Conar Model 224 Valve / Tube Emissions Tester

[Gorey48]

The meter is BER and I need to find a replacement/substitute. No info on the meter at all. 
Chris

[boater sam]

I do not know this tester, any information on it or a photo even?

The meter must have a physical size, full scale deflection current or some attribute that you can share with us so that we can try to help.

Without more info, we will struggle.

[boater sam]

There is some info on Elektrotanya, user instruction and a schematic but no details of the meter.
It appears to be a very simple American 117v  tester, if you can establish some parameters for the meter it should be easy to find a substitute.

[Gorey48]

Thanks for quick response. You are correct I do need to provide more data. I will do this with photos. I have the handbook which includes a schematic. I have also removed the meter which had been savaged by the previous owner. There is no data the item at all. I hoped that someone may own or had restored one and could provide data. Working on phots and dimensions now.
Thanks
Chris

[Gorey48]

5 PHOTOS ATTACHED. DIMENSIOS FOR 1 TO 1 REPLACEMENT METER ARE
68MM DIAMETER METER SURROUND.
MOUNTING PLATE IS W 114MM H 102.
NO MARKINGS AT ALL. WHILST I HAVE FORGOTTEN HOW NO DOUBT FROM THE CIRCUIT I SHOULD BE ABLE TO CALCULATE FSD CURRENT IF I MEASURE VOLTAGES. ANY GUIDANCE WELCOME AS MY 76 YEAR OLD BRAIN IS NOT WHAT IT USED TO BE

[Gorey48]

G-AYMG

[Gorey48]

SO STRUGGLING TO FIND A WAY TO SEND PHOTOS DUE TO SIZE ON JPG.

[Mike Watterson]

I used a commonly available meter of completely different much higher rating and deflection on an AVO valve tester. I forget which model.
Ironically the owner had two AVO transistor testers that used the same meter. Those two meters sadly also scrap.
I photo-edited the original scales to fit new meter and used an op-amp amplify voltage on a resistor equal to original meter resistance. I didn't have a low enough offset op-amp (expensive instrumentation type needed) so I used a dual with a split supply and split reference and the 2nd op/amp then fed an offset to the amp on the dummy meter load. A preset to electrically zero after meter is mechanically zeroed. Due to amps being on one chip and split supply via two diodes from one secondary winding, the zero preset on 2nd amp worked with no observable drift with time, temperature or mains voltage.
I forget if it was a 20uA or 37 uA meter originally.
I also replaced meters on an AVO VCM163, but in that case the meter spec was close enough and I only had to photo-edit new scales.

The actual AVO test meters with bigger meters seem to mostly to be OK, but they definitely had valve and transitor testers from mid 1950s to 1960s that used meters where the magnets went weak or something. I've seen maybe 4 or 5 duff meters now from AVO gear that "moved" but had reduced sensitivity. Also some sticky.m

[Gorey48]

PHOTOS

[Mike Watterson]

I downloaded this PDF, cleaned it and converted to 4 bit PNG.
It's a typical pass/fail basic USA tester like the Hickock, intended to sort new vs worn tubes. Not so great for vintage as a 1/3rd emission tube that's not faulty might be OK and irreplaceable now.
Sold in an era when getting a replacement tube was cheap and trivial
   

Indeed there is no clue about meter spec. Could be 50uA or more likely 1mA as the capacitor is huge.
SWB selects heater from 0.75 (hearing aid) to 117 (the rectifier that has a heater running direct off mains, 117Zsomething in Battery/Mains valve radios).

There is no separate anode and screen/g2 supplies, because each valve/tube socket connection goes to either 0V/common, heater/filament (0.75V to 117V) or HT (AC).
I think:
The rectifier is used only when the neon is in series, otherwise the valve/tube under test is the rectifier.
SW A selects one of four settings using 2 alternate HT voltages for "Normal"
SW D selects normal or leakage test with the rectifier in series.

SW 1 to SW 12 set each pin of the valve to 0V/Common, heater supply (0.75V to 117V), or the AC HT, which has four settings, but just two AC HT voltages.

Personally I'd use it for the heater supply and leakage test. Add my own new meter and separate Anode and Screen voltages each adjustable from 45V to 250V, also a 0 to -20V grid supply. This tester sets the g1 to 0V.

I'd guess one AC HT volts (positions 1, 2 & 3 of SW A) is 30V for battery valves and diodes and the other 250V is more "mains" valves. The 5.1k position 1 might be for diodes.
The 80V is AC, so 113V peak, enough for the neon to strike. I'd do a leakage test differently.

I'd not restore this as it was, as that's not very useful. I'd use it as the basis for a better tester and the SW 1 to SW 12 would need to be really 6 way, not 3 way:
1. 0V/Common
2. Heater
3. grid voltage
4. screen voltage
5. spare
6. Anode HT

The 250V transformer tap could feed two adjustable HT supplies.
The 30V tap could feed a 0 to -35V grid supply.