I have been working on a 1 tube reflex radio from the Radio Broadcast magazine from Nov. 1923 and did get it to work although the sensitivity and selectivity is really poor. In the Jan 1924 magazine there is a modification to add a seconf tube which is what I am now trying. I cannot get any amplification from the second tube and it actually decreases the volume.
I have included the schematic of the Jan 24 version and the revised schematic I did sine I am not using plugs.
Have I missed something here?
Can someone verify or correct the second schematic?

Thanks

The schematic looks fine. The second tube should provide considerable amplification so there may be a construction mistake.

Still have not been able to get the second tube working in this circuit so I connected the speaker lead to the end of the primary in T2 (marked 2 on the schematic). this bypasses the second tube. I can get the radio to play with enough volume but it soon cuts out. If I touch a lead from another B+ tap on my power supply to T2 (2) I can get the radio to work again for a few seconds.
I hooked up my volt meter to the B+ (90V) and B- and see the voltage drops quickly to zero, I lose the sound at about 60 V. Something is draining my B+. It only goes thru the speaker and then to T2 back end of the primary.

If I turn off the filament the voltage holds.

If I disconnect the Plate on the tube the voltage holds.

With the tube out the voltage holds.

I have tried 3 different tubes to rule out a tube.

If I break the connection between A- and B- the radio does not play but the voltage holds.

Any thoughts?

What's providing the A and B bat supply?

What are you using for CR?

Rich

Rich

You have a good point. Use a germanium diode. A silicon diode has too high of a voltage drop and may not give enough signal. Silicon doesn't work at all as a TV video detector.

Are the tube socket contacts, and pins clean, and do they sit firmly in the socket?

The B is supplied by 4 AA batteries and the B is a series of 9 volts batteries.

I am using a germanium diode.

I have taken the socket apart and cleaned and added some tension to the spring contacts.

I assume you mean the A supply is 4 x AA battery in series. What are the tubes you are using?

Rich

Brian

If you are using 4 AA battery to light 01A filaments it's probably not enough. These tubes draw .25 amps each. Tubes will look lit with only 3 volts but emission will be down.

I have also tried 112 tubes

Should I try a 6 volt lamp battery with a rheostat instead?
Would that draw the B+ down?

Brian

Your 112 tubes are worse. They draw more current. If 112A they draw .25 amps just like 01A.

Mesaure voltage at tube pins and see what you read.

Edit: Yes a 6 volt lantern battery would be better. Rheostats, R1 and R2, are shown on the first schematic.

Well, that pretty much takes care of that thought.

The 'big mystery' is the vanishing B+ and nothing discussed so far would account for it. I had wondered if there was something amiss with the power supply but there's not a lot to go wrong with a series string of 9V batteries, which should be able to handle the current drain even if both tubes were at 0 bias, unless one or more of them have gone high resistance.

Just to clarify, you do have an audio transformer driving the second, audio amp, tube, right?

Should be able to measure B+ current? An 01A with negative 4 1/2 volts bias and 90 volts on the plate should only draw 2.5 ma. Wouldn't expect this circuit to be drawing a lot more?

http://frank.pocnet.net/sheets/021/0/00A.pdf

Currently I have bypassed the second tube to trouble shoot the first stage by attaching one lead of the speaker to T2-2.
In the morning I will post the circuit I have with just the one tube.

Yeah, that's what I mean. Normal current shouldn't be a problem at all but if you look at the plate curves even at 0 bias an 01 shouldn't pull more than 7mA and I don't think they could pull enough to kill B+ even if the filaments were wired backwards.

That means there's either something wrong with the batteries, there's a defective component somewhere, it isn't wired as we think, or the measurement isn’t valid for some reason.

How could the filaments be wired backwards?