Messages

46

Mild Modifications / Re: Hub Centric Adapters

« on: June 14, 2015, 04:09:59 AM »

We'll hope for OP to come back here and give a definitive answer, but the way I'm reading his last post is that he had the adapters made after extensive balancing efforts were tried without adapters, but to no avail.
Adapters were then fitted which fixed the vibration problem.

47

General Discussion / Re: 68 - 69 am/fm stereo question

« on: June 13, 2015, 12:56:32 PM »

What was the first chevy to have am/fm stereo as a single unit receiver i.e. all in one, no external bits?

Have found a part answer to this question. Seems that 73 Camaros had am/fm with integrated stereo and fader - 4 speaker connections on the rear.

48

Decoding/Numbers / Re: 68 radio am am/fm date code?

« on: June 12, 2015, 05:37:06 PM »

Ah, from nastyz, if it still has the original power transistor, then there looks to be a date code on it in the form of yyww e.g. 6745 = 45th week of 1967

49

Restoration / Re: ko-lek-tor, what is going on with your car?

« on: June 12, 2015, 03:45:28 PM »

Great thread ko-lek-tor!
I don't have friends anymore, couldn't stand the same question over and over - 'are we there yet-are we there yet....' and me coming up with some lame response over and over 
Between me and the car, I'm not sure which of us is in the greater suspended animation!!

But no, I jest a little, my project is moving ahead, in greater leaps and bounds lately, but so many research questions I keep coming up with and it's back to the computer to give google another hiding!

50

Originality / Re: 124379N605752

« on: June 12, 2015, 02:43:32 PM »

I agree with the possibilty of "listing errors" being "fee ducking". Seen it happen more than a few times -

Regards,
Steve

Some use ebay to simply test market place value

51

Decoding/Numbers / 68 radio am am/fm date code?

« on: June 12, 2015, 02:34:07 PM »

I have a question mark in the title as I'm not certain that any of the numbers on the radio label have anything to do with a date code.
For 68 am/fm 7303241 I have seen:
41FPK - 6070
41FPK - 7166
41FPK - 01484

Also, they are listed on the label as the serial number, which is actually the application/type code [41fpk] and some numerals.
I think the last 4 - 5 numbers are no more than an incrementing serial number.
Thoughts appreciated.

52

General Discussion / Re: 68 - 69 am/fm stereo question

« on: June 11, 2015, 04:27:39 PM »

Yes, I initially thought that the diag. was showing the multiplexer with integrated controls - under dash style = no console, simply on the basis that it says  "Remote control head - Part of 7305221".
However, the diag. clearly shows a harness connecting from the multiplexer to the console mounted controls and has the word console in brackets at the top.
Was getting late at night here - 'what was I thinking'! lol

I think your right that the one you pictured is a later revision. Maybe the delco designers decided that a single cable with power output audio [speaker level] running through it was too much of a crosstalk problem, so split the single harness into two harnesses, or perhaps they decided that two harnesses with a 6 pin plug on the ends was easier to manufacture than a single harness with an 11 pin plug on it.

Also just as a side note, when I use the word 'composite' I'm not particularly referring to the type of harness [multicore] but rather the signal coming from the radio to the multiplexer. Only one shielded single core cable is needed to carry the composite L-R signal from the radio to the multiplexer.
The other wires in that harness [radio to multiplexer] would be for carrying one channel of the decoded/volumed/toned/L-R balanced signal back to the power amp in the radio and + - power.
The other channel is fed to the power amp in the multiplexer.
Then those power outputs would have to be fed back to the controls for front/rear fading, at least this is how I'm understanding it so far.

So to summarize U69 [am/fm] and U79 [am/fm stereo] for 68:

U69 am/fm
Radio pn 7303241 - could be ordered with aux. rear speaker U80, but not rear antenna U73.
U80 also includes the fitting of a front/rear fader to the tuning shaft.

