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: 16,581
Threads: 574
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: 16,581
Threads: 574
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: 7,305
Threads: 270
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: 16,581
Threads: 574
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: 16,581
Threads: 574
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
|
|
Part numbers to model cross
|
| Thank you morzh, that is exactly what I was looking for. Now , is there some where that shows pinouts for Philco power ...Jim Dutridge — 11:37 AM |
|
Restoration of the Canadian General Electric A-87
|
| Thanks for your help Michael. In fact, this video is only an intermediate result. Later I had to apply another tinting l...RadioSvit — 09:01 AM |
|
Restoration of the Canadian General Electric A-87
|
| Great job on the cabinet.
PS. In the US notation, "kenotron" refers to specific type of tubes; we call re...morzh — 08:24 AM |
|
Part numbers to model cross
|
|
This document has at least some tables of models and parts used.
Example: Choke 32-7572, used in 604 radio.
Search f...morzh — 08:19 AM |
|
Restoration of the Canadian General Electric A-87
|
| I also checked all the radio tubes on my Hickok 530 tube tester. The 5Z3 kenotron turned out to be faulty, all the other...RadioSvit — 08:02 AM |
|
Restoration of the Canadian General Electric A-87
|
|
Well... While the varnish is drying up, I started repairing the chassis...
Of course I started by replacing the pa...RadioSvit — 07:12 AM |
|
Philco Model 38-7: what caps & resistors do fail typically?
|
| Hello Martin,
Welcome aboard our little community what great Model 38-7
Sincerely Richardradiorich — 12:30 AM |
|
Philco Model 38-7: what caps & resistors do fail typically?
|
| Welcome to the Phorum Martin.
I count about 9 paper caps, the 3 electrolytic caps and 2-Y2 safety caps to replace th...RodB — 09:44 PM |
|
Part numbers to model cross
|
| Jim,
We have this index put together by Dale Cook but I don't think that is quite what you are looking for.
The Parts...klondike98 — 09:37 PM |
|
Philco Model 38-7: what caps & resistors do fail typically?
|
| Yep the dim bulb test is OK but I'd definitely replace all those electrolytics before I did it. Since those #47 conden...klondike98 — 09:18 PM |
|
Who's Online
|
| There are currently no members online. |
|
 
|
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
