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Ashdown Mag 300 VU back light


Steve48
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Hi Guys,
Has anyone ever replaced the VU bulb on a Ashdown MAG 300 head. Mine stopped working a few weeks back and I want to sell the amp but would like to get the VU backlight working again before I advertise it.
If so is it easy enough to do and what bulb do I require.
Thanks in advance.

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  • 2 years later...

Hi, mine has also ffailed. I decided to replace the bulb par 3 leds. To access to the bulb, disconnect the mains, open the Mag 300 head, take care to the radiators where ther some high residual voltage.

To acces to the Vu meter, you have to remove all rotative knobs, remove all screws for the potienmeters and the jack plugs, and to remove the 2 small screws on the DI plug.

Then it is possible to remove the front panel

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Following -
Then it is possible to remove the front panel PCB from the front panel. I had to push on the Vu meter glass and to move it with a screwdriver, because the vu meter is attached via double face tape both on the PCB and on the front panel.

Once the PCB is removed, the bulb can be seen on the PCB, behind the Vu meter. The bulb is horizontal, soldered on the PCB and is not fixed on the Vu meter. Anyhow, it seems (very) difficult to replace the bulb without removing the Vumeter from the PCB.

I removed the Wumeter ( unsoldering it, it was soldered by 2 large plots of solder). Then I removed the bulb.

The bulb is supplied by something like 15,5 V DC ( I measured on mine 15,7 V DC). I replaced the original by 3 leds in serial.
Each Led receive 18 mA, through 3 resistors 180 Ohms in serial.
I have build a small PCB for the 3 leds and the resistors. The PCB have been fitted beteween the Vu meter and the main PCB, and I have added 2 plots of mastic to avoid vibration or displacement.

Its works now, with the same color (amber) as original. Nevertheless, I was not having blue or white leds, which I sgould have prefered.
It took me around 3 hours to do it ( including test and measurement of leds that were in my spares box, and the building of the small PCB,

Good luck,
Remi
The Leds lights the Vu meter by transparency, but it still possible to distinguish 3 spots of light .

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