Old tube receiver connection symbols?

[Poultrygeist]

I recently acquired a Martel/Rotel FAX-150c tube receiver made in the 1960's. Stamped on the rear chassis beneath the speaker screw connections are the following:

right 0 8 0 8 left

So is the 0 the positive or is the 8 the positive?

Under the FM/AM group the following is stamped on the chassis beneath the screw connections:

FM G AM

Would I use the G ( only ground I see ) to connect the phono ground wire?

The phono inputs are marked MAG and X-TAL so the MAG would refer to a magnetic cart but what is X-TAL?

[markw]

I recently acquired a Martel/Rotel FAX-150c tube receiver made in the 1960's. Stamped on the rear chassis beneath the speaker screw connections are the following:

right 0 8 0 8 left

So is the 0 the positive or is the 8 the positive?It doesn't matter which is which as long as you are consistent. Logically, I would use 8 as the positive.


Under the FM/AM group the following is stamped on the chassis beneath the screw connections:

FM G AM

Would I use the G ( only ground I see ) to connect the phono ground wire?No, that's for antenna connections. For a phono ground use a screw on the metal chassis. Many receivers have a knurled knob for this purpose but any screw on the chassis will do in a pinch.

It sounds like the receiver has only 300 ohm twin lead connections for FM. The antenna would be connected to the FM & G connections. A long-wire AM antenna would go to the other.


The phono inputs are marked MAG and X-TAL so the MAG would refer to a magnetic cart but what is X-TAL?Correct. The MAG input is used for a magnetic cartridge. XTAL refers to old, obsolete high-output crystal (or ceramic) cartridges that aren't used any more. That input lacks the gain and RIAA curve required for magnetic cartridges.

[Dual-500]

"0" will be the common which may or may not be floating from chassis ground. As such, "8" will be the hot or "+" and should be in phase with the input signal.