UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Lowe HF-150 cleanup and LCD backlight

SiriusHardware · 3rd Nov 2021, 9:33 pm

Thanks, but I confess I am slightly baffled, as that circuit appears to show the signal from the AUDIO IN jack going to the input of what I suppose must be an audio-level-to-voltage converter feeding the S-Meter.

I've never seen an SP150 but I can only assume that these would normally have REC OUT from the HF150 connected to AUDIO-IN on the SP-150, in which case surely that meter reading can only be audio-level derived?

At the same time you're talking about having modified the AGC circuit so that you can derive a meter output from that - that's more like the kind of thing I was expecting.

At work, we have amber LED backlight panels which are I would guess about 2cm by 4cm and maybe 1.5 - 2mm thick and they give out a uniform amber glow across the whole panel. (I can be more precise about dimensions tomorrow).

The units these are in tend to get dropped a lot and that takes out the display but not the backlight, so I can always rescue a working backlighter from a dud display.

I don't know how much space you have between the insides of the legs of the display? Also, how much of a gap is there between the rear face of the display and the main PCB when the display is fitted?

3rd Nov 2021, 9:33 pm	#7
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,559	Re: Lowe HF-150 cleanup and LCD backlight Thanks, but I confess I am slightly baffled, as that circuit appears to show the signal from the AUDIO IN jack going to the input of what I suppose must be an audio-level-to-voltage converter feeding the S-Meter. I've never seen an SP150 but I can only assume that these would normally have REC OUT from the HF150 connected to AUDIO-IN on the SP-150, in which case surely that meter reading can only be audio-level derived? At the same time you're talking about having modified the AGC circuit so that you can derive a meter output from that - that's more like the kind of thing I was expecting. At work, we have amber LED backlight panels which are I would guess about 2cm by 4cm and maybe 1.5 - 2mm thick and they give out a uniform amber glow across the whole panel. (I can be more precise about dimensions tomorrow). The units these are in tend to get dropped a lot and that takes out the display but not the backlight, so I can always rescue a working backlighter from a dud display. I don't know how much space you have between the insides of the legs of the display? Also, how much of a gap is there between the rear face of the display and the main PCB when the display is fitted?