U79 am/fm stereo
Radio pn 7303421
Stereo multiplexer with integrated controls pn 7304621 [for vehicles without D55 console]
Stereo multiplexer with separate console mounted controls pn 7315221 [for vehicles with D55 console] [two versions of wiring harness have been noted]
4 speaker system [2 on rear parcel tray, 2 in front kick panels]

edit: Ah, I see now that the 7304621 arrangement is drawn at the bottom of the other page in your pics

53

General Discussion / Re: 68 - 69 am/fm stereo question

« on: June 10, 2015, 04:48:20 PM »

Mark, your pic is unique, all the pics I have stored of 68 U79  console controls show the speaker connections coming from the controls box.
The 68 AIM is not totally clear, but does seem to show this - U79 A3 item 4.
The 69 AIM looks another minefield with regard U79 and tape player, will navigate that later! 

54

General Discussion / Re: 68 - 69 am/fm stereo question

« on: June 10, 2015, 03:02:36 PM »

Had a realization about a couple of things.
For 68 at least, U69 am/fm and U79 am/fm stereo is still the same radio 7303241. U79 just had the extra bits to go with the mpx decoder [multiplexer] 7305221 w/D55 console [console mounted controls] or 7304621 w/o D55 console [mpx and controls in one unit under dash]

So it seems that for those radios without the stereo multiplexer, there's still a [dummy] plug in the multiplexer adapter socket on the underside of the radio, to link the composite audio back to the audio amp in the radio.
This plug can be seen in many/all pictures of the am/fm U69 radio you find on the net.
If that's true, then any U79 radio can be made to work 'stand-alone' as per U69 so long as you insert the dummy plug or figured out which two pins [holes] to link together.

I also suddenly realized that auto radio designers would have suddenly found themselves with their backs to the wall when fm stereo hit the airwaves.
The concentric dual gang pots for volume and tone were not going to work in the stereo world, you needed quad gang - two for volume on the inner shaft and two for tone on the outer shaft - all getting a bit cumbersome in what is already a tight space inside an auto radio.
No wonder Delco decided on separate controls for fm stereo. Other radio designs had separate controls built in to the radio, but sitting side on 'thumb wheel' style.

So the volume/tone in the radio must not do anything if a multiplexer is plugged into it.

Edit: I've just noticed that there is a conflict of multiplexer p/n's and wiring diag. arrangements as referred to in the last paragraph in my previous post.
If the wiring diag quoted 7304621 ilo 7305221 I'd be happy, but it doesn't....hmmm

55

General Discussion / Re: 68 - 69 am/fm stereo question

« on: June 09, 2015, 06:19:52 PM »

Thanks heaps for the pics Mark, has cleared the muddy water quite a bit!
With regard controls, if we just consider the volume control for the 68 setup with remote controls, we end up with two volume controls, one on the radio and one on the remote panel. Did both volume controls affect the volume level?

I'm pretty sure the multiplexer is a legit mpx stereo decoder, not simulated stereo.
The grey lead running from the head to the multiplexer in you pic above is muticore [from other pics I have seen] and I'm sure it would have carried the composite demodulated audio [L+R, L-R and 19khz pilot] from the radio to the multiplexer for demuxing to left and right stereo.

The other give-away is the green stereo light on the remote controls, if that is off when your not tuned on a fm station or the station signal is weak and on when you tune a fm station of good signal strength, then that's pretty good evidence that it is a true mpx stereo decoder that's driving that light.

The audio path required to include front/rear fade when you only have two output stages, is rather convoluted I must admit, especially since the two outputs are located in different places!

I think the difference your seeing between your pic and the top wiring diag. is that your pic is of the setup required when you have D55 - console, whereas the wiring diag. is what you have when you don't have a console - multiplexer and controls all in one unit.
This is also borne out by the fact that it says on the controls for the top diag. "Remote control head - Part of 7305221" which is the multiplex adapter.
So the speakers are still connecting to the multiplex adapter, it's now just in the same box as the controls.

