hebjam

Looking for someone to look at why this is not passing signal. power supply seems fine.

https://groupdiy.com/index.php?topic=69215.msg882252#msg882252


Harpo

Re: Reliqua Api 312 Quad needs work, anyone?? (Ontario, Canada)
« Reply #1 on: June 13, 2018, 06:55:01 PM »
The wire links crossing the polarity relays (from your pic in the lower right corner of each preamp pcb) seem missing. Maybe fitted from traceside ... see silkscreen of crossing in the upper left corner of preamp pcb http://www.hausverwaltung-heger.de/al_leck_trick/312/PsuWireSchem312.PDF

A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

Harpo

Re: Reliqua Api 312 Quad needs work, anyone?? (Ontario, Canada)
« Reply #2 on: June 14, 2018, 03:19:23 AM »
Thanks,  would this cause there to be no sound? 
Yepp
Quote
Sorry I don't know where the polarity relays are.
::)  " (from your pic in the lower right corner of each preamp pcb)"
A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

hebjam

Re: Reliqua Api 312 Quad needs work, anyone?? (Ontario, Canada)
« Reply #3 on: June 14, 2018, 04:48:51 PM »
It seems connected underneath

Re: Reliqua Api 312 Quad needs work, anyone?? (Ontario, Canada)
« Reply #4 on: June 18, 2018, 01:02:22 PM »
There's a lot of rust in there... did the seller say what happened to it? Flood? Quick swim in the ocean? Just a really humid environment? Anyway, something could be fried if there's water damage.

Really stupid one and probably leading you down the wrong path but...I noticed that the molex connectors for the mic input have four sockets on this build, and there will only be two posts on the pcb for the input. So check to make sure that the two sockets that are actually being used line up with the posts. If they were inserted wrong (and it would be weird for all four channels to be that way but you never know), then the signal won't get past that point.

It looks to me that the gain knobs are just potentiometers and not stepped gain knobs, meaning that pile of resisters near the top of each board are just sitting there doing nothing. So either the builder didn't know what they were doing, or they were planning to use a stepped gain knob at a later date and never did. Anyway, make sure there's a jumper to the left of the resister pile so that the gain knobs can do their thing. You did mention on your thread in the lab that turning up the pots increases hiss so maybe you're okay here? I can't tell from the resolution of the picture.

Also on your thread in the Lab, the voltages you mentioned for the phantom power were wonky, +45V on one board, and -38V for the other. Did you get this sorted out? And another stupid question, but have you been testing it with a mic that needs phantom power? And are all four channels behaving exactly the same way? If it's a dynamic mic and all channels are the same we can probably rule this out as the issue, but you'll still want to fix that phantom voltage if you haven't already done so.

It doesn't look like a very complicated circuit, but I'm not sure how much care went into every aspect of the build. Even the parts don't match between boards--eg on channel 3, C1 and C2 are noticeably smaller electrolytics than on the other channels, and CD1 and CD2 are a different form factor as well. It likely doesn't have much--if any--effect, it's just the lack of consistency is odd. If you're desperate you're welcome to send it up to me in Nova Scotia if you pay for postage both ways and toss in a few extra bones for my effort, though I can't make any promises. But I expect you will be able to find someone closer to you for something like this and save yourself shipping costs.

Re: Reliqua Api 312 Quad needs work, anyone?? (Ontario, Canada)
« Reply #5 on: June 20, 2018, 09:09:42 PM »
Looking for someone to look at why this is not passing signal. power supply seems fine.

https://groupdiy.com/index.php?topic=69215.msg882252#msg882252

It looks like he's doing more live stuff these days, but if he has the time this is your guy:  http://zimbelaudio.com


 

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