Hi guy's,
Brought an old 630 home and hooked it up to my variac.
All tubes light as well as bulbs.
Has no sound at all, not even hum or static.
Tried swapping a few tubes, but no luck.
Lookes like someone years ago replaced a couple of the electrolitics. Did a messy job of it too.
I replaced those 2 with no change.
Any suggestions on what I should check next?
I am leaning toward output transformer or maybe even speaker?
This looks to be a difficult one to work on. Typical Philco I guess.
Thanks,
murf
Check for high voltage on the + of the first filter cap. That being ok, which by the way, may be exceeding 450 volts and the rating of your replacement cap, move on to the 2nd one. No voltage there = open field coil, if there is voltage on the 2nd cap + report back.
Looks like 230 and 240 vdc on the 2 caps.
Checked voltage on the speaker, and checks the same.
It's a Philco.
ANswer your question?
As a friend of mine once said, trying to troubleshoot a radio before recapping is like trying to start a campfire with wet matches.
^^^ Seems strange to me that anyone would still try to use old caps, electrolytics and even resistors, although the values "seem" to be fine, and have "recently" been recapped. (20 years ago, or so). The values can go right out the window, once they're powered up. I recently got onto the habit of changing out the resistors now, when I'm in there. Easier at that point. Might as well, as the results are noticeable, and it's only a matter of time before they'll all go out anyway, if you don't.
Would love to have it working before re-capping it.
Very hard to diagnose the problem without some sound.
Quote:RE: philco 37-630 no sound
It's a Philco.
ANswer your question?
It wasn't so much of a question as it was a suggestion. As others have said, recap it, replace resistors. I bet it makes noise then...
OK All of the above is good advice. So, the next thing I would check for NO audio output is continuity across the primary of the output transformer. Check the secondary and the speaker voice coil too but these are far less likely to fail.
Replace all of the paper and electrolytic caps.
You could try next to inject a signal on the grid cap of the 75. You can just touch it IF YOU KNOW WHAT YOU ARE TOUCHING. Listen for hum. Don't get electrocuted.
Check for B+ voltage on the plate of the 6F6 output tube. If you have voltage on the screen grid pin but not on the plate then the output transformer primary is open.
You should have about 250V on the screen and slightly less maybe 240 or so on the plate.
I had the same problem with mine. The output transformer mounted on the speaker was open. Got one from Playthingsofthepast.com for about 8 bucks plus shipping. I troubleshot it by hooking up an old speaker across the contacts of the transformer. Don't remember which two contacts, but you'll figure it out.
For what it's worth, I like to get my sets working if possible before doing a re-cap. I test for sound after each cap R&R. That way I know immediately if I screwed up. Yes, I've had a couple get all smokey on me...but so far, nothing serious or un-fixable happened.
Also check to open RF, ant, osc and IF coils. Philco's notorious for corroded copper wire at terminals and/or in the windings themselves.
Chuck
Hi All;
You could also use a 60 hertz (cycle) tone to find about where your signal is not getting thru..
Take a cap about .01 and tack it to one side of the 6.3 filament winding, and attach a jumper cable or small wire to the other end. And go from the speaker back.. You should get a 60 cycle hum from the speaker as you work your way back toward the front of the radio circuit.. Where it disappears is where you need to start looking for the problem..
THANK YOU Marty
Thanks for all the info guy's.
Some of it sounds pretty technical, but it gives me some different avenues to explore.
murf