6 volts DC for 2 inch TV

Its a long time since I opened a geranium car radio, but typical practice decades ago was an LC input on the power line.

For load dump proof reg ccts, check out National Semiconductor's app notes series, now online.

NT

Delco used a very thin double sided PC board at the input as a "Spark plate", followed by a large filter choke. Anything over the voltage rating of the gap arced over from the input lead, directly to the radio's case.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Or even half decent performance on a car radio?

--
*Errors have been made.  Others will be blamed.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

And this was used to protect against voltages of 50 or so? I really can't see that being a reliable method in the hostile environment of a car.

BTW, the first transistor car radio I had was a hybrid kit where only the AF was handled by transistors. Early '60s. No sign of anything like that on it. Perhaps Lucas electrics couldn't produce much over 14 volts. ;-)

--
*On the other hand, you have different fingers*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Well, I think I could totally solve this problem by not running the engine when I'm watching tv. I wasn't planning on actually driving and watching tv, a fully charged battery should last a long time at only 1.6 watts. Plus I have a Battery Buddy that disconnects my battery when it is getting pretty low, while leaving enough to start the car. It works great.

But I won't be starting the car, nor running the heater fan, or anything more than the courtesy lights.

If you are inclined to email me for some reason, remove NOPSAM :-)

Maybe not since they only provided for 4 AA battery operation.

If you are inclined to email me for some reason, remove NOPSAM :-)

....

This wouldn't work for me.

At the company Xmas party a few years ago, I won the raffle at the end and won the boom box our boss had bought for music during the party. He gave me the receipt too, with the suggestion there might be something else I want more. The only thing the small store sold in the same price range ($100) was this tv, so even though I didn't pay for it, I have 100 dollars invested in the tv.

I don't want to spend the money for 8 rechargeable batteries for a tv I have barely used in 10 years, and which will be obsolete** in 2 1/2 more years, PLUS a charger, plus the nuisance of connecting the charger enough to have charged set when the other ones die, and interchanging the batteries every time. I know you're helping, but really, even ignoring the cost, I don't consider that easier at all, compared to building something from parts I have around the house.

**Maybe I would find some other use for these batteries when the tv is obsolete, but I haven't had such a use in all these years.

Thanks for the suggestion, though.

If you are inclined to email me for some reason, remove NOPSAM :-)

This sounds great but complicated. But something I would like to do. OK, I looked into it during the intervening period and it's not complicated. Mouser has the parts for under 3 dollars. Radio Shack had the voltage regulator for 2.50, but Mouser wants about 90 cents iirc. Shipping is free because I"m already ordering things.

Or,

So far all the power adapters I've found with google are dedicated to particular devices, like GPSes etc. I've seen them in the past.

If you are inclined to email me for some reason, remove NOPSAM :-)

No, I'm not. I googled load dump and read three of the sites, but I picked wrong I guess and didn't learn much.

If you are inclined to email me for some reason, remove NOPSAM :-)

If I decide never to use the tv when the car is running, would that prevent the high voltage problem? I don't see how it can go over 12.6 when the car is not running.

Maybe it will turn out that it won't work, but I can test the tv with various images on the screen, all black, all white, or with no picture and just sound, and find the minimum current that it uses, and choose the resistor accordingly.

If the higher value resistor prevents the tv from working with a mostly white screen, then I can go to a more expensive or more complicated solution.

It couldn't be unless your attributing a cost to my relaxation time, which this would be part of.

Well I have all the parts now (for the resistor plan, not yet for the votage regulator plan), and I do allocate time to relaxation and projects like this.

If you are inclined to email me for some reason, remove NOPSAM :-)

Not much these days will work efficiently on raw volts from alkaline cells.

--
*Sleep with a photographer and watch things develop

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I'd not bother anyway. It's a red herring now. Might have been relevant 50 years ago.

--
*Don't squat with your spurs on *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I dont think 50v would jump that. The LC is what does the work. The L limits how much i will flow during load dump, and the C means that i flow results in little v change.

I presume it had an LC power filter.

Last time I had Lucas electrics it boiled the battery.

NT

Far from. Alternators are still as inductive as they were, and a read of National's app notes explains the whole thing and gives load dump proofed circuits. Your kit may survive if you ignore it, but I'd say the risks are significant.

NT

I'm trying to think how many home made electronic additions I've got on the old car - but it's lots. Things like a PDC. Electronic charge indicator (useful with Lucas alternator) Timer for rear window. Better controller for the central locking. 'One touch' electric window mods - and sunroof too. And plenty others (I have a new car too and want some of the toys on the old one and it's a hobby).

And none of them containing anything other than the usual smoothing and decoupling. All using just basic op-amps, timers etc. And not one has blown up. Perhaps it's because I didn't know about 'load dump' Now I do they'll all start failing...

--
*Why is it considered necessary to screw down the lid of a coffin?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

You have met Mr Murphy, have you not? :)

Ken

It was paper thin phenolic PC board, and Delco claimed that it would arc over below 50 volts when I went to the factory school. I asked the engineers so many questions that they stopped answering. They thought that I was after their jobs. ;-)

Delco was building hybrids in the late '50s with a DS501/2N441 doorknob germanium output transistor:

Industry Number : DS501 NTE Device Number: NTE105 T-PNP, GERMANIUM AUDIO PO, TO-36 Case

Other companies used tubes designed for 12 volts on the plates in the aerly '60s while Delco was building all transistor units.

No sign of anything like that

From what I've heard about Lucas you were lucky it didn't go up in flames the first time it was turned on.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

50 years ago there were no semiconductors in a car's electrical system to worry about.

If your battery develops an open cell, or the cable falls off you'll lose lots of electronics. Go to news:sci.electronics.design and tell them that "Load Dump" in automotive electrical systems is a myth. They will tell you just how wrong you are.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

The current load will vary with brightness and volume changes. Not a good idea, unless you want to damage the TV.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida