UA LA 610mk2 phantom power gone
« on: October 26, 2019, 02:01:29 PM »
Hi

Sorry, I was rushing last night when posting and absentmindedly put down 2-610 when I meant LA 610

Has anyone had a problem losing phantom to the mic input XLR on a LA-610 mk2?
I was trying to find a relay that corresponded to the switch but  all the relays seem to be accounted for between pads, phase and input source and gain.  No test points marked for voltages and I am getting 24v from the PSU.
any ideas where the phantom is generated?

thanks in advance
« Last Edit: October 27, 2019, 10:22:11 AM by skeptic12 »


moamps

Re: UA 2-610 phantom power gone
« Reply #1 on: October 27, 2019, 05:13:12 AM »
Could you post a good quality picture of the PS board?
If it is same board as on attached picture, check out the voltages on a two two-pin connectors (with phantom engaged with kip switches). The phantom PS  part is marked with yellow rectangle.
« Last Edit: October 27, 2019, 05:49:07 AM by moamps »

Re: UA 2-610 phantom power gone
« Reply #2 on: October 27, 2019, 08:46:37 AM »
Could you post a good quality picture of the PS board?

+1
I was responsible for the original 2-610 design but I don't recognise the board that Moamps posted.  Several parts missing over the original such as protection diodes around the heater reg, and I'm not seeing the 783 regulator that was there before for phantom.  Is it just a zener reg on that board?

Khron

Re: UA 2-610 phantom power gone
« Reply #3 on: October 27, 2019, 09:52:22 AM »
Gotta increase them profit margins, eh?  :-\

Several parts missing over the original such as protection diodes around the heater reg, and I'm not seeing the 783 regulator that was there before for phantom.  Is it just a zener reg on that board?
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

Re: UA 2-610 phantom power gone
« Reply #4 on: October 27, 2019, 11:35:55 AM »
Gotta increase them profit margins, eh?  :-\

I guess so  ::). That must have saved them all of $2 at the quantity they buy parts.

Just noticed that I replied to Mo's response which is labelled 2-610, but Sceptic is asking about the LA-610 which is showing a switching supply.  So, I'm off the hook.   
I was involved in the 6176 channel strip in which I added an H.T. regulator/cap multiplier to the linear supply over the 2-610 but the LA-610 is after my time.  Sorry.
Good luck though Sceptic

moamps

Re: UA 2-610 phantom power gone
« Reply #5 on: October 27, 2019, 12:29:58 PM »
Just noticed that I replied to Mo's response which is labelled 2-610, but Sceptic is asking about the LA-610 which is showing a switching supply.
Sorry but that wasn't my fault. :)
@sceptic
IIRC, LA610 uses four SMPS, one "primary" for getting 24VDC from mains, which supplies two step-up high frequency SMPSs, one for HT, second for phantom, and one step-down high frequency SMPS for heaters. Please find out rated voltages on marked electrolytic caps so you will  know which one is which. If the phantom voltage  is dropped to 24V, most probably the  power BJT or MOSFET in phantom SMPS is defective.

Re: UA 2-610 phantom power gone
« Reply #6 on: October 28, 2019, 01:17:53 PM »
Sorry but that wasn't my fault. :)

Yep, I realise now after reading the edited first post  :)

I don't want to hijack this thread but, if you have internal pics of the revised 2-610, I'd be interested in seeing what else was changed from when I did the Mk.1 version.  Maybe there's a more appropriate thread for them if you have 'em, dunno?

Your suggestion that a power MOSFET in the 48v SMPS could be bad sounds like a good path to explore in this particular case,. Good luck Sceptic12, let us know 👍

moamps

Re: UA 2-610 phantom power gone
« Reply #7 on: October 28, 2019, 03:59:24 PM »
I don't want to hijack this thread but, if you have internal pics of the revised 2-610, I'd be interested in seeing what else was changed from when I did the Mk.1 version. 
The picture is taken from the official site here:
https://help.uaudio.com/hc/en-us/articles/215479643-Replacing-Tubes-in-Your-UA-Analog-Hardware
I have no better ones. :(


 

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