[GregP]

I want to bench test a couple of radios that I have (69 GTO am/fm & 77 Trans Am am/fm).
Never done this before but I assume I hook up a speaker, hook up power wire to pos of battery, (also hook up wire for light to pos). Is this correct? Do I need to ground the radio or is there even a ground wire?
thanks,
Greg

[jmt455]

Yes, the radio needs to be grounded.

The connector on the back of the 69 radio will have 3 terminals. (I don't remember what the '77 connector looks like; it might be the same).

One is for +12V, one for the front speaker (+) and one for ground; they are labeled on the case, adjacent to the terminals.

The speaker (-) and the radio ground go to the battery's negative (ground) terminal.

When in the vehicle, the lamp voltage feed comes from the headlight interior rheostat. You can test it by applying 12V to the lamp holder's single wire. The lamp housing must be installed to the radio case because it is grounded through the case.

ALWAYS use a 10 ohm speaker for testing these Delco radios. If you use a 4 ohm aftermarket speaker, you can damage the radio.

Don't forget the antenna!

[GregP]

Originally Posted by jmt455

Yes, the radio needs to be grounded.

The connector on the back of the 69 radio will have 3 terminals. (I don't remember what the '77 connector looks like; it might be the same).

One is for +12V, one for the front speaker (+) and one for ground; they are labeled on the case, adjacent to the terminals.

The speaker (-) and the radio ground go to the battery's negative (ground) terminal.

When in the vehicle, the lamp voltage feed comes from the headlight interior rheostat. You can test it by applying 12V to the lamp holder's single wire. The lamp housing must be installed to the radio case because it is grounded through the case.

ALWAYS use a 10 ohm speaker for testing these Delco radios. If you use a 4 ohm aftermarket speaker, you can damage the radio.

Don't forget the antenna!

Thanks for the detailed information! Are all speakers marked with the ohm's? I think I have an old set of Jenson 6x9 speakers somewhere from the late 70's I was going to test with.
Greg

[jmt455]

I've never seen a speaker that didn't have the nominal resistance marked somewhere.

Check the magnet holder and the label; the resistance should be there somewhere.

Most automotive/marine aftermarket speakers are 4 ohm.

[j69shep]

You can test that radio with just about any speaker although long term you will need 8-10 ohms as that is the load the amp is designed to drive. For just testing your Jensen will work just fine. Common ground on those. If those Jansens are old ones, they are likely 8 ohm anyway. Good luck.