#250

Hi, my DIY Teletype has a problem of cv output voltage limitation.
Have you ever faced the similar problem?

When I type “CV 1 V 1”, cv 1 output is 1v. It’s OK.
When I type “CV 1 V 3”, cv 1 output is 3v. It’s OK.
When I type “CV 1 V 4”, cv 1 output is 3.1v. It’s problematic.
When I type “CV 1 V 10”, cv 1 output is 3.1v. It’s problematic.

DAC output seems OK (DAC output is 0.25V @ setting 1V. and 2.5V @ setting 10V.)
op amp is supplied power +12V and -12V.
All of cv outputs has the same behavior.

If the problem can’t resolve, I will continue to use cv output range 0-3v and append telexo expander.

#251

Where’d you get your board? Very odd symptoms, almost like your opamp rail voltage 3v3. Weird.

#252

Normal alpha 10k works fine.

#254

I bought from pusherman as smd populated pcb.
I finished to assemble and the problem occured. So I replaced new opa4171 bought from mouser. But the problem reproduced.
Yes weird. Slowly I will try to solve.

#255

Did you get the 20k resistors on there?

#256

I bought 2 pre-populated boards from Pusherman.

One had a missing resistor and both (from memory) has signs of reworking in or near the power section.

Otherwise they were ok though, and both boards eventually worked ok when fully assembled.

Also worth noting that not all the surface-mount components were pre-soldered, and, significantly, it was the more expensive ICs that were missing.

That was ok for me, as I’ve soldered many fine-pitch ICs now, but worth bearing in mind if you’re less experienced with these kind of parts.

All the 0402 passives Were done though (with the exception mentioned above), which was the main thing, from my point of view.

2 Likes
#257

Yeah man, I’ve got one assembled on my bench waiting on standoffs so I don’t fubar the display. Didn’t realize the holes were <m2.5; thought about threading them with an m2.5 standoff but didn’t want to damage anything. I flashed it yesterday and LEDs were blinking, didn’t throw an error - off to a good start.

Really appreciated the 0402 stuff being soldered because I hate the pitch but more importantly have no real stock of 0402 components. The fact that I only had to fool with with the ICs was worth it. Plus if those ICs had already been on it would’ve more than doubled the price.

In regards to the overlapping planes near the usb socket mentioned earlier in the thread: when I first powered on that part of the board was getting hot to the touch - no where else on the board was that the case. After leaving powered on for 10-15 minutes And programming that heat went away and was cool to the touch. That’s a first for me in synth diy as I feel most of the time that’s a sign that something is going to die or is dying - very odd. I did all that without the display attached so perhaps take my findings with a grain of salt.

I’m excited to get some standoffs and see if it’s all working.

2 Likes
#258

Oh the pre populated resistors (R52, R53, R66, R67) are 20 ohm.
I replace to 20k and the problem is resolved.
Thank you so much!

I will share the information to pusherman soon.

1 Like
#259

It’s odd that it should cool down after a while. but it’s not unusual for Euro modules to get hot, in my experience.

Several Antumbra module boards get almost too hot to touch in places, in normal operation.

#260

The shorted part of the board might’ve burnt itself up like a fuse.

1 Like
#261

Ha, true. It sounded like the module was still working though, so that seems unlikely…

I did make up an STM32-based module that seemed to be running ok, but the MCU got really hot.

Turned out a tiny fragment of desolder wick had broken off and become trapped behind the pins on one side of the chip, creating a short.

Eventually, the IC failed (presumably it overheated).

I was able to desolder it with hot air, and it was only then that I discovered the source of the problem.

I soldered and flashed a new STM and all was well.

#262

That’s kind of what I thought because the overlap between the planes wasn’t that substantial. Also, while it was too warm to hold for a long period of time I know that when stuff is really shorted it gets way hotter - I’ve burnt up a few 4.7 ohm resistors in my day. Wish I had the display hooked up - if something was wonky with the power I probably would’ve seen more to guesstimate on.

Standoffs should be here Wednesday, I’ll let y’all know if I’ve got a functional teletype.

#263

does pusherman actually test/prove what he sells?

#264

Honestly I really doubt it…

I read about faulty pcbs from pusherman on the Facebook group from time to time…

This all started as a group-buy thing but transferred into a one man business without the quality-control (as far as I can see) :confused:

#265

First of all…Many thanks that this beautiful module is now available as open source. I also bought a Pusherman PCB with pre-soldered 0402 SMDs and I think it is ok so far. Nevertheless I have also started with a bugfixing. TR A is always ON; I get an constant LED and CV signal. On the software level I can turn it on and off, but that does not change the hardware output signal. Any ideas where I have to re-solder something? The other TR Outputs work fine for now.

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#266

I’d check around the tl074 for r12 and r38 and make sure those connections were good as well as pins 5, 6, 7 of the tl074. If everything is good there I’d double check the MCU and make sure everything is good there.

There isn’t much to go wrong, the gate/trig comes straight off the atmel chip to the 074 for gain/buffer.

1 Like
#267

thanks for the quick response and your detailed help. R12 was actually not soldered correctly on one side. to see this, a microscope was very helpful. TR A is now operating as expected.

2 Likes
#268

In Phil’s defence, I communicated with him for quite a while about the pre-soldered Terminal boards. It took him some time after receiving the boards before he eventually put them up for sale in his webshop.

My understanding was that the delay was caused by him not having time to assemble and test one of the boards, so I’m assuming he did eventually get around to it, and the issues some of us have been experiencing weren’t present on all the boards.

I’ve bought quite a few PCB/panel sets from him over the past couple of years, and never had any functional issues with them, previously.

The black anodised panels are nice, too, and nobody else does them.

5 Likes
#269

Can also confirm, that Phil did a test built. Beside the C5 (?) Tantal exchange everything was okay with my built. Phil knows now about this issue and will correct this for upcoming boards.

3 Likes
#270

I built a test board for Phil and it had the 5v short problem. So it’s obvious he tests the boards before selling them. The board i tested was the one of the first runs, and he did not list the boards until a few weeks later, so it’s my assumption he actually does test the boards before he sells them. I got two of the boards from the second run (non assembled smd) and have two happy Teletype diy modules. Phil is to be trusted, my 2 cents :slight_smile:

4 Likes