CurtPalme.com Home Theater Forum

stefuel · Posted: Sat May 09, 2009 1:42 am Post subject: Tube pin-out question

While looking at a AmPro neck board trying to figure the best way to mod it for Thompson tubes, I noticed that all tubes seem to have three pins for G1. The P19's have it on pins 5, 11 and 12. The AmPro neck board only uses pin 12 for this. If it simplifies the modification, is there any reason I could not just simply nip off the unused G1 pins?

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

I guess you could do it, i have a few DVB's here with missing pins and they work fine. When i did the mod for the Marquee VNB's I put a jumper on each G1 to see which looked better and then on all together and it made no difference.

Chip, How did that used Green tube come out on the sencor tester?

And its a Thomas Tube, not Thompson Wink

Athanasios

stefuel · Posted: Sat May 09, 2009 2:16 am Post subject:

We have not put it to the Sencore test yet. Probably this weekend. If I can eliminate the unused pins it greatly simplifies modding the plastic socket on a Ampro neck board. I'll have to catch up with Heywood to grab the Sencore.

Am I missing something? I don't see arc suppression on the Thomas tube.

All I have left to re-wire for is the two heaters and cathode. The unused G1 pins were getting in the way. Problem solved (snip snip) Laughing

"snip snip" Oh god that brings back painfull memories Shocked

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

the arc suppressor was one of the pins in the key area. I think pin 2. I used a 100kohm resistor to ground on the marquee's Neck Board. You should use 1Mohm , i need to try that on mine, but the 100k one worked for me.

Athanasios

stefuel · Posted: Sun May 10, 2009 11:38 am Post subject:

Not done yet but most of the re-wire is figured out.
The first thing you have to do is remove the dummy pins you will find in the socket at pin locations 4 and 13 or the card won't plug onto the tube.

For G2, you install a jumper on the trace side between pins 5 and 6. On the component side, snip the leg of pin 6 and bend it out for connection to the heater later.

G1 will come in on the previously unused pin 13 location. On the trace side, simply install a jumper between pin locations 13 and 12.

The heater connections are a little tricky. They are on pins 9 and 10. You must locate the traces on the board where they connect to L6 and L7 and cut the traces. On the component side, install a jumper between L7 and the leg of the old G2 you snipped and bent out earlier. On the trace side install a jumper from L6 to pin 7 which was previously unused.

The cathode now comes in on pin 10 which was one of the heater connections with a trace that has been cut. On the trace side, install a jumper between pins 10 and 8.

There is spark gap circuitry (SG2) in the neck board associated with G1 and connected within the plastic tube socket with what looks like association with pins 1 or 2 or both. I have to investigate that more. I may have to ask tse about that one.

stefuel · Posted: Sun May 10, 2009 5:17 pm Post subject:

We did test the tube with the Sencore today and it passed with flying colors. Now I feel a little better about mounting it up.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Glad to hear its a good tube, it has some wear but for testing it should be fine. Hope this works out and now anothe use for the Thomas tubes will be documented.
You should have taken pics of the board modification.

Athanasios

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Whats the part # on the tube ?

stefuel · Posted: Sun May 10, 2009 9:57 pm Post subject:

Well this is the test board. If it works OK I'll take pictures of the next one. The next step is to mount it in a Marquee housing, rotated 180 degrees so that it works in my mutant 4600HD. Now there's something you won't see every day, a AmPro with Marquee optics and Thomas tubes Laughing

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

stefuel · Posted: Mon May 11, 2009 12:49 am Post subject:

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

if you can do it carefully, the end piece socket that surounds the pins on the tube can be removed and turned for your ampro. just mark on the side of the tube what each pin is.
I had Aferg set all the tubes for a marquee VNB.

Athanasios

stefuel · Posted: Mon May 11, 2009 10:15 am Post subject:

stefuel · Posted: Sun May 24, 2009 12:09 am Post subject:

OK the tube assembly and neckboard mod is complete. All that's left to do is plug it in and push the button. I'll do that in the morning. Lets hope there is no magic smoke Wink

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

stefuel · Posted: Sun May 24, 2009 1:25 pm Post subject:

I'm porked until I can get ahold of Heywood. He has my whole blue tube assembly. AmPro won't let you test fire with a single tube assembly installed. You get a "open interlock" error message and it won't let the PJ power up.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

stefuel · Posted: Sun May 24, 2009 3:20 pm Post subject:

stefuel · Posted: Sun May 24, 2009 10:02 pm Post subject:

First test not so good. I don't know what the problem is. I used switch 4 to defeat interlock but I don't hear HV coming up. I did get one snap from the tube and the filements are glowing so I think I'm on the right track. I'll try a different HVPS first. If that doesn't do it, then I'll slide in two more tubes with electronics attached re-adjust switch four and try again.
We are having a nasty t-storm right now with hail so I think I'll call it quits for a while.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

My Test tubes snapped as well chip, i think it is crud on the guns that need to burn off. I had to tap mine for a good 20 seconds or more while it was fired up to clear them up but after it worked fine. Does your sencor have a cleaning feature on it? Also if the guns are glowing but the tube is not lit check your G2 line on the neck card, make sure you have it right and not to G1.

Athanasios