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PSU 5.33 not within range of trim
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PSU 5.33 not within range of trim

by knobToucher on Wed Jul 03, 2019 11:20 pm

Hi there, I'm hoping there's someone still active on this forum that might be able to help. I've just begun building my x0xb0x. I've been using my Multimeter to test along the way and everything is within range. However, when it came time to set the 2k trimpot to 5.333v unfortunately that value is JUST beyond the reach of the trim. I get a range of (when measuring the 3rd pin of J4) 4.99v - 5.32v.

I read a few posts on this forum by people having similar problems which led me to re-check all the resistor values. They are all correct and in the right spot. I've recorded the voltages on the 6562 and also the voltages of several junctions on the board that were requested in another person's post. Hopefully they help identify my problem/s!

6562 Voltages...
1: 11.81
2: 5.32
3: 5.32
4: 0
5: 4.83
6: 5.32
7: 5.32
8: 31.07

Junctions
d44 & d45: 0.55v
d45 & r5: 1.096v
r5 & tm6: 1.889v
tm6 & r4: 2.485v
r4 & d46: 4.23v
d46 & d47: 4.79v
d47 & r3: 4.81v
r3 & r2: 28.02v
r2 & r1: 31.45v

Any help would be greatly appreciated! Thanks in advance.

knobToucher
 
Posts: 3
Joined: Sun May 05, 2019 5:15 am

Re: PSU 5.33 not within range of trim

by stinkleton on Fri Jul 05, 2019 2:17 pm

Are you doing the testing & calibration steps for the io/power from the fabrication manual?

If so, that's good news since there's very little that could have gone wrong yet!

I guess one place to start would be testing the resistance of that trimpot, maybe it's just pretty far off spec..

Are you using an actual AN6562 and not an LM358 instead?

Are you sure you are using an LM336Z-5.0?

stinkleton
 
Posts: 5
Joined: Sat Jun 29, 2019 10:22 am

Re: PSU 5.33 not within range of trim

by knobToucher on Fri Jul 05, 2019 8:53 pm

Hey mate thanks for your reply! Yep I've done all the PSU tests as per the fab manual. Using a 6562 and an LM336Z-5. I did attempt testing the 2k trim but I wasn't really sure what I was doing.. should I wind it all the way to the right and then test the further most legs?

I emailed a guy that sold me some of the parts, he said he had a similar problem and that I should try replacing the LM336Z as sometimes they can be pretty far off spec? Is there a way to test and see if this could be the case? I went ahead a purchased 5 more new LM336Z just to give this idea a go.

knobToucher
 
Posts: 3
Joined: Sun May 05, 2019 5:15 am

Please be positive and constructive with your questions and comments.