[Pepperoni]

I had to overhaul this set due to all the bad wiring along with a bad power transformer that was not original, 84 rectifier converted to 5Y3 and a bad audio output transformer. I found a power transformer that's good and I put in a 125B audio transformer from Radio Daze that I'm using pins 5 & 6 for the output with pin 5 to ground. Tried pins 1 & 3 as suggested but there's no difference in volume. I left the 5Y3 in place. The set has all new tubes, capacitors and resistors. Original filter cans and capacitor block restuffed. All of the IF coils read good. The #13 RF coupling reads about 5 ohms rather then the 3.5 ohms called out on the schematic. I've checked all my voltages but on the schematic no voltages are associated with the 7A6 2nd Det. or the 7C6 1st Audio. 7C6 plate is at 125Vdc. The voltages on the 1232 RF and the 6J8 (this is a run 4 set) are high. Plate of the 1232 is 205Vdc (S/B 160V), grid is 204Vdc (S/B 105V). Plate of the 6J8 is 208Vdc (S/B 180V if it were a 7J7) but the grid pin 4 is 83Vdc and the other plate is 168Vdc. S/B 80V and 150V respectively. Here's the schematic from NA and a pic of the chassis.
http://www.nostalgiaair.org/PagesByModel...013339.pdf
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The set is working but has problems. Station 620 comes in where it should on the dial along with 1260kHz coming in where it should at the higher end. Problem is 1260 comes in all over the dial and in the SW bands. I performed the "good radio next to my Philco radio" test and set them about 455kHz apart and there is reaction between the two sets telling me my oscillator is doing it's job. The radio seemed to align okay when I performed the alignment.

EDIT: I'm addidng this picture to show what I believe to be an anomally. I have an untouched 40-185 that works to make comparisons with. While ringing out my -190 I noticed that the bus on the pushbutton assy. reads 1.4 ohms to chassis gnd. except when the 1st PB is engaged then it reads open to gnd. My -185 reads open to chassis gnd. all the time. Could this be where part or all of my problem is? I can't find any errors in my rework.
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So I'm kinda stuck. I'm hoping someone can lead me in the right direction here. In the meantime I'm gonna go ring out all of my connections to make sure I didn't foul something up.
Thanks,
Pepper

[Texasrocker]

Check for oscillator problems, adjustments and proper alignment procedures according to schematic using a reliable signal generator. Sounds like your set may be tuned to a second harmonic instead of first harmonic (stronger signal) from your signal generator? Just a possibility.

[Pepperoni]

The oscillator is working as stated above. An alignment is showing me nothing and I've checked all my connections and they are correct. My big question now is the 1.4 ohms that I see between the pushbutton bus and ground. This 1.4 ohms doesn't show on my -185 (same chassis) and the same schematic applies to my-190. My -185 even has the run 4 6J8 in place of the 7J7. Should I have this 1.4 ohms on the PB bus?

Pepper

[Arran]

I don't know if this is related to your problem but you missed one capacitor, there is a two section wax dipped mica capacitor at one end of the pushbutton coil assembly that can go bad apparently. Other then this I would go back and check the wiring, make sure that it matches the schematic for the correct code number and production run (aside from the 5Y3 mod). The audio output transformer should normally have B+ going to the center tap of the primary, and from that center tap to the screen grid of one of the #41 output tubes and throught a 3900 ohm resistor to the screen grid of the other #41 tube. The two outside legs of that transformer going to the plates of the #41 output tubes, one side of the secondary should go to chassis ground or common negative.
Regards
Arran

[Pepperoni]

Thanks Arran but the wax dipped mica you mention is actually two individual 370pfd caps and they read well within tolerance. Micas I usually don't replace unless they're way out of tolerance or bad or "Micamolds".

B+ is connected to the CT of the output transformer but the other two primary legs go directly to each plate of each 41 output tube. They're in push-pull configuration. This can be verified by looking at the schematic. My problem doesn't appear to be in the audio circuit but in the front end of the set. The RF section. I've already highlited two schematics verifying all of my connections. I just finished verifying all the bandswitch connections. So far I've found nothing out of place. Tomorrow I'm going to remove the pushbutton assy. and take another look at the underside of that. I'm still pretty baffled. I can't find the problem.

Pepper

[Arran]

Thanks Arran but the wax dipped mica you mention is actually two individual 370pfd caps and they read well within tolerance. Micas I usually don't replace unless they're way out of tolerance or bad or "Micamolds".

