Eagle PSU conversion - UK Vintage Radio Repair and Restoration Discussion Forum

Herald1360 · 28th May 2012, 12:03 am

I'll put this here (rather than in Test equipment or Home brew) both of which could apply, since it was a success.

Nothing very special, but a pleasant hour or so whiled away messing with a gash PSU from a freebie rummage bag picked up at the end of the last Harpenden auction.

The label said 9V 500mA, but a quick check showed about 13.5V off load, 8.5V on load, so it clearly wasn't anything special. In fact it was just transformer, fullwave rectifier and 1000uF 10V(!) capacitor. Plus a few bits showing its age- a proper mains on/off switch and a neon power indicator (seriously blackened bulb there). Output was from a pair of reasonable 4mm plug/binding post connectors.

The ac across the full secondary was about 19V, which triggered an idea- what about a PSU to run the shed Hacker, rather than the tiring restuffed 18V (now 12v) "PP9" in there at the moment?

Anyway, the Hacker still sounded fine at 12V, and a quick rummage turned up a LM340T15 (7815 clone), a NOS 2A RS bridge, a 2200uF 35V capacitor and a couple of 1uF 63V polyesters, so a 15V regulated supply was on the stocks.

The bridge (a wire ended one with AC and DC conveniently on opposite sides) fitted neatly onto the TX secondary tags, the 2200uF hung tidily between the bridge DC wires and there was even a spare 3mm hole in the bottom of the case to screw the regulator down. Some minor origami with BTC and silicon rubber sleeving followed and the result was 15.05V, rock steady up to 150mA (100R test resistor). It should be OK up to about 200mA with the unheatsunk 7815.

Tried on the Hacker- slightly more volume than the tired old battery (no surprise there) and no audible trace of hum. Job's a good'un.

I have a couple of the strangest looking silicon diodes I've ever seen left over- the package is a sort of black plastic pill about 8mm diameter by 3mm thick with an insulated wire coming out from each side, the cathode wire having a faint red marking a few mm from the pill. No other markings of any kind visible.

AC/HL · 28th May 2012, 2:09 pm

This is what I've done with my VHF Herald but, (look away now those of a sensitive nature) it is built in internally for household use. It was a boot-sale find with a damaged rear grille and truncated aerial.

28th May 2012, 12:03 am	#1
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Eagle PSU conversion I'll put this here (rather than in Test equipment or Home brew) both of which could apply, since it was a success. Nothing very special, but a pleasant hour or so whiled away messing with a gash PSU from a freebie rummage bag picked up at the end of the last Harpenden auction. The label said 9V 500mA, but a quick check showed about 13.5V off load, 8.5V on load, so it clearly wasn't anything special. In fact it was just transformer, fullwave rectifier and 1000uF 10V(!) capacitor. Plus a few bits showing its age- a proper mains on/off switch and a neon power indicator (seriously blackened bulb there). Output was from a pair of reasonable 4mm plug/binding post connectors. The ac across the full secondary was about 19V, which triggered an idea- what about a PSU to run the shed Hacker, rather than the tiring restuffed 18V (now 12v) "PP9" in there at the moment? Anyway, the Hacker still sounded fine at 12V, and a quick rummage turned up a LM340T15 (7815 clone), a NOS 2A RS bridge, a 2200uF 35V capacitor and a couple of 1uF 63V polyesters, so a 15V regulated supply was on the stocks. The bridge (a wire ended one with AC and DC conveniently on opposite sides) fitted neatly onto the TX secondary tags, the 2200uF hung tidily between the bridge DC wires and there was even a spare 3mm hole in the bottom of the case to screw the regulator down. Some minor origami with BTC and silicon rubber sleeving followed and the result was 15.05V, rock steady up to 150mA (100R test resistor). It should be OK up to about 200mA with the unheatsunk 7815. Tried on the Hacker- slightly more volume than the tired old battery (no surprise there) and no audible trace of hum. Job's a good'un. I have a couple of the strangest looking silicon diodes I've ever seen left over- the package is a sort of black plastic pill about 8mm diameter by 3mm thick with an insulated wire coming out from each side, the cathode wire having a faint red marking a few mm from the pill. No other markings of any kind visible. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

28th May 2012, 2:09 pm	#2
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Eagle PSU conversion This is what I've done with my VHF Herald but, (look away now those of a sensitive nature) it is built in internally for household use. It was a boot-sale find with a damaged rear grille and truncated aerial.