HUNTS CRB Analyser.

[GMB]

There is a copy of the manual on my web site, see http://air-ministry.uk

[mike1 ryan1]

I have a copy printed out thanks

[ronbryan]

The magic eye target voltage is very low at 35V. What type of meter are you using to measure this parameter? The loading effect of the meter could be important as the target is fed via a 1M resistor, but if the 1M resistor is high resistance that also could cause a low reading.

You have not recorded the eye cathode voltage - was there nothing to measure, or was the measurement omitted?

It would also be useful if you could put a known resistor in the test terminals, select the correct resistance range and measure the eye grid voltage as balance is approached, by adjusting the calibrated scale. The grid voltage you measured of -30V will cut off the tube but when bridge balance is approached, the grid voltage should decrease towards zero and allow some cathode current to flow.

Ron

[ronbryan]

I have made some measurements of the Y63 voltages on my Hunts CRB. It still retains the original selenium rectifier, so the power supply seems poorly regulated. I used a Fluke 8060A DVM. Maybe these readings will help your investigation.

Bridge balanced (widest dark shadow) with 10k resistor on R1 (divide by 100) range:

Anode 173V DC
Cathode 2.1V DC
Target 14.7V DC
Grid 0V DC

Bridge unbalanced.

Anode 207V DC
Cathode 38V DC
Target 122V DC
Grid 38V DC

So, when the bridge is unbalanced, the poor old Y63 takes a lot of grid current rectifying the large AC off-balance bridge output, but the anode current is cut off by the large negative grid bias. No wonder that the design added a 1k cathode resistor (not shown on the original 1945 instruction manual circuit) presumably to limit the grid current and prolong the life of the valve.

So, my suggestion is that you should measure the cathode current (i.e. the voltage across the cathode resistor) of the Y63 and see what it is and if it varies when bridge balance is achieved.

Just to be clear, re. your post #19, the 'S' position of the function switch is 'Standby', with no HT applied to the Y63 anode and target.

Ron

[mike1 ryan1]

Thanks for your info very much appreciated. I will replicate your test as soon as I get a chance and post the results on here. Thanks again.
Mike

[ronbryan]

I have repeated and re-posted the measurements of the Y63 voltages on my Hunts CRB, because of an error in my choice of the ground point for the measurement - apologies. I used a Fluke 8060A DVM as before. Maybe these (revised) readings will help your investigation.

Bridge balanced (widest dark shadow) with 10k resistor on R1 (divide by 100) range:

Anode 174.6V DC
Cathode 3.2V DC
Target 39.2V DC
Grid 0V DC

Bridge unbalanced.

Anode 174.5V DC
Cathode 3.4V DC
Target 94V DC
Grid -37.7V DC

So, my suggestion is that you should measure the cathode current (i.e. the voltage across the cathode resistor) of the Y63 and see what it is and if the target voltage varies when bridge balance is balanced and unbalanced.

I've attached a photo of the Y63 base connections for reference.

Ron

[mike1 ryan1]

Hi Ron,
Going off your picture of the valve base I realised that I had the anode and target wired the wrong way round! After correcting that the valve now works, however all of the change on it occurs to the far right of the scale, with the balance point almost on the far edge of the scale. I checked the resistance of the 2500 ohm balance pot and it only goes up to 1.3K, so I have ordered a new one and we will see if that corrects the problem.
Mike.

[ronbryan]

Hi Mike

I'm pleased that you have fixed the eye problem. Do you have two working eye tubes now?

With regard to the second part of your post #27, did you check the pot resistance out of circuit, as in circuit you could be reading the 2k5 pot resistance in parallel with the 2k2 2 Watt resistor, which is not far off 1k3 ohms.

The balance point of the bridge will only be at the centre of the balance pot travel if the resistor on test is equal to the appropriate resistance scale reading at the centre of travel. Otherwise it will be offset to the left or right according to the resistance value.

Ron

[mike1 ryan1]

I tried a few different values that should have been across the scale and they all balanced at the far right of the scale. As for the test of the pot I didn't think about unsoldering it although I should have. Think I'll have to leave it for a bit and come back to it with fresh eyes, getting a bit frustrated with it which doesn't help.
Thanks for all your help.
Mike

[Chris55000]

Hi!

There is some confusion over the correct connections to GEC/British octal–base eyes, these are NOT the same as the Russian replacement 6E5S type!

Y63 connections:–

1:– NC, 2:– h 3:– a/d 4:– t 5:– g 6:– n.p. 7:– h 8:– k

Pin 4 (target) is the cone–shaped fluorescent electrode, rated @ 250V, pin 3 the triode anode/deflector electrode, recommended resistor 1M as per most end–viewed eyes, and the nominal grid voltage is –22V for zero shadow angle.

Most Y63s I've come across don't have the indicator–section "space–charge–grid", denoted by g' in British valve basing and normally connected internally to cathode, but EM34s and some of the Continental eyes do!

NB! If you get a Russian replacement eye, the anode resistor and the h.t. connects to the target anode on pin 6.

