04-10-2020, 05:17 PM
Began doing voltage checks on tube pins. So far, they are showing to be much less than they should be. Hmmm......
Philco 38-3 completely redone no reception
04-10-2020, 05:17 PM
Began doing voltage checks on tube pins. So far, they are showing to be much less than they should be. Hmmm......
04-11-2020, 03:26 PM
Working on a Philco 38-3.
Completely recapped, good tubes, new resistors. It had been playing fine, now it's not. Took the meter and ran pin voltage checks vs schematic. Here are the tubes with what they should read on left, and actual read on right: Output 6Fg (with chassis upside down, this is the output tube on the left) S 240v 226v P 230v 198v H 6.3 vac 6.7 vac H 6.3 vac .025 vac Output 6Fg (with chassis upside down, this is the output tube on the right) S 220v 186v P 235v 201v H 6.3 vac 6.6 vac H 6.3 vac .027 vac RF 6U7G P 235v 219v S 90v -.316 (I thought I had crossed my probe wires here, but I took it several times. Same result) H 6.3 vac .025 vac H 6.3 vac 6.5 vac IF 6K7G H 6.3 vac 6.5 vac H 6.3 vac ZERO P 240v 215v S 90v -.03 (See "S" under RF 6U7G above) OSC Control 6N7G P 180v -1.5 (See "S" under RF 6U7G above) P 180 Could not reach this without removing one of the bathtub bakelite (all of which were gutted and recapped) H 6.3 vac .022 vac H 6.3 vac Could not reach without moving tub above DET. OSC 6A8G Osc. Plate 125v -1.65 H 6.3 vac 6.53 vac H 6.3 vac .025 vac P 230v 216v S 90 v -0.32 2ND DET/1ST AUDIO 6Q7G H 6.3vac 6.5 vac H 6.3 vac ZERO P 135v 94v DISCRIM. 6H6G H 6.3 vac ZERO K 6.3 vac 6.5 vac Now, all of that being said, I did have an incident with the power plug. The screws holding down the AC lines inside the plug came loose, with the result that plugging it in became a little fireworks show at the plug only. The power strip shut itself off, I replaced the plug and this time soldered the screws shut. The power cord goes into one of those oh-so-much-fun to get the goo out of and replace the caps inside bathtubs. In this particular tub where the power attaches I installed a pair of ceramic .015 mf ceramic safety caps. It had originally held a pair of 0.15 wax/paper factory installs that were buried in the tar. When I had it playing I had alligator clip leads on some components (electrolytic caps that have to be installed in proper pos/neg orientation). I wonder if it's possible I reversed one of those caps when I soldered it together? Did a resistor fail? I'm just stuck right now. Thanks!
04-11-2020, 04:33 PM
I merged your two threads together. Please keep all posts about one radio within the same thread.
From the Phorum Rules: Quote:II. Multiple threads on the same subject not allowed. https://philcoradio.com/phorum/showthread.php?tid=4586 -- Ron Ramirez Ferdinand IN
04-11-2020, 04:42 PM
Oops! Sorry, Ron - Thought I was adding to my original post.
04-12-2020, 07:59 AM
Dumont, The Nostalgia Air print isn’t clear at all, not sure about some tie point dots whether it’s there or not, but a quick glance at the schematic shows resistor 46, a 1K as a good suspect. Measure for voltage on both sides and measure value of that resistor. Hope this helps!
Ron Bendix 0626. RCA 8BX5. RCA T64 Philco 41-250. Philco49-500 GE 201. Philco 39-25 Motorola 61X13. Philco 46-42 Crosley 52TQ Philco 37-116. Philco 70 AK 35 Philco 46-350 Philco 620B. Zenith Transoceanic B-600 Philco 60B. Majestic 50 Philco 52-944. AK 84
04-12-2020, 08:35 AM
Start with an audio signal at the speaker and work back. Once you get to the detector, change to a modulated RF signal at IF frequency and keep working back toward the antenna. Jumping around and guessing will get you nowhere ...... follow the path ..... think like an electron travelling thru the radio
"BE the electron"
04-12-2020, 02:50 PM
The 38-3 is up and working. Found an improper value resister in the power circuit, which had burned out. Replaced with proper value, and it's working. How many times do we tell ourselves to double and triple check our own work????
Thanks, all!
04-12-2020, 04:34 PM
I am forced to double and triple check my work. This includes sketching out the location of components. Double and triple check values and location against schematics. Then do the same after replacing components. I have to do this because I have few skills with diagnostics.
« Next Oldest | Next Newest »
Users browsing this thread: 1 Guest(s) |
|