silvertone issues with setup
 

hey guys was wondering with these roundies like the silvertone i have and it seems to be the same with most when setting them up and you cant get the color lines in the setup mode. like in setup when the 3 color adjustments are advanced you should be able to see the line but it seems that most have the problem where one color dont show up. so what could be some reasons for this as well as having to use the bias adjustment all the way up and then you get the drive lines across the screen but lower the bias and the lines go away but your left with a dark picture. i dont think its a bad boost diode all the time since i have changed the diode and still had the same problem and the tubes are fine. so would there be a specific resistor in a specific place to look into when it comes to something like this. where is the best place to check boost voltage without taking the chassis out and im sure it should be around 700 volts. making sure tubes, crt, and electrolytics are all ok what else is known to do this in these old roundies. and one more thing excessive hissing from the hv cage, new hv reg tube, new flyback, no sharp edges on the solder for the rectifier tube. i will try a new rectifier tube which may be alittle weak but tests ok and there is no dust at all , super clean and the hv is set to 24.5 kv. thanks guys :D

On roundies sometimes you can pull back the CRT socket &
measure there to look for problems like yours. Just be careful
to hold the base as you rock off the socket.

As far as the arc goes run it with the lights off & you may see
it. The HV fillament wire & plastic HV cup are the usual suspects.
The cups seem to attract all sorts of disgusting mung & get
holed sometimes. Dont forget the filament is riding at 25KV
so can be arcing anywhere. It sucks to change it, we always
went solid state rectifirer to save time.

73 Zeno:smoke:

i tried solid state rectifier and still sounds like hiss in the area of the plastic cup

But did you cut out the filament wire ?
Pull the cup first & clean the crud out of it.
Be sure to use something that wont leave a residue like
91% isopropal alcohol. Maybe someone else has a better way,
we just changed them.

73 Zeno:smoke:

its not so much the hiss but rather the drive lines and the bias having to be maxed and wanting to get the problem solved with those lines.

You got 24.5 KV? Wow. Some of the ones I've worked on couldn't get over 20kv, and worked just fine.

I'd carefully disassemble the HV cup and clean it. You should hear no hissing there.

well i put a new flyback in as the old one turned into a candle, wax... the hv rec tube socket may be bad.

I would imagine that the socket was inspected while you were replacing the flyback. However, any sharp points/lead dress are important here as well as checking for carbon tracks too. If there are any unused pins you may be able to remove those too. As for the cup, clean as mentioned and inspect for any (carbon) pinholes in it. You could coat the floor of that cup with some liquid-ey windshield silicone and let it set up too.

Even as an easy check you could unscrew the rectifier socket and "carefully" position it away from the cup just a little and see if that makes any difference.

Just shooting some ideas here.......

yup im going to go and do that tomorrow and hope its a simple thing as well as check some tubes here too for these lines i have going on here.

Post the model # and maybe I have a manual & can help.
Check the horz blanking tube.
It was the late 70's since I worked on a roundie so
I cant do it off the top of my head like most SS sets.

73 Zeno

The RGB Y tube sockets could easily be cooked, too. I know the twin triodes they used on the RCA sets would cook.

Check the plate resistors on those triodes also. They tend to cook down in value raising the plate voltage on the tubes. This will upset the CRT voltage on the grids (altering the brightness of a given gun) and cause a very short life of the color triodes as well.

well i also have a focus issue that when the set is turned on the picture appears clear at first but in a few seconds its not focused enough to read words but after about 7 minutes its focused enough to read but it could be better. the focus voltage is just shy of 5 kv so im thinking i will change the focus rectifier, i have one coming as the one in there may be leaking a bit. and the fly is new and so is the hv rectifier and the hv regulator tube and the hv is at 24.5 kv. i did lower the RGB drives and the drive lines did let up a bit so that is better, its really the focus issue thats got me now. i did check the tubes, demod and 6gu7s, all ok.