For my Pilot Radio Model 274T it´s a AC/DC circuit, the radio is working but with some components changed...like a silicon rectifier for the supply

:For my Pilot Radio Model 274T it´s a AC/DC circuit, the radio is working but with some components changed...like a silicon rectifier for the supply
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How about some info on that unit as to its vintage and its full tube lineup as well as the functions..AM...FM...power amp..that it has.
Hope, that the PS circuitry was changed to compensate for the higher B+ developed with a S/S rectifier !
73's de Edd

The tube line-up is: 6K7, 6K8, 6K7GT, 6Q7GT, 25L6, 6E5 and a 25Z5 with only the filament conected to the circuit (AM with 3 bands, Broadcast and two Short Wave). The radio is made in USA, maybe for export only (I´m from Argentina). I was looking for the schematics because some components were replaced with modern ones, like caps and the silicon rectifier.
Many thanks for your help!

Certainly looks like that puppy must date after 1934 with the introduction of that 6A7 that it uses and the getting away fron some of the older tubes used for its AF output tube with the use of the newer 25L6 for its output...BUT...not the equal upgrade of a 6SQ7 feeding it, but instead the retention of the older capped 6Q7. So with that mix looks like it might end up ---->1934 until, at, or just under 1937.
Soooo... hows about trying on the G180 series for size and see if it fits:
BTW...hope you're adept with ESL on the above.....en que, no pueda a usar su Espanol....pero, no problema con las schematicas!

http://www.nostalgiaair.org/PagesByModel/466/M0014466.pdf
http://www.nostalgiaair.org/PagesByModel/467/M0014467.pdf

73's de Edd

German, buenos noches.

Is your utility voltage there 120V or 220V? I'm wondering how the heater string adds up to the line voltage? Is there a dropping resistor in there somewhere?

The original rectifier (25Z5) is a full-wave rectifier. It was replaced with two silicon diodes? That's fine, but it eliminates 25V from the heater string.

:The tube line-up is: 6K7, 6K8, 6K7GT, 6Q7GT, 25L6, 6E5 and a 25Z5 with only the filament conected to the circuit (AM with 3 bands, Broadcast and two Short Wave). The radio is made in USA, maybe for export only (I´m from Argentina). I was looking for the schematics because some components were replaced with modern ones, like caps and the silicon rectifier.

:Many thanks for your help!
:

:The original rectifier (25Z5) is a full-wave rectifier. It was replaced with two silicon diodes? That's fine, but it eliminates 25V from the heater string.

"The original rectifier (25Z5) is a full-wave rectifier. It was replaced with two silicon diodes?"

I hope not since the sil diodes are instant power and the
wait for the power output and its companions to warm up are going to leave the PS unloaded with quite a peak voltage jolt going to the PS filters initially. With the
orig rect being tube the power onset would be gradual, just like its companion tube warm up periods.

IF still in Argentina trying to use that unit, and not presently being stateside with the unit.
I certainly think that he has 220VAC power, to be acquired with the most common round plug pins being for its AC power connector.
If a conversion of a US 117V AC/DC unit was done, to be used with that 220VAC supply, the simplest manner possibly might have been the utilization of a hefty AC line series diode, polarity oriented so that only the + nodes are passed. That, possibly along with a series current limiting resistor.
Sooo that might be what is being referred to.

73's de Edd

::The original rectifier (25Z5) is a full-wave rectifier. It was replaced with two silicon diodes? That's fine, but it eliminates 25V from the heater string.
:
:"The original rectifier (25Z5) is a full-wave rectifier. It was replaced with two silicon diodes?"
:
:I hope not since the sil diodes are instant power and the
:wait for the power output and its companions to warm up are going to leave the PS unloaded with quite a peak voltage jolt going to the PS filters initially. With the
:orig rect being tube the power onset would be gradual, just like its companion tube warm up periods.
:
:IF still in Argentina trying to use that unit, and not presently being stateside with the unit.
:I certainly think that he has 220VAC power, to be acquired with the most common round plug pins being for its AC power connector.
:If a conversion of a US 117V AC/DC unit was done, to be used with that 220VAC supply, the simplest manner possibly might have been the utilization of a hefty AC line series diode, polarity oriented so that only the + nodes are passed. That, possibly along with a series current limiting resistor.
:Sooo that might be what is being referred to.
:
:73's de Edd

Hi guys!!!! I was working in the radio and found that there was no sense in the use of the silicon diode, because the 25Z5 tested 100%!!!! The G-184 is quite similar to my radio and I realized that the use of the 25Z5 is for half-wave rectification but with the two diodes in parallel so I conected that way and worked fine, there a resistor for the voltage drop installed in the speaker chassis. The voltage of the filaments are apropiated for each ones of the tubes so I think that resistor is a factory adpatation for the 220AC in my country or maybe some technician do it...
There is only one thing that I was wondering, in place of the 6A8 in the radio were a 6K8 (¿?)
Many thanks for your great help!!!!

The 6K8 and 6A8 came on the scene in ~ 1935. The 6A8 using the dual construction of the units and the
introduction of the forerunner of the later 6SA7 and 12BE6 pentagrid converter tubes, with that initial
6K8 design. The elements all being within one unitized framework and within one electron flow path.
The former separate plate function now being fulfilled by a grid also being used as a plate.

Ref:
http://www.nj7p.org/Tube4.php?tube=6K8
http://www.nj7p.org/Tube4.php?tube=6A8

73's de Edd