polyphase finished

[lowstar]

hi everybody (and especially nelson),

i finally finished the polyphase today.
i don´t know if it´s working completely though...
in one mode of the switch, the feedback + rate pots work, giving the usual phasing (i have some very loud ticking, though)
in the other mode, the envelope sens + feedback pots work, but no matter how i change the setting of the env mod + mod rate, nothing changes in the sound.

i just quickly wanted to post that it´s at least half working, now i go back to debugging.

thanks to nelson for the project ! 

cheers,
lowstar

[lowstar]

duuh, i adjusted the trimpot wrong...ts ts ts 
i was so eager to try it out that i quickly looked on the dmm which was fluctuating a little bit, then i gave it a little turn and looking back, i could swear it said 6.7...well now i checked back and it was around 5 only !
so set at 6.7V, the mod depth + mod rate pots do indeed change the sound, and now in envelope mode it goes wooooaayyooowouwouwouwou 

now the only thing left is the ticking...the wires to my dpdt switch are pretty long (6"), maybe that´s one of the reasons, and my pots are not board-mounted but wired (2.7").

cheers,
lowstar

[Dave_B]

Regarding the ticking, are you using the revised board?  Looking at the trace side, there should be a large copper fill in the lower-right corner. 

I finally drilled the improved board yesterday.  At this rate, I'll finish by 2009. 

[jimbob]

where can i find a pcb layout and scematic?

thanks

[lowstar]

yep, it´s the revised board with the copper fill.
i used parallel 4.7+10µF electro´s btw instead of the 15µF, and the whole thing is above unity gain...i think i´ll include a small trimpot to adjust volume.

jimbob, you can find the project page here http://topopiccione.atspace.com/PJ17EHPolyphase.html

cheers,
lowstar

[jimbob]

thanks- now thats a project! I hope to get that done before the year is out. Its good to see its verified and works.

[nelson]

Great news!

Well done. Just the minor ticking issue to take care of.


The wires to all the pots and the wires to the DPDT should be as short as possible, preferably sheilded too. Keep wires connected to the LFO away from sections/wires that carry audio.

The layout has been reported to work with no tick.

You know, I havent built the updated version myself. I have just been putting up with the tick in the old layout.

Good news on the thermistor front too, I have traded for an original polyphase and will be able to measure it. I am also going to check the factory schematics I have against the original. The project encompasses parts values and differences of both the deluxe phaser and polyphase factory schematics. It bugged me that I couldnt find one iota of info on the therm in the schematic.

The 15uF capacitors can be subbed for with 10uF caps. Infact, that is the value used in the polyphase factory schem.   

[lowstar]

great news about the thermistor...i´m curious which one it will be, since i googled endlessly about the original name of it to no avail, and also my dad´s old part catalogs and books were no help.

it won´t fit in a 1590bb though (at least mine won´t, also not into a 1590c, maybe a cc which is essentially a 1590bb that is a few centimeters bigger in footprint), so at the moment i have no fitting enclosure to put it into, which is too bad because 1) i can´t try out if the ticking disappears in the box and 2) I can´t take it out to play 

i will try to shield some of the wires and see what happens.

maybe i also try to change the 4.7+10µF combo to just 10µF which will fit better.

and i will go over the solder side once more, maybe there´s a little prob somewhere (because the envelope mode exhibits just the slightest ticking noise when the lfo kicks in, but the sweep mode has the ticking really loud).

cheers,
lowstar

[woolley]

hey lowstar,
mine fit pretty nicley in one of the 1790NS sovtek boxes.
it's a bit bigger than a BB but only a touch taller.
http://www.smallbearelec.com/Detail.bok?no=567

[Dave_B]

Good news on the thermistor front too, I have traded for an original polyphase and will be able to measure it.

Is the thermistor mounted like a standard resistor on the original?  I always thought the whole point of a thermistor was to have it in physical contact with something to compensate for temperature changes.

[nelson]

Good news on the thermistor front too, I have traded for an original polyphase and will be able to measure it.

Is the thermistor mounted like a standard resistor on the original?  I always thought the whole point of a thermistor was to have it in physical contact with something to compensate for temperature changes.

