Rehabing 42-854 AM/SW Portable - Printable Version
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+--- Thread: Rehabing 42-854 AM/SW Portable (/showthread.php?tid=14647)
RE: Rehabing 42-854 AM/SW Portable - morzh - 05-27-2016
I am too lazy to trace the whole thing but am I correct to understand that the heaters use rectified voltage for heaters.....yeah I think I am as they are directly heated and use the filaments as cathodes so they are referenced to the common.....this is just....inconvenient.
Kirk! Do not get me any of these to restore.
RE: Rehabing 42-854 AM/SW Portable - Radioroslyn - 05-27-2016
Check post 8 !
The filament wanders back and forth that's why I drew it out so I could follow it with out getting ein Kopfschmerzen . My Russian is pretty good ! Yes the dc for the filament is derived from the B+ though a divider, 1800 ohms in series and 680 ohms in parallel with the voltage. This drops the 120vdc or so down to 9vdc. A 200mf (sorry don't know how many nf that is) is used to decouple the 9v from the hv.There are 6 1.5v tubes connected in series to equal 9v. String starts at the 680 ohm resistor and ends at the osc coil as the - return (a little odd).
Kirk! Do not get me any of these to restore.
Between Sam and I we have 3 of them!!!!
Terry
RE: Rehabing 42-854 AM/SW Portable - morzh - 05-27-2016
Feeling a little masochistic, eh? Gluttons for punishment, aren't we?
Kirk! You need to stand behind and keep lashing them with a whip while they are fixing those
They love pain!
RE: Rehabing 42-854 AM/SW Portable - sam - 05-27-2016
RE: Rehabing 42-854 AM/SW Portable - Radioroslyn - 05-27-2016
Hey Sam,
You know he turns to putty when I say the magic word HAMBURGER!
Terry
RE: Rehabing 42-854 AM/SW Portable - morzh - 05-27-2016
Yeah but only when the hamburger is within reach. I need to see the hamburger, smell the hamburger, taste the hamburger....a mere mentioning the hamburger does not affect me much
RE: Rehabing 42-854 AM/SW Portable - Radioroslyn - 05-27-2016
Nutz!!! Foiled again.
Terry
RE: Rehabing 42-854 AM/SW Portable - sam - 05-27-2016
Hmm terry
Try holding a garlic burger and a Guinness
RE: Rehabing 42-854 AM/SW Portable - morzh - 05-27-2016
Moldy Guinness trumps burgers!
RE: Rehabing 42-854 AM/SW Portable - Radioroslyn - 05-30-2016
Well for all you kats and kittens that are waiting with baited breath to hear what is happening with the 42-854 the resistor for the filament voltage divider came in the mail the other day. Had a little surprise as I thought I was get just 1 but got 3. So this afternoon I removed the old one and install the new. Thought I'd take a few pics before I power it up and it burst into flames! Also replaced a few pieces of rubber wire and broke the socket for the 1LB4. I think I can repair it, the center part pulled up though the socket and the cover popped off. Off to put the tube back and add some power/watch for smoke!
Terry
RE: Rehabing 42-854 AM/SW Portable - sam - 05-30-2016
really your just gona let us hang here
RE: Rehabing 42-854 AM/SW Portable - Radioroslyn - 05-31-2016
After I installed #56 still no joy! This getting a little ridiculous!!! Measured the current though the string and it was a little like 60ma. Hmmm. I replaced the 117Z6 w/a silicon diode which increased the voltage a little but didn't what I was hoping for. Went from 8.0v to 8.5v. Then I remembered that it did work before I replaced the caps in the IF and Mixer stages. So by looking at my hand drawn filament diagram (looking at the schematic will give you a headache) I zeroed in on #51 and that thing was shorted. It knocked 1.5v down to .5v. HA HA I found it!!!!!!!!!!. So now on to more troubleshooting now that all the tubes have the correct filament voltage. There is still some amiss as when I touch the ant post I got nothing.
Terry
RE: Rehabing 42-854 AM/SW Portable - morzh - 05-31-2016
You'll get there. The harder the you know what the sweeter the you know what is
RE: Rehabing 42-854 AM/SW Portable - klondike98 - 05-31-2016
Great thread Terry. I like following your troubleshooting. Wish I could offer more help.
RE: Rehabing 42-854 AM/SW Portable - Radioroslyn - 05-31-2016
This thing wants to fight me tooth and nail. Both audio stages are working but won't pass a rf signal. If I connect the gnd side of the generator to the chassis it modulates everything with 60cy hum. So I rigged up a gimmick cap ( some twisted hookup wire) to feed in a IF signal. Fed the 2nd IF amp tube plate w/ 455 signal and got a little output from the spkr. Tried the grid and get zip. Plate and sg voltages look ok so I guess it's onward to the 1500 ohm #50 filament return resistor. Come to think of it I should double check the filament voltage on the tube too.
Terry