Posts: 79
Threads: 13
Joined: Feb 2014
City: Bristol, RI
Hi,
I have a Philco 37-670 with an inoperative shadow meter (the newer style). Not familiar with this meter; it's the first time I've dealt with one. Pretty cool! Anyway, here is what I know and have done so far. Any suggestions?
1. The meter coil is good. It measures out to about 1,450 ohms.
2. I removed the magnet from the coil assembly. I've read that they lose their magnetism. I tried to remagnetize it with a neodymium magnet and think I succeeded; it's now magnetized enough to pick up a small paper clip.
3. I reinstalled the magnet, etc. The shutter that swings back and forth is in good condition, moves freely.
4. With the radio on, I am getting about 215 volts on either side of the shadow meter coil. The voltage doesn't change much (a few volts) when I tune in and out of a strong station. The vane moves a touch, but barely enough to make much difference in the width of the shadow.
Any suggestions on what to try? Should I be seeing a greater variance in voltage in/out of stations?
Thanks! Here's the schematic:
http://imgur.com/NozIIBg
Posts: 5,205
Threads: 276
Joined: Nov 2012
City: Wilsonville
State, Province, Country: OR
Sorry no experience with them. I suspect you have seen this but just in case you haven't, there is some shadow meter info on Philco Repair Bench.
Posts: 1,411
Threads: 71
Joined: Oct 2007
City: Linn Creek, MO
Your shadowmeter may be just fine. It sounds like there isn't much change in the AVC voltage, you may just need to use a longer antenna or the radio may need an alignment.
Steve
M R Radios C M Tubes
(This post was last modified: 02-04-2015, 12:25 PM by Steve Davis.)
Posts: 79
Threads: 13
Joined: Feb 2014
City: Bristol, RI
(02-04-2015, 12:22 PM)Steve Davis Wrote: Your shadowmeter may be just fine. It sounds like there isn't much change in the AVC voltage, you may just need to use a longer antenna or the radio may need an alignment.
Steve
I'm thinking that may be the case. Antenna is plenty long enough, but have not yet aligned the set.
Hopefully the magnet has enough magnetism in it.
Posts: 79
Threads: 13
Joined: Feb 2014
City: Bristol, RI
(02-04-2015, 12:46 PM)Diverted Wrote: (02-04-2015, 12:22 PM)Steve Davis Wrote: Your shadowmeter may be just fine. It sounds like there isn't much change in the AVC voltage, you may just need to use a longer antenna or the radio may need an alignment.
Steve
I'm thinking that may be the case. Antenna is plenty long enough, but have not yet aligned the set.
Hopefully the magnet has enough magnetism in it. Looked at the alignment info, and it calls for the use of a variable condenser of about 350 mmfd in several of the steps. What is this? The alignment instructions seem amazingly complex in this set, and call for parts and procedures I've not seen before. Anyone here recently align this set? Thanks!
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
Almost all old tube sets have variable capacitors (aka condensers.) An awful lot of 5 or 6 tube superhets use a two stage tuning capacitor, the larger (more plates) is as often as not 365 or so mmfd. So if you can srounge up one, you're probably good to go. I'd loosen up the padder (screw adjustment capacitor) of the scrounged part.
Posts: 5,205
Threads: 276
Joined: Nov 2012
City: Wilsonville
State, Province, Country: OR
If you don't have a junk set they aren't too expensive.
Users browsing this thread:
|
Recent Posts
|
Rogers Majestic R-646
|
By the way, the bypass you suggested is a rare solution in some circuits.
For example, this schematics solution is used...Vlad95 — 01:43 PM |
Rogers Majestic R-646
|
No, you are wrong, because you did not know the details.
Unfortunately, only ONE winding out of six is intact in both t...Vlad95 — 01:14 PM |
Rogers Majestic R-646
|
The output 45s are still in push-pull because the transformer secondary winding is still in the grid circuit providing o...RodB — 11:52 AM |
Rogers Majestic R-646
|
Thanks RodB for the help.
But this is not a real solution to this situation, not even a temporary one. Because the firs...Vlad95 — 11:34 AM |
Philco Model 16 wiring question
|
I was going to check the voltages as you suggested and hooked it up to my dim bulb. It appears I have a short. The bul...bobclausen — 10:34 AM |
Rogers Majestic R-646
|
You can bypass the interstage transformer by disconnecting the primary, connect a load resistor of about 10k - 20k to th...RodB — 09:40 AM |
HiFi (Chifi) tube amp build - but my own design.
|
So, here's Prince on stage halfway through Purple Rain when he stoops down to his tech and says "Rod, pull out that...RodB — 09:17 AM |
Rogers Majestic R-646
|
Today I finished inspecting all the parts. The result is not very pleasing.
The first positive news:
1) The power tr...Vlad95 — 11:40 PM |
HiFi (Chifi) tube amp build - but my own design.
|
Well, found muh culprit. After using socket test adapters and finding voltages all ok, swapping 6V6s, no avail, swapped ...TV MAN — 11:18 PM |
HiFi (Chifi) tube amp build - but my own design.
|
Well, maybe - maybe not :lol: It's been an interesting project so far! Something so simple, yet so cranky. The 1st one ...TV MAN — 05:12 PM |
Who's Online
|
There are currently 977 online users. [Complete List] » 1 Member(s) | 976 Guest(s)
|
|
|

|