AFA-MINERVA portable detector tester EMI - UK Vintage Radio Repair and Restoration Discussion Forum

FIXITNOW · 13th May 2014, 9:54 am

AFA-MINERVA portable detector tester EMI
picked this up looks like it needs a lead anyone any info on this item
cheers
vince

G6Tanuki · 13th May 2014, 10:07 am

AFA-Minerva were a company who installed/maintained burglar-alarms and fire-detection systems in the 1970s and 1980s - one of my old mainframe computer-rooms had a Minerva heat-detector that if activated could release vast quantities of Halon gas into the room.

I suspect that what you have is a device for testing heat/smoke-detectors.

bagpuss_24 · 9th Jul 2014, 4:51 pm

I can tell you exactly what that device did!
I worked for Thorn Security as an Intruder Alarm engineer during the 1990s- (Thorn took over AFA in the 1980s).

One of the Fire-Alarm guys had one of these devices.
They are for calibrating the old F35 / F50 smoke detectors, which were fitted on the CT1 and CT6 fire alarm systems.
These systems were the staple of Minerva / AFA-Minerva installations across the country since around 1967.

The system- operated at 220v DC, each smoke detector had a valve in it's base (hence the 220v DC)- and the system was activated by a short circuit across the pair. Usually - a 220k resistor was fitted across switches and detectors.

Every so often- I think about every 12months or so; the detectors would each require testing / calibrating.
Using this device, you would plug in a detector and it would give a calibration reading as to the quality of the detector.
Dodgy detectors were replaced, and returned to AFA for refurbishment.

These detectors are now (and have been since the late 90s) illegal to store in quantity due to the large amounts of Radioactive material in them- it is something daft like 60% greater than current devices.
Many of the removed ones were sealed into silicone bags and are now stored in a concrete bunker underground at Sellafield....

Any old Woolworths, C&A, M&S, BHS, most Rolls-Royce and many shopping centre sites built from the lat 60s on had these systems installed.

The system was powered by a 24v wet cell battery, which was pumped into an inverter circuit to generate the 220v DC.
Larger installations had a 24v DC powered Dynamo.

I never dabbled with any of these as much of my work was keeping many of the old AFA 1950s/60s fitted burglar alarms running!
They were so reliable, keyholders refused to replace them. (Until they saw the price of replacement Flag batteries)

I hope this helps.

Also- the test device looks as if it dates from the 1970s- as the "AFA-Minerva" style branding was introduced on their bell-boxes around 1970.

By the late 70s, the CT1 and CT6 panels were getting old hat.

bagpuss_24 · 13th Jul 2014, 9:52 am

The talk of AFA-Minerva got me plondering through my archives.
I do have a circuit diagram for the CT1 and CT6 control panel.
Not sure how I came by it, as I dealt with intruder alarms!

It has circuits for the separate modules that made up the Inverter Board, Alarm Board, and "Flasher" circuit.
The latter would flash a neon lamp on the base of the detector activated.
In actual fact, the flasher would pulse 220v DC down the entire zone, the detector lamp would be switched by the valve inside the detector....ish.

I also have the base connections too.
So if you want to get the kit working- you can.

Secondly- the device was rare as rocking horse s**t - so I wouldn't consider stripping it for parts just yet!
AFA got rid of most of theirs as the CT1 and 6 panels became old hat.
The odd old school engineer sat on theirs and stuck them in the garage.

The circuits are probably no use to anyone these days, but none the less a good impression on how they did things before transistors and chips were used widely.

13th May 2014, 9:54 am	#1
FIXITNOW Octode Join Date: Feb 2007 Location: Ely, Cambridgeshire, UK. Posts: 1,976	AFA-MINERVA portable detector tester EMI AFA-MINERVA portable detector tester EMI picked this up looks like it needs a lead anyone any info on this item cheers vince Attached Thumbnails

13th May 2014, 10:07 am	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: AFA-MINERVA portable detector tester EMI AFA-Minerva were a company who installed/maintained burglar-alarms and fire-detection systems in the 1970s and 1980s - one of my old mainframe computer-rooms had a Minerva heat-detector that if activated could release vast quantities of Halon gas into the room. I suspect that what you have is a device for testing heat/smoke-detectors.

9th Jul 2014, 4:51 pm	#3
bagpuss_24 Retired Dormant Member Join Date: Jul 2014 Location: South Yorkshire, UK. Posts: 4	Re: AFA-MINERVA portable detector tester EMI I can tell you exactly what that device did! I worked for Thorn Security as an Intruder Alarm engineer during the 1990s- (Thorn took over AFA in the 1980s). One of the Fire-Alarm guys had one of these devices. They are for calibrating the old F35 / F50 smoke detectors, which were fitted on the CT1 and CT6 fire alarm systems. These systems were the staple of Minerva / AFA-Minerva installations across the country since around 1967. The system- operated at 220v DC, each smoke detector had a valve in it's base (hence the 220v DC)- and the system was activated by a short circuit across the pair. Usually - a 220k resistor was fitted across switches and detectors. Every so often- I think about every 12months or so; the detectors would each require testing / calibrating. Using this device, you would plug in a detector and it would give a calibration reading as to the quality of the detector. Dodgy detectors were replaced, and returned to AFA for refurbishment. These detectors are now (and have been since the late 90s) illegal to store in quantity due to the large amounts of Radioactive material in them- it is something daft like 60% greater than current devices. Many of the removed ones were sealed into silicone bags and are now stored in a concrete bunker underground at Sellafield.... Any old Woolworths, C&A, M&S, BHS, most Rolls-Royce and many shopping centre sites built from the lat 60s on had these systems installed. The system was powered by a 24v wet cell battery, which was pumped into an inverter circuit to generate the 220v DC. Larger installations had a 24v DC powered Dynamo. I never dabbled with any of these as much of my work was keeping many of the old AFA 1950s/60s fitted burglar alarms running! They were so reliable, keyholders refused to replace them. (Until they saw the price of replacement Flag batteries) I hope this helps. Also- the test device looks as if it dates from the 1970s- as the "AFA-Minerva" style branding was introduced on their bell-boxes around 1970. By the late 70s, the CT1 and CT6 panels were getting old hat.

13th Jul 2014, 9:52 am	#4
bagpuss_24 Retired Dormant Member Join Date: Jul 2014 Location: South Yorkshire, UK. Posts: 4	Re: AFA-MINERVA portable detector tester EMI The talk of AFA-Minerva got me plondering through my archives. I do have a circuit diagram for the CT1 and CT6 control panel. Not sure how I came by it, as I dealt with intruder alarms! It has circuits for the separate modules that made up the Inverter Board, Alarm Board, and "Flasher" circuit. The latter would flash a neon lamp on the base of the detector activated. In actual fact, the flasher would pulse 220v DC down the entire zone, the detector lamp would be switched by the valve inside the detector....ish. I also have the base connections too. So if you want to get the kit working- you can. Secondly- the device was rare as rocking horse s**t - so I wouldn't consider stripping it for parts just yet! AFA got rid of most of theirs as the CT1 and 6 panels became old hat. The odd old school engineer sat on theirs and stuck them in the garage. The circuits are probably no use to anyone these days, but none the less a good impression on how they did things before transistors and chips were used widely.