[BUILD] All things RackNeve

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AW

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What is the 16vdc molex connection next to T2 on the main board for?
 

Ilya

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What is the 16vdc molex connection next to T2 on the main board for?
This is regulated -16V rail. If you ever want to use an off-board regulated PSU, you can hook -16V here directly. Otherwise leave unpopulated and unconnected. This also serves as a convenient test point for checking Vreg output voltage.
 

AW

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Thanks, I also noticed in one of your pics you have chassis ground and audio ground jumper-ed
on the main board.
 

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Ilya

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Thanks, I also noticed in one of your pics you have chassis ground and audio ground jumper-ed
on the main board.
This is a point where you may want to link signal GND with chassis GND. Depending on the particular system this may be not the optimum point, but it's a good starting position. In your situation this is the main and first option. Make a connection there and if you still get any hum, we'll see what's the problem.
 

AW

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Sounds good, still waiting to get the transformers delivered,
 

AW

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Is there a substitute for the Cinemag CMLI15/15BPC,and CMOQ-2
 

Rob Flinn

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I used Gardeners 10k:10k on the input & Sowter API for the outputs. But then I built mine into a 2U rack so I had more options.
 

Ilya

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Is there a substitute for the Cinemag CMLI15/15BPC,and CMOQ-2
Input transformer is PCB mounted, so there's probably no compatible replacement. If you opt to mount the transformer off-board, any high quality 1:1 line input transformer will do just fine - Sowter, OEP, Lundahl - anything you like.
The output transormer is mounted off-board, so you have more options here. You need 1:4 output. This may be a quad-filar wound transformer like the one used in API output stage. Or you can check other manufacturers catalogs for comparable products.

Cinemags in PYE are rather standard, they either should be in stock, or built very quickly - these are very commonly used transformers. If you're looking for something less expensive, you can go probably with Edcors. And don't chase the "H" version of CMOQ-2 - it won't do justice to PYE, it's too clean for this compressor. Steel will work just fine.

P. S. For testing you can omit the input transformer completely (don't forget to install temporary links so the signal passes through). You'll get a bit of hum, but otherwise you'll be able to test the unit.
 

AW

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I am a little confused about the orientation of the male 10pin LVL, and GR connector on the meter board see attached pics, the stencil on the PCB looks like it indicates it should be install like I show it on the right, but yours is flipped 180?
 

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Ilya

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Follow the silkscreen on your PCBs. Your PCBs are another revision, so the connectors orientation may be different.
 

AW

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Before I commit in clamping the wire on the 10pin connectors, can you verify this wiring is correct for the LVL(left image) I assume the GR will be the same.
The right image shows the red wire on the opposite side ???
 

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AW

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Looks like what I show is correct, pin 1(10pin connector) goes to pin 1 of Um54 which is connect to D53i anode on the LVL indication PCB via the flat 10 conductor cable.
Your photo on the right must be a different version.
 
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Ilya

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Looks correct. The first pin on the connector is located to the right of the notch. The first pin on the indication board is denoted with a square pad. They should align.
And the reason the connector got rotated in later revision is to avoid twisting the flat cable.
 

AW

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I almost got everything together, all the LVL, and GR led's are on that's probability because I haven't installed LM339's yet, waiting for them to be delivered, and also the cinemag transformers. I installed a 100ohm voltage drop resistor in series with V1_DC output to drop the voltage from 39vdc to 24vdc, I am getting -17.75vdc for B-, shouldn't I be getting -16vdc don't think the 1.75 increase should matter?
 

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Ilya

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The LEDs should be on without LM339 - the comparators shunt LEDs to turn them off, and now all LEDs are powered by constant current sources so they are all lit.
In the Build guide I state that I've increased B- to -18V. So your readings look fine.
 

AW

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The LEDs should be on without LM339 - the comparators shunt LEDs to turn them off, and now all LEDs are powered by constant current