Thanks Nigel, I see what you're getting at regarding LED intensity. Typically it's necessary to use a current regulated power supply to adjust LED brightness, whereas incandescent bulbs generally use a voltage regulated power supply. So it might be possible to add an adjustable current limiter, but it's much easier if I can find an incandescent bulb. I once built a current regulated power supply to dim an LED for use as a microscope illuminator and it worked out very well. Actually, I'd be very happy if I could just find a supply of replacement bulbs on the internet. This is about as close to what Dave described as I was able to find. http://www.bulbs.com/T--Type/Under_5W/Lead_wires/results.aspx?Ns=P_Wattage+S ort|0&pid=279 The diameter of the first bulb is 0.125 inch which is about 3 mm Perhaps that's the right one?? Thanks for all the help. I've enjoyed learning about the optacon! John -----Original Message----- From: optacon-l-bounce@xxxxxxxxxxxxx [mailto:optacon-l-bounce@xxxxxxxxxxxxx] On Behalf Of Pentronics Sent: Monday, June 13, 2011 4:32 PM To: optacon-l@xxxxxxxxxxxxx Subject: [optacon-l] Re: Replacement light bulb for optacon camera Hi John, Dave answered your email before I got the chance - it was a holiday weekend here. The one thing I will add is that LED's will not work. It will not be possible to vary the lamp intensity to achieve the correct threshold range. The brightness of the lamps is critical for this. The correct threshold setting is achieved by setting the Threshold control on the front panel to approximately 10 o'clock, the camera zoom to maximum and adjusting the Intensity pot VR2, (in the front right hand corner of the power and timing board), so that approximately 50% of stimulators are driver. This will occur in the top and bottom potions of the array and progress to the centre as the brightness is adjusted. Nigel Herring Pentronics 33B Sheppard Road Emu Plains NSW 2750 Tel. +61 2 4735 7355 Email. service@xxxxxxxxxxxxxxxxx Web. www.pentronics.com.au -----Original Message----- From: optacon-l-bounce@xxxxxxxxxxxxx [mailto:optacon-l-bounce@xxxxxxxxxxxxx] On Behalf Of johnobuttons@xxxxxxxxxxx Sent: Monday, 13 June 2011 10:29 AM To: optacon-l@xxxxxxxxxxxxx Subject: [optacon-l] Replacement light bulb for optacon camera Hello, I trying to fix an optacon for a friend. After removing the ancient battery, the unit appeared to be working. However one of the two light bulbs in the camera (scanning) unit is Not lighting. Can anyone give me any advice on replacing this bulk. Has anyone ever tried using an LED replacement? Thanks for any and all help! John Hamilton to view the list archives, go to: www.freelists.org/archives/optacon-l To unsubscribe at any time, just send a message to: optacon-l-request@xxxxxxxxxxxxx with the word "unsubscribe" (without the quotes) in the message subject. Tell your friends about the list. They can subscribe by sending a message to: optacon-l-request@xxxxxxxxxxxxx with the word "subscribe" (without the quotes) in the message subject. to view the list archives, go to: www.freelists.org/archives/optacon-l To unsubscribe at any time, just send a message to: optacon-l-request@xxxxxxxxxxxxx with the word "unsubscribe" (without the quotes) in the message subject. Tell your friends about the list. They can subscribe by sending a message to: optacon-l-request@xxxxxxxxxxxxx with the word "subscribe" (without the quotes) in the message subject. to view the list archives, go to: www.freelists.org/archives/optacon-l To unsubscribe at any time, just send a message to: optacon-l-request@xxxxxxxxxxxxx with the word "unsubscribe" (without the quotes) in the message subject. Tell your friends about the list. They can subscribe by sending a message to: optacon-l-request@xxxxxxxxxxxxx with the word "subscribe" (without the quotes) in the message subject.