I assume that is the point too. However in the absense of knowing anything about the thermistor, ie dimensions or value, in order to keep the layout as small as possible I just used standard resistor pads. The layout works fine without the thermistor. Once I know the temp/resistance curve of the thermistor I will look for a current production equivelant, in the meantime dont feed the pedal a high amplitude signal. Fitting the therm with flying leads should be fine.

[Dave_B]

I assume that is the point too. However in the absense of knowing anything about the thermistor, ie dimensions or value, in order to keep the layout as small as possible I just used standard resistor pads.

I'm with you.  On this topic, I 'screened' the component side of my Polyphase board the night before last.  Instead of copper traces, it shows you where the components go and what their values are.  If you've never tried this, it can be a big help when assembling a large circuit like this.  I used the standard iron-on method with a sheet of magazine paper.  There's no need to use real Press'n'Peel material for something like this.

[nelson]

I assume that is the point too. However in the absense of knowing anything about the thermistor, ie dimensions or value, in order to keep the layout as small as possible I just used standard resistor pads.

I'm with you.  On this topic, I 'screened' the component side of my Polyphase board the night before last.  Instead of copper traces, it shows you where the components go and what their values are.  If you've never tried this, it can be a big help when assembling a large circuit like this.  I used the standard iron-on method with a sheet of magazine paper.  There's no need to use real Press'n'Peel material for something like this.

Maybe another thread with photo examples is in order?

[Dave_B]

Maybe another thread with photo examples is in order?

Until then: http://www.davebales.com/me/polyphase/index.html
Check out the photos at the very bottom of the page. 

[nelson]

Maybe another thread with photo examples is in order?

Until then: http://www.davebales.com/me/polyphase/index.html
Check out the photos at the very bottom of the page. 

Great work!


BTW, I worked from both a polyphase schematic and a deluxe phaser schematic for the layout. One of them had 15uF caps the other had 10uF caps.

[object88]

Is a "tempco" a what you guys are talking about?  The Synthtech MOTM kits used them in some VCOs and other modules.  You needed to use some thermal paste for good contact.  Unfortunately, I sold the modules that had tempcos, part numbers are not supplied in the manuals, and the layouts aren't to scale.  But this does mean that they are currently available.  It seems to me that the leads on a tempco were slightly larger than typical... but then again, the tempcos used were 3W, so that might explain the large leads.

I tried seaching for a part number for a "tempco" resister, but came up with a big, fat nothing.  So then it occured to me... is a tempco nothing more than a resister with a very low temperature drift...?  Then I looked back in my MOTM manual.  And... I found a part number.  RN55E; go figure.  And in fact, yes, it would seem that a tempco is a low temperature drift resister: normally 200 PPM per 1-deg C (i.e., 200 ohm per 1-deg C for a 1M-ohm resistor) vs. 0 +- 50 PPM per 1-deg C.

So, yeah... um.  That mean anything to anyone? 

[Dave_B]

Not me.     MusicFromOuterSpace.com sells a tempco at the bottom of this page.  They also reference their source, Precision Resistor.  With all the oddball resistor values in this circuit, there's no reason to assume the tempco is a common value.  The good news is that I've yet to see anyone have an issue with it's absence. 

[object88]

Dang, and here I thought I was contributing something kinda sorta vaguely new-ish.   

(Not that I was suggesting that the tempco used in the MOTM VCO was the right value, just that I finally figured out a part number, and the catalog page has size specs...)

[lowstar]

changing the 10+4.7µF combo for just 10µF worked fine yesterday, noise still there, though.
actually it is more than just a ticking, it sounds like shugg....shugg...shugg and the sound of it changes when i turn the feedback pot. there is also a kind of hiccup in the cycle that reminds me of analogkid´s post a while back, but checking over the filtering caps did not show anything so far. every now and then, a different cycle is thrown in, like shugg....shugg...shugg...shuggugg...shigugg...shugg etc.

have to work looong shifts for the next three days, though, so i guess no lab for me until tuesday...

cheers,
lowstar

[lowstar]

i found something else (though sadly it did not cure my problem):
the 2n5088 on the lower right-hand corner has the cbe letters right, but the flat side is drawn reversed, so i had soldered it in backwards. i changed it now, but actually it had no effect on the tick, maybe the lfo swings differently now..? i wonder how it was able to work with the reversed tranny ?

cheers,
lowstar

p.s. woolley, did you board mount your pots ? if so, how did you put the whole thing in box ? maybe a pic of the insides would be nice