Voltage check issue / page 52 / 6.3vDC reading [resolved]

[Souter]

Hi, I'm getting a reading of 11.5v when testing the 6.3v solder pads.
The 275v reading is fine.

Could this be a dodgy solder?

Thanks in advance for any help.

[Paul Birkeland]

I would double check that the 124 and 499 ohm resistors are in the correct spots, then add a little more solder and quite a bit more heat.

[Souter]

Hi Paul, thanks for your advice
After re-soldering the resistors I’m now getting the correct reading.
Much appreciated.

[N72826]

Hello, I am having the same issue. I have tried resoldering the 124 and 499 ohm resistors as well as every other pad on the board. I receive a reading of 12.1 on the 6.3vDC solder pads while the 275v solder pads are within the expected range.

[Paul Birkeland]

Are you 100% positive that the resistors are the correct values?

[N72826]

Are you 100% positive that the resistors are the correct values?

I'm not sure I understand your question. If you are asking if I am certain I am using the correct resistors in the correct orientation, then yes I am. I can attach a photo but I can assure you my 124 and 499 pads look identical to the photos provided in the manual. After resoldering, I received a reading of around 12.5v on the 6.3vDC pad instead of 12.1v. The 275vDC pad sits at around 350v, just as before.

And just for clarification, I have tried to simply reheat the pads and let it cool just in case there was a cold joint, I have tried removing the solder completely with solder wick and reapplying it, and I have even carefully applied a tiny bit of solder from the top of the board. It's a very difficult spot to reach because of the heatsink, and I'm not sure how I would even take it off temporarily because the solder wick doesnt seem to suck up much of the solder around the heatsink pegs.

Please let me know if you need anything else from me, I appreciate the help. I'm trying to continue my build and this is driving me crazy.

[N72826]

Ah fuck. I found the culprit in another thread of someone having the same issue where you determined the issue was in an incorrect regulator, not the resistors.
https://forum.bottlehead.com/index.php?topic=13786.msg125850#msg125850
I mounted the LM1085 on one of the c4s boards. At least I resolved the question, now the hard part is going to be exchanging the MJE5731A and LM1085. I saw in that thread you suggested "The blue spring loaded solder vacuum pump will do this job pretty well." so I will have a go at that instead of solder wick because as I said in my previous reply, solder wick wasn't really doing jack on those massive heatsink pegs.

Edit: Just remembered I don't need to remove the heatsink, I just unscrew the regulator and desolder it.

[N72826]

Nevermind I guess. I replaced the regulator and now 6.3vDC is reading ~11.2v and 275vDC is reading ~375v

I'm lost.

[Paul Birkeland]

How do the pads look for the 1085 regulator?  How do the 124 and 499 ohm resistors measure now?

[N72826]

How do the pads look for the 1085 regulator?  How do the 124 and 499 ohm resistors measure now?

Not home at the moment but I will send a photo later. I can see that being an issue because the 1085 had already been soldered and the leads had been clipped. So when I went to solder it again on the regulator board, the leads just barely made it to the pad. And what readings should I expect when testing the 124 and 499 ohm resistors?