Late 1920s Eveready Model 1 TRF Set need info

[vortalexfan]

Originally Posted by Kevin Kuehn

Forgot to mention..I honestly can't think of any good reason you'll need film caps rated for 630v for bypass in this radio. Folks use them simply because they have them on hand and the rational better safe than sorry. I'll be surprised if the B+ swings above 250v for more than a couple seconds on power up. It should settle out around 170v at the second filter cap. The 71 output tubes had a 180v max design value, which I doubt they exceeded.

OK, so maybe a 250vdc film caps for the bypass caps would be acceptable then? Those would be much smaller and would probably fit into the cans better than the 630vdc ones.

[Kevin Kuehn]

Originally Posted by vortalexfan

OK, so maybe a 250vdc film caps for the bypass caps would be acceptable then? Those would be much smaller and would probably fit into the cans better than the 630vdc ones.

Probably. But once you get that power supply operational and measure we'll know more precisely.

[vortalexfan]

Originally Posted by Kevin Kuehn

Probably. But once you get that power supply operational and measure we'll know more precisely.

Ok. I was able to get my hands on an old desktop PC power supply to get the wires off of for the radio, and it didn't cost me a dime.

[vortalexfan]

Well I got the power supply umbilical rewired with new wire that I nabbed out of an old desktop computer power supply, and I was able to use the same color wires as the original wires too.

Now all I have left to do is replace the dry-rotted wiring in the power supply itself and that is only a couple sets of wire going to the plugin for the power supply umbilical cable for the tuner section of the radio and then put some color coded shrink wrap on the dry rotted wiring that's not replaceable (the wires coming out of the power transformer for the 80 Rectifier Tube Filiments) and then stick a power cord onto the radio and also replace the wiring for the dial lamp socket, and I'll be ready to do a test run of the radio once I get the replacement loudspeaker in once I get it ordered Friday.

[vortalexfan]

Just a little update, I have nearly finished rewiring the radio and I will be getting paid tomorrow so I will be getting the speaker and some resistors
and the two filter caps tomorrow to finish rewiring this radio, and get a cord wired up to this thing.

[vortalexfan]

OK so a little update:

I finished rewiring the power supply on this radio and got a temporary cord wired up to this radio and powered it up without the rectifier tube in circuit and the unit was drawing a little over an amp once it settled down.

Which that sounds about right (even though I don't have the original cover from this radio that had the power consumption label on it) and nothing smoked and nothing sparked or arced and the pilot lamp worked as it should.

I think we're off to a good start with this thing (of course I didn't have a speaker hooked up to this thing or the output tubes in either so that might affect the current draw as well.

I wasn't able to monitor the B+ voltage because I'm not sure where to hook up my DMM to monitor that.

So it seems we might have a winner here!

[Electronic M]

With the rectifier out there's no B+ to measure. There is the high voltage winding on the power transformer that supplies AC to the rectifier that you could measure by sticking your DMM leads in the skinny pin holes on the 80 rectifier socket and fishing around for the contacts.

[vortalexfan]

Originally Posted by Electronic M

With the rectifier out there's no B+ to measure. There is the high voltage winding on the power transformer that supplies AC to the rectifier that you could measure by sticking your DMM leads in the skinny pin holes on the 80 rectifier socket and fishing around for the contacts.

High Voltage is working as it should it seems. I measured the plate voltage for the 80 Rectifier Tube socket (the small pins) as you suggested and there was a little over 400V AC on the plates of the Rectifier Tube socket which sounds about right.

[vortalexfan]

OK so I checked the B+ voltage with the rectifier tube in (just the rectifier tube in) and I got around 320V DC and with the 2 71A output tubes in it dropped to 160V DC so I think the B+ voltage is working as it should, which I think the voltage will drop down to around the 90V DC ballpark range specified on the schematic once the tuner section is hooked back into the circuit (that will add the rest of the 5 tubes in the radio into the circuit).

So it seems like besides having to install the modern plate resistor into the circuit in place of the old fuse style one (by soldering it onto the connector leads under the chassis for the plate resistor socket above) I think this radio will be ready to go once I get the replacement speaker in.

[vortalexfan]

OK so an update:

I installed the 47K Ohm resistor for the plate resistor, and hooked the tuner portion of the radio up to the power supply and installed the tubes and powered it on and monitored the B+ voltage and it was nearly spot on at around 89.7 VDC, so it looks like everything is working as it should!

Now all I need to do is wait for the replacement speaker to come so I can repair the speaker for this thing and so I can test the radio out and see if it can pick any stations up!

[Titan1a]

Bravo!

[vortalexfan]

Originally Posted by Titan1a

Bravo!

Thanks! I figured this thing wasn't going to be too hard to get going seeing as there isn't much to these old TRF sets, mainly all I had to do was replace a bunch of old crumbling wiring which was pretty easy because all I had to do was steal the wiring out of an old junk desktop computer power supply and use that to replace the old crumbling wiring in the radio and I was pretty much set to go!

[Titan1a]

I hope all your work bears fruit. I've always loved old radios. I look forward to hearing that your radio works. I still have one radio project left.

[vortalexfan]

Originally Posted by Titan1a

I hope all your work bears fruit. I've always loved old radios. I look forward to hearing that your radio works. I still have one radio project left.

Yes, me too. I also have a GE L-640 and a Philco 116B up next to finish up and then I have someone on another forum I'm a part of that's sending me a couple more radios to monkey with, and then someone else from that same forum has an eye out for me for some radio parts that came from someone that was part of the Schenactedy Radio Club that recently passed away. So I'll be quite busy for a while.

[Electronic M]

When you say new speaker it makes me wonder; have you made sure the speaker impedance is correct in your replacement. 20's speakers were usually some where in the 1k-10k impedance range and new ones are usually 3-8 ohms (which won't sub for a high impedance speaker without a matching transformer).