pedro's sync generator

[mattias]

hey pedro and others. i found my old "solder free mounting board" yesterday, along with a bunch of resistors and capacitors, so i thought i'd give the circuit a try. i'm getting the ic tomorrow, but i just had a couple of questions. forgive me if they're too stupid. i'm good enough at this to know when to ask questions, but not good enough to not having to ask. ;-)

why are there r6 and r7 simply connected in parallell? no cheap 75k ones around or what?

also, there seems to be a lot of mismatches between the schematic and the board designs. not that it would matter much, but is r1 180k or 200k? and isn't r13 (r10 and r11?) supposed to be called p2 for adjustable line level? and more alarming: where's c10? is it supposed to be there or not, and if so, where?

either way, do i need the regulator circuit? can't i just feed it 5 volts or so from a regular battery? if so, would that require different resistors on the "input side"? i can't imagine the amperage being that high?

and finally: how would a "plug in power" mic jack respond to a circuit like this?

thanks a lot.

/matt

[MovieStuff]

Hah! This reminds me of the old Steve Martin plumbers joke.

There was once a lawn maintenance supervisor working on a Findley Sprocket with a Langstrom 7 inch Gangley wrench. Just then a little assistant leaned over and said,"You can't work on a Findley Sprocket with a Langstrom 7 inch wrench!" Most annoyed, the supervisor looked it up in the 5th edition of the Kensley manual where it said, indeed, a Findley Sprocket can be used with a Langstrom 7 inch wrench! At that, the assistant leaned over and said, "It says 'sprocket' not 'socket!" Heh, heh, heh.....

Anyway, you had to be there, I guess.

Roger 8O

[S8 Booster]

Don´t know if this is exactly the same design (I think it is) but you may have a look to see if it is of any help.

http://server42.hypermart.net/super8/html/1000hz.html





R

[mattias]

thanks. that's not the exact same circuit, but the parallell resistors, the missing c10 and the 200 ohms becoming 180 is still there. anybody actually built one of those? :-)

/matt

[Pedro]

Hi Matt,
first, the circuit is working that way. Don´t be so accurate with the exact values, they are not critical at all. The 200 kOhm resistor (R1) and C1 are mathematically calculated for creating exactly 1000 Hz. But as the design is made for a SMD board, you must buy what ya can actually get at your local store, and 200 kOhm is harder to get that the E12 value 180 kOhm. A little bit different frequency doesn´t matter at all.
Same shit with the 75 kOhm resistor. Hard to get in SMD in a not specialized store. If you get one, put it in! If not, use 2x 150 kOhm in parallel, there is enough space for them!
C1 is not missing, it´s 47 uF on the left corner of the board on the upper side.
The voltage regulator is neccessary to provide a constant output level. Without regulator, the output would go down together with the battery becoming weaker.
The R13-P1-R14 section is for dividing the output down to mic level and adapting the output impedance to the correct value and is ok that way!

What´s not perfect with this circuit and what had been the main reason for me to redesign it, is that the AV output doesn´t work with all heads. Too weak level for the modern super small AV heads. Also, the integtated DC-erasing circuit with the transistor doesn´t meet the required security for synchronisation. Therefore my new circuit R1008MD (for mic output) and R1008AV (for head or line output) are diferent and use c-mos technology and a FET transistor for recording level stabilization.

But for mic and line use, the present circuit is working perfectly and you can built it for an apple and an egg.

Pedro

[mattias]

Don´t be so accurate with the exact values, they are not critical at all. [...] and 200 kOhm is harder to get that the E12 value 180 kOhm. A little bit different frequency doesn´t matter at all. Same shit with the 75 kOhm resistor.

that's what i thought. thanks.

C1 is not missing, it´s 47 uF on the left corner of the board on the upper side.

*lol* too big. didn't see it.

The R13-P1-R14 section is for dividing the output down to mic level and adapting the output impedance to the correct value and is ok that way!

yeah, i know what it's for, ;-) but r13 is a potentiometer in the layout and a in the schematic, so why isn't it called p2? that's all i meant. it doesn't matter at all, but when you find one error like that, you start questioning the integrity of it all...

one more question: do you know what the minimum power for the timer is? can i drive it with 3 volts? i seem to remember from school that 1.6 volts or so is the very minimum for all such (non cmos) ic's...

and another: is there a need for an on/off switch? it *seems* like it shouldn't consume any power if there's no sync pulse, but i guess there could be some drain on the reset pin or whatever?

and another: what's your thoughs on the "plugin power" issue?

anyway, thanks a lot for your reply and for your design. i did build it in a simulator today. worked just fine (of course).

/matt

[Guest]

mattias:
as the 556 is a standard bipolar twin timer circuit, it requires about 5 V. Using the cmos version, it would start working from somewhat 2,8 V upwards. But in this configuration, the peak output voltage is nearly the same as the operation voltage, so the output circuit, specially for magnetic head use, must be redesigned. My new design I implemented in R1008AV, AVS and MD includes a cmos timer and a FET transistor for current stabilization instead of voltage stabilization of this version. A constant CURRENT thru any head coil results in rather constant recording levels and you just can adjust the ocillator in a way, that the tape output keeps 0 dB. For secure pulse recognition, a proper tape registration is essential... it should work better than wild sync!
Pedro