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Just finished recapping this B 1750 Radio (with phonograph) - it's from 1954. Put tubes in it, plugged in and ZIPPO - not a thing. It's completely lifeless. None of the tubes glow, nothing gets warm, nothing lights up, no buzzing or humming - almost as if I didn't plug it in. I really took the time and did a good job on the caps - make sure all connections were tight, used insulation on all exposed cap wires, and checked my work.
I did not replace the power cord yet - but there is continuity between the prongs on the plug and where it connects into a buss terminal - so I believe the power cord is NOT shorted or severed inside.
All tubes check out good and I even have another set of them - which I tried as well - same thing - completely dead. The on/off pot seem to be solid, not loose or anything, but not sure how I would go about checking to see if it's good as there are like 3 different rows of terminals on it.
The transformer you see on top of it in the photo is an audio transformer - so I believe even if that were bad, I'd still get some tubes lighting up, if nothing else.
I did not turn it on before I recapped it so I don't know if it worked before I recapped it - but I was the first one in there since 1954 - it was completely untouched and unrestored. All wires seem to be attached to wherever it is they are soldered to - although I will look more closely later.
Any suggestions as to where to start looking for a problem that would cause this thing to have ZERO power when switched on? Thanks [Image: http://philcoradio.com/phorum/images/smi...on_sad.gif]
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First of, do not put all tubes in when powering.
At least have your rectifier out.
Now, when you have your power switch ON, do you have continuity between the two prongs of your power plug?
Simple yes or no will suffice.
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OK next step is to measure the resistance across the off/on sw to see if it is open. Do this with the set unplugged. If that is OK next measure the heater pins on all of the tubes to see if you have an open one that will cause the problem you are having.
Terry
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I have no sch for it.
If it is a transformer radio you could stop right there if your switch works and the cord is OK, as your transformer is open.
But likely this is the switch.
If it is ACDC radio, one of the tubes might have an open filament. Or a pilot light, or...
Give a link to the sch.
OK. Found it. It has doubling rectifier and is an AC transformerless set (doubling does not work with DC).
After checking the power yswitch check all tubes' filaments.
Also there is R18, a 100 Ohms resistor, check it too.
(This post was last modified: 10-08-2014, 07:30 PM by morzh.)
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Pins on all tubes seem to be good. Plus, I have another one of these Philco's that I restored last year (same exact model) which runs great. I put all the tubes into the 1st restoration and it still works great, so it's not the tubes. With the thing unplugged, I used a continuity meter to see if the on/off control was working - and it does. I used an ohmmeter as well. There are two separate sets of terminal posts, each with 3 terminals. One set, the reading ranges from 186 ohms to about 260 ohms - i think these are the terminals which control the volume. The other set of terminals range from about 300 ohms to 380 ohms - this varies when I mess with the tone control. So it seems like the on/off switch and volume/tone controls are working. Tubes seem to be good. Not sure where else to look. There is a lot of old insulation on these old wires, but no bare wires and all connections seem to be in place. Although I prefer not to, I can swap the on/off/volume/tone control pot from my first restoration and see if this fixes the problem. There are soooo many wires, several capacitors a couple of resistors connected to this control, so I will use this as a last resort, unless someone else comes up with some other stuff to check !!
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On the schematic I have, there is no R18, the highest it goes is R17. Just the same, I'm gonna start checking the resistors. On the previous B1750 I restored, all of the resistors were good, but you never know. Will have to get back to u with the results in a day or two. Thanks
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I mean the resistor in the middle of the chained tubes filaments.
It is pretty simple: when ON, you have to have continuity in hundreds of Ohms between the AC plug's prongs consisting of filaments and that resistor I mentioned.
There is a tap from the rectifier filament for the pilot light, if we assume 1/2 the filament is dead and the lightbulb is too, or another 1/2 of it is dead, or any tube's filament is dead, then there will be no continuity.
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Those resistance readings are all wonky. The power switch (should be two terminals at the back of the control, the other two sets of three are the volume and tone controls, which should read MUCH higher than you measured!) should read less than 3 ohms, and that's just basically the resistance in your meter leads. If it measures more than a few ohms, it's bad.
