[Milsurplus] National R-1230 countermeasures receiver

[J. Forster]

Peter,

You have to be really careful with that approach. Quite a few radios do
not ground the (-) side of B+, as an example.

If you return B- to ground on an R.1155, you will upset the bias badly.

On some radios, you will mess up the DC bias on the output tube and burn
out the Output Transformer. Output transformers are no longer available in
many cases.

Best,

-John

=================


> Ah, I see, not so easy in that unit.  The tube extenders will help, and
> you can
> also guess something from ohming out to the fuseholders as well.  The high
> current ones will be filament connections.
>
>
> On 12/1/2011 8:29 PM, HL wrote:
>> Peter:
>>
>> Many thanks.  I have travelled down that road to some extent.  The power
>> plug is an Amphenol 18-1 with ten pins, A through J.  "H" is probably
>> ground. "A" and "B" are probably 115VAC. "F" and "G" are tied together
>> and not used --unless as a bridge.  The other pins go through fuses to
>> hidden areas in silver module boxes as seen in the photo I took of the
>> bottom interior:
>>
>> http://online.sfsu.edu/~hl/R-1230FLR.html
>>
>> The receiver has 28 tubes and assorted lamps that receive ACV from four
>> taps on the separate power transformer: 6.3V at 0.5A,
>> 18V at 4.0A, 5VAC at 5.0A, and 7.3VAC at 30.0A. Note from my photo that
>> the tube bottoms are hidden in these modules, so if I don't find the
>> schematic,
>> I will have to use Vector 9-pin and 7-pin tube extenders to trace the
>> filament connections of each tube individually to determine how they are
>> grouped.
>>
>> I enjoy this kind of mystery solving, but, alas, this receiver weighs 65
>> pounds.
>>
>> Regards, Hal KK6HY
>>
>> On Dec 1, 2011, at 4:36 PM, Peter Gottlieb wrote:
>>
>>> You should be able to figure out several pretty easily.  Start with
>>> ground, then use an ohmmeter to track back from a 6 volt tube to the
>>> 6.3 VAC pins, same for a 5 volt tube.  Find a plate of some output tube
>>> and that should lead you to B+ input (175 VDC?  or is there a separate
>>> supply run by 115 VAC inside?).  Either way you will know, and
>>> presumably there is some 115 VAC transformer in there from which you
>>> can ohm out those input pins.  That kind of technique should get you
>>> pretty far.
>>>
>>> On 12/1/2011 6:44 PM, HL wrote:
>>>>
>>>> Wanted: manual, schematics for National Radio Company’s 1963
>>>> countermeasures receiver, Models R-1230 (aka: R-1125 or AN/FLR-11 or
>>>> AN/FRA-54). (Manual ID: NAVSHIPS 94581) I think I can deal with its
>>>> 65kHz IF output, and I can provide the needed power voltages, but am
>>>> stymied without a schematic by the power connector with its ten
>>>> unidentified pins (A through J) for 175VDC, 6.3VAC, 18VAC, 5VAC,
>>>> 115VAC, etc. Would love to get this wonderfully built, complex beast
>>>> operating! Any info will be appreciated. Holiday greetings, Hal KK6HY
>>>> _
>>
>>
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>>
>>
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