Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
I think I'm missing something here. I'm feeding a 455Hz signal in to troubleshoot. I get a good strong signal to the voulme control, and also on the top of C424 (.006mfd). But I get nothing on the top side of R419 right above it. Resistor ohms out just fine. Anyone lead me in the right direction? I hope this schematic is readable. Thanks.
[img] [Image: http://i1367.photobucket.com/albums/r796...jhkvn7.png][/img]
Posts: 16,510
Threads: 572
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
C423 shorted?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(09-03-2018, 05:07 PM)morzh Wrote: R423 shorted?
Did you mean C423?
Posts: 16,510
Threads: 572
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Yes, I did.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
No, C423 is O.K. I just checked it even though it's new.
Posts: 7,301
Threads: 269
Joined: Dec 2009
City: Roslyn Pa
I'm missing something too. If you apply a rf signal to the volume control you shouldn't hear it. The rf signal must be rectified to covert it to an audio signal. If you want the use rf @ 455kc connect it to the control grid of the 7H7 (p6 I think). Make sure your mode switch is good and clean.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 09-03-2018, 08:38 PM by Radioroslyn.)
Posts: 16,510
Threads: 572
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
What I did not appreciate was it was 455kHz. C423 simply shorts it.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(09-03-2018, 08:37 PM)Radioroslyn Wrote: I'm missing something too. If you apply a rf signal to the volume control you shouldn't hear it. The rf signal must be rectified to covert it to an audio signal. If you want the use rf @ 455kc connect it to the control grid of the 7H7 (p6 I think). Make sure your mode switch is good and clean.
I'm using an Eico 324 RF generator with internal modulation AF out, not a strict RF signal. I just finished recapping the chassis and am in the process of alignment. Guess I should have explained that. Sorry. I'm working backwards from the amp section to find out why I'm not getting audio.
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(09-03-2018, 08:59 PM)morzh Wrote: What I did not appreciate was it was 455kHz. C423 simply shorts it.
It's AF modulated RF. I used to use a "Mosquito" for tracing. Remember those?
Posts: 1,824
Threads: 114
Joined: Jul 2014
City: Sneedville, TN
I restored a 48-482 back in 2014. The toughest part was aligning the FM converter, but it can be done using a regular modulated sig gen if you carefully follow the instructions in the Philco service paperwork, it tells this alternate method. You may find my thread on this project of use. http://www.philcoradio.com/phorum/showth...?tid=10134
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
Read through your thread. Might be some useful information there if I ever get through the BC part.
Posts: 16,510
Threads: 572
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Patrick
Where exactly is it that you feed the IF signal to?
I am still not sure.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(09-04-2018, 08:46 AM)morzh Wrote: Patrick
Where exactly is it that you feed the IF signal to?
I am still not sure.
I took a step back, and used the Philco troubleshooting guide. I have a strong IF signal at the grid of the 1st IF amp. I have only a very weak signal at the plate of the converter. That would indicate a problem at the 1st IF transformer, Z400. So it appears the problem most likely is there, and I was just going off on a tangent somewhere.
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
Found the problem! Z404, a choke/cap combination, was wired to the white lead on Z400 instead of the green lead. The two connection points are right next to each other. That caused a very weak signal from the plate of the converter. Connected it properly, aligned the IF, and picks up stations. I really think the stock speaker is too small for this radio.
Users browsing this thread:
|
|
Recent Posts
|
|
philcorepairbench.com - shadow-meter
|
| Thanks Ron.fenbach — 02:43 PM |
|
Model 70 Cabinet Trim
|
| Thank you, Gary. Before making my original post, I had clicked on "Steve Davis Cabinets" only to find that it...musar — 02:25 PM |
|
philco predicta
|
| Welcome to the Phorum, cgl18! I am not your resource for television repair, but lots of friendly help is available here...GarySP — 02:12 PM |
|
Model 70 Cabinet Trim
|
| Welcome to the Phorum, musar! You can send Steve Davis a private message (PM). The site is at the top of the Home page...GarySP — 02:09 PM |
|
Model 70 Cabinet Trim
|
| How do I contact him? The only contact information for him I could find when searching online was a telephone number th...musar — 10:38 AM |
|
philco predicta
|
| Hello, good afternoon, I would like to ask what the possible problem could be if I don't have an image on the screen. I ...cgl18 — 10:19 AM |
|
Philco model 38 code 121 not receiving signal.
|
| So one last question before I finish this radio. Regarding the speaker and output transformer. I salvaged the original o...Stormlord5500 — 09:31 AM |
|
462ron
|
|
It’s on the bottom of the homepage of our Philcoradio.com homepage!
Ron462ron — 07:20 AM |
|
Model 70 Cabinet Trim
|
| Steve might have some trim left.
Not sure he is making anything.morzh — 06:12 AM |
|
Model 70 Cabinet Trim
|
| Hello musar,
First all welcome to the forum and yes that is true that steve stopped making trim .
Sincerely Richar...radiorich — 12:13 AM |
|
Who's Online
|
| There are currently no members online. |
|
 
|
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
