[F-1540]

I am pretty pleased with the sensitivity of the F-1540 now.  Certainly some of my issue was noisy LED lighting, a noisy bench supply and the covers off the radio.  

I’m getting about 206 B+ voltage and it is looking pretty clean.  My schematic and service info I can find do not contain voltages.  I’m thinking this is about normal?  I was getting a decent signal on the bench at about -94 dBm. I’m thinking that is pretty good.  I hooked the radio to an end fed long wire and was happy.  I’m moving on to the cosmetics.   
The auto restoration suppliers had reproduction knobs and tuning bezel parts I needed.  The grill cloth had a hole poked in it so I tore into the speaker enclosure.  The speaker has about a one inch tear in the cone.  I suspected that as at higher volumes I could hear a bit of fuzz.
I’m thinking there may be a way to fix this with some kind of goo or patch.  Any thoughts?   It is an original field coil speaker and I would rather not replace it if I don’t need to.   
This has been a fun and interesting project but a little pricy as I was not in the hobby and most of my home electronics bench supplies  needed a refresh.  Maybe I need another project to justify the test equipment ?

Bill

[RodB]

Hi Bill, the tear in the speaker cone is easily patched with a strip of printer paper soaked with wood glue. Carefully smooth the paper over the tear, maybe with a cotton swab. Now here's where the purists will disagree. They'll say to use an acid neutral paper and acid neutral glue. I do use the correct glue and paper but only for the preservation of the cone. Some will have you use a coffee filter or even just cover it with the glue. I disagree with these. The cone is meant to be stiff so it moves as one unit. If you use a flexible patch it won't move the way it's supposed to. The flexible part of the speaker is the surround and should be repaired with a flexible material.

[F-1540]

Progress continues on the 1540 with a small patch to a tear in the speaker cone. I cleaned out the dual electrolytic can and installed 4.7 and 10 mf caps adding a wire through the base to pick up chassis ground. Attached picture.   It worked pretty well cutting the cap around a the neck just above the base.  I can slip the top of the can over the narrower piece left on the base and it looks original except fo the extra white coming out of the base on the component side. 
 I’m putting some new speaker grill cloth in and touching up the paint.  I’m still awaiting on couple of resistors to bring in to the correct value.  It sounds good when I hook it to a wire antenna.  Unfortunately the 1938 Woodie Wagon is not available for a while to try on the installed antenna. I suspect we will run into noise issues with the motor running as the car is not outfitted with any of the suppression mods. The  sensitivity is running about -85 dBm… not sure what an original may have been.

This forum has been an outstanding  resource for me. 

Bill

[RodB]

I saw the words "common positive" on the electrolytic can. Did you join the plus wires of the caps and connect them to ground?

[F-1540]

RodB
That twisted my mind up a bit at first and I was scratching my head for longer than I want to admit but it eventually sunk in with what they were doing.  Let’s put it this way… I’m glad I bought a few set of caps.  
I had some nice French non polarized made caps I temporarily wired under the chassis so I could press on but they were a bit too big. And I did not like the way I had to scab them in.   I liked the end result re-stuffing the can once I understood the configuration.  Getting that old cap out of the can was a but time consuming but a little heat was my friend.

[fenbach]

F-1540,
RodB commented, I saw the words "common positive" on the electrolytic can. Did you join the plus wires of the caps and connect them to ground?

I sure hope you didn't connect the positive leads to ground. The caps will likely explode!
Take a look at the schematic. Counterintuitively, the NEGATIVE lead of the 8uf cap is connected to the positive ground of the radio. To the radio chassis, that is. The chassis IS negative relative to the cathode of the rectifier tube, where the positive end of the cap connects. By more than 200 volts! The can itself rests on the case and is grounded also.
The 2 "common positive" leads of the 4uf and 8uf caps are connected to each other and to the cathode of the rectifier tube. In any event, neither contact on the bottom of the cap can connects to ground. Only the case itself is grounded.

[radiorich]

Hello Bill,
Well Done and I have early old school powersupply build to test car radios because back in the day before I owned my business They did factory warranty work and installs for ford .

Sincerely Richard

[Chas]

Earlier in this thread the Nostalgia Air URL for this radios schematic was posted. Apparently there is an error in the URL. This URL for the Ford F-1540 should work.

http://www.nostalgiaair.org/PagesByModel...014008.pdf

I do note: That the radio can have either positive or negative connection to the source (battery).

Also, the filter electrolytic can part #62 does have a common positive as the earlier image of the OEM can suggests. The negatives are respectively connected to each side of the filter choke that is in the B- of the power transformer. The chokes resistance also serves as the bias source for the output circuits.

As for noise management in the vehicle:

A.H. Ghirardis Radio Troubleshooters Handbook will provide all the data needed to effectively "noise-proof" the "Woodie":

Hard copy pages are: 505 to 548.

This book was available online but has since been withdrawn. There is one site that offers the handbook but one must register...

https://booksclub.online/book/ezV_ibH0px...538/1939//

This copy is still poor resolution.

The file size I have is 290 MB for the entire handbook, too big to email.

I was able to snip away all but the Auto Radio Service but it is still too big to post, even if the PDF is g-Zipped. I can email to you as a PDF, snipped, it is 18mb within my clients limits. My original PDF copy is poor resolution but by making image file size changes when viewed, the "fine print" can be deciphered.

"Renovated Radios" did have a copy that was hand scanned offered on C-D. Seems since ownership changes, the C-D is no longer available.

Chas

[F-1540]

Chas

Thank you for all the information and help with this.  I have a couple of resistors that I will replace as they have drifted up in value and I think I’ll be done.

Interesting observation about the polarity requirement.  The station wagon is still 6 volt positive ground and the owner has no interest in changing to 12 negative so I will not have to worry with that.  A lot of the antique car community likes to convert over.   

I appreciate the offer of the noise reduction documentation.  I think we are not going to worry with it at this point as we feel this is may only get used a little at shows just to show off a working radio.  It will be a bit before we can install it as the wagon is currently having some other maintenance done.  Ford also addresses some of this in their service bulletins.  

I’ll have to post some pictures when I finish up.  The radio is not much to look at being a black iron box, but beauty is in the eye of the beholder, right.

Thanks for taking time to provide me with more helpful input.

Bill