56

General Discussion / Re: 68 - 69 am/fm stereo question

« on: June 08, 2015, 05:44:13 PM »

Hi Mark, glad you dropped in here 
Am I right in assuming that for 68's e.g. the right channel was fed back to the power amp in the head and the left channel went back to the multiplexer to use its power amp?
Where was the fade control in 69's - not enough shafts on the head?
Do you have any functional block diags. that show the interconnections and signal paths between the 3 components in 68's?
Cheers

57

Maintenance / Re: Starting problems

« on: June 08, 2015, 12:44:17 PM »

It seems to me that the resistance in the solenoid would cause less load and that the voltage would read high at the solenoid.

Mike.

Correct

58

General Discussion / Re: 68 - 69 am/fm stereo question

« on: June 08, 2015, 09:23:19 AM »

From pics I have seen of the whole setup, the radio is still just mono output as there is only 1 output transistor [DS501]
The multiplex unit that bolts up under the dash has a similar heatsink as the radio with another DS501 transistor mounted on it and must also be the left/right mpx decoder.
The console mounted controls may well be just a bunch of dual gang pots with an r/c network for tone. Mark C, where are you? I/we need help.

What was the first chevy to have am/fm stereo as a single unit receiver i.e. all in one, no external bits?

59

General Discussion / Re: Your worst automotive nightmare/facepalm.

« on: June 08, 2015, 08:59:37 AM »

Good stuff guys, the things we get caught out with! Keep 'em coming 

The runaway tractor story prompts me to add to my dilemma that it was good fortune that I had disconnected the ignition coil before testing my starter. Had I left the coil connected and the engine started, the glass door would have been dead in microseconds with my car ending up in the pool just on the other side!

Tim's mustang story is painful reading to say the least!

60

General Discussion / Your worst automotive nightmare/facepalm.

« on: June 07, 2015, 03:45:00 PM »

Ok, c'mon crew. Let's have a few "D'oh" stories to chuckle over. I'll start the ball rolling.
Mikefam's starter motor thread was the inspiration to recount this epic facepalm of mine.

I was tinkering with another car I had at the time - many years ago now - a HR Holden, GM-H Aust. car.
I needed to crank [no start - coil disconnected] the engine and just reached in through the drivers window to turn the key. The engine started cranking but was still in first gear and the whole car started moving forward. I was used to autos at this time and forgot about this car being a manual.

To my horror, when I let go of the key, the starter motor did not disengage and kept cranking the car forward, which was only a couple of feet from a glass pane sliding door!!
I dove full length through the drivers window and started banging at the shifter to knock it into neutral, but only succeeded in banging it straight past neutral and into second gear!!

I was now frantic, there was only inches left to the glass door and the car was now moving even quicker towards it!
Some more [now judicious] slapping of the shifter and I finally managed to hit neutral. The car stopped just shy of the glass door and the starter disengaged.
I slid out the door and collapsed on the ground.

What caused all this mayhem?
The starter had developed an intermittent issue whereby the solenoid would always operate, but the starter motor would not crank the engine.
I had traced the problem to the solenoid sometimes not connecting the battery terminal to the starter terminal.

When I pulled the solenoid apart, I could see the problem. The heads of the main terminals inside the solenoid cap had eroded away.
I removed the terminals from the cap and built them back up with an oxy and some bronze, but added a little too much height of bronze.

When I reassembled it, everything would have worked fine, except for the fact that I had left the car in gear.
When I let go of the key, the solenoid de-energized but couldn't fully release because the car was in gear keeping the starter pinion loaded and engaged on the ring gear.

Ordinarily, this restricted movement of the solenoid is still enough to disconnect the main terminals [design criteria] and stop the starter motor, but 'bunny' here had built the heads up too much and now the solenoid could not disconnect the terminals under restricted movement conditions.

If it weren't for the fact that I had left the car in gear, I would have never realized the problem I had created and maybe some other unsuspecting bunny was to get caught out with it and have the car crank him straight over the edge of a cliff!

Moral of the story - make sure you understand the exact design criteria of anything electrical, mechanical or electromechanical before toying with it.
Not all design criteria are obvious on first sight!