Weird Neotec NT-2702 variant 03V-0. Correct B+?

racer

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Working on some of these neotec chassis for a friend. Both of them work with small issues (vertical jittering, missing colors etc).

He has two variants which we can't find info on anywhere. Both of the ones he has are labeled 03V-0 on the main PCB. Chassis #1 has a significantly different neck board labeled "NT-2002" and has no pincushion daughterboard. Pincushion still works. The remote board also has different pots for contrast, V position, and pincushion. Chassis #2 has a regular Full Family neck board and remote board, and has the pincushion daughterboard. The only other info I could find was this thread: https://forums.arcade-museum.com/threads/neotec-2701-9e-03v-0.378083/

These are definitely some sort of revision to the Full Family design. Friend did a recap on them, C502 came out as a 2.2uf but on a Full Family it's a 4.7uf. He put the 4.7uf in erroneously and the brightness was wrong, so I put the 2.2uf back in and that issue was fixed.

The manual and all info online state that B+ should be at 100v, and this is correct on his other monitors which say Full Family on the main board. Both of these with the 03V-0 main boards have a B+ adjustment range between 120v-150v. The other secondary voltages are all correct. Looking at the SMPS section, the components are all identical except for the transformer which is appended "-A" on the Full Family version. I haven't pulled them and measured the windings to see if they're actually different.

So my question: does the higher B+ for this 03V-0 variant seem correct?
 
Haven't looked at these since making this post, but I'm picking them up from my friend tomorrow because he needs them for the weekend. Did a little research and found this video from Mike where he is working on an 03V-0 revision NT-2701, and shows the B+ is supposed to be at 100vdc just like the regular full family version. This is the 2701--not the 2702, so I'll pull a working 2702 chassis tomorrow and check myself if the VGA version is a higher b+.


I'll go over the SMPS and report back. :)
 
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I don't know the B+ voltage to answer your question, but I also have a strange 03V version of that monitor and have some information about mine in this thread here:


My C502 was as you explained your buddies was where it had a 2.2uf cap on there but the instructions said to put a different rating on it.

I'm not sure if that will be of help at all but thought I'd post it in case you or anyone else needs some info on it.
 
if its on the original tube and monitor yoke you could cheat and dial in the heater (6->6.3, DC for that model) nominal. should make the b+ in the range+/- 8 v I would suspect.
you can check the jumper by the smps too I should have some notes on that.. j1/j2/j3.. depending on that set called for a dif b+, but not always definitive. i would verify heater on top of that.
 
Thanks Chad! That makes total sense. The heater on one of the chassis in question is now bang on at 6.3v and the B+ landed at 120v. Another landed at 125v, however it appears to have a different heater resistor and outputs around 5v on the heater pin--probably for a different tube. Might have been a Thomson? He should have the tube for it in storage, but failing that, I can figure out the heater resistor swap so it's the correct brightness on the RCA tube.

EDIT: Ah looks like someone previously swapped one of the limiting resistors at R181. Mystery solved. :)

I worked through the first one today and was successful.

Symptom: Green stuck on with raster lines, early shutdown when B+ turned up. Missing red

C906 was installed backwards and vented
C430 was installed 100uf, supposed to be 10uf (looks like xray protect circuit)
C502 was installed 4.7uf, supposed to be 2.2uf
There were several weak traces around the drive transistors on the neck board. The chassis was previously serviced by PNL if that says anything.
There was a bodge between the emitter of the red drive transistor, and a cap near the video amp. The wire had rubbed against the heatsink and insulation was melted. Didn't appear to touch anything but wasn't good. Replaced bodge with silicone insulated wire.
Shorted Q901 2SC4367
C952, a newly installed 10uf 50v cap, was failed. Looks like when the pad was lifted, the trace was incorrectly bridged above it to L903 (attached to blue drive output...) instead of to the pad of C953 to the left where it should go.
Red missing. Reflowed input connector to fix.
 
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