Casio Rapman pitch conundrum

the_zombiest · February 18, 2011, 11:31:53 AM

I'm having a vexing time fitting an LTC1799 to my RP-1.
I know the LTC is sound as the same one works well on the crystal of the Voice Effektor.
I've removed the main crystal and identified the correct point for the osc in of the main chip but it's just not working.
I can hear the standard pitch whistle from the speaker as I turn the LTC pot, but no pitched hip-hop beats.
Chips got me buggin' yo. Mad props to the pimp with the shizzy and whatnot. word.

Bogus Noise · February 18, 2011, 06:20:21 PM

What's the range of your pot on the LTC? Try a 10k trim pot and a 47k pot, or 22k if you have it.

That works pretty good on an SA2, I got about half a pot worth of useful range on a 47k, so figure the 22k should do pretty well!

I've actually been meaning to post that on here in the SA thread for a couple of months now, wanted to be sure but was waiting for 22k pots from Rapid for ages, but been busy with other stuff in the meantime and so haven't had a chance to test them in there yet! Curse the curse of too many projects on the go at once.

the_zombiest · February 18, 2011, 08:57:59 PM

my pot's 100k, I have a 47k trim in series.
I've done a load of keyboards etc with LTC1799s in the past and have never had this much difficulty installing one.
Maybe it's just one of those clocks that can't be tampered with.
That prospect makes me sad

Circuitbenders · February 18, 2011, 09:06:20 PM

could be you need to set the LTC to a different range setting by connecting pin 4 to either 5v or leave it open.

Doesn't seem likely that a toy would use a clock that fast though..........

the_zombiest · February 18, 2011, 09:14:02 PM

tried that too. Again, nothing. Really perplexed by it all. I'm gonna invest another half hour in the morning to it and after that, maybe try different crystals or something. I will get some low-down dirty orchestral hits even if it bloody well kills me!

Circuitbenders · February 18, 2011, 09:21:03 PM

is the crystal labelled and are you even sure its the right crystal? I take it there isn't a ceramic resonator you've missed on the board somewhere?
On the VSS200 theres a crystal, a coil and the resonator. The resonator and the coil control the samples and preset sound respectively, and the crystal seems to set the clock speed for the actual system independently.

It'd probably be helpful if you had a scope for this kind of thing.

the_zombiest · February 18, 2011, 09:41:09 PM

There are 2 crystals, non-ceramic almost poly cap looking and 3-pinned. One controls the the clock rate of the pitch effektor. This can be pitched as you would expect with the LTC. The second, identical in looks but not value, is for the main IC. the effektor value is 15.3. The main IC is 16.3.

There are what appear to be, 3-pin ceramic capacitors on board. None of which are resonators, i'm sure. They are labelled 'PC-XX'. There are 2 near to X1 - the main IC crystal and 1 near X2 - the voice effektor chip.
Granted, I'd not notiiced these before but some similar ones closer to the power supply labelled 'EF-XX' or similar.

krinklesack · February 22, 2011, 01:30:59 PM

While you are talking about the Rapman, is there a secret to keeping the power running when the circuitboard is detached from the case? I can't for the life of me find what I need to short together to keep the battery running! I am pretty much a first time bender so i'm not too savvy with this yet!

(Sorry for the off topic)

Circuitbenders · February 22, 2011, 02:25:05 PM

Quote from: the_zombiest on February 18, 2011, 09:41:09 PM
There are what appear to be, 3-pin ceramic capacitors on board. None of which are resonators, i'm sure. They are labelled 'PC-XX'. There are 2 near to X1 - the main IC crystal and 1 near X2 - the voice effektor chip.

hmmm, again, a scope would come in handy here as it'd probably help to identify what they are, and help track down where the other clock signal actually is. A three pinned ceramic cap seems a little unlikely, although i guess it might be something else entirely.

I was bidding on a Rapman on ebay last week just so i could find out the answer to this, but cleverly forgot about the auction.

Quote from: krinklesack on February 22, 2011, 01:30:59 PM
is there a secret to keeping the power running when the circuitboard is detached from the case? I can't for the life of me find what I need to short together to keep the battery running! I am pretty much a first time bender so i'm not too savvy with this yet!

Mr Zombiest can probably answer that one better, but if its that annoying casio front panel slider power switch you can take a look at the metal contacts on the rear of the slider and at the gray pads on the board under it, and probably work out what its actually connecting when you switch it on. Then just trace the pads back along the circuit board to the nearest solder points, and use some wire to make the same connections that the switch would.

