Using 1N4001 as Zener Diode

Someone who has one of these things should just remove the lid and check. :)

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voltage

biased

You have to wonder why they did not use an 11 volt zener instead of a 10 volt and 2 1N4004's, unless the additional .2 to .4 volts were important....which I can't see right now....I don't have a data sheet on that SCR but perhaps it needed a little more voltage....guess I will have to study this one a bit more too....Ross

That approach is now glorified with the name, "evolutionary design".

--
John Popelish

I agree...It kind of looks like a custom zener!....Ross

Sørensen):

on

the

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You know Baphomet, a bunch of us may end up in the garage tonight simulating this damm thing...it should be simple....famous last words!.....Ross

[snip]

Could be for TC reasons. Zeners above 5V have a positive TC, diodes have a negative TC.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

to

It sounds to me like you hit the nail on the head Jim....since this device most probably gets pretty warm under heavy use it makes a lot of sense. And hey, I found it for 18 bucks at a camera shop. I also found a link that somewhat speaks exactly to your comment.....good one...that one went right past me....here is the link...

And hey, I like to cook with wine too....on mushrooms especially....yummmm.....Ross

We need an archival web site, StunninglyBadElectronicDesigns.com.

Hey, a google of 'bad design' has some cool hits, like

John

[snip]

My rule-of-thumb for zeners, while not perfect, is fairly close:

TCz = (Vz-5)mV/°C

for diodes:

TCd = -2mV/°C

I have a *little* experience in that area: At Motorola, in the '60's, my nickname was vBE-Thompson, since I fixed everything with diodes. I even have some patents on TC-ing alternator regulators.

Mushrooms in wine sauce over filet = To Die For ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

10

on

have

device

And

right

Thanks for the formulas, I figured you must be the diode man to know them so intimately.... .....and hey...mushrooms in wine and butter sauce spread over a filet...can't argue that formula either....I better put the potatoes on now! I guess I will be off to the kitchen to prepare a meal for the football game tonight....thanks for the tips Jim, Ross

Jim...

We went through a long song and dance to show that the crossover from -tc to +tc was just a bit above 6 volts (in 1966). Have things dropped to 5 volts now?

Jim

Jim Thompson shared these priceless pearls of wisdom:

->

->Could be for TC reasons. Zeners above 5V have a positive TC, diodes

->have a negative TC.

->

-> ...Jim Thompson

That's just my old rule-of-thumb. 6V works even better with the OP's circuit ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Boy that guy is really bad at taking a good LOOK...

Tim

-- "That's for the courts to decide." - Homer Simpson Website @

I thought it was called "empirical clairvoyance".... :)

Bob

If that's the case and the diodes were reversed then the SCR would be prevented from firing until the 120Hz DC ripple voltage was ~ 12V below the voltage of C1a times the ratio of R3/R3+R4..? Or perhaps the idea is to keep the SCR off when the voltage drop from the gate to C1a is grater the XXX volts to prevent the SCR from supplying current to the flash tube after the caps are discharged..? Keep in mind the time constant of R1 X C2.

M2

[old news, stupid sigs, and angle bracket pyramids, left behind by string of bottom-feeder^H^H^H^H^H^Hposters, snipped]

The 1N4001s are there to temperature-compensate the zener. They have opposite temperature coefficients, but WAGing from the circuit, I'd say that the zeners TC is probalby closer to -2x the 1N4001's than -1x. And what the transistor's for is to amplify current. And the diodes NEVER have more than a forward diode drop across them in the forward direction (albeit that drop might get up to some volts before the diode explodes) until they open. The whole string conducts. I'll have to look at the circuit more to say any more; I didn't memorize it yet! ;-D

Cheers! Rich