RADAR TT Re-activator - UK Vintage Radio Repair and Restoration Discussion Forum

peter10tv · 14th Dec 2012, 11:46 am

I have an extremely ancient RADAR TT tube re-activator which I wish to try out. It is probably self explanatory but I would like to know what the 'A' stands for on the 'Re-activate' switch which has 'A' '1' '2' '3' positions. Would it stand for ageing perhaps? Does anyone have one, is the Radar any good at its job?
Thanks. Peter.

MotorBikeLes · 31st Dec 2012, 12:23 pm

I used to have one of these, but modified it to my own design, just keeping the transformer etc. If I recall, the "A" position is for monitoring heater current. The 1,2 and 3 are boost levels. I MAY have a circuit I drew out, if I find it I will check it. I serviced and resold many CRT testers, mostly Video Circuits V33 and V35 I think. (Should have their circuits too) but my own modified Radar was the best of the lot. (Having said that, the modifications went through Mk!, Mk2, Mk3 and Mk 4 stages as I recall, including a new case off something else; of course it handled colour). I still have it, as well as a top end German one (Muter BMR95). All for sale if anybody wants them.

I bought the Muter one for when I wrote an article in TV mag 20 years ago, but I moved house and never found time to do the final article. Too late now!

I just looked in my CRT tester folder. I have info on Video Circuits V33, V35, Grunther "Beamec", Leader, the Muter, and various designs of my own. I also used to do a modification for the V35 to improve it. It was more likely to kill a CRT than reactivate it as supplied! I have just found a circuit which includes a couple of valves, one being an 85A2 neon stabiliser. Does the Radar have these? If so, this is the circuit I drew out for it. If not, it could be a design I was thinking about. Obviously the Radar was a mono only tester, but was easily modifiable.

I have a strange Telequipment tube characteristic tester, and I will probably write something about that under a separate thread later on.

MotorBikeLes

peter10tv · 31st Dec 2012, 5:43 pm

Hello Les
Many thanks for your reply.. There are no valves in the Radar TT.. just a couple of trans and the switches.. I have tried to boost a Mazda CRM 121 but to no avail.. whether this is the tester or just the Mazda tube I don't know.. The heater volts rise when putting the reactivate switch to 1,2,3 and there is about 150 volts across the cathode to grid pins.. but no visible sparking in the gun is visible. Whether the tube had been blasted in the distant past may have a bearing on this. So I must search out a good Mazda tube... if that's possible!

Peter.

MotorBikeLes · 31st Dec 2012, 6:33 pm

Hi, I begin to remember it now. One transformer had the main heaters and the 150v winding, and the second one was an auto transformer to vary the heaters.
But I could be wrong. I do not appear to have the original circuit.
There were three Video Circuits testers, V31A, V33 and V35. It was the V31A I always modified. With any of these boosters, you need to increase the heater volts BEFORE you try any boosting. Without winding the heaters up a bit, you are likely to kill the CRT off straight away.
In fact, just leaving it in test mode, but with elevated heaters may well increase emission.
All these testers were built with positive grid voltages. Far better to have a negative grid, but with higher anode voltages for testing purposes. Too many of them will give good emission readings when they are NBG.
That does not happen with a negative grid.
I once came upon a new transformer in a box with a circuit. It was labelled "Type IP12 Special purpose Transformer". The accompanying circuit showed a tapped heater winding for the tube, a 150V winding rectified by a 5Z4 (??) rectifier, with a 5V winding for the valve. The main heater windings were all set at + 25%, a 4UFd cap smoothed the HT supply, and a 20mA meter also in the circuit. A 7.5K resistor loaded the circuit, which was connected from G1 to cathode of the tube.
The sheet then said that at switch on, the milli-ammeter current will be zero, rising to 10 to 12 mA after 4 hours. The HT connection should then be removed, and run without it for a further hour. The CRT should then be refitted to the receiver.Les.

Cobaltblue · 22nd Nov 2020, 10:10 pm

Thread Re-opened at Alistair D Request.

Cheers

Mike T

Alistair D · 23rd Nov 2020, 12:34 am

The attached file contains 7 copies of the schematic. The first is the as published version. The remaining 6 are stripped down versions showing the active circuitry for each position of the function switch S1.

