Sencore CR70 issue ...

[cwmoser]

Obtained a nice Sencore CR70 CRT tester.
Tried it out and apparently it does not put filament voltage onto the F1 and F2 pins.
This is what I found:
- I can adjust the meter to a filament voltage such as 6.3 volts
- I ohmed the connection from the F1 and F2 pins into the circuit at a Molex connector.
- When I set up the CR70 for 6.3 volts, all my meter will show is 0.43 volts AC. At DC, nothing there either.



The above is the setup for a 10BP4 CRT I was attempting to test.



Here is the bottom side:


Like I mentioned, I have continuity from F1 and F2 to the molex connecter above.

The tag on the CR70 mentions a warning about using the proper fuse. Cannot find a fuse in this either.

Anyone have any ideas about this issue?
Don't have a Schematic - is there one I can download?

Thanks

Carl

[bandersen]

I assume you are using the universal adapter ?
You need to set the H1, F2, K, etc. knobs to positions 1,2,3,4,5 rather than the CRT pins.
I made the same mistake when I got mine .

Here's a scan of that section of the manual.
http://www.bobandersen.com/manuals/s...cr70/CR702.jpg

[Phil Nelson]

Bob is right, you need to reset those K, etc., controls on the front panel.

On my CR70, I set them as follows when using the universal adaptor:

F1: 1
F2: 2
K: 3
G1: 4
G2: 5

Then you clip the leads from the UA to the CRT pins as given in the book: F1 to pin 1, F2 to pin 12, and so on.

This is mentioned in the manual, but easy to overlook.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[cwmoser]

Thanks. Another operator error. I feel kinda stupid for disassembling this thing:-) Put it all back together and got it working. Thanks much.

An observation: After learning how to operate the CR70, I tested a 12LP4 with the CR70 and a Sencore CR133 CRT tester. The CR70 has a "Cut off" test and my 12LP4 tested as having Poor Contrast. I noted also that the subsequent Emissions test is dependent on the Cutoff setting. The CR133 tested the 12LP4 without any issues. In addition the CR133 had a socket in lieu of individual pin connectors. Interesting.

Carl

[bandersen]

I've tested a bunch of CRTs with mine and get a wide range of results for the cutoff, but they worked fine it sets.
One other odd thing I've noticed is that the cutoff results are affected by the bias setting. However, the emissions reading seems to only depend on the cutoff position, not the bias.

[Kevin Kuehn]

It looks like there's enough parts in those 70's that they ought to make the CRT display a test picture.

[cwmoser]

Thanks Bob for your observations about the CR70.
If you think of any others, I'd like to know.

Both my Sencore CRT testers are really nice. I need more experience using them.

Carl

[cwmoser]

Thanks Phil. Now that I've been burned by needlessly opening the chassis on my CR70, I don't think I'm going to forget this. If you think of any more helpful hints, I would like to read them.

Carl

Originally Posted by Phil Nelson

Bob is right, you need to reset those K, etc., controls on the front panel.

On my CR70, I set them as follows when using the universal adaptor:

F1: 1
F2: 2
K: 3
G1: 4
G2: 5

Then you clip the leads from the UA to the CRT pins as given in the book: F1 to pin 1, F2 to pin 12, and so on.

This is mentioned in the manual, but easy to overlook.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[bandersen]

Here's another tip. If I have a CRT hooked up in the emission testing mode and turn off the CR70, the meter pegs to the left. So I've gotten in the habit of switching to the filament set mode before powering off.

[kvflyer]

Carl, I have also done trouble shooting for the same "problem" using the universal adapter. Even after Bob said how to set it up, I drew a blank and still set the switches to the pin number of the tube. Guess what? No filament voltage to the filament. I even had two Sencore CR-70s with the same "problem". Well, it was the idiot trying to test the tube, not the Sencore. Mind you, I took mine apart three times and even traced the wires and fixed a bad connection to the large cable connector.

Thanks for sharing and I hope all of our other members read this and don't have the same problem. The instructions were correct. Only the operator (me) had a brain cramp and didn't interpret them correctly...

[kvflyer]

Originally Posted by Phil Nelson

Bob is right, you need to reset those K, etc., controls on the front panel.

On my CR70, I set them as follows when using the universal adaptor:

F1: 1
F2: 2
K: 3
G1: 4
G2: 5

Then you clip the leads from the UA to the CRT pins as given in the book: F1 to pin 1, F2 to pin 12, and so on.

This is mentioned in the manual, but easy to overlook.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

I am embarrassed to say, "Yup"...

[bandersen]

Speaking of being an idiot. I owned mine for 6 months before discovering that I had a set of adapters under the lid I created my own UA and later purchased a NOS UA while having one inside the lid the whole time

[kvflyer]

Bob,

I think that you "exposed yourself" about that earlier. Glad that we all have that behind us now. Thanks again...

[cwmoser]

If someone would have told me about how to set those switches beforehand, I might be repeatedly making this mistake over and over. But, going through the agravation to needlessly remove the chassis from my CR70, its something I won't easily forget. In fact, I'll remember this every time I open the CR70:-)

Carl

[kvflyer]

I even went so far as to test the electrolytic capacitors and all connections inside. Kinda nice looking inside though. I assumed that it was producing filament voltage since you could vary it via the fine adjustment control. What I did was to start probing for the voltage, found it and noted the color of the wire. Then, traced it to the universal adapter and the light bulb went off! But mind you, I had this thing apart at least three times, only to put it back together with disgust. And how could two of them have the same problem?

I know the answer to that question! I had another stupidity attack...