[don'tdomelikethat]

On the RCA Victor 18T I currently have had on the bench for weeks, I get no station reception at all. I do get audio, and interference buzz from overhead fluorescent lights, and plenty of loud buzz and clicks when touching the center post of the volume control and other places throughout, so I know I have audio. I've replaced all caps, resistors, checked tubes 2-3 times, checked all coils 2-3 or more times.

http://www.nostalgiaair.org/PagesByModel...014801.pdf

When I first tried the radio after replacing caps and resistors, I faintly received one local strong station. Volume started fading, however, and I thought it needed a good alignment. Several days later, I turned it on and this time, no station at all. Have tried troubleshooting several times. I can send a 455kc signal through and the IF transformers seems to adjust well when looking at them with a scope, but when you turn the screws on the IF transformers, no increase in volume occurs, and the volume of the sig. gen. signal is faint, even with the sig. gen. turned all the way up.
The voltages on tubes (except heater volts-they are all fine) are low when measured with my DMM. They are as follows:
both 6K6: 224 volts DC (should be 240) on SG of both 6K6's
222 volts DC (should be 235) on plates of both 6K6's
18 volts DC (should be 19) on Ksups of both 6K6's

6SF5: 89 VDC on plate (should be 60)
.8 on cathode (should be .9)

2nd det. 6SQ7: plate 80 VDC (should be 64)

6SK7 IF: plate 228 VDC (should be 240)
screen grid 85 VDC (should be 88)
cathode 1.5 VDC (should be 1.1)

6SA7: plate 228 VDC (should be 240)
screen grid 85.5 (should be 88)

6SK7 RF : plate 227 VDC (should be 240)
screen grid 87 VDC (should be 88)
cathode .7 VDC (should be .6)

In Rider's 12-85 for RCA changes, it mentions a coil that was added, a low frequency oscillator push button coil, that I believe my set has. It is potted in black tar. If I attach one leg of the coil to where it was soldered when I first started working on the set, the above voltages go WAYYYY down. I get the above voltages with this coil out of the circuit. In either case, with this coil in the circuit, or out of the circuit completely, I still get no stations.
I'm thinking I have a bad new capacitor somewhere. I did change crumbling rubber wiring, but I was very careful replacing the new wires, however not all rubber wires were replaced. If anyone has any thoughts where I should look next, I'd appreciate them. THANK YOU!

[exray]

Your voltages seem ok. Have you tried using a second radio to confirm if the oscillator is working or not? Here's how:

Tune radio #2 (sitting nearby) to about 1200 kc or so. Tune the RCA's dial to about 750, sweep its dial back and forth to see if you hear any effect in radio #2. You should hear quieting or maybe a beat note. It will be obvious, nothing you have to struggle to hear.

http://www.nostalgiaair.org/PagesByModel...014801.pdf

[Radioroslyn]

Also check pin 4 of the 6SA7. That is the plate for the osc. Make sure your bandswitch is clean and you aren't in the push button mode.
I've got one of those sets good player!
Terry
ps. Here's an ad for it:

http://books.google.com/books?id=MUoEAAA...00&f=false

[don'tdomelikethat]

Exray, I tried the "2nd radio" test, and it failed. No beat note or anything heard in the 2nd radio when held up closely to the RCA and tuning it on the AM band. 7est... I have voltage on the plate and screen grid of the 6SA7... This one is absolutely stumping me. I will try to clean the bandswitch again, and tube sockets.

[exray]

That certainly narrows it down to the oscillator part of the 6SA7. I gather you don't get any shortwave reception either?

[Radioroslyn]

As Exray sez don't think your osc is running. One other thing to check is measure the voltage from the cathode and control grid of the mixer. Do so by connecting the - lead of a hi impedence meter ( dvm or vtvm) to the cathode and the + the the control grid if the osc is working you will see a small - voltage like a volt or 2 if not it will read 0 or a + voltage.
Also you could have a look at the cathode to ground voltage should be 0 if the bandswitch is good and clean.
Try swapping your 6SA7 with a working one. If no go look at R5 and 23, C23.
Terry

[don'tdomelikethat]

Well, I absolutely cannot get this set to oscillate. I've tried swapping tubes, and checking the parts mentioned to make sure they weren't bad, even though they are new, all to no avail. I've checked the coils, and everything checks out with good continuity, so I'm thinking there's an incorrect wiring issue.

