Questions about Philco 37-611
The power switch on this chassis has multiple positions, can someone explain.
Also the power portion of the one I'm looking at to revive is non operational, is this a common issue,
that can be repaired?
This chassis uses a powered speaker? One that has no permanent magnet and uses a matching transformer ?, what can be used if you do not have the original speaker, at least in the short run to test it.
On the Chassis I have the speaker wires exit the chassis unprotected from the metal and have been damaged by rubbing on the chassis. Was there originally a rubber grommet to protect them?
Is there a owners manual online that covers this chassis. ( I did find the schematic/parts listing)
Before jumping in and replacing caps / resistors I want to evaluate it's current condition.
There are NO previous repairs. It's totally unmolested.
I will test the tubes shortly, once the sw was jumped the chassis drew current not excessive.
And yes, of course it was on an isolated B&K variac through a lamp for safety.
That's where I stopped until I can get at my hickok tester to check the tubes.
Unrelated to the above.
The chassis is destined for a custom cabinet.
I noticed that this chassis has no RF amp, that makes me question it's sensitivity?
Wondered if the cabinet is prepared to accept this chassis is there a superior chassis I could keep an eye out for that will have the same mounting / dial/ knob configuration that could be substituted in the future?
Which brings to mind ,on the 37-611, what would work for an antenna that doesn't require me to run a 20 foot wire out through a wall to a tree? This radio has 3 bands I believe.
Hello. Thye power switch/on-off is also the tone control.
Don't know what you mean by power portion your looking to revive is non operational.
There is a 1 page schematic on the Nostalgia Air web site.
If you don't have a speaker for it, there is a way to test with a perm. magnet speaker. You might try searching for how to do that. I have not tried myself. Be carefull where those speaker wires come through the chassis. They have very high voltages on them. Good luck.
(08-05-2015, 11:53 AM)Mike Wrote: [ -> ]Hello. Thye power switch/on-off is also the tone control.
Don't know what you mean by power portion your looking to revive is non operational.
There is a 1 page schematic on the Nostalgia Air web site.
If you don't have a speaker for it, there is a way to test with a perm. magnet speaker. You might try searching for how to do that. I have not tried myself. Be carefull where those speaker wires come through the chassis. They have very high voltages on them. Good luck.
On the power switch it clicks into 4 positions.
The power line goes to the 2 terminals on the back.
That switch is NG. Wiith the On OFF in any position that switch does not make contact.
I'm not familiar with this vintage radio, could it be some sort of standby mode? or as you say different tone positions.
The point being it's not a VR.
That is why I was asking. I mean at some point I'll investigate it myself and pull it apart but I'd like to know what I'm getting into before I get there. I'm sure this issue has come up before.
I was surprised that the schematic I saw do NOT include voltages, like the Sams schematics that came later.
There are 4 wires for the speaker, 2 from what I see would go to the matching transformer, 2 to provide power to the speaker electromagnetic.
I wondering where the best place is to get at ground to take readings and connect a signal tracer.
I assume the variable control is the volume, which I should be able to connect a signal tracer to without the speaker for now.
Yes it has came up before on the power switch/tone control. They can be hard to find. Go to philcoradio.com at bottom of page and under resources look up Mark Oppat. He sells many type of old radio switches.
That is a transformerless radio . Be warned that the chassis can be energized based on the way you have plug in outlet.
If you run the radio without a speaker for a load you could do damage to the rectifier tube.
hey think
whats your name would be easyer
did you try cleaning switch with contact cleaner ?
i think mark can rebuild or fix it if not working
or you can put external switch to it to get working
sam
As for the speaker, a high watt resistor that matches the field coils resistance will work, then connect the pm speaker through the transformer secondary leads as long as the pm speaker cone coil ohms match the original.
The cheap and dirty way to fix the off/on/tone control is to replace in with a volume control. Wire the pot as the tone control. So now you'll have a variable tone control instead of a switchable one.
Terry
(08-05-2015, 01:02 PM)sam Wrote: [ -> ]hey think
whats your name would be easyer
did you try cleaning switch with contact cleaner ?
i think mark can rebuild or fix it if not working
or you can put external switch to it to get working
sam
It's Steve
For now I'll just jump it out, later I'll pull it and see exactly what is going on and report back
So, these switches are first click on then tone variations?
I looked for a "owners" book that would cover a model that used this chassis but couldn't find one, that would have answered the question....since I'm not familiar with these at all.
(08-05-2015, 12:51 PM)Mike Wrote: [ -> ]Yes it has came up before on the power switch/tone control. They can be hard to find. Go to philcoradio.com at bottom of page and under resources look up Mark Oppat. He sells many type of old radio switches.
That is a transformerless radio . Be warned that the chassis can be energized based on the way you have plug in outlet.
If you run the radio without a speaker for a load you could do damage to the rectifier tube.
Thanks Mike
I may have dealt with Mark years ago.
I have a "light" current limiting jig and I also connect any of this vintage stuff through a B&K isolation supply.
I was reluctant to use the speaker it came with because it is a atwater kent speaker added to it that appears to be in poor condition, also I don't know if it's a good match, though it seems to have been there for a long time.
I will trace out the wires on the chassis and reconnect the speaker removing the damaged wiring.
One wire is darker in color than the other 3 I assume one of the wires to run the field coil...but will have to check.
I suspect the load is somewhere between 1to 5k
How much voltage is used to drive that speaker field coil?
Thanks for the help.
Steve
Yes, that's the way the switch works. If it's 4 position 1st is on, the rest are different tone levels.
(08-05-2015, 05:24 PM)tab10672 Wrote: [ -> ]As for the speaker, a high watt resistor that matches the field coils resistance will work, then connect the pm speaker through the transformer secondary leads as long as the pm speaker cone coil ohms match the original.
This sounds like a plan!
Thanks
Now I just have to determine which are the field wires of the 4 on the radio side.
Hopefully the speaker they used in the past was a close match for what is suppose to be used.
Look at the schematic, you can determine which is which by finding the two that are connected across the filter caps which will probably be the easiest to trace back.
(08-05-2015, 09:28 PM)tab10672 Wrote: [ -> ]Look at the schematic, you can determine which is which by finding the two that are connected across the filter caps which will probably be the easiest to trace back.
I removed the damaged wiring traced it out and re-connected the speaker.
I actually have audio - meaning the amp is working. I'm sure it will be a lot better with new caps but I can put a signal in at the volume control and I hear it from the speaker.
What i don't have is any radio, nothing no static nothing.
The schematic, the factory Philco one has on the first page for 37-611 a block diagram with voltages on the filter and the tubes.
They show a 2.4vdc voltage on the det/osc and the IF amp.
It looks like it saying on the cathode... does this make sense.
I'm measuring the voltages they call out using the neg of the main filter.
All the other voltages they printed, are very close, however there is no 2.4vdc on those tubes.
Steve
steve why don`t you change caps first then try
sam
(08-06-2015, 02:25 AM)sam Wrote: [ -> ]steve why don`t you change caps first then try
sam
I know that it is the conventional method. I may just do it, actually correction, I will do that eventually. Old habits die hard. I was a Tech in a repair shop for a lot of years and we never would consider such an idea. We fixed what was wrong.
I guess it's mostly the challenge, also the chance that before knowing the condition where your starting from, you don't know if you injected issues or they were there to start.
However, I'm a bit rusty on my tube theory, which was long ago replaced by solid state & microprocessors circuits.
Steve