B+ is connected to the CT of the output transformer but the other two primary legs go directly to each plate of each 41 output tube. They're in push-pull configuration. This can be verified by looking at the schematic. My problem doesn't appear to be in the audio circuit but in the front end of the set. The RF section. I've already highlited two schematics verifying all of my connections. I just finished verifying all the bandswitch connections. So far I've found nothing out of place. Tomorrow I'm going to remove the pushbutton assy. and take another look at the underside of that. I'm still pretty baffled. I can't find the problem.

Pepper

How did you test the micas? Did you test them with an ESR meter or a resistance-capacitance bridge where you can put some high voltage across them? When you have replaced everything else and everything seems to be where it should be, failing micas caps is a possibility just due to process of elimination.
Regards
Arran

[Texasrocker]

Take a closer look at your schematics again. If necessary, use jumper wires with alligator clips on each end and take your pushbutton assembly totally out of the circuit by direct wiring under the chassis for all your checks. By isolating your PB assembly will get you back to what is working correctly and not. Always remember, your schematic never lies to you! You just have to know how to read it and "isolate" problems all the way thru the circuits in both RF & AF stages using your test equipment. Do you have test equipment?, and know how to use it? If not, your guessing is doing nothing more than confusing us here trying to help you. No dissing your abilities to trace down problems intended from me at all. Completely Isolate those pushbuttons and get back with what is working and not in your set. What type of bench test equip are you using? Knowing that will help all the techs here help you isolate your problems. Never give up! It is a learning process and once you defeat it, it will be rewarded on your next restorations!

[Texasrocker]

As an add to my last post, I still think you may have oscillator probs. Let everyone here know what type test equipment you are using, how you are using it, and be assured that the techs here will help you find your problem! Best of luck with all your restoration! We ALL get "stumped" sometimes!! Just want to help you!!

[Pepperoni]

First and foremost guys I'm just a hobbyist. I've been working on antique radios for about 6 years now. Retired early after 27 years with Boeing as a tech due to a bad heart. 1st attack at 43. I'm no engineer but I am familiar with my test equipment (listed below) and know how to use it. I took 4 years of electronics in high school in the 60's and many classes after that just to keep up with the ever changing technology that I needed to perform my job. It had nothing to do with vacuum tubes. I've fallen in love with this hobby and work at it 7 days a week just because I'm not the kind of guy to sit on his butt. I work on tons of radios and every once and a while I have one like this that I just get stuck on and need help. Most of the problems I encounter are due to mistakes made by me in wiring the set back up. This is why I started having my schematics blown up to 11X17 and using a highliter to mark off every part or wire that goes back into a set. It's helped a lot. But once I've gone over that wiring 2 or 3 times and everything is correct I start looking at other areas where the problem could be. But I'm not a genious with these things and I don't believe I ever will be. Here's what I have.
Fluke 179 Multimeter
Elenco CM-1555 Cap Meter
Eico 320 Sig. Gen.
Protek 9100 Freq. Counter
Variac
Heath IT-21 Tube Tester
Simpson 260 Series 6P
I used to have a nice digital Tektronix o-scope but I never used it so I sold it.

Last night I removed the pushbutton assy., coils and padder strip to get under it to check out my work. I'm gonna go do that now. As for how I tested the micas I just had them isolated from the circuit and measured them with my cap meter. As you can see I don't have a bunch of sophisticated equipment. The 2 370pfd caps that were questioned read so close to that, I left them in as I did with all the micas in this set. All well within tolerance. I do understand that these components can be breaking down when power is actually on the set but I don't see a lot of bad mica caps.

EDIT: I've installed all my jumpers to the PB assy. and it's out of the way. Went back over the schematic again and verified all my component and wiring connections and I don't find anything installed incorrectly. Even compared these connections with my -185 that's working. If it is the oscillator then I'm not sure what's wrong with it. Resistance readings across all the pins on it match what's on the schematic and the osc. in the -185. For the heck of it I cleaned all my Loctal sockets again. Pins on the tubes are scraped nice and shiny with a sharp blade. Still have the same problem.

Thanks for the help,
Pepper

[codefox1]

Kinda hard to diagnose, but according to the schematic should this bus be zero to the ground, or another value? Could this be another infamous rivwr to the chassis gone bad over time?

[Radioroslyn]

Hmmm could be. But I think you meant rivet. Or maybe a bad one on the pushbutton assembly
Terry

[Pepperoni]

Got me guys. I've got other stuff to work on. This one's given me a headache.

Pepper

[Pepperoni]

New .05 cap between 7B7 pin 3 and ground bad. Replaced it, set works fine.

Pepper