The PHILCO Phorum
marconi 157 - Printable Version

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RE: marconi 157 - morzh - 11-23-2016

Well...I don't remember if you answered Russ' question if you have checked all resistors.
Then, are there any longer than necessary wires that were installed if any?
Also, any of them are rerouted or bent in a shape different from before?
Any wires that used to rung along chassis that are removed from it?

Last, I am surprised I am not seeing any decoupling caps other than the electrolytics.

And, you replaced ALL caps? (There are three electrolytics ).

RE: marconi 157 - the picker - 11-23-2016

I did not think about the resistor on tube 6u5 could some one tell me the value because I can not see it on the schematic thanks I will follow up on the other questions after I get this straight

RE: marconi 157 - morzh - 11-23-2016

Do you mean R14? It is 1M. Typical value for any eye tube.
But it is not likely to cause your trouble.

Still....if you have not checked the resistors you should.

RE: marconi 157 - the picker - 11-23-2016

I thought it was r-14 and 1 m but it is shorted out so I jumped one in to try but nothing changed but now I have another question should I get continuity from one of the four wires from the 6u5 tube with tube out to another wire because the black is ground so I should with all three of the others but not with one of the other wires with another correct or not thanks

RE: marconi 157 - morzh - 11-23-2016

I'm not sure what you asked but all pins are separate. One gnd, one B+, one B+ via 1M resistor and one is AVC signal through the battery.

RE: marconi 157 - the picker - 11-23-2016

what I am asking is if you check continuity from lets say b plus and the avc signal pins on the 6u5 tube socket should there be continuity or any other combination

RE: marconi 157 - morzh - 11-23-2016

I am not sure how to answer, the sch pretty much says it all by showing what 6U5 pin connects to what. Like cathode is Gnd, target is B+. There should be 1M between the target and plate. The grid is connected ia battery so we cannot talk continuity.

In any case, your motor boating is not likely caused by the 6U5.

RE: marconi 157 - the picker - 11-23-2016

so that being said if the 6u5 tube is the problem what would be a plan to trouble shoot thanks

RE: marconi 157 - morzh - 11-23-2016

6U5, I think, is not. Actually I think pulling it and leaving the socket empty would not stop the radio from working. But if it were, replacing it would be a start.
If you have any pin-compatible tube like 6E5, thoigh not quite the same, it would work.

RE: marconi 157 - the picker - 11-23-2016

i might have another tube but if i do not have one and i leave it out and the radio should still work then if i still got the motor boating problem how do i proceed to trouble shoot

RE: marconi 157 - morzh - 11-23-2016

Poke around 6R7 tube.
See if the audio works: touch 6R7 grid, see if it hums.

RE: marconi 157 - Arran - 11-24-2016

 Just for the record, this set takes a 6Q7 not a 6R7, electrically they are somewhat different but even so that should not be causing a motorboating problem as the pinout is the same.
  Just a thought, but is the pushbutton for dial tuning pressed in? Unlike most sets it's pushbutton number six rather then pushbutton number one. Are all of the tubes in the correct sockets? Are any of the tubes not of the type specified on the schematic? The eye tube and the motorboating issue are unrelated, as Mike said you can pull the 6U5 out and the set will work fine.
   If it is not one of these basic things then it may be something like a poor solder joint, or one end of a capacitor is connected to the wrong terminal. C19 and C21 are two capacitors that should be checked.
Regards
Arran

RE: marconi 157 - morzh - 11-24-2016

I am still surprised at the absence of decoupling caps. Though this obviously worked out for them....

RE: marconi 157 - the picker - 11-24-2016

(11-24-2016, 06:28 AM)Arran Wrote:   Just for the record, this set takes a 6Q7 not a 6R7, electrically they are somewhat different but even so that should not be causing a motorboating problem as the pinout is the same.
  Just a thought, but is the pushbutton for dial tuning pressed in? Unlike most sets it's pushbutton number six rather then pushbutton number one. Are all of the tubes in the correct sockets? Are any of the tubes not of the type specified on the schematic? The eye tube and the motorboating issue are unrelated, as Mike said you can pull the 6U5 out and the set will work fine.
   If it is not one of these basic things then it may be something like a poor solder joint, or one end of a capacitor is connected to the wrong terminal. C19 and C21 are two capacitors that should be checked.
Regards
Arran
since schematic reading I have problems with what are the connection points of cap 19 and 21 to make sure I give you guys the correct information back thanks

RE: marconi 157 - morzh - 11-24-2016

C19 is from the minus of the battery to the GND, C21....no good way to describe but one end is at the top lug of the volume pot (if you face the rear of the pot and the lugs look down then the leftmost lug, if the lugs look up, then it is the right one) , and the other C21 pin goes between the two resistors on the sch.