentiate if it's a 2100 or 2300, is if it has the AutoVari64 rhythm unit, and Touch Tempo. Those are on the 2300 series.

[Jyvoipabo]

Hello,

This is a very classic class AB Amplifier.

From : https://archive.org/stream/23001/230...ge/n0/mode/2up

Class AB means there is a idle current. It must cause a little heat of each power transistors after a few minutes warm up.
If they are Cold or Different temperature or Hot as you can't hold your finger on the case, there is a problem.

The DC out is stabilized by the input differential pair.
If there is a loud 'honk" in the headphone when you insert or remove the jack, there is also a problem.

If you have meter check +32 Volt and -32 Volt supplies,Vout = 0 Volts and V across C7 = 16 Volts approx.
And finally check the idle current. 40mA cause 13 mV Voltage drop accross 0.66/5W resistors. This delicate measure is not necessary if the temperature of the power transistors is correct.

JP

[swfrx]

I have a Concorde 2300 and really like it. I was doing some cleaning on mine and the vertical connectors on the upper manual synthesis are offset and I think i have mine off because the percussion doesn't work on part of each octave. If it's not too much trouble could you post a picture of those connectors?

thanks