If that made any kind of sense?

the_zombiest · February 24, 2011, 09:47:54 AM

Quote from: Circuitbenders on February 22, 2011, 02:25:05 PM
Quote from: the_zombiest on February 18, 2011, 09:41:09 PM
There are what appear to be, 3-pin ceramic capacitors on board. None of which are resonators, i'm sure. They are labelled 'PC-XX'. There are 2 near to X1 - the main IC crystal and 1 near X2 - the voice effektor chip.

hmmm, again, a scope would come in handy here as it'd probably help to identify what they are, and help track down where the other clock signal actually is. A three pinned ceramic cap seems a little unlikely, although i guess it might be something else entirely.

I was bidding on a Rapman on ebay last week just so i could find out the answer to this, but cleverly forgot about the auction.

Quote from: krinklesack on February 22, 2011, 01:30:59 PM
is there a secret to keeping the power running when the circuitboard is detached from the case? I can't for the life of me find what I need to short together to keep the battery running! I am pretty much a first time bender so i'm not too savvy with this yet!

Mr Zombiest can probably answer that one better, but if its that annoying casio front panel slider power switch you can take a look at the metal contacts on the rear of the slider and at the gray pads on the board under it, and probably work out what its actually connecting when you switch it on. Then just trace the pads back along the circuit board to the nearest solder points, and use some wire to make the same connections that the switch would.

If that made any kind of sense?

I was bidding on the very same one. They don't seem to come up very often and it would've been nice to have one to keep and another to sell fully pimped yo. I've taken a couple of photos. One of the xtal removed from the main IC and one to show how to power-up with the board flipped.

[/url]
x1 from casio rapman by icanfeelmyselfrotting, on Flickr[/img]

[/url]
power-up & volume casio rapman by icanfeelmyselfrotting, on Flickr[/img]

Hope this pictures work. I've not really posted images on here for a long while.

I tried swapping out the xtal for similar 3-pin resonators. I bought 8, 12 & 16Mhz thinking that the original xtal was 16Mhz, judging from the '16 3' printed on it. The replacement 16Mhz resonator was the only xtal to have any positive effect. The pitch dropped a little.

With that in mind, perhaps what is needed of the LTC1799 is a sweep of just a few Mhz, maybe 14 - 18 would work. There is an Excel-based calculator on the Linear Technologies website called 'OscCalc' which can do the maths. I only have open office and can't get it to work the macros. So anyone with Excel, if you could help, I would be eternally grateful!

krinklesack · February 25, 2011, 01:07:16 PM

Thanks very much to the both of you! I should really think about things instead of just poking around

I have Excel, according to the calculator, the 1799 will indeed do 14-18Mhz no problem! Is this what you are asking? Seems a bit pointless me saying this as the LT website states it does 1khz to 33mhz!

I'm at work with access to Excel for another 5 hours, if you get back to me within then with whatever parameters you need I can test with the calculator for you!

Cheers

Circuitbenders · February 25, 2011, 02:46:27 PM

i'm not entirely sure what that part actually is, although my first thought was that its a box capacitor. labelled as X1 and with 3 pins it seems a little unlikely though.

I can only assume that it must be a ceramic resonator of some sort. Its a bit odd that replacing it would have little or no effect though.

the_zombiest · February 25, 2011, 05:51:50 PM

Krinklesack, The calculator allows you to find out the component values required to run a tighter frequency range. That's the info that I need, I just don't have excel. I think you input what frequency you want on the main page, click 'go' on the LTC1799 section and the component values pop-up. If you could input 18000khz and let me know the value components I need, I'll give you all the karma in the world and I'll also share my results with the world... which I should probably do anyway :p

Crusty Paul, it's defo a ceramic resonator. It's the same make as the one in the casio sa-1 I just opened, but not the same value. The SA-1 won't pitch with the ltc1799 either, but does with crystal replacement. The numbering on the SA xtal was 09 1, so maybe it doesn't correspond with the frequency output. I should probably invest in an oscilloscope.

krinklesack · February 28, 2011, 02:20:28 PM

Cool, the LTC1799 will run at 18000 as will the LTC6900 and the LTC6905

The LTC6902 Switching Regulator Clock will also do 18000!

Cheers

Circuitbenders · February 28, 2011, 03:01:05 PM

to run an LTC1799 at 18khz you need a 55k resistor.

14khz needs a 71k resistor