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by guest
Sat Aug 08, 2020 4:58 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

did you go through all the 157 lines and compare them with the A/B select, to make sure the switches are working? you dont need to figure out the connection for this, just check in1,in2,out,switch and see if it selects the right thing. if thats all good, and all the data and address lines toggle, th...
by guest
Sat Aug 08, 2020 11:22 am
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

also, as far as i can tell, the DAC is still doing the wrong thing when in ADC mode.
by guest
Sat Aug 08, 2020 11:14 am
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

you can just measure the ins/outs of the 157s first and see if they are doing the right thing (or just replace them all without testing).
by guest
Fri Aug 07, 2020 10:11 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

well, it might be worth it to see if the rest of the digital data lines to the SRAM are doing the right thing. and take another sample of data from the DAC to see if its doing the right thing now.
by guest
Fri Aug 07, 2020 12:04 pm
Forum: Music Tech DIY
Topic: active matrix mixer
Replies: 8
Views: 256

Re: active matrix mixer

sometimes youll also see it referred to as 0.6V, but the actual value varies with how much current is flowing through the diode, and the way the diode is made. if you look at the datasheet for the diodes you are using, they should have a V-I curve in them, which will show how they will behave.
by guest
Thu Aug 06, 2020 7:15 pm
Forum: Music Tech DIY
Topic: active matrix mixer
Replies: 8
Views: 256

Re: active matrix mixer

as Elahrairah mentioned, the diodes dont do anything until you get 0.7V or so across them, at which point they start conducting, and the gain of the final stage gets reduced. so in this application they act as a limiter, or soft clipping circuit. so they will start to distort the signal above +/-5V ...
by guest
Thu Aug 06, 2020 11:09 am
Forum: Music Tech DIY
Topic: Analog Waveform divider / multiplier
Replies: 14
Views: 377

Re: Analog Waveform divider / multiplier

yeah, i had the same problem but was able to find the paper elsewhere, and it was summing various x^n circuits to implement the trig functions for sin(m*x) functions. the x^n were all implemented with translinear circuits.
by guest
Wed Aug 05, 2020 3:25 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

i was just thinking that if the place you were ordering from for the logic had it, it would save on shipping to give it a try. right now its looking like either the SRAM or the 157, one of those two has a stuck pin.
by guest
Wed Aug 05, 2020 2:42 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

did you pick up a new SRAM as well? or is that a little harder to come by?
by guest
Wed Aug 05, 2020 11:55 am
Forum: Music Tech DIY
Topic: rhythm wolf teardown: any questions?
Replies: 187
Views: 8005

Re: rhythm wolf teardown: any questions?

for trig, i got a 4ms pulse that went to 3.3V. this then gets combined with the accent, to create an accent pulse of 5ms that varies in hieght with the accent level: 3.4V, 6.8V, 10.2V.
by guest
Tue Aug 04, 2020 11:53 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

yeah, that explains it
by guest
Tue Aug 04, 2020 11:05 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

yeah, that 157 is super suspect.
by guest
Tue Aug 04, 2020 10:07 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

im wondering if it would just be easier to replace those digital ics, in comparison to doing a bunch more debugging. they are super cheap.
by guest
Tue Aug 04, 2020 9:16 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

also, it looks like there are some timing issues. the data doesnt always line up as it should with A0. the clock pulses should be symmetric, as they are generated with a D flip flop, but they are not. also, if its sampled at 24MHz, there should be 2 high followed by 2 low for the clock, and instead ...
by guest
Tue Aug 04, 2020 9:06 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

ok, so theres definitely a problem with A4. the output of the 157 is not following the input address. this could be an issue with the 157, or maybe the SRAM. if youve seen A4 toggle on the SRAm before, then its the 157 (or a connection to the 157).
by guest
Tue Aug 04, 2020 5:52 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

looking at the M4, it seems like the the A/B pin (pin1) should be toggling with the 6MHz clock. so maybe sample at 24MHz just in case there are propogation delays and you might miss the changes.
by guest
Tue Aug 04, 2020 5:22 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

no, the signals should enter and exit the same 157. the 157 is a digital switch, which selects an address line from either the uc or the dsp. can you check the A/B pin (select pin) and enable pin of the 157s? what levels are they at? do they ever change? it seems like they shouldnt change unless you...
by guest
Tue Aug 04, 2020 12:54 pm
Forum: Music Tech DIY
Topic: Akai Tom Cat Mods
Replies: 9
Views: 147

Re: Akai Tom Cat Mods

if you end up reversing the schematic, id be curious to see how much they reused. its odd to me that the layout isnt 100% the same, and makes we wonder if the circuits arent as well.
by guest
Tue Aug 04, 2020 12:40 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

i opened them in wordpad and it worked for me (notepad did not). they both contain the same data as far as i can tell. from those data, it definitely seems like the address lines are note being decoded correctly, but it would be good to test a few more, just to be sure that youre doing the test corr...
by guest
Tue Aug 04, 2020 12:18 pm
Forum: Music Tech DIY
Topic: 808 BD PCB problem (will ship extra PCB who will help solve this)
Replies: 7
Views: 145

Re: 808 BD PCB problem (will ship extra PCB who will help solve this)

are you applying the gate/accent signals and have all the pots attached when testing?
by guest
Tue Aug 04, 2020 12:12 pm
Forum: Music Tech DIY
Topic: TL022 Necessary?
Replies: 14
Views: 273

Re: TL022 Necessary?

you can always socket it and put in what you have on-hand to begin with, and if its noisey, buy the 022 and use that instead.
by guest
Mon Aug 03, 2020 9:42 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

what format are the files in? i cant seem to read them like i did the others.
by guest
Mon Aug 03, 2020 4:39 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

working from this image here: https://ua726.co.uk/wp-content/uploads/2019/10/midiverbII-inside.jpg it looks like a similar layout, with the 574 buffering the data lines, and the 157s buffering the address lines. the pinouts might be different, so maybe it would be good to start by verifying what goe...
by guest
Mon Aug 03, 2020 4:31 pm
Forum: Music Tech DIY
Topic: Broken Midiverb II: Troubleshooting Tips?
Replies: 152
Views: 1426

Re: Broken Midiverb II: Troubleshooting Tips?

great, thanks for that. so it sounds like all instructions are stored off-board, which is good. so if the 2 is setup the same as the 3, then there are the 2 selector switches that select whether the SRAM is controlled by the uc or dsp. if one of those switches is bad, then the dsp might not be getti...

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