Philco Safari Problem - raster and weak sound, but no picture - please help!

[goat1981]

Hey guys,

I just got done taking voltage readings of all the IF stage transistors, the Video Amp transistor, and the Video Output transistor and found some interesting results (especially the video out transistor...)

Here are the readings in order of what's specified on SAMS and what I read with my multimeter.

Supply Voltages:
-5v -- reads -4.4v
+11v -- reads +8.2v
-11v -- reads -8.8v

First IF Transistor (X1)
Base -- 1.5v -- reads 0.85v
Collector -- 0v -- reads 0v
Emitter -- 2v -- reads 1.22v

Second IF Transistor (X2)
Base -- 2.0v -- reads 1.27v
Collector -- 0v -- reads 0v
Emitter -- 2.2v -- reads 1.57v

Third IF Transistor (X3)
Base -- 8.5v -- reads 6.62v
Collector -- 0v -- reads 0v
Emitter -- 8.6v -- reads 6.77v

Fourth IF Transistor (X4)
Base -- 8.5v -- reads 6.37v
Collector -- 0v -- reads 0v
Emitter -- 8.6v -- reads 6.58v

Video Amp Transistor (X5)
Base -- 10v -- reads 7.28v
Collector -- 4v -- reads 2.84v
Emitter -- 9v -- reads 7.5v

Video Output Transistor (X6) -- here is where the problem is...
Base -- 9v -- reads 6.65v
Collector -- 9.5v -- reads -8.66v (!)
Emitter -- 0.5v -- reads 8.11v (!)

Could it be a bad Video Output transistor? I haven't replaced any of the diodes, which are the original 1N60A germanium diodes -- these seem pretty common and I can replace them if you think it'll help.

What do you guys think about these readings? If you missed the schematic, I included it in a previous post.

Thanks again for your help!

[goat1981]

An update!

I found broken circuit traces on the Video/Audio/Sync board! This TV must've undergone some kind of trauma in the past. Maybe it was left in the heat or dropped?

I found four traces that lacked continuity. I found this when I was checking voltages and two points on the same trace had different voltages...

https://app.box.com/s/s3yxjeabwn8b6k27act3jygq3k2ou2uv

I soldered in some jumper wires and got a picture and sound!

https://app.box.com/s/pjip2xjvoovx1dz86p9l2ztkmjgziflw

There are still some issues, but this is progress. The focus and linearity aren't that great. Also, I am having trouble getting clear sound. There is a buzz that slowly goes in and out in the sound. I uploaded a video of this behavior on my box account. Link:

https://app.box.com/s/txgqhar3szysgyitb9jta9evc6f6fvua

I am wondering if it's the type of modulator (a cheap one I bought at Walmart) that I'm using, because the same thing happens on a Sony 5-303W that I have. Either that, or both TVs have the same problem (I haven't really worked too much on the Sony yet).

Thoughts? Could it be bad diodes? Again, thanks for all of your help!

P.S. Sorry for the huge pictures. Any way to control that?

[Zenith26kc20]

The modulators can produce the hum, especially when graphics are present. A lot of us use agile modulators to prevent that. I use a Blonder Tongue AM-60-550A. You can get one at a reasonable price on our favorite auction site.

[goat1981]

Originally Posted by Zenith26kc20

The modulators can produce the hum, especially when graphics are present. A lot of us use agile modulators to prevent that. I use a Blonder Tongue AM-60-550A. You can get one at a reasonable price on our favorite auction site.

Thank you for your suggestion - I will look one up.

Any suggestions for improving the picture quality (especially brightness/contrast and focus)? I haven't replaced any resistors; and many of them may be out of spec. I'm sure it needs to be aligned as well. I'd like to learn to do this, but know that it requires a lot of equipment that I don't yet own.