Teletype hardware: open

[in-fm]

Had some free time today so I fixed up some of the problems I had with my build from a few months ago. Finally got the PARAM knob and IN jack working properly but the CV LEDs still won’t light up. All four outputs are working as they should, just not the LEDs. Similar to @Gerald_Stevens, they will light up if one is lightly connected to another but after checking all the components and such related to this part of the circuit, I’m stumped. Anyone else have this problem? Hopefully this doesn’t come to replacing any chips…

[jmsiener]

Are the dacs outputting correct voltages when a command is input to the TT? If so, I’d check the 10k resistor and LED orientation. If not I’d make sure the DAC then the op amp were doing their respective jobs. The Leds just receive the dac output and if you’re testing with output voltages < ~2V (im sure someone can correct me with a more accurate value) then you probably won’t see it light up because the forward voltage to the LED won’t be enough.

[in-fm]

Just checked again and no I’m not getting correct voltages (thought I had checked this earlier but apparently not). Gave the DACs a reflow and still no luck. Can’t find anything grounded or not making a connection though. I suppose this means I need to replace the chips as others did?

[jmsiener]

Have you measured the dac outputs from the chip and not the jack? I think the highest voltage you’ll get from them is 2.5V and the op amp does an x4 on that to get to the 10V max. It could be the amplification/op amp or the dacs. See if the dac responds then you know it’s the amp stage and if there is no response it’s the dac.

[koen]

make sure it is the chips are the culprit. I also thought this was the problem, but after replacing the chips the problems remained.

[arev]

Did anybody try to use the AD5687BRUZ (non R version) with an external 2.5 vref? I tried to check the teletype/main.c which does not seem to write anything reference related to the dac, soo theoretically it should work right?

[tehn]

R version i think just means it comes on a reel. same part? check the datasheet.

[arev]

Nope, I checked the datasheet, the ‚R’ refers to the internal voltage reference.

[tehn]

cool, thanks for checking. haven’t tried it, but i figure the SPI protocol is compatible.

are the R version sold out everywhere?

[arev]

Yeah mouser, digikey, distrelec, farnell & arrow are all sold out and unfortunately the non-R version is currently only available at arrow. So this seems to be the only possibility to build a teletype right now

[b0wlb0y]

I have a new DIY terminal build using a pusherman semi prepopulated board, I used the at32uc3b0256 and a white display that was recommended and in stock, the Newhaven NHD-2.7-1286-4WDW3

Do I need R48 jumper for this display? My display is not working but I would like to know if R48 should be on, then that will be one thing out of the picture so to speak.

[walkindude125]

Edit: got it to program just fine! Now at the welcome screen, LEDS 5-8 cycle on and off in a neat little pattern. I haven’t hooked a keyboard up to the module yet. Is THIS behavior normal?

Hey everyone! I just finished the SMD components of a build and plugged the board into a power supply to test it before I add the screen. On power up pre-programming, I see that LED1 and LED2 light up solid, but none of the other LEDs turn on. Is this normal behavior before the firmware is flashed? I haven’t added the screen yet; do you recommend I add it before flashing the firmware? What kind of LED behavior should I expect once I flash the firmware?

Thanks for your help!

[jmsiener]

If I remember correctly I had a kind of random LED lighting before the firmware was flashed. I think the firmware flashing guide even mentions that some leds might be lit, might not, just flash it.

[walkindude125]

Thanks so much! I was able to flash successfully but now I need to grab a keyboard and test all the ins and outs. Before I put the jacks and pot on, do you have a suggestion of how I should go about testing everything? Walk through the Teletype studies?

[jmsiener]

Yeah, that’s what I did. Use the studies to familiarize yourself with the commands then pulse some gates and use a meter to make sure your CV range is the full amount. Get a simple something on each script and then trig inputs to make sure everything is working.

[raw]

I finished building my Teletype today (Pusherman pre-populate PCB).
It was fun and it looks good.

Everything seems to work except the CV out. No light, no voltage. I don’t know where to look for my mistake. TR outs works perfect.

Edit: I measured 3.3V on C28 and C24 and reflow U3 and U4. Reflow U2 left pins. Everything seems fine, but i have not CV output.

Edit 2: Researching and taking references I see that everything is fine … but U3 and U4 are AD5687, not AD5687R. What does not work the CV is a matter of capital R?

Thanks!

[zebra]

the difference is that the _R parts produce an internal reference voltage.

(sorry, read your post backwards the first time… i am not 100% if we use the internal ref. or disable it via SPI at startup. let me take a closer look.)

… ok so from firmware side, it looks like we are not sending the SPI command that would disable internal reference at init. from schematic, it’s less obvious but i don’t think VREF is connected anywhere. (hopefully @tehn can correct me if i am missing it.)

so tentatively i would say that this part substitution will not work.

[raw]

Thank you very much! I also don’t see the VREF connection in the schematic.

I don’t know how I could make this mistake buying. I’m looking for two AD5687R. No stock . If any of you have a secret supplier, please tell me.

[nshe]

I might have some left. Where do you live?

Did anyone have problems fitting the light pipes (PLP1-350-F) to the pusherman panel? Some holes can’t fit the pipe, while others only let it half way through.

[raw]

Thanks @nshe! I sent you a PM.

I used these round light pipes with the pusherman panel:
https://www.mouser.es/ProductDetail/bivar/plp1-350/?qs=RaByzyhmEWj7cqlQfXwCHg==&countrycode=DE&currencycode=EUR

The plain version was out of stock, so i try the round version and fit. I need to apply some force in 2 or 3 holes. I think the rounded version is easier to fit if there are tolerance problems.