79 TA extreme heat issue
 

QUESTION?

We are re wiring our dash components. We got the AM radio/8track player working but..... the circuit board gets extremely hot. Any ideas?

In our TA.

What speakers are you using? You must use original type 10 ohm speakers with the old original factory radios. I've read that using modern 4 ohm speakers will heat up and damage an original radio.

Ohhh geeeze I’m not sure I think they say midland on them they were in the car when I bought it, I will pass this info on to Mike and have him check that.


Thanks! Having a few things to check I’m sure we’ll get it. Hopefully!

Sorry I meant Pioneer speakers in the back, 10 ohm in the front. Midland is the CB.

pioneer aftermarket car speakers are definitely 4ohm. you can add a resistor of the right value to the positive wire to increase them to 8 or 10ohm & get better sounds since they are probably 2 or 3 way speakers vs the single cone stock speakers that sound like CRAP compared. or find some new or used OEM style 10ohm speakers or look at some of the retro sound stuff that may have a 2 way with 10ohms.

I think we’re just going to buy new speakers instead of re building the ones in the car. I looked it up and looks like Best Buy might have what we need. I wish radio shack was still in business that was always my go to place for stuff like this. Not really sure who to go to to get what we need.

unless best buy carries OEM style 10ohm speakers... you cant use the normal aftermarket brands of car audio, they are all 4ohm & not compatible with the factory radios in these cars... yes they will "work" but will overheat like you found & eventually damage the radios amp....or you need to add a resistor in the positive speaker wire of each speaker to increase the ohm from 4 to 8-10.

check ames or other places like classic for the right ohm speakers for these stock radios. most carry this brand called retro sound or others that are the right ohm rating for factory radios.

https://www.retromanufacturing.com/

As 78w72 said, I doubt you'll find a 10 ohm speaker at Best Buy. They're obsolete speakers. But another place to find 10 ohm speakers is www.turnswitch.com .

S&M Electrotech in Minnesota has replacement speakers that wlll work with vintage Delco radios: http://www.turnswitch.com/speakers.htm

They discuss the issue with modern 4 ohm speakers on their website:

Note: Many replacement speakers now sold by the discount stores, auto parts stores and mail order restoration parts houses are labeled as "4 to 8 ohm compatible" and are in fact 4 ohm speakers. These speakers can damage the older transistor radios. 4 ohm speakers will measure around 3.2 ohms with a DC ohmmeter. An 8 - 10 ohm speaker will measure around 7.4 ohms with a DC ohmmeter. The DC resistance is the critical number for the Delco radios as the output transistor is in series with the speaker. A properly operating Delco radio should have 1.5 volts DC across the speaker voice coil. A 4 ohm speaker will draw twice the current of an 8 ohm and cause the amplifier transistor (the half dollar size device mounted to the black finned heat sink on the back of a Delco radio) to run very hot.

Once you listen to the 8-track you may decide to have a separate radio instead and speakers that suit.

I did hear it, and I had the same single unit set up in my 75 TA and the sound was fine.

Thanks everyone, I found the correct 10 OHM oval rear deck speakers at Parts Place on e bay. I still need a 4”X6” rectangle 10 OHM for in dash.

Found out from a local car stereo guy he could rebuild my stock radio/8 track unit to accept a 4 OHM set up.

So we have choices.