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I went back to it and looked at it again. The the two terminals at the back of the control read 7 ohms. The middle set of terminals (3 of them) read about 300 Khoms (not ohms). And the other set of terminals read very low ohms.
This is starting to look like a switch problem I believe. Do they make replacement switches for these things or do I have to pull a working one out of another Philco? The Philco part # on this on/off switch is 33-5563-60 according to the schematic. On the switch itself, it says: Philco 137326. Thanks
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What I cannot understand from your posts is this:
In post #3 you said "No" to the question of continuity across prongs of the power plug when the switch is ON.
Now your switch is working (dirty but OK), your tubes are fine and the pwr cord is OK too.
Unless your wiring inside is bad or your tube panels are badly oxidized you should have that continuity.
Go check EVERYTHING along the filament chain, starting with prongs.
Prong-switch pin 1, switch pin 2 -1st filament pin1, 1st filament pin 2 - 2nd filament pin1 and so on so forth.
PS. The switch typcally can be taken off the potentiometer and cleaned. BTW the pot itself can benefit from some dab of lithium grease and Deoxit mix.
When everything else works.
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OMG - this thing is driving me crazy. Havent' checked the filament chain yet but as far as the on/off volume/tone POT: here's what I've got:
1. If this is what you meant - I put one probe of the continuity meter on one side of the wall plug prong and the other probe on the other one. There is no continuity whether the set is on or off. It's the same thing with another radio that works fine, but maybe you meant to do something else?
2. With the switch turned off, there is no continuity if I put probes on the rear two terminals on the POT . If I turn on the POT, there is continuity.
3. There are two sets of terminals, each with 3 posts. On the set most towards the rear of the POT, if the switch is OFF and I measure resistance between the middle post and the uppermost pot, it reads 28 ohms. If I turn on the switch, resistance then ranges from 1.37 Megaohms to 1.65 megaohms depending on whether the volume is turn up or lowered. Resistance from the middle post to the lowest post reads 1.65 megaohms with the switch off and/or at lowest volume setting and reads 17 ohms at full volume.
4. Set of terminals towards front of POT (controls tone)- middle to upper post resistance ranges from 1.15 megaohms to 148 ohms if the switch is off or tone all the down. Middle post to lower post resistance is 16.33 megahoms when switch is off and goes to 87 ohms with highest setting.
I'm not sure what to make of all this. The schematic for this double POT indicates one section is 5 megaohms and one section 3 megaohms. Interestingly, I noticed when I was replacing some caps that bottom terminal of the front most set of terminals was bent and contacting the metal casing of the radio. When I check the resistance of the terminal I get the 16.33 megahoms reading - I wonder if that means it is fried. Still, the on/off control does create continuity on the rear terminals, so you would still think the set would get some power coming through even if the tone control part of the POT was fried?
I will check all the other stuff over the weekend. Thanks for your patience.
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http://oldtech.net/Beitman/14-89.gif
This is the sch, I think.
If you look at the prongs, one (top) goes to the filament string, then the end of the string goes to the switch and the other prong.
The resistor in the middle is an NTC thermistor, it starts at about 1K and drops to 100 Ohm as it heats up.
So you should not have a short, but you should have about 1.6kOhm or so when the switch is ON.
Your pot sections DO NOT control power, the switch does. The pot sections control volume or maybe tone.
It'd be nice of you to eventually post the link to the sch if you know where it is. I am not sure whether the one I have is accurate.
(This post was last modified: 10-09-2014, 09:09 PM by morzh.)
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That is the schematic you have it right. I looked at the continuity across the power cord plug prongs again however. On my GOOD radio, there IS continuity across the power cord prongs when the on/off switch is on. On this new one we are talking about - there is no continuity when the switch is on. I'll check out the filament string shortly, but my gut feeling at this point is that the switch may be fried. Thanks for your help.
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In your #10 post Didn't you say you have 7 Ohm across the switch? Or did you confuse the switch with something else?
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