Resistior Values..
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Resistior Values..

by rarara on Mon Mar 25, 2013 5:44 am

I have only now went through my box and checked all resistors (why didn't I do this in the beginning :oops: ) and have found a few that are potentially wrong/faulty but would appreciate some help....

All resistance values have been tested in-situ, and initially I thought there were some issues around R74-90 but remembered that quite a few are in parallel, so give 100k readings rather than 200K. So...

....are there any other places where resistors are effectively in parallel and so will give a measurement that is different from the BOM? :?: :?:

Other than that there are a few discrepancies:

R64, R65, R109, R112, R116 - should be 10k but measuring 6.8 or 7.4K. Are these withing acceptable limits or worth swapping?
R60 (22k) - actual reading 17.6K. Again, not miles away but more than 5%

R63 (220k) - actual reading 60k
R102 (100k) - 70k
R103 (220k) - 75k
R105 (10k) - 2.9k
R118 (100k) - 13k
R128 (220k) - 52k

I will swap the above, but are any more important than others in terms of the overall sound?
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Re: Resistior Values..

by aminoacid on Mon Mar 25, 2013 8:38 am

hi rarara!!


are you aware that you cant get a correct reading from measuring them while they are solderd in circuits!

if you wanna be sure you have to de solder and lift one leg of the resistor.
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Re: Resistior Values..

by rarara on Mon Mar 25, 2013 8:51 am

most of them were spot on with the likes of R77 (200K in parallel) giving almost exact readings of 100k, while next to them R78 gives 200K?

are you sure that principle applies in all situations? and not just to say some of the components I listed which are different to what i expected?
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Re: Resistior Values..

by antto on Mon Mar 25, 2013 9:28 am

you really have to look (and understand) the circuit to be able to tell if you can really measure a given resistor as it is - in circuit
the multimeter runs a small amount of current and it *can* and *will* flow thru all possible ways, not just thru the resistor you're measuring, which would make your measurement incorrect

i don't know enough about electronics to tell easily which of the resistors you can and which you can't measure in-circuit.. i'd personally desolder and test
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Re: Resistior Values..

by rarara on Mon Mar 25, 2013 9:51 am

think i will trust the accurate readings ( :roll: ) and the dodgy readings will desolder one leg (would have to do it regardless) and see the reading that gives...
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Re: Resistior Values..

by rarara on Tue Mar 26, 2013 5:40 am

well i tested all the so-called dodgy resistors and desoldering one leg showed that they were all OK. going to trust the ones that gave correct readings without desoldering are OK

bit annoying though, as I was hoping one of the resistors would be the reason I was getting a harsh non-303 sound :cry:

am i going to have to remove caps and test their values now??
Last edited by rarara on Tue Mar 26, 2013 12:32 pm, edited 1 time in total.
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Re: Resistior Values..

by aminoacid on Tue Mar 26, 2013 12:12 pm

Both resistors and caps are marked for their values.

See if you find digits ön the caps such as 103 which means 10 with 3 zeros after. 10000pf which is 10nf which is 0,01uf.
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Re: Resistior Values..

by rarara on Tue Mar 26, 2013 12:35 pm

i have visually checked the caps and they seem ok, but am running out of things to test so will have to pull a few and measure their capacitance next :evil:
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Re: Resistior Values..

by aminoacid on Tue Mar 26, 2013 3:14 pm

I do admit that wrongly placed resistors etc are most common when building.

However, what transistors do you have in your box?
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Re: Resistior Values..

by rarara on Tue Mar 26, 2013 4:10 pm

its an early adafruit so fairchild 733's and 536's that have just been replaced with 945's. no difference to the sound
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Re: Resistior Values..

by aminoacid on Tue Mar 26, 2013 5:27 pm

Does both saw and square sound harsh?

Does it feel as harsh in a mix together with drums etc?

The 303 Can also be some harshy.
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Re: Resistior Values..

by rarara on Tue Mar 26, 2013 5:39 pm

no, the square is fine by comparison. not perfect though since neither have enough squelch or wow
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Re: Resistior Values..

by aminoacid on Wed Mar 27, 2013 7:36 am

First id like to hear how it sounds with high reso settings.

Then id perhaps say , try different caps in the vco and vcf. Transparent yellow nichicons (yx series i think they are called) or polystyrene(a bit hard to find in larger values). And set r97 for more ut less self resonation.
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Re: Resistior Values..

by rarara on Wed Mar 27, 2013 5:55 pm

OK, here are a couple of examples of saw and square. Resonance is always max (except for a bit at the end where I lower it) and starting from zero cutoff and env/decay/accent are initially at min, then mid, then max:

https://soundcloud.com/#rarara_rara_ra/saw

https://soundcloud.com/#rarara_rara_ra/square

Strangely enough the recorded files (straight from headphone out to audacity in my laptop) actually sound a bit better in playback that I reckon the box actually sounds whether listening in phones or through my mixer. Go figure.
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Re: Resistior Values..

by aminoacid on Thu Mar 28, 2013 6:12 pm

Sounds pretty Good.
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