Voltage drop during start

[Zed Head]

I  just did a Google on "power interrupt radio capacitor" and the first hit was some guy annoyed that his CD player was losing its spot when he started his car.  So he devised a fix.  Unfortunately, there's a diode involved.  He didn't say what type or year of car.  Hail, hail, the brain full of trivia.

http://blog.iharder.net/2010/07/29/radio-how-to-keep-your-radio-on-when-you-start-your-car/

[Zed Head]

Remembered, halfway, also, that the power that was getting interrupted with the early switches was probably coil power.  Little to do with this problem.  So the early/late switch comment is probably not relevant.

Most of my posts in this thread have been rambly and off-topic.  If the yellow wire has constant power as the instructions direct, the radio should work as expected.  You might try disconnecting the solenoid wire from the starter just to see if it's the big starter current draw causing problems or a switching problem.  You won't get the drop to 10.5 volts without the starter motor kicking in.

Here's the Retro site for those interested.

https://www.retromanufacturing.com/collections/all/1971+datsun

https://www.retromanufacturing.com/pages/wiring-your-radio

 

 

 

[Zed Head]

Also.  12.2 volts is a partially charged battery.  ~50% by the chart shown here - http://modernsurvivalblog.com/alternative-energy/battery-state-of-charge-chart/

Could be a part of the problem.

 

p.s. I'm not a survivalist.  That site just had the best-looking and informative chart.

[rossiz]

not exactly the same problem, but i have problems with the same radio...

my retrosound unit has a couple annoying issues:

1) the clock is fast - picks up 10min. a week, maybe more. kinda funny because the good ol' analog clock in my dash is swiss-train perfect. wish i could turn off the clock on the radio but no such luck.

2) from time to time it randomly switches between functions (radio, bt, aux1, etc) and i have found no rhyme or reason to this behavior. it's been wired in for over a year and works perfectly (clock notwithstanding) most of the time so i can't imagine it's the install. flakey electronics i think. i would toss the thing in a heartbeat for another unit that looks more period correct (chrome pushbuttons!) but had modern inputs for my phone...

[Captain Obvious]

I'm sure you know this already, but you shouldn't need any diodes or capacitors. If you've got 12V between ground and the yellow "constant" yellow wire, that thing shouldn't be losing it's memory. And it shouldn't matter at all what is going on with the "IGN/ACC" red wire. You should be able to make and break the connection to the red wire at any time, as many times as you want. As long as you have a good constant source of 12V (or something not too far from it) between the black and the yellow, it should maintain memory.

 

But you're right in that it just might be an issue with the radio design itself and for some reason it's not tolerant to a quick "turn on, back off, and back on again" kind of situation. I would have expected Retro to have tested for that, but I have seen that kind of weird corner case before causing undesired effects.

 

Some things to consider...

 

First, what type of meter are you using for your investigation? Most digital meters update way too slowly to catch short transient voltage changes. Your constant +12 might actually be dropping out and your meter might just not be fast enough to display it.

 

Second, I took a look at the wiring diagram for 71, and originally there wasn't any "always hot" connection to the radio. The original radio had no volatile memory to be maintained, and the only power to the radio was a blue wire that went hot only in ACC. So if you've got a constant +12V source at your radio, it's something that you or a previous owner spliced into somewhere. You had said earlier in the thread that your constant +12 was a light blue wire that the previous radio was hooked to. I think that's a non-stock addition and you might want to look into that a little more.

 

Where does the switched (ACC) 12V source come from? Is that connected to the blue wire that went to the original factory radio?

 

Just some stuff to think about when you get back to town.

[Captain Obvious]

rossiz, Weird that your clock isn't accurate. I'm sure it's crystal derived inside the device and that's usually about as accurate as a cheap local time source can be.

While I was looking through the Retro documentation, I did see some stuff about the clock... I didn't see any way to "turn it off" completely, but it does appear to be configurable whether it's the "primary" display or if the current radio station is the primary display. It's also configurable whether it's displayed while the radio is off or not. The default is clock ON while the radio is off.

So you can't get rid of it completely, but you can maybe minimize it's impact?

[rossiz]

hmmm... i couldn't find any way to turn it off while the radio is off - that would be perfect, as the radio display shows when the radio is on, the only time i see the clock is when the radio is off. i'll go back through the little booklet and see what i can find. seems like there are pages and pages of useless info about how to go to all sorts of submenus on your phone (while driving???) but the simple stuff is hidden in the weeds.

[Captain Obvious]

Well to be honest, not knowing which model you have, I may have made an assumption that is not true. I went to Retro's website and randomly opened up one of their owner's manuals.  But you may not have that model and they may not have incorporated the same features in all their offerings.

The one I was looking at was for the Redondo and I was looking at the User's Manual here:
https://cdn.shopify.com/s/files/1/0932/8664/files/redondo_manual-low_res.pdf?17019323021407945183

On page 25, they talk about the clock features. The clock controls are in the Clock sub-menu.

Hope I didn't get your hopes up for nothing, and I apologize if that's the case.

[rossiz]

i ran out to the car to check this, but sadly, i am SOL - my retro is the "model 2" not the "redondo" (would that it were not so!) which does not have that submenu. 

 

[Captain Obvious]

I wouldn't call SOL yet... Here's a link to the Model 2 manual:
https://cdn.shopify.com/s/files/1/0932/8664/files/Model_Two_Owner_s_Manual.pdf?10807432948100287839

On page 20, they list the same clock sub-menu and features as the Redondo. So according to the documentation, it's in there.

[rossiz]

no love...

[Captain Obvious]

Bummer. It looks like they must have recently added that ON/OFF feature between when you purchased yours and now. Looks like yours just skips right over that one. I took another look at the current manual, and I couldn't find a copyright date on it, but it must be a newer version with some updates.

I guess one last thing would be to actually look for that feature on your radio (if you haven't already) in the slim hopes that it's a documentation issue and that feature actually IS in there, but isn't mentioned in the manual? I'm thinking you already tried that, but it's my duty to ask.