Motorola 9T1 Restoration

[bandersen]

Right, 15 watts is way too small. The 9T1 draws around 100 watts so that 15 watt bulb looks like a dead short in comparison. I'd even go higher than a 75 watt bulb if you can.

[Jon F]

Tried a 60 watt bulb, lights up just as bright. I went ahead and swapped in diodes for the rectifiers and no change, bulb still lights.

I'll try to find a 100 watt bulb and see...

[bandersen]

Do the tube filaments light up ? They won't be full brightness with that bulb in series, but with the lights out you should see a glow.

[Jon F]

Tried a 200 watt bulb and it still lights dimly.

Left on just long enough to check tube filaments. All light up after some re-seating.

[bandersen]

That's good. A 200W bulb will still glow with a 100W set.

[Jon F]

Indeed, after the set warms up for 30 seconds or so I can get some music from a local radio station(Q877) that is the same freq as CH 6.

Looking promising, I have to replace the remaining ecaps, and then is there anything else to check before I try with the CRT? What is the discharge procedure for this set after I turn it off, as it does not have the typical HV lead to the tube? (I assume the HV is run in the neck connector)

[bandersen]

Nothing else to check that I can think of. Right the HV is one of the base leads. The CRT doesn't have an aquadag coating so doesn't buildup a HV charge like it's bigger cousins. Good luck.

[Electronic M]

The HV should discharge it's self within a couple minutes after being turned off.

[Jon F]

Thanks guys, just finished the electrolytics, so far I've replaced all paper caps, all electrolytic caps, & selenium rects are now diodes with 30ohm resistors.

Powered it up with the CRT, got a decent raster but no image. The picture also doesn't get any taller than in the image below. I do have sound. No idea where to go from here. Unfortunately I don't own a tube tester so I have no idea the state of the tubes in the set.

Any ideas before I order some tubes to swap out?

Thanks!

[Electronic M]

If the video detector crystal diode is bad it could cause there to be no video. You can probably grab a decent sub at radioshack and try subbing the original.

[kvflyer]

Originally Posted by Electronic M

If the video detector crystal diode is bad it could cause there to be no video. You can probably grab a decent sub at radioshack and try subbing the original.

To go along with what Tom has said, I had the same issue with my VT-71. The diode was indeed open. Below is my restoration thread on ARF. It goes on several pages but you can see the progress and solution. Unfortunately, the images have gone away over the years. I only found this thread using a google search.

Hope you are able to get 'er goin' as they say.

http://antiqueradios.com/forums/view...p?f=3&t=144209

BTW, I host my own pictures now so that they won't go away when the forums have upgrades.

[Jon F]

Thanks for the tips, per the thread I removed the rectangular can, and checked the diode with my multimeter. It reads a voltage drop of 0.31V which seems normal.

[Jon F]

I left the set plugged in for a few minutes (without the light bulb) and after messing with the controls I did get a low contrast image, see attached.

The tubes on the set are getting pretty hot, too hot to touch, is that normal?

[holmesuser01]

Tubes get hot.

Glad to see that picture!

[Jon F]

Thanks, I attribute not getting a picture at first due to my ignorance on how to properly adjust the set.

With the brightness all the way down, and the contrast all the way up, I get the best picture. With an RF modulator, the image is still rather noisy, and the sound has an awful buzz, but I'm really glad what results I've gotten so far.