The PMT in control of the Devil

[Steve Anderson]

I think you've got that around the wrong way, the Philips/NXP versions are better. But even so, in this application both are fine, we don't need anywhere near 10MHz.

Steve A.

[Harry Dalek]

I think you've got that around the wrong way, the Philips/NXP versions are better. But even so, in this application both are fine, we don't need anywhere near 10MHz.

Steve A.

Ok Steve so far i have only found cd4046be versions looking at what i have handy at home i am just checking before i order in case i have one

[Steve Anderson]

It has to be a HC4046 version (or HCT4046), as does all the other logic, CD/HEF simply won't work. The maximum frequency you'll get out of a CD/HEF version is 1MHz at 5V, maybe 2,5 at 12V. We need around 3.5MHz at 5V.

Steve A.

[Steve Anderson]

Harry, first part of the timebase logic - the base frequency generation. You'll more than likely have to fiddle around with the values of R101, R102 and C101. The cap having the biggest influence. This should give you a frequency as noted with the pot in the centre of its track and a reasonable variation plus and minus. Do not take R101/102 below 3k0.

Keep stray capacitance, especially around C101 to an absolute minimum. If you're using a socket for IC101 I'd be tempted to bend pins 6 & 7 upwards and 'tack' the cap onto them.

Steve A.

[Harry Dalek]

It has to be a HC4046 version (or HCT4046), as does all the other logic, CD/HEF simply won't work. The maximum frequency you'll get out of a CD/HEF version is 1MHz at 5V, maybe 2,5 at 12V. We need around 3.5MHz at 5V.

Steve A.

OK understand will look into getting the wanted version.

[Harry Dalek]

Harry, first part of the timebase logic - the base frequency generation. You'll more than likely have to fiddle around with the values of R101, R102 and C101. The cap having the biggest influence. This should give you a frequency as noted with the pot in the centre of its track and a reasonable variation plus and minus. Do not take R101/102 below 3k0.

Keep stray capacitance, especially around C101 to an absolute minimum. If you're using a socket for IC101 I'd be tempted to bend pins 6 & 7 upwards and 'tack' the cap onto them.

Steve A.

Great Steve that gives me some thing to start on i can just make it via ic sockets till i have the ic's BTW does the 4040 have to be the HC too as marked any case i have to order 3 i think you mentioned .
I will use a multi turn trimmer on the 4046...and ok take your advice on pins 6 and 7 .
Thanks Steve

[Steve Anderson]

As I said before, at these frequencies everything needs to be HC logic, CD/HEF simply won't work. Well, at least you can get away with CD/HEF in the frame timebase counter (not drawn/posted yet), but stick to one family of logic. I'm not keen on mixing them...though many do. The speed difference can result in hard to track down glitches.

Steve A.

[ppppenguin]

If your HC4046 is struggling you can tweak the supply voltage. Run your logic at 5.5V and it will all go that little bit faster.

I did something similar with a DAC once, in a professional design. It potentially needed to run at 81MHz but at 3.3V it was only spec'ed to something like 75MHz. If it was a one off you just try it and see if it works but this was for series production. You could run it up to 5V but then power disspation went up and compatibility with the 3.3V logic driving it was marginal. So I ran it at 3.8V. Good for 81MHz according to the data sheet but still OK for interfacing to 3.3V logic.

[Harry Dalek]

If your HC4046 is struggling you can tweak the supply voltage. Run your logic at 5.5V and it will all go that little bit faster.

I did something similar with a DAC once, in a professional design. It potentially needed to run at 81MHz but at 3.3V it was only spec'ed to something like 75MHz. If it was a one off you just try it and see if it works but this was for series production. You could run it up to 5V but then power disspation went up and compatibility with the 3.3V logic driving it was marginal. So I ran it at 3.8V. Good for 81MHz according to the data sheet but still OK for interfacing to 3.3V logic.

I ended up getting some if its good enough the mm74HC4046N its a night mare trying to pick these things i was tying to get the philips but the postage was high for the chips 2 ic's i got here 10 for a bit over 7 dollars free postage ...theres a lot of CD versions of the HC ...so CD74HC4046 more of those made than any thing by the looks of it .
Boy the good ones do have a high frequency range Jeff ...lucky for me it looks like its under 3.3mhz on Steve design ...The philips ics were around the 20 dollars 17 dollars postage bit of a difference i suppose you get Quality if you can .

[Steve Anderson]

As long as they are the HC version, they'll be OK for this. The CD/HEF versions won't be. The company I use for chips doesn't stock CD/HEF any more, special order only, minimum quantity 1000, delivery one month. You can tell they just don't want to carry the stuff as it's slow moving and ties up capital...and stock room space.

HC will probably go the same way in the not too distant future.

Steve A.

[Harry Dalek]

As long as they are the HC version, they'll be OK for this. The CD/HEF versions won't be. The company I use for chips doesn't stock CD/HEF any more, special order only, minimum quantity 1000, delivery one month. You can tell they just don't want to carry the stuff as it's slow moving and ties up capital...and stock room space.

HC will probably go the same way in the not too distant future.

Steve A.

The letters before the chip are confusing to me apart from ones a 12v and the other a 3 to 5 volt version ..reading up on the HC family i can see this is the way to go .
Glad to hear the ones i picked should work ,i'll start making it via ic sockets just have to wait till the 4040 and 4046 DAC turn up.

[Steve Anderson]

The prefix before the 74 is usually a manufactures code, often there's none at all - it makes no difference to us. As long as there's 74HCxxxx then all should be OK.

Steve A.

[Steve Anderson]

Harry, here's the second part of the timebase circuits. Be sure not to mix up the supply voltages. I've coloured them hoping that it will stand out. Don't forget good decoupling/bypassing on all three supplies.

Keep the lead-length to/from SW101 as short as possible.

I've just noticed an error, the three lines going to SW102 should be 1I, 1J and 1K, the frequencies are correct. I'll update the master AudoCad file.

Steve A.

Schematic below corrected.

[Harry Dalek]

Harry, here's the second part of the timebase circuits. Be sure not to mix up the supply voltages. I've coloured them hoping that it will stand out. Don't forget good decoupling/bypassing on all three supplies.

Keep the lead-length to/from SW101 as short as possible.

I've just noticed an error, the three lines going to SW102 should be 1I, 1J and 1K, the frequencies are correct. I'll update the master AudoCad file.

Steve A.

OH Fantastic Steve thanks for that theres a lot of work there in those parts to the circuit so i do understand !
Yep i will take note on the power rails and the other hints .
I will get started on this i can make it via ic sockets and plug every thing in when i get the correct ic's...
In the mean time i will study your schematic ...

[Steve Anderson]

I forgot to mention, if you need a negative-going ramp, swap pins 2 & 4 on the DAC-08, though this could also be done in the deflection amps. Also an arrangement for swapping line/frame between vertical/horizontal. More later...though it is quite simple.

Steve A.