Chris Williams

PS!

The EM35 has also cropped up on this Forum once or twice – this was made by Philips/Telefunken and is a Maltese–Cross type eye of the single–sensitivity type, electrically the same as the Y63 in characteristics and base pinout!

[mike1 ryan1]

I knew a sleep was needed. Left it and did something else for a couple of days then had another look and found the problem, I had made a wrong connection. Now works and is spot on accurate. Doesn't discharge the test capacitor in 's' position so need to look at that but very pleased. Thanks for all the help and suggestions.
Mike

[mike1 ryan1]

Is actually very accurate with the couple of capacitors I've tested. I've wired the power factor pot the wrong way round too but my soldering iron has decided not to work so will sort it out another day.

[davebms]

hello all, I hope its ok to post on an existing thread ? I have a hunts crb and using the circuit on here ,,I have straightened the case work (its been bashed a few times in the past !!) some capacitors broken due to shock
damage ? so I have replaced the capacitors and new y63
I don't think its a Russian tube big Wight letters cv1103 (grey box 1966)at first the HT voltage very low swapped rectifierfor diode plus 100r
the magic eye only opens at full open on balance dial (with or without component in place

HT 202 volts in S
168 volts in r
265 L L1 ??
L2 fast flash (trying to test my fluke 25)
I think 265 is unloaded HT so possibly 270/82k not in circuit ?
sorry to ramble on.. how do I fault find this tester

dave

[ronbryan]

With a (say) 10 k resistor across the measurement terminals and R1 (divide by 100) range selected, check what voltage are you getting across the 2k5 balance pot end terminals. It should be around 50V AC 50Hz. Check that the pot wiper (centre terminal) is still connected to ground.

If that is ok, check the switch contacts for continuity, or clean them. If still no improvement, check (in this case of range R1) the 1k59 refererence resistor, or see if you get an AC voltage across the 10k resistor on test, to prove that the bridge excitation is reaching the device under test (D.U.T.).

Ron

[davebms]

thank you for the reply. I have 64 volts at the 2k5 and 64 across the test
resistor, both reference resistors are spot on. I have checked all of the components it all seems fine ?I took out the 250ohm power factor pot (it got dirt in the spindle re lube its ok, with a clean it 1.250 ohms (the 1 .is very faint )it looks original I don't think its the reason the tester does not work ?
I have cleaned the selector switch several times.. probably the only way is to take the front plate of try to check continuity (I get lost with rotary switches)

dave

[ronbryan]

What do you read if you select the R1 range and put an AC voltmeter between one end of the 2k5 balance pot and the pot wiper and move the spindle from one end to the other? The meter reading should vary between the 64 volts you measured in post #35 and zero (or vice-versa).

Ron

[davebms]

sorry I missed the last post.. I am in the process of checking /cleaning the selector switch I will report back as soon as I get I re assembled

thanks dave

[davebms]

sorry its taken so long to get back to this !!

from post *26

in position R1, across 10k resistor 59.6 volts ac
2k5 pot end /end 59.4 volts ac
2k5 pot end to centre 59 to .007 volts ac

voltage at valve the HT goes to pin 4 target (as per photo *26

widest dark shadow
target 171 dc
anode 27 dc
cathode 1.3 dc
grid -2 dc

unbalanced

target 168
anode 94
cathode 1.4
grid -10

the grid volts will go to -75 volts dc if dial rotated fully
the eye only opens in OPEN position on dial

completely lost as to what wrong

thanks for the help so far

dave

[ronbryan]

Dave

The first thing to say is that I have crossed over the target and anode/deflector labels in post #26, which showed the voltages on my instrument - apologies. The target (pin 4) is the electrode connected direct to HT+ and the anode/deflector (pin 3) is connected to HT+ via the 1M resistor. I should have read Chris55000's subsequent post more carefully and realised my mistake.

It appears that your readings show that your bridge is working pretty much correctly, with the eye grid voltage tending to zero (actually -2V) and the anode voltage low (27V) when approaching balance (where the pot wiper voltage matches the potential at the junction of the selected standard resistor and the 10k resistor on test) and an increasing negative grid voltage and increasing anode/deflector voltage (94V) when moving away from balance, presumably this is when moving away in either direction.

You also say that at bridge balance the eye shows the widest (dark) shadow, which is correct; this wide dark shadow is the indication of balance you should be adjusting the balance control for and is what you should see for zero grid voltage.

Can you please clarify your last statement "the eye only opens in OPEN position on dial". What does the eye do in the SHORT position of the dial? What is the grid voltage in the SHORT position?

Ron

[ronbryan]

I've taken a picture of the Y63 eye tube display at balance on the R1 (divide by 100) resistance range, with a 2k2 resistor being measured. I chose 2k2 as the D.U.T. to put it into the middle of the balance control range.

I've also uploaded pictures of the eye display with the same D.U.T. as above, but with the balance control set at the extremes of travel in the SHORT and OPEN positions.

Ron