Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
Hi, Nick.
You're right. I realized my mistake when I was daydreaming about this radio today. I'm hoping to find an original or suitable replacement speaker setup so I put an ad in the want ads.
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Actually what you have will work fine. Just need to add a resistor from the plus side of 26A to the plus side of 26B. If it hums alot increase the value of 26A and B.
Simple fix. Osc coil is probably OK. That was a red haring.
Terry
Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
Just need to order some more caps then I'll let you know how it turns out.
Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
Well, I put in the 47uf caps and a 1000ohm resistor between the positive leads. I hear a hum through the speaker kind of like a fluorescent light. When I touch the center tab of the volume control, I hear one station faintly but it stays the same up and down the dial. Should I put in higher rated caps or is something else wrong?
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Guess what it's something else. So sounds like the audio, IF and detector stages are working. Are all of the tubes good and in the proper sockets?? Did you adj any of the trimmer caps?? Are the leads on the osc coil connected?
Terry
(This post was last modified: 05-12-2015, 05:16 AM by Radioroslyn.)
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
Schematic here: http://www.nostalgiaair.org/PagesByModel...014176.pdf
Agree, check above suggestion, problem is most likely "left" of the IF. Make sure Loop antenna and antenna coils are connected properly and shows continuity. Voltage checks should be done as well. See if connecting a length of wire to external antenna changes anything, and if you have a known good one, swap out the 7A8, as they can be difficult. Many now replace the carbon resistors whilst doing a recap job.
Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
Well, I put in the 47uf caps and a 1000ohm resistor between the positive leads. I hear a hum through the speaker kind of like a fluorescent light. When I touch the center tab of the volume control, I hear one station faintly but it stays the same up and down the dial. Should I put in higher rated caps or is something else wrong?
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
You guessed it something else! Check all tubes good and in the proper sockets? No solder bridges across connections or gnd?
Measure voltage with - probe connect to off/on sw. 7B7 pin 2 and pin3. 7A8 pin3, pin5, and pin 2.
Report back.
Terry
Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
OK, dumb question. Which tab on the on/off switch do I connect the negative probe to and does the radio need to be plugged in?
Tubes are in the correct sockets and I can't see any solder bridges. The antenna coil has no continuity so I will rewind it. I noticed someone fixed a couple breaks in the wire so I have to assume there are others. I haven't touched any of the trimmer caps. The leads to the osc coil are connected.
I'll get back later with the voltage readings once I'm sure how to do it.
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
OK, dumb question. Which tab on the on/off switch do I connect the negative probe to and does the radio need to be plugged in?
Well if you think about it if you are going to be measuring voltages the off/ on sw would have to be on. And it would need to be plugged in. If the sw is on it doesn't matter which side of the sw you are connected to, it's shorted.
Every once in a while I get an easy one.
Terry
Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
Sometimes it takes a while for the gears in my head to engage. I'll measure the voltages tonight.
Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
With the DMM set to 500v, 7B7 shows 4v on pin 1 and 163v on pin 2. 7A8 shows 162v on pin 3, 85v on pin 5, and 161v on pin 2.
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Ok hows about pin 3 of the 7B7 and pin 4 of the 7A8. - attached to off/on sw. Other voltages look ok .
Pin 3 should have +150 or so pin 4 should have - 3 or -4 volts.
Terry
Posts: 101
Threads: 11
Joined: Nov 2014
City: Castro Valley, CA
Pin 3 on 7B7 shows only 90v. Pin 4 on 7A8 shows -3v.
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Well the problem is your set works we just don't know it. What did you end up using for the antenna coil??
Terry
Users browsing this thread: 1 Guest(s)
|
Recent Posts
|
Jackson 715 not working
|
Now that you posted the schematic, I don't know why that Sprague electrolytic cap is across the meter, as it is not indi...MrFixr55 — 05:51 PM |
HiFi (Chifi) tube amp build - but my own design.
|
What may be lacking in the PP Tube amps may be the 2nd harmonics, which some, especially RCA back in the day called &quo...MrFixr55 — 05:32 PM |
Jackson 715 not working
|
Usually in an emission tester, the tube under test is measured as if it were a diode. So, some testers connect all the g...RodB — 04:17 PM |
Restoring Philco 37-604C
|
Yep. F5 is green, D5 is Red.
Red is Bad.
Green is Clean.morzh — 01:30 PM |
Jackson 715 not working
|
I did start to do that but I stalled out because I could not figure out how the grid and plate get voltage. In this diag...daveone23 — 11:52 AM |
Restoring Philco 37-604C
|
(Insert Homer Simpson "DOPF" Here.)
When all fails, look at the can. Took the Ron Ramirez advice, red Caig D...MrFixr55 — 09:23 AM |
Philco 91 Speaker Replacement
|
From your text I am not sure if you intend to use the existing speaker with a resistor instead of the field coil.
It wo...morzh — 08:44 AM |
Philco 91 Speaker Replacement
|
My field coil is bad. I am still hoping to find an original, but if I can't I will go with a fitting Philco speaker, 125...dconant — 08:34 AM |
Philco 91 Speaker Replacement
|
As Rod said, it is OK to use a fitting speaker, and then look for an original one.
If you buy a Hammond 125 output tr...morzh — 08:15 AM |
Philco 91 Speaker Replacement
|
Yes, I often have to substitute, then keep an eye out for an original. In the meantime, the radio is working and being e...RodB — 08:02 AM |
Who's Online
|
There are currently 4457 online users. [Complete List] » 1 Member(s) | 4456 Guest(s)
|
|
|
|