daven model e radio scored

[Bob E.]

Originally Posted by wa2ise

The 1st generation of radio technology was probably similar to the 1st generation of automobiles. Many small makers, eventually narrowed down to just several major companies. Which probably means that you may not be able to find a schematic. But odds are Daven followed a conventional design, likely a reference design created by the tube companies. Here, a "reference design" was a design created by the tube engineers to demonstrate circuits that would make the tubes work well, to help their customers like Daven get the most out of the tubes. The tube manufacturer wants happy customers.

It has already been pointed out that this is not a Daven, I just wanted to add that, to complicate WA2ISE's post, Daven made their own tubes, with their own numbering system!

--Bob

[stusnyder]

I recieved a "generic" 3 ohm reostat from playthings of the past on friday. I contacted them and he said he had none with a switch on the rear. So today I gutted it. After some drilling and soldering, I have a control that will work like the original I hope Reese you were right about the switch, it does switch on the B+ power according to the diagram.
Check out the pics. the wire in the center is the feed.

[Reece]

Hooray! However, the switch controls "A" power, right?

[polyphase]

If the rheostat has been vandalized on this set, I would be concerned with the audio transformers as well (there are 3 of them).
Are they present? are they correct? Do they have continuity?
Audio transformers, at least in my experience, have been the major issue in getting these sets working.

[wa2ise]

Originally Posted by polyphase

Audio transformers, at least in my experience, have been the major issue in getting these sets working.

Heard it said that, of all things, ringer modules from old fashioned Ma Bell telephones can be substituted for these transformers. Seems that the ringer has a pair of windings, which can be repurposed to become a primary and a secondary. And possibly the bobbin holding the windings can be inserted into the old transformer laminations, if you're lucky.

[stusnyder]

Yea the transformers are there. Reese, according to the dia. the switch does switch the power to the tubes. I did'nt look real close to the dia. yet. I will check all wiring when I install the switch.

[stusnyder]

well put the rheostat in, powered it up. 4 tubes are no good. At least 1 of the transformers are working, have not checked the other 2. Somebody before I owned it had their fingers in it. I'm trying to find another diagram on it....the one I got sucks

[leadlike]

Clean up the pins on those tubes and resolder the pins, as it's rare to find so many bad 01As in a set like that. That is, unless the previous owner hooked up B+ across the filament power by accident....

[stusnyder]

I worked on it abit tonight. Transformers appear good. Went over those 4 tubes, they are def. blown So I have to get more tubes. Schematic is very vague...anyone happen to have a better one?

[stusnyder]

Got new tubes yesterday. Found one wire missing, thats why the rear row of tubes were not lit. Hooked up a old silvertone speaker from that era and was greeted with static. Could not pull any stations in and I have it hooked up to a outside longwire. There are 2 ancient caps in it, just wondering if I should try replacing them

[leadlike]

You can try replacing them. Most of those radios took 1 UF or 2 UF caps, values are not too critical. Did you check to make sure your grid leak resistor was good?

[stusnyder]

Caps are 00025 uf and 0025 uf. The grid leak resistor appears ok, not sure how to check it? What kind kind of voltages should I have on the 2 thin pins of the tubes. Again this schematic is not very detailed. The volume control does work and the brightness of the tubes increase and decrease via the volume control. I was just wondering if this is standard AM band or something else?

[Reece]

You can do a few checks before changing any parts. Grid leak is supposed to be 3 megohms. Anything within a few megs at this point should work for starters. Check with your ohmmeter the caps and as long as they aren't shorted the set should work somewhat.

Touch your finger or a screwdriver with your finger on it to the grid of the first audio tube: should get scratches and hum from the speaker if first and second audio tubes and second audio transformer are good.

If that works, take your antenna wire loose and touch it to the stator of the tuning condensor that goes to the detector tube. If your detector and audio stages are OK should hear a station by tuning around, maybe not too loud. If no noise, suspect the first audio transformer.

Move the antenna wire back to the next stator before the detector and test, and finally to the first one. If you lose signal somewhere look for a problem in that stage.

Problems could be open coils. Can just check each coil for continuity with your ohmmeter. Ditto each audio transformer winding. Not much to go wrong in these sets.

[stusnyder]

how's it goin reese,
I worked on it this morning, first of all the grid leak is rated 3 m-ohm. I got nothing when I used my dvm, but also have problems with that meter on anythng above 1 m-ohm.
Next went to the first audio tube, used a screwdriver, and got scratching out of the speaker. Next I checked voltages on the first and 2nd rf tubes (small dia pins) and got 91.4 v on each tube.
I then went to the first audio tube, checked the small dia pins for voltage, got 43.3 v and alot of noise out the speaker. Measured the 2nd and 3rd and got 85.2 and 82.8. When I got to the last one (detector) I got no volts. The transformer near the detector had no volts .The .002 mfd cap tested shorted, so replaced it with exact value orange dip. Then I checked the transformer and now I have voltage in and out of it. Also now checked the small dia pins on detector tube and got 124 volts. Tried the antenna lead thing and got what sounds like it's trying to tune in to stations, across all 3 stators. What I did take notice of, is there is some kind of wire wound shunt attached to one of the coils, and a clamp over it. I can see somebody was messing with it, it;s one of those things if you loosen the clamp, you can slide it to different posistions.
Also I'm running all 201a tubes in it. According to the manual, it should work satifactory with all 201a in all sockets. A special detector tube can be used in socket marked detector. Also if louder volume is needed you can use a wx112 or cx113 in the 3af socket. C power would have to be hooked up to this configuration.
What to try next?

[Reece]

According to the schematic there should be around 45 volts going into the detector audio transformer primary so check your wiring; should not be getting 124V at the detector plate. Check between plate terminal and B-.

Try bridging the grid leak with a high value resistor, anything from 2 meg to 5 meg should be OK. Just tack it in temporarily for now. Old grid leak may be open.

Did you check all of the RF coils for continuity with the ohmmeter?

Does the "shunt" look like a wire wound resistor with slider? Don't see anything like that on the diagram. Where is it exactly per the schematic?