CR-70 and a 10MP4

[jeyurkon]

The CR-70 has settings for testing a 10MP4 CRT. Since it works well testing an 8BP4 I thought I'd give it a try on the 10MP4. One of the advertisements for a Sylvania CRT tester says the triode tubes like the 10MP4 and 12VP4 cannot be tested.

Well, The CR-70 says the tube is dead even though it works well for me. They also have you hook the universal adapter's G2 lead up to pin 10. While the tube does have a pin 10, it is not connected according to the data sheet.

I've seen this CRT listed with a couple of other testers. I don't remember if they were Senecore or not.

Could there have ever have been another CRT with the same designation or is this just a mistake?

John

[jr_tech]

I doubt if the RMA/RETMA/EIA would have allowed two different tubes to exist with the same type number. The RMA registration (to Sylvania) 10/16/49 shows NOTHING connected to pin 10. I suspect an error in the tube checker data. Do you get a reading if you tie the extra wire to the anode button?
I have never seen a 10MP4 ... what set was it used in?

jr

[Phil Nelson]

I looked in my CR70 book just in case, but it also says G2 to pin 10 for 10MP4. Not all of the CR70 books are the same, for reasons that escape me. bandersen's book does not list 7JP4, but mine does. Go figure . . .

Phil

[bandersen]

I just checked mine and it also show G2 to pin 10.
My book is quite different from the scanned pages I've seen from Phil's. Almost all the 'scope' CRTs are absent from mine.

[jeyurkon]

Originally Posted by jr_tech

I doubt if the RMA/RETMA/EIA would have allowed two different tubes to exist with the same type number. The RMA registration (to Sylvania) 10/16/49 shows NOTHING connected to pin 10. I suspect an error in the tube checker data. Do you get a reading if you tie the extra wire to the anode button?
I have never seen a 10MP4 ... what set was it used in?

jr

It was used in the Sylvania 1-076, about '49-'50

John

[jeyurkon]

Originally Posted by jr_tech

I doubt if the RMA/RETMA/EIA would have allowed two different tubes to exist with the same type number. The RMA registration (to Sylvania) 10/16/49 shows NOTHING connected to pin 10. I suspect an error in the tube checker data. Do you get a reading if you tie the extra wire to the anode button?
I have never seen a 10MP4 ... what set was it used in?

jr

I didn't try the anode, but I did something similar earlier. Using my B&K CRT tester I wired in a 10KV supply to the anode. I was able to check the G1 cutoff this way, but not the emission. I figured if the G1 was good then the CRT stood a good chance of being good.

The set has always worked best with over the air signals. My laserdisc player gave the next best results. Recently it seemed like it wasn't performing as well as it did a few months ago. After trying to test it with the CR-70 I tried hooking the laserdisc player up to an Agilant modulator to see if that would be better. The laserdisc player was completely dead. That may have been the cause. Seems like the bridge rectifier has given up the ghost. Some more repair work ahead.

Thanks for the confirmations everyone.

John