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Marantz 4400 CRT replacement by 2bp1

2AP1 and 2bp1 are almost the same tube, they should interchange, 2bp1 being an even better performer. If you have the 50tb1 tube did you try it in the 4400 to verify the circuit works?
 
Camman said:
Hi Craig,
Even though the connections look correct, I did not use a 2AP1 connected to my Marantz 4400.
I just used the pin layout to determine the matching connections of the 5LO38M. (They both have 11pins.)
Attached pictures of connections I used and adapter I constructed to maintain stock CRT socket.
Hope this helps.
Let me know!

View attachment 576055
Click to expand...

All right, we are practically the same. However, my +/-X is reversed to yours. Could this actually cause no image on the tube face though?

Thank you,
craigr
 
No, I don't believe so.
If moving left/right, up/down and intensity pots don't show an image, I would say there is a problem with the 4400's circuitry or CRT.
 
bktheking said:
2AP1 and 2bp1 are almost the same tube, they should interchange, 2bp1 being an even better performer. If you have the 50tb1 tube did you try it in the 4400 to verify the circuit works?
Click to expand...
The 50TB1 is the OEM tube and yes, it is installed in the tuner. The tuner is a Model 2110.

The 2AP1 and 2BP1 have similar specifications, but different pinouts. I am trying to test with a 2AP1 first to just get the 2AP1 working to verify the concept. The 2AP1 has an identical pinout to the 5LO38M and I want to use the 5LO38M. The 5LO38M is the Russian copy of the 2AP1, but has blue phosphor.

The 5LO38M tubes are extremely difficult to get and the 2AP1's are easy to get which is why I am testing with a 2AP1 first.

All of this is just to get a blue phosphor tube in the scope. It may be worth it in the end, but I did not expect to have this level of difficulty!

Thanks,
craigr
 
Camman said:
No, I don't believe so.
If moving left/right, up/down and intensity pots don't show an image, I would say there is a problem with the 4400's circuitry or CRT.
Click to expand...
Everything works perfectly with the OEM 50TB1 tube.

So I don't think there is anything wrong with the tuner (2110) circuitry.

craigr
 
Hmm, Ok.
Maybe check with lights dimmed?
Otherwise, I would do a voltage comparision of each pin for both tubes.
 
So after confirming my wiring with what Camman provided I went ahead and wired up the 2AP1 again with the same polarity on the deflection that Camman used. As expected changing the polarity had zero effect. I then tried turning brightness all the way up, moving horizontal and vertical centering all over the place, and even trying the horizontal and vertical offsets on the PCB and this also had no effect. I was in a dimly lit room as well.

So having confidence in the wiring being correct by a second set of eyes I went ahead and wired in the 5LO38M. Unfortunately, this tube also shows no illumination no matter where I set the controls :tears:

So at this point neither the 2AP1 nor the 5LO38M are working for me :no:

I put everything back together and have given up for now. I will think about it some...

Thanks to all for the help, especially you Camman.
craigr
 
One thing I just though of... when testing these tubes I have had them sitting next to the tuner on the table and have connected them to the tuner using wire leads with alligator clips to the OEM socket. I have not removed the 50TB1 OEM tube and have not installed the electrostatic electromagnetic shield over the new tube.

Could it be possible that the shield is required for the tube to function properly? By not testing with the shield, could this be causing all my woes?

craigr
 
Plug in the new tube, turn it on for a minute set to tuning and shut it off in the dark, you should see it center after it loses voltage.
 
Craig,
The 50TB1 is removed from socket while the 2AP1 is connected?
Did you check that there is the same voltages directly at the 2AP1 tube pins?
 
Camman said:
Craig,
The 50TB1 is removed from socket while the 2AP1 is connected?
Click to expand...
Yes, only one tube at a time is connected to the tuner.

Camman said:
Did you check that there is the same voltages directly at the 2AP1 tube pins?
Click to expand...
I did not check that. I would be shocked if the 50TB31 worked if there was a voltage problem, but again I am grasping at straws so it's worth a look.

*I noticed that I have been saying 50TB1, but I actually have the "blue" 50TB31 phosphor OEM tube. Pinout is the same so this should not be any issue.

craigr
 
Camman said:
One other thought,
When making the connections looking at the back of the 2AP1, pin one is on the right of the keyway 2,3,4-11 pins are then counterclockwise.
Click to expand...
When looking at the tubes from the back the pins are number clockwise and I have been going by that. Do you think they are actually numbered backwards on the tube socket?

Left is the 5LO38M and right is the 2AP1.

tubes.jpg


Thanks,
craigr
 
One other thing is that I am using an external power supply for the 6.3 volts on the heater. The 2110 only has a .3 amp fuse on the heater power supply and the .6 amps of the 2AP1/5LO38M cause the fuse to blow (obviously). I also don't want to double the heater load on the hard to replace transformer.

craigr
 
CIR Engineer said:
One thing I just though of... when testing these tubes I have had them sitting next to the tuner on the table and have connected them to the tuner using wire leads with alligator clips to the OEM socket. I have not removed the 50TB1 OEM tube and have not installed the electrostatic electromagnetic shield over the new tube.

Could it be possible that the shield is required for the tube to function properly? By not testing with the shield, could this be causing all my woes?

craigr
Click to expand...
All right, I think this idea may have possibly lead me to the solution. I am not motivated enough to try again today, but maybe tomorrow after work.

I have been working on the new tube by laying it next to the tuner. There is about 8" of shelf and then next to that is a speaker that is shielded, but the new tube is still only about 4" from this large speaker. I think the magnets in the speaker are pulling the beam off the face of the tube!

I just took the cover back off the tuner and slid the tuner close to the speaker. The electromagnetic shield is on the installed tube, but even still, the trace went from center to nearly off the bottom of the tube and I didn't even get the tube as close to the speaker as the test tubes have been.

So it just may be that this issue has nothing to do with the tube or wiring and everything to do with an unfortunate placement of the experiment.

We'll see I guess.

craigr
 
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