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Author Topic: Laney Vc30 - 112 almost no sound  (Read 3444 times)

bunzonoise

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Laney Vc30 - 112 almost no sound
« on: September 06, 2011, 05:56:50 AM »
Hello everybody, I'm pretty new here.
I've a problem with my Laney VC30 - 112, and can't find in any troubleshooting guide the symptoms I'm getting from it.
Hope somebody can help: Power is on, all 7 tubes are normally orangy, but I can get only a very weak, faint distorted sound(like headphones) from the amp, and only if I max the volume knobs. This happens in both clean and drive channels.

What I tried already: plugging the send/return jacks - swapping tubes - checking the power supply voltage - looking for evidence(by sight) of something burnt on the board, or broken joints on the valve tube grids.

Another thing I notice is that when you turn the standby switch on, it's not doing the low frequency sound that usually does(something like 60hz hum) when is working properly.

I didn't change any tubes recently and the amp has always been well kept and didn't see much stress.


Hope somebody can spread some light.

teemuk

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Re: Laney Vc30 - 112 almost no sound
« Reply #1 on: September 07, 2011, 02:00:13 PM »
Your post unfortunately does not give much to work on but I try to give a few pointers...

"power is on"... I assume means the indicator LED is on. This alone does not tell much, merely that the +-17V winding powering the LED and bunch of solid-state circuitry is operational.

The HT winding for tubes is separate and the standby switch controls whether its hooked to the circuit or not. You might check that HT voltage is actually present; OT center tap measures about 290V, filtered supply dowstream measures slightly less, powering both screens, PI and preamp circuits. While you're at it - and if the meter is showing zero volts in there, check the HT fuses.

..in fact, check all the fuses. Are heater fuses intact; that also including the V1 filament fuse, which (if I understand correctly) is located on a regulator board. Heaters are working in all tubes, right?

Since the problem troubles both O/D and clean channels it's originating either in the stages before the switch that directs signal to OD or clean signal paths, or after the other half of the same switch that selects between OD and clean signal paths. So far that is still quite a lot of area to troubleshoot. I would try to narrow it down.

"plugging the send/return jacks"... can be done to different extents. Did you try whether you get clear preamp signal from send jack and if plugging to return jack gives clear power amp signal without the described attenuation? This check alone would isolate the problem to either side of the loop; narrowing the troubleshooting area.

Schematic
http://www.bymcomunicacion.com/pvecino/john/laneyvc30.pdf
« Last Edit: September 07, 2011, 02:07:15 PM by teemuk »

 

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