Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
I've started doing a little chassis work on my 60MB that was damaged in shipping:
http://www.philcoradio.com/phorum/showth...p?tid=6399
The only damage to the chassis appears to be the dial lamp and pointer smashed into the dial scale and shattered it. I've already bent them back into position.
[Image: http://farm9.staticflickr.com/8382/86412...31c7_c.jpg]
[Image: http://farm9.staticflickr.com/8534/86401...f410_c.jpg]
Here's the chassis after a little cleaning and rust removal.
[Image: http://farm9.staticflickr.com/8106/86412...d58b_c.jpg]
It would be nice to find a couple vintage electrolytic cans to mount in that holder.
[Image: http://farm9.staticflickr.com/8254/86412...315f_c.jpg]
It appears the speaker has been reconed in the distant past and they did a great job
[Image: http://farm9.staticflickr.com/8252/86412...9594_c.jpg]
(This post was last modified: 04-11-2013, 03:40 PM by
Bob Andersen.)
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
I did some quick resistance checking and discovered the bias wirewound resistor has an open section.
Amazingly though, all the coils and power transformer test good - even the dreaded antenna and oscillator coils
[Image: http://farm9.staticflickr.com/8405/86401...1d93_c.jpg]
Now for the bad. I noticed the band-switch shaft was bent and tried to straighten it out
[Image: http://farm9.staticflickr.com/8400/86412...c737_c.jpg]
(This post was last modified: 04-11-2013, 03:44 PM by
Bob Andersen.)
Posts: 4,612
Threads: 51
Joined: Sep 2008
City: Sandwick, BC, CA
It's a good thing the bandswitch only has two positions, not sure of how many contacts but it can't be many with only two bands. If I'm not mistaken the switch works by shorting out a section of the oscillator coil and the antenna coil, I think when it's in standard broadcast mode.
Regards
Arran
(This post was last modified: 04-11-2013, 10:25 PM by
Arran.)
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
Oops, my mistake again! I meant the tone switch - certainly the least important of the controls. It's really just a rotary on/off (SPST) switch.
(This post was last modified: 04-11-2013, 10:24 PM by
Bob Andersen.)
Posts: 4,612
Threads: 51
Joined: Sep 2008
City: Sandwick, BC, CA
Interesting, that's the same control shaft that's missing on my Philco 3118, those switches must have that as a weak point? I was debating on whether to replace it with another switch or a linear tapered pot, the pot would not be original but it would allow more variation then high or low. That set probably needs more work then your 60MB but since I found out that it's cabinet was different then the U.S 118B I would like to fix it up.
Regards
Arran
Posts: 80
Threads: 10
Joined: Apr 2012
City: Waterford, NJ
Bob,
Does the bandswitch work? Both of mine were frozen. The 66mb was broken in the back and it had to completely come out and be epoxied back together. I am sure you know but heat on the shaft and something like wd-40 will unfreeze that. Tone control might be an easy fix. When you remove it, I believe the caps are in a small box that the shaft goes to. Might be able to replace just the shaft if my memory is working today. Great all your coils are in good shape. It is a great sounding radio when complete. I got involved with the forum restoring the 66mb. Hardest final part was the grill cloth- that was the closest I could come to the small piece still in the cabinet.
Joe
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
Yes, the bandswitch does work
I think the power/volume has been replaced and it's also working. I did a meticulous restoration of a 60L a while back that had all the usual problems with open coils, frozen controls, etc. This one is going much easier (aside from the broken shaft).
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
I finally realized I was using the wrong schematic when I noticed the box cap has five leads and not four. I believe that makes this August 15, 1933: Run No. 3 or perhaps October 1, 1933: Run No. 4.
(This post was last modified: 04-12-2013, 05:16 PM by
Bob Andersen.)
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
I finished restuffing the bakelite blocks and tacked in a few replacements for the box cap and electrolytics. I'll restuff the box and try to dig up some electrolytics to restuff later.
Next I tried powering it up, but no B+
A little checking revealed only ohms of resistance between B+ and ground! Time to do some troubleshooting.
[Image: http://farm9.staticflickr.com/8265/86495...7ce3_c.jpg]
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
I tracked the short down to this trimmer cap. The lug with red wires was brushing up against the grounded shield.
With that fixed, I was able to power the set up but only silence on the BC band and weird howling on SW. I checked the 6A7 with a scope and found odd waveforms. Maybe the oscillator coil is bad after all
[Image: http://farm9.staticflickr.com/8383/86512...c22f_c.jpg]
(This post was last modified: 04-14-2013, 11:03 PM by
Bob Andersen.)
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
After a lot of checking, re-checking and head-scratching under the chassis, I finally took another look at the topside. Bingo!
I had removed the tuning cap to replace the shock mounts and forgot to re-solder the connections
[Image: http://farm9.staticflickr.com/8524/86427...9905_c.jpg]
[Image: http://farm9.staticflickr.com/8406/86527...1fa3_c.jpg]
It's alive
It sounds OK on the BC band, nothing on SW but I only had a short antenna. Terrible microphoncs when I tap the chassis too, but it's definitely progress.
[Image: http://farm9.staticflickr.com/8122/86516...20cd_c.jpg]
(This post was last modified: 04-15-2013, 11:33 AM by
Bob Andersen.)
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
Rummaging around my junk box produced this 3 X SPDT rotary switch. That's overkill because only a single SPST is needed, but the shaft is perfect for Philco knobs and just a bit too long. Much better than being too short ;)
[Image: http://farm9.staticflickr.com/8099/86569...efcc_c.jpg]
[Image: http://farm9.staticflickr.com/8118/86569...fce8_c.jpg]
I managed to dig up a couple hex knobs too.
[Image: http://farm9.staticflickr.com/8102/86558...c0bd_c.jpg]
(This post was last modified: 04-16-2013, 08:45 PM by
Bob Andersen.)
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
Sometimes it's any old port in a storm...
Maybe you can add a solder blob to the detent
track to make it operate like original switch.
Chuck
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
LOL - good idea. I just finished restuffing the capacitor box, removing my temp caps and wiring the box back in.
I used five yellow axial caps soldered together at one end with a tail of bare buss wire going to the box for ground. Some large diameter heat shrink did a great job of holding them together. I used some cloth covered push-back wire for the leads. Looks much better now I think
[Image: http://farm9.staticflickr.com/8103/86575...832bb1.jpg]
[Image: http://farm9.staticflickr.com/8118/86575...e53fe3.jpg]
[Image: http://farm9.staticflickr.com/8117/86575...fb426d.jpg]
[Image: http://farm9.staticflickr.com/8126/86575...0cd684.jpg]
(This post was last modified: 04-17-2013, 02:06 PM by
Bob Andersen.)
Posts: 795
Threads: 42
Joined: Dec 2008
City: Chicago, IL
I finally remember I had a mid 30's Philco chassis in storage and ventured out between thunderstorms to retrieve it.
[Image: http://farm9.staticflickr.com/8126/86586...7534_c.jpg]
The bias resistor is a little different in that it has an extra tap but the resistance values are within 10%. It also has a three position tone control that quite a bit bigger but might just fit.
[Image: http://farm9.staticflickr.com/8113/86597...a52f_c.jpg]
(This post was last modified: 04-17-2013, 08:28 PM by
Bob Andersen.)
