Plate voltages for UV-200 tubes - Printable Version
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Various and Sundry Categories (https://philcoradio.com/phorum/forumdisplay.php?fid=37)
+--- Forum: Other Radios (Non-Philco) (https://philcoradio.com/phorum/forumdisplay.php?fid=12)
+--- Thread: Plate voltages for UV-200 tubes (/showthread.php?tid=10151)
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Various and Sundry Categories (https://philcoradio.com/phorum/forumdisplay.php?fid=37)
+--- Forum: Other Radios (Non-Philco) (https://philcoradio.com/phorum/forumdisplay.php?fid=12)
+--- Thread: Plate voltages for UV-200 tubes (/showthread.php?tid=10151)
Pages:
1
2
RE: Plate voltages for UV-200 tubes - NostalgiaRadioTime - 07-29-2014
Sorry for the delay in replying to all of you kind people for your generous help. A little thing called a job has a bad habit of taking away from my radio hobby
As such, I got home and went downstairs to take a few pictures of what I'm dealing with.When I received this set, all of the original wirewound resistors in series with the tuning caps were missing and replaced with 'modern' resistors, albeit of the wrong value. There were 1000 ohm resistors instead of the 600 ohm's called for on the schematic (link in my first post). I replaced them with 680 ohm's, as that's the closest I had on hand until I order the correct one's. I figured they are closer than the 1000's that were in the set when I got it, and the minor difference from 600 to 680 shouldn't prevent the set from receiving. They are soldered to the grid terminal of the 1R and 2R UX-201 tubes, and the other end attached to the screws on each of the two tuning capacitors. Can anyone tell me if that is how the original wirewound one's were attached to the T C's? See pics below:
1R:
2R:
(See the last pic in this post)
Under the 2R you can see the .3 mfd RF Bypass Condenser I replaced with a .33 mfd. It was missing altogether on my set.
The 250 pf Grid Condenser, seen in the pic below, checks out fine. I tried disconnecting it and gator wiring in a modern 250 pf capacitor with no difference.
Here's a bottom view of the 1R section for reference. Sometimes it's better to have more sets of eyes looking at a project that may see something amiss that I might be missing. So I welcome your thoughts / ideas on why, despite the audio output section working fine up to the Grid Condenser, I'm not able to receive any stations, only static that varies with intensity as I increase or decrease the rheostats.
Can anyone explain exactly the function of the 3 position antenna knob?
Is it a low / medium / high sensitivity?
RE: Plate voltages for UV-200 tubes - NostalgiaRadioTime - 07-29-2014
Sorry the 2R pic got misplaced at the end of the previous post instead of where it should've been... below the 1R pic.
Regarding the antenna, when I connect my meter on continuity on the center connection of the first coil (section 1R), and stick the other meter lead in the antenna port, I hear a beep at each of the 3 positions of the switch as I turn it. So I believe the switch is connected right.
However when the set is powered up, all I'm getting is static, despite having my long antenna wire hooked up (I was able to get Chicago... 120 miles away... with this antenna wire on my AK model 40). When I touch the antenna port, I get no response or change in sound. So the antenna connection is working to the switch on the front panel, but apparently not going through to the coils & tuning capacitors. Yet the coils all check out for continuity on their primary and secondary windings.
RE: Plate voltages for UV-200 tubes - gregb - 07-29-2014
Hi Greg:
If you have a signal gen throw some signal into the antenna terminal and start tracing with a scope or signal tracer and see where it goes or doesn't. Wont take more than a minute to track down.
Gregb
RE: Plate voltages for UV-200 tubes - Ron Ramirez - 07-29-2014
NostalgiaRadioTime Wrote:A little thing called a job has a bad habit of taking away from my radio hobby
I know the feeling, brother! But the job also helps to pay the bills, while spending money on radios doesn't.
RE: Plate voltages for UV-200 tubes - Mondial - 07-29-2014
Looking at the photo of the underside, it appears that you connected the .33 uF bypass cap in the wrong place. From what I can see, the cap is connected between ground and the plate of the 1st RF amp tube. If this is the case, you are bypassing all the received RF signals to ground, so it is not surprising that you have no reception.
The bypass cap should connect from the 67 V supply line to ground, not to the tube plate. Try removing the cap and see if you get any reception.
RE: Plate voltages for UV-200 tubes - NostalgiaRadioTime - 07-29-2014
You're so right, Ron! I was just being facetious; all of us with full time (or even part time) jobs know the drill...you have to squeeze in the hobbies when we can around the work schedule.
Mondial, you just may have become my hero for the day (again!). I will try that tonight after I finish KP duty
RE: Plate voltages for UV-200 tubes - NostalgiaRadioTime - 07-29-2014
Well it just proves the old adage true... a picture is worth a thousand words. Mondial spotted a stupid mistake I made, and one misplaced cap prevented the whole she-bang from receiving any stations (and had me pulling out the few strands of hair I have left atop my noggin' last night!). The radio plays beautifully now.
Just by disconnecting the cap from the plate of the tube made it come to life. And by gator wiring the removed end to the CORRECT location on the 67 volt supply line, the radio STILL played, perhaps with a slight reduction in hum. So my hats off to you, Mondial, and my deepest gratitude. Should our paths ever cross in person, I'm buying dinner!
And to all of the fine folks here with head scratching radio problems, I urge you to take a moment, take some close up pics of the area of your chassis in question, and post them here. The more (highly experienced Phorum member) eyes "looking over your shoulder", the more likely you'll find a solution to the problem. Or in my case, having someone spot a dumb, simple error that can prevent your radio from working!
RE: Plate voltages for UV-200 tubes - NostalgiaRadioTime - 07-29-2014
Here's a pic of the radio back together. Was listening to the Milwaukee Brewers game on it on 620 AM WTMJ tonight!