I believe the base schematic is from an issue 4 manual.

Al

14th Dec 2012, 11:46 am	#1
peter10tv Pentode Join Date: Oct 2008 Location: Essex, UK. Posts: 108	RADAR TT Re-activator I have an extremely ancient RADAR TT tube re-activator which I wish to try out. It is probably self explanatory but I would like to know what the 'A' stands for on the 'Re-activate' switch which has 'A' '1' '2' '3' positions. Would it stand for ageing perhaps? Does anyone have one, is the Radar any good at its job? Thanks. Peter.

31st Dec 2012, 12:23 pm	#2
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: RADAR TT Re-activator I used to have one of these, but modified it to my own design, just keeping the transformer etc. If I recall, the "A" position is for monitoring heater current. The 1,2 and 3 are boost levels. I MAY have a circuit I drew out, if I find it I will check it. I serviced and resold many CRT testers, mostly Video Circuits V33 and V35 I think. (Should have their circuits too) but my own modified Radar was the best of the lot. (Having said that, the modifications went through Mk!, Mk2, Mk3 and Mk 4 stages as I recall, including a new case off something else; of course it handled colour). I still have it, as well as a top end German one (Muter BMR95). All for sale if anybody wants them. I bought the Muter one for when I wrote an article in TV mag 20 years ago, but I moved house and never found time to do the final article. Too late now! I just looked in my CRT tester folder. I have info on Video Circuits V33, V35, Grunther "Beamec", Leader, the Muter, and various designs of my own. I also used to do a modification for the V35 to improve it. It was more likely to kill a CRT than reactivate it as supplied! I have just found a circuit which includes a couple of valves, one being an 85A2 neon stabiliser. Does the Radar have these? If so, this is the circuit I drew out for it. If not, it could be a design I was thinking about. Obviously the Radar was a mono only tester, but was easily modifiable. I have a strange Telequipment tube characteristic tester, and I will probably write something about that under a separate thread later on. MotorBikeLes

31st Dec 2012, 5:43 pm	#3
peter10tv Pentode Join Date: Oct 2008 Location: Essex, UK. Posts: 108	Re: RADAR TT Re-activator Hello Les Many thanks for your reply.. There are no valves in the Radar TT.. just a couple of trans and the switches.. I have tried to boost a Mazda CRM 121 but to no avail.. whether this is the tester or just the Mazda tube I don't know.. The heater volts rise when putting the reactivate switch to 1,2,3 and there is about 150 volts across the cathode to grid pins.. but no visible sparking in the gun is visible. Whether the tube had been blasted in the distant past may have a bearing on this. So I must search out a good Mazda tube... if that's possible! Peter.

31st Dec 2012, 6:33 pm	#4
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: RADAR TT Re-activator Hi, I begin to remember it now. One transformer had the main heaters and the 150v winding, and the second one was an auto transformer to vary the heaters. But I could be wrong. I do not appear to have the original circuit. There were three Video Circuits testers, V31A, V33 and V35. It was the V31A I always modified. With any of these boosters, you need to increase the heater volts BEFORE you try any boosting. Without winding the heaters up a bit, you are likely to kill the CRT off straight away. In fact, just leaving it in test mode, but with elevated heaters may well increase emission. All these testers were built with positive grid voltages. Far better to have a negative grid, but with higher anode voltages for testing purposes. Too many of them will give good emission readings when they are NBG. That does not happen with a negative grid. I once came upon a new transformer in a box with a circuit. It was labelled "Type IP12 Special purpose Transformer". The accompanying circuit showed a tapped heater winding for the tube, a 150V winding rectified by a 5Z4 (??) rectifier, with a 5V winding for the valve. The main heater windings were all set at + 25%, a 4UFd cap smoothed the HT supply, and a 20mA meter also in the circuit. A 7.5K resistor loaded the circuit, which was connected from G1 to cathode of the tube. The sheet then said that at switch on, the milli-ammeter current will be zero, rising to 10 to 12 mA after 4 hours. The HT connection should then be removed, and run without it for a further hour. The CRT should then be refitted to the receiver.Les.

22nd Nov 2020, 10:10 pm	#5
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,865	Re: RADAR TT Re-activator Thread Re-opened at Alistair D Request. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk