Posts: 797
Threads: 42
Joined: Dec 2008
City: Chicago, IL
Posts: 797
Threads: 42
Joined: Dec 2008
City: Chicago, IL
Here's what I found inside when I pulled the chassis.
Tube lineup - 80, 24A, 56, 24A, 35, 6H6, 6F5, 2A5, 6U5. Not exactly stock!
[Image: http://farm9.staticflickr.com/8541/89704...6ba0_c.jpg]
The most confusing modification was the 6H6 and 6F5 tubes because there's no 6.3 winding on the transformer secondary.
[Image: http://farm6.staticflickr.com/5443/89716...c025_c.jpg]
Nice blue Acrturus globe 56 where a 27 should be.
[Image: http://farm4.staticflickr.com/3817/89716...9fe0_c.jpg]
Finally, here's what I found underneath. What a mess! The IF and LO on the right seem original, but the rest has been radically altered. Two multi-section box caps, a filter choke, tapped bias resistor and most of the bakelite blocks are all gone Instead, I have a few new caps one power resistor and a small 6.3 VAC filament transformer.
[Image: http://farm8.staticflickr.com/7409/89704...3927_c.jpg]
So what do you guys think ? it's already been suggested I just start looking for a new 90 chassis rather than attempt to restore this one.
Posts: 403
Threads: 40
Joined: Feb 2011
City: McPherson, KS
You may have the only 90 with an eye tube!!!!
Posts: 1,114
Threads: 14
Joined: Feb 2013
City: Irvington, NY
Why not try and get it working as is. From the look of the under chassis work, it appears that the person who did the mods knew what he was doing. He used shielded cable for the audio wiring to the volume control, and the filament wiring of the 6 volt tubes is done properly with twisted pairs instead of using the chassis as a ground return.
So its not exactly original, but its performance will probably be better than a stock 90. The mods appear to be to only the audio section and the 2A5 will give better audio with less AC hum than the 47.
I kind of like working on a set like this, because without trying to maintain originality, you can make further mods without feeling guilty about messing up a pristine original.
Posts: 15,705
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
I kinda agree. You don 't stop it from being a tube radio and in a way, from being a 90 either....
Posts: 52
Threads: 1
Joined: Mar 2013
City: Minneapolis, MN
It looks clean and you could easily get rid of the six-volt tubes by using a 56 for both diodes of the 6H6, (See the use of the 76 in the 38-116 schematic), and by using the triode of a 55 for the 6F5.
Posts: 52
Threads: 1
Joined: Mar 2013
City: Minneapolis, MN
PS. There is a 2.5 V eye tube and if you don't want one, the 2nd detector is even easier.
Posts: 797
Threads: 42
Joined: Dec 2008
City: Chicago, IL
The thing is I'm not sure whoever modified it did know what they were doing. The original 6 mfd x2 plus filter choke has been replaced with a 40 mfd and 20 mfd x2. That's a lot of stress for an 80 rectifier tube. I'm not sure how they dealt with the two missing metal box caps that housed 5 caps in total.
Here's an unmodified 90 chassis showing the box caps, choke and bias power resistor.
[Image: http://mcclellans.com/images/Philco90/ChassisAfter.jpg]
(This post was last modified: 06-06-2013, 07:26 PM by Bob Andersen.)
Posts: 1,114
Threads: 14
Joined: Feb 2013
City: Irvington, NY
I would not be too concerned about 40 uF as a capacitive input filter on an 80 tube. It is electrically the same as a 5y3 and many later radios used it with a 40 uF input cap. You will be changing the cap anyway so if you feel more comfortable, replace it with a 20 uF. The other cap after the field winding can be much larger with no extra peak loading of the rectifier. What it looks like is the power supply of a late 40's model.
Most of the caps in the metal box were used as decoupling filters for the two 27 audio stages which are now eliminated. The 6F5 is taking the place of the two 27's and bias is now provided for the 6F5 by what looks like a few thousand ohm cathode resistor. There is a plate resistor and a coupling cap to the grid of the 2A5. Looks pretty much as it should be done.
You may assume that the mods were done many years ago by the vintage of the parts added, and that the radio worked properly at that time. I would not be at all reluctant to retain the mods and at least try it with proper precautions.
(This post was last modified: 06-06-2013, 07:56 PM by Mondial.)
Posts: 1,958
Threads: 146
Joined: Jan 2013
City: Westland, MI
Take a shot at restoring the "Frankenphilco" as it is. At wosrst case you can always hunt down another chassis and resore it to original. In either case, you still have a better than usual cabinet. I kinda like the tuning eye also. Take care. Gary
"Don't pity the dead, pity the living, above all, those living without love."
Professor Albus Dumbledore
Gary - Westland Michigan
Posts: 52
Threads: 1
Joined: Mar 2013
City: Minneapolis, MN
If the original circuit used a 27 as a plate detector, the selectivity and sensitivity of the receiver are probably degraded by the 6H6 which loads the IF transformer much more than the original circuit. A diode detector makes sense only when you want AGC and/or the eye tube.
Posts: 15,705
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
The speaker is not original either. Who knows maybe this one is better.
Posts: 797
Threads: 42
Joined: Dec 2008
City: Chicago, IL
(This post was last modified: 06-06-2013, 11:06 PM by Bob Andersen.)
Posts: 15,705
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
80 tubes are inexpensive. I got some from eBay for a very moderate price.
A new eye of 6E5 type is 20 bucks new. And if you are willing to go to a Soviet 6E5S it may be even cheaper. And there are used tubes that may be as good as new.
Posts: 797
Threads: 42
Joined: Dec 2008
City: Chicago, IL
Oh I didn't mean to imply that I was in need of tubes as I have plenty of spares. I just thought I'd mention it. I was really hoping the eye tube had some life though as I don't have any others with the GE logo.
I just discovered something else. The lower left and right controls have been replaced with full round shafts. I'll have to file a flat on them if I'm going to use the Philco rosette knobs I dug up.
Users browsing this thread: 2 Guest(s)
|
Recent Posts
|
Philco 91 Speaker Replacement
|
I can't remember, but there was a particular product for loosening glue on the more modern "spiders", used pos...MrFixr55 — 09:43 PM |
Philco 91 Speaker Replacement
|
The spider is glued on the cone and so is the voice coil. I think you can use a cotton swab dipped in acetone and carefu...RodB — 02:42 PM |
Restoring Philco 37-604C
|
Yes I saw that. If I knew, I'd probably try to arrange for getting it myself. But I have just got one.
Which does not m...morzh — 01:44 PM |
Philco 38-2 Automatic Tuning
|
When you push the lever, you are supposed to rotate the disk to the desired station.
Then the magnetic tuning will acqu...morzh — 01:42 PM |
Philco 38-2 Automatic Tuning
|
I figure out the muting from another picture that helped. Now I need to know how the automatic tuning works. When I push...dconant — 12:11 PM |
Philco 91 Speaker Replacement
|
How would I go about removing the spider from the cone?dconant — 12:04 PM |
Philco 38-2 Automatic Tuning
|
Hello, I am having trouble getting my automatic tuning to stay unmuted. If I play with the tuning handle I can get it to...dconant — 10:51 AM |
Does anyone make photofinish replacements?
|
Here’s the link to the DIY photofinish section of our site:
klondike98 — 09:46 AM |
Delco car radio Peko vibrator converstion issues
|
Hi Richard,
Thx for posting the schematic. As I remember as a kid, these were great performers for the time, likely...MrFixr55 — 08:56 AM |
Delco car radio Peko vibrator converstion issues
|
hello mr Fixr,
The Electro Powersupply that I am powering the radio with has a huge choke plus a 10,000ufd electrolyti...radiorich — 10:58 PM |
Who's Online
|
There are currently 1934 online users. [Complete List] » 2 Member(s) | 1932 Guest(s)
|
|
|
|