#311

Could you post a picture of the pcb. Sometimes a second pair of eyes helps to spot the problem.
I spent hours looking on a pcbs without seeing the obvious mistake I made…

1 Like
#312

20200829_114534
20200829_1145341960×4032 2.9 MB
20200829_114609
20200829_1146091960×4032 2.55 MB

#313

One thing which is unlucky written on the pcb is R22/C22. The text is exchanged vice versa. C22 should be in the middle of R22 and R28. I think you didn´t done it correct? - bad luck. You may double-check this in the eagle file. But if this solve your problem… I would at first clean the area around U3/4.
grafik

2 Likes
#314

If there’s ever a v.2 of the hardware, I’d love to see the CV output LEDs fixed so they work for the entire output voltage range, and replaced with bi-colour ones to show polarity.

#315

just checked: TL074 corresponds to the trigger outputs.
but should be corrected anyway if R22 and C22 are on their wrong place…

@Gerald_Stevens:
U4 isn’t connected to VREF by design. don’t worry about that.

bit hard to tell from your photos if there’re some bridges, colder solder points etc.
as @KitKatAndy said, it would be a good idea to clean the pcb to get rid of the flux

Edit: @Gerald_Stevens: it would be worth to check following resistors:
R17 R23 R35 R39 R52 R53
in relation to their solder joints and their values

and U3 and U4 and it´s C30, C28 etc…

Bildschirmfoto 2020-08-29 um 21.20.38
Bildschirmfoto 2020-08-29 um 21.20.381296×972 11.4 KB

#316

Thanks, I’ll check all those. I have reflowed just about every pad… that’s why the flux mess. Also, should point out that I used a couple stereo thonkiconn Jack’s cause I ran out of mono. The CVs should originate at U3, but don’t. That probably means U7 is borked? The Param Pot also runs to U7, and that ain’t working either.

#317

as far as I can interpret the schematics (please correct me if I’m wrong):

the CV 1-4 out information comes from the AT32. So AT32 and U3/U4 having a conversation about the outputs. U7 handles the CV input and the Param Pot and sends these informations to the AT32.
in short:
U3/U4: output dac. (U3 is responsible for CV out channel 1, 2 and U4 for 3,4.)

U7: input adc.

So it´s possible that you’re having two different problems.

1 Like
#318

@KitKatAndy You were absolutely right - and this solved my TR2 being 3V instead of 10V problem! Progress!

1 Like
#319

Yes - it looks like you’re right @reijo . U3 and U7 share VREF, but not much more. So, I checked pins 12, 13 and 14 on U3, and they’re connected to the right pins on the AT32. That’s all there is to this chip - some digital inputs from AT32, and some analog outs, and all that looks good. I wonder if this is the first chip I have ever fried electrostatically?! I live by the ocean - not a lot of static around here, especially in the summer. There is nothing left to check that I can think of - U4 is working and shares the digital inputs of U3, so… do I buy a new DAC chip?

And coincidentally, neither IN or PARAM is working. IN is fixed at 0, PARAM knob gives two values, around 16000 and 15000. The pot is wired right - gives an output of 0-2.5Vish that makes it to the right pin on U7. U7 has so few pins that do anything, and I checked them all - they’re wired to the right inputs and outputs.

This board is fighting me pretty hard.

#320

The outputs on the TT are unipolar so I don’t think a bicolor LED would do much.

2 Likes
#321

My other point stands, though.

#322

Hi everyone,
I’ve recently completed a pair of teletype builds, and after getting them flashed and booted up I am beginning the process to test that they work. I’ve confirmed all the trigger outs toggle on both but only output 3.24V and I’m not seeing the correct behavior on the cv outs.
On unit 1 I can send the command:
CV 1 V 1 and it outputs 1 volt,
but if I try:
CV 1 V 5 then it outputs 2.97V and after further testing any voltage above 3V never outputs more than 3V.

On unit 2 I am not seeing any voltage on the CV outputs at all, while triggers appear to work the same as unit 1.

Has anyone run into this issue before?

I have found the calibration procedure for the CV in and PARAM and was able to complete that process on both units.

Any suggestions would be appreciated.

Jesse

#323

It looks like I may need to adjust the placement of the trigger op amp cap and resistors ala @KitKatAndy’s suggestion to address the trigger voltages.

1 Like
#324

Yeah, I was going to ask if this was a preassembled pusherman board or not? If so, there aren’t any 20k resistors populated and you‘d be sending a trigger through a buffer since there wouldn’t be feedback for the gain ie the voltage you’re getting. Either way, I’d start around the tl074. Pretty much the same situation on the CV outs - there are 20k resistors that need to be populated in between the jacks. I’d check all those passive because if you’re getting the signal it sounds like you’re not getting the gain. This would probably be helpful if you haven’t found it already.

#325

I’m fairly certain I got all the 20k resistors in there, but I will double check, thanks for the suggestion, and thanks for the link to the schematic, that will be a huge help.

#326

Under U3 and U4 are four vias that output the four CV channels prior to the TL074. At 10V they should be at 2.5V. This helps you confirm if the problem is in the gain stage.

#327

My experience of a pre populated pcb of pusherman.

Fix CV output voltage limit is:

And fix Trigger output voltage limit is:
Replace pre populated resistors R37, R38, R46, R47 about 10 ohm to 20k.

(PCB manufacturing lot may be vary. So the experience may differ.)
(I’m positive because pre populated PCB is very helpful for my hand soldering skill.)
(edit): About this time, additional work needed. Thanks to community for resolving.)

#328

…not so much if you end up having to replace a lot of the components (as you seem to have had to).

1 Like
#329

Next, I’m planning to connect DIY teletype
with PS/2 keyboard (by serial port),
DIY grid AND DIY arc by usb or i2c or serial port
with modifying firmware.
Has anyone already tried similar idea?
(It may be so hard project for me. So alternate way, I will get Ansible etc module if I can find.)

#330

sorry off topic. I’m newbie of monome platform.
After rethinking, using usb keyboard may be the best use case of Teletype as live coding macro sequencer for me.
I will plan to use Grid and Arc with Norns etc.