[exray]

A few thoughts...
1. Using a metal 6SA7, right? 6SA7GT glass may not work.
2. Any chassis ground connections made via rivets? Might dab them up with solder.
3. How did you test C23-68pf? If in doubt, replace it.
4. You mentioned cleaning the bandswitch wafers...are they now 'waterlogged' or anything like that? Some cleaners will soak into the wafers causing leakage.
5. Although the schematic doesn't show a trimmer on the tuning cap oscillator section, is there one? If so, clean it up and make sure its not shorting. For that matter, confirm that the oscillator section of the tuning cap is not shorted somehow.

Just guessing Good luck.

-Bill

[Radioroslyn]

To add to Mr X's comments, Check the resistance from pin 6 of the 6SA7 to ground Should show a very low resistance. As you turn the bandswitch from band to band it should show a low resistance like an ohm or 2. If it high bandswitch is at fault.
Measure the resistance from pin 5 to ground. Should see 33K bandswitch shouldn't matter. If it doesn't read 33k replace the 33k grid leak resistor.
If you like I can take some pic's of my 18T if it will help you.
Terry

[don'tdomelikethat]

Well, I'm almost to the point of storing this set, advertising, & searching for another 18T chassis, and starting over from scratch as it seems this chassis will continue to refuse to cooperate with me. It amazes me that I can get higher end sets like a Philco 16, 116 with all the restoration issues they could have to play perfectly, but middle of the road sets like this RCA, and little AA5's befuddle me sometimes.
Terry, I measured the resistance while turning the bandswitch as you suggested in your last reply. At most I get 4 ohms on one of the bands, the other positions, 1 or 2 ohms so apparently the bandswitch is ok. The 33K resistor you mention was changed to 56K in my run of the set, and that's the reading I get from pin 5 to ground on the 6SA7. My 6SA7 is metal, I replaced the new 68pf mica cap with another new cap, and cleaned the trimmer cap on the tuning capacitor as Exray suggested. Nothing has helped.
What stumps me is the fact that at "first turn on" after the rebuild, I HAD A SIGNAL, a small one of a local powerhouse AM station, then it faded away to nothing. Days later I turned it on again, this time no station received at all. Except for the fact I have plenty of audio and interference from overhead fluorescent lighting, this radio just DIED, and said "NOPE..I'm retired, not playing for you..."
The only possibility of something I did wrong that I can think of is that I did use some oil on the tuning cap (ball bearings in front, other turning point friction areas) to loosen it up a bit so that there wouldn't be undue stress on the old dial cord. I just wonder if some oil didn't sneak in & drip into somewhere it shouldn't have gone. I could clean it all out again, and see what happens.
There is a bit of a mystery burning smell coming from a coil, I think, but apparently the coil isn't burning out as all resistances check out.
As mentioned in my original post, my set has the added coil for push buttons. It's potted in tar and seems to get warm. I've disconnected it for the time being, but connected or not, no change, and when connected the voltages on tubes go way down to almost nothing. Disconnected, the voltages are decent as I reported in my 1st post.
So, I'm stumped and ready to search for another chassis, I guess.
Terry, I would appreciate pics of your set if you wanted to go through the effort (e-mail to ebm421 AT frontier DOT com) . My chassis might be a later version of yours though since you mentioned the 33K grid leak res., and mine has the 56K changed resistor as mentioned in the service data.

[Arran]

Could there be a wiring error perhaps? In recapping a radio it's easy to get two adjacent tie points mixed up. I'm wondering about the pushbutton assembly, normally it has to be connected for the set to work and be connected properly if it uses tuned circuits and switches, normally these electric push buttons connect between the antenna and oscillator stages. Does this set use a loop antenna or does it have a proper antenna coil? Have you tried the set on short wave with an external antenna?
Regards
Arran