09-10-2018, 01:56 PM
I also forgot about the one with fried input termination resistors. Somebody had somehow made a video source with about +5V of DC offset. This will certainly fry the input 75R termination. It's actually a pair of resistors that give 75R but the effect is the same.
After I found and fixed the fault he fessed up to what he'd done. I think we agreed on a £20 donation to the VIntage Wireless Museum.
I now have the unit with the suspected lazy xtal on the bench. It worked perfectly of course, even when starting from fridge temperature. At freezer temperature the xtal was still running but the analogue output seemed to be in trouble. Similarly if I use freezer spray on the analogue output area. I will investigate further.
Tomorrow I should be getting a unit where the report is "no output". I'm keeping an open mind on that one but have a fairly strong feeling it might be user error.
Yet another one is due to be brought to me in person soon. With a fault described as looking like intermittent twitch on line hold. This has been reliably witnessed (John Wakely) and I have no idea at all as to what might be causing it.
After I found and fixed the fault he fessed up to what he'd done. I think we agreed on a £20 donation to the VIntage Wireless Museum.
I now have the unit with the suspected lazy xtal on the bench. It worked perfectly of course, even when starting from fridge temperature. At freezer temperature the xtal was still running but the analogue output seemed to be in trouble. Similarly if I use freezer spray on the analogue output area. I will investigate further.
Tomorrow I should be getting a unit where the report is "no output". I'm keeping an open mind on that one but have a fairly strong feeling it might be user error.
Yet another one is due to be brought to me in person soon. With a fault described as looking like intermittent twitch on line hold. This has been reliably witnessed (John Wakely) and I have no idea at all as to what might be causing it.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
