I have purchased a Philco 625b at an antique store. The cabinet is in great shape, the chassis is complete and looks unmolested as far as I can tell. Since this is my first antique radio to restore, I need some guidance. I have attached some photos for your amusement. I mainly want to restore this radio for my own use from time to time in my library. I am a bit of a perfectionist, so doing it right is important to me. I also want to learn as I go, as I really enjoy working on radios and electronics in my retirement.
As I stated in my phorum introduction, I have some experience working with tube radios, but not much, and certainly not with anything this old. My questions right at first are how far should I go... Strip the chassis, re-paint and do a complete rewire, or should I test the set first to see what if anything is working? I have a variac and I can slowly apply power to check for smoke. I do of course plan on replacing the caps and so forth during the rebuild.
My next question is the cloth covered chassis wiring. Most of it still looks reasonable for it's age. If necessary I can replace all of the wires with either modern wire, or purchase some cloth wire from Radio Daze. What would you do?
Last question for now is if you just brought this radio home, what would be your very first steps? I have the schematics and literature already. I am ready to order the replacement caps and any other parts I may need.
Any guidance and advice would be very much appreciated!
Thanks! Bud - KI5OMM
(This post was last modified: 11-07-2023, 08:53 PM by KI5OMM.)
The chassis WAS molested a bit. The tubular electrolytics are not original.
1. No. Do not strip the chassis.
2. Do NOT test the set.
3. Do not replace the cloth covered wire unless frayed or in abd shape overall.
My recommendations (actuially, my routine, which works just fine):
- Remove all tubes, use a variac and test the transformer outputs (Hi-V and filament(s)).
- If it is all good, then do full recap. This includes your tone control.
- Then check your resistors and change as necessary,.
- Test all tubes.
- Test all audio transformers (interstage, if applicable and the output). If good then:
- After that put all tubes back, plug the speaker, put the meter on the Hi-V, using variac slowly make sure it rises to a reasonable value, bring it to 110VAC and....in my case I enjoy listening to a local station in about 80% of the cases.
- Do check thte RF coils for opens. Especially if the radio refuses to play.
- Align.
PS. Windex works fine for cleaning chassis without rust. As well as the tubes.
PPS. When cleaning tubes, be gentle, as anythig you use could take the marking off; note what tube it is before cleaning, and if the marking is rubbed off, mark the tube with a label or perm marker before you forgot what it was.
PPPS. Do use an isolation transformer at least when bringing it up and, actually, all the way through the repairs until fully assembled.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 10-22-2023, 08:00 PM by morzh.)
yes, that's the idea. With all the tubes out (one of which is the rectifier) everything is unloaded, so this is a good way to test the xfmr.
Put on Variac, put the meter on AC and the probes to the rect tube's panel's between the plates (right in the holes), and see it rising to 500-600VAC or so while bringing the Variac to 110VAC (gradually). If this is OK, then it is more likely than not that the filament winding is also OK, but check it nevertheless, same way, probes into the rect tube's panel's filament holes.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 10-22-2023, 10:39 PM by morzh.)
I'll add to Mikes do's and don'ts. Do not clean the dial with water or soap. The print will wipe right off. Instead use mineral spirits and gently clean it.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
For cleaning the aluminum, I like a soft scotch brite pad (the white one) and a bit of WD-40. It is a little smelly but does evaporate after a day or two.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 10-22-2023, 11:08 PM by Radioroslyn.)
OK thanks all for the great advice. I need to get my isolation transformer set up with my variac first. I plan on mounting the two on a piece of plywood and mounting it to the wall. I am moving my workbench area, so everything is in disarray. Hopefully by the end of the day I can start work on the radio.
Is there a list of component suppliers on the site someplace? I'll need to buy capacitors and a few other items. Lastly, what about those black bakelite condensers? How to I replace those? They have several leads and I have never seen that type of component before.
Thank You again!
Bud - KI5OMM
(This post was last modified: 10-23-2023, 08:11 AM by KI5OMM.)
OK I think I answered my own question about the condensers. I found and read the instructions on the philcoradio website. Lots of great information there that I did not see initially.
For this set you don't really need an isolation transformer as the power transformer isolates the ac line from the chassis. Typically, you'd use one when working on sets that don't have a power transformer or have series wired heaters. These sets will have one side of the ac line connected to the chassis (early design) or a floating B-. This means that one side of the line is connected to the - side of the power supply and most of the - returns. Sometimes the chassis ground is used for a rf ground. You might find a small amount of ac volt between the chassis and ground. This is from #69 passing a few micro amps of the 120vac. It poses no shock hazard if the therein are not leaky or shorted. When leaky they act as a resistor and couple the ac volt to the chassis...
Use the parts list as your guide for buying. The micas in the front end should fine. There are 2- 110mmf #39 & 40 I think they are foil/paper caps in disguise. 67A is a 1000v job. I don't really know it's there for but I'm not a designer. If you wanted to replace it w/something tubular, you could restuff w/two .002mfd 630v in series. This would give you .001 mfd @ 1260v. Gut the Philco cap and reseal the ends w/ brown hot glue. It's used to glue on women's hair extensions. #69 use safety caps (XY rated) when they fail, they fail open not short and explode. The filter caps I'd go w/ 2x 10mf @ 450v and a 22mf @ 450v.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Oh, also if you grab the tuning shaft and wiggle it up and down and the tuning cap jiggles along with it you'll need six of these: http://www.renovatedradios.com/product.php?product=320 It's very common for these to fail over the years and disintegrate.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Personally, with an unknown radio, I use isolation transformer with any type whatsoever.
1. Possible leakage / breakdown, when the transformer itself is working. Rare but possible.
2. Those Y-caps (the AC input filter) going from one of the AC plug wires to Chassis. Their values are way over what today's regulations allow for the touch current. Won't kill but might deliver a nasty sting.
Philco16 for you. The chassis will float at 60V when ON, at 0V when Off and the Neutral pin faces Neutral, and at 120V when the Neutral pin faces Hot (non-polarized plug).
And Philco 66. Always under the potential.
The touch current in the latter case is 0.67mA rms or 0.96mA peak. It won't kill you but you will feel it. Medical equipment is required to be down to 0.3mA rms.
I am better safe than sorry.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 10-23-2023, 05:09 PM by morzh.)
I am having a hard time finding the set screw on the dial hub. It wiggles but it is securely fastened onto the shaft. I removed the front dial scale, but I am unable to remove the band arrow mask until I figure out how to remove the zinc dial hub. Any suggestions?
Next question is the warning about water washing the lettering off the dial. Are you talking about the amber colored dial scale that I just removed?
Do not use water or water-based cleaner to clean that amber-colored dial or the pointer mask. Use odorless mineral spirits (oms) on a cotton swab using light pressure.
(This post was last modified: 10-23-2023, 08:37 PM by RodB.)
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