The PHILCO Phorum
37-604 Repair Project - Printable Version

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37-604 Repair Project - radioalfa - 07-14-2018

Hi Folks,

I recently acquired a Philco 37-604. Cosmetically it is in nice shape, it was working although not all that well. This radio was discussed here in an earlier thread regarding its sale and my ultimate purchase on eBay. I have started to disassemble it to undo previous repairs that had been made.
So far my to do list includes;
-Remove electrolytic capacitors that have been tacked on and installed under the chassis, put new ones in the can where they belong
-Rebuild all Bakelite blocks
-Replace wires going to speaker that have been spliced
-Remove fuse holder that is installed next to a tube (tube shield was either not present or removed to make room for the fuse)
-Replace cord with cloth covered cord
-Remove diode installed on socket for 25Z6 GT, and replace the bad tube with a good one
-Replace the 25Z6 tube socket, pin 5 is missing
-Replace reproduction dial
-Repair or replace lamp mask
-Remove the broadcast coil; 1 to repair a broken wire, 2 to anchor the coil to the mounting bracket
-The bias cell has been removed, will install an LR44

So far mostly what I have done is to take photos and notes, and as mentioned above, some disassembly. I scrounged up two tube shields to use in place of the missing ones, machined some bushings for the control shafts, made some checks of chokes and transformers. Removed old electrolytics from their can. Still lots to do, and I suspect my list will grow.

I will replace the tube socket next, and go from there.

Russ

[img][Image: https://farm1.staticflickr.com/845/29541727628_c29668a084_b.jpg]37-604 by rtalfa, on Flickr[/img]

[img][Image: https://farm1.staticflickr.com/834/29541728648_17a98536ac_b.jpg]chassis top front by rtalfa, on Flickr[/img]

[Image: https://farm1.staticflickr.com/927/43412049811_a6a93d9261_b.jpg]chassis by rtalfa, on Flickr

[img][Image: https://farm2.staticflickr.com/1762/43412050381_7ac58187cc_b.jpg]Mask by rtalfa, on Flickr[/img]

[img][Image: https://farm1.staticflickr.com/916/43412051191_8595d22e6e_b.jpg]chassis top tuning rem by rtalfa, on Flickr[/img]

[img][Image: https://farm1.staticflickr.com/917/43412051941_d41831af17_b.jpg]electro 1 by rtalfa, on Flickr[/img]

[img][Image: https://farm1.staticflickr.com/916/43412052901_cf36cdd3a8_b.jpg]electro 2 by rtalfa, on Flickr[/img]

[Image: https://farm2.staticflickr.com/1828/43412056031_902626fb5d_k.jpg]DSCN3445 by rtalfa, on Flickr

RE: 37-604 Repair Project - radioalfa - 07-20-2018

Things are progressing, slowly but surely. The electrolytics are in their can and connected, the 25Z6 tube socket has been replaced, 3 of the 4 bakelite blocks have been rebuilt.

I have a question on R20, the parts list shows it as being a 200 Ohm wire wound resistor, part number 33-3010, the schematic shows it as being 300 Ohms. Any idea which one is should be?
It measures 329 Ohms.

Russ

RE: 37-604 Repair Project - PhilcoPhan1936 - 07-20-2018

Are you working off of the paperwork for the 604C or 37-604C? I see yours is the later version. I looked at Nostalgia Air for the paperwork for the 37-, but it wasn't listed. I know there were changes between the 2 models, most notably, the tubes used.
I would think any changes would be documented in Philco Service Bulletins, but I couldn't find any around the web for that model. Hopefully someone here will have access to one.
That said, part number 33-3010 is rated at 300ohms, so if it measures 329, it is within 20% of rated value. I'd leave it alone. Icon_thumbup

RE: 37-604 Repair Project - Radioroslyn - 07-20-2018

What that resistor does is control the gain of the mixer stage. I would go w/the higher value, it may have been updated to stabilize that circuit by lowing the gain. As things go I doubt you notice the difference in gain between the two values but the lower value it would be more pron to oscillate.
You can find the missing Philco/Rider's here. https://www.americanradiohistory.com/Rider-Manual.htm

GL

RE: 37-604 Repair Project - radioalfa - 07-20-2018

Thanks Jeff and Terry,

I am working with a print for the 37-604 from Riders. Since either the parts list is wrong or the schematic is, based on comments above I will lean towards the schematic being right and will leave it alone.

Thanks again,

Russ

RE: 37-604 Repair Project - radioalfa - 07-22-2018

Well, the patient has survived and is playing pretty well. For now I am using an AA battery in place of the bias cell, I will get an LR44 installed tomorrow.

One concern though, the chassis in the area of the Candohm resistor is getting very hot, though I do not have the means to measure the temperature.
Voltage across the resistor is 45V, and if calculations are correct it is consuming about 13 Watts. Overall the radio is supplied with 112VAC and is drawing 390 milliamps.

No asbestos in the cabinet in this area, would there have been?

Thanks,

Russ

RE: 37-604 Repair Project - radioalfa - 08-04-2018

Here is a look at the chassis after new electrolytics were installed in their can, Bakelite blocks rebuilt, other caps and resistors replaced. The power cord is temporary, I have since installed a cloth covered cord. In a way it does not look too much different, but at least it is neater.
I made a mask out of tan paper that I laminated. Not award winning, but it does the job. I tried various materials, manilla folder, paper sprayed with clear coat, milk bottle jug, and white paper. Some of the tests were not cut to shape as I was only trying out the material. The original mask is the second one in the middle row.

Russ

[img][Image: https://farm2.staticflickr.com/1796/43851561091_089f898e8e_k.jpg]chassis after by rtalfa, on Flickr[/img]

[img][Image: https://farm1.staticflickr.com/937/43851561961_6a1f829302_k.jpg]mask on by rtalfa, on Flickr[/img]

[img][Image: https://farm2.staticflickr.com/1813/43134168774_9ce4936232_k.jpg]mask trial by rtalfa, on Flickr[/img]

RE: 37-604 Repair Project - Radioroslyn - 08-04-2018

Looks nice, neat and tidy. Your fine w/a rubber cord as I'm pretty sure that '36 was the last of the cloth cords. The 37-602 I've been working on has the same HOT spot on the chassis. Same heater circuit. Makes it very uncomfortable to do the rf alignment as the dial is mounted to the cabinet. Ended up having to go back and forth taking the cabinet off and on to get the oscillator to track the dial calibration.  Eventually I figured out that I could place the set on block and lift the cab off/on was flipping it over and handling the hot chassis dropping it into the cab.


[Image: http://philcoradio.com/phorum/attachment.php?aid=16888]

RE: 37-604 Repair Project - radioalfa - 08-07-2018

Hi Terry, thanks for the confirmation on the hot chassis, I checked my 37-602 also and found the same. I guess that is just the way they were....
Interesting info about the change from cloth covered to plain rubber cords. Oh well, I will leave the cloth one on.

Russ

RE: 37-604 Repair Project - Ron Ramirez - 08-07-2018

It was actually duing production of the 1937 models that Philco switched from cloth to rubber AC cords. I've found some 1937 Philcos with cloth-covered AC cords which had every appearance of having been installed at the factory.

"Waste not, want not" was the catchphrase of the day...if Philco decided to switch to rubber AC cords, you can bet that they first used up their stock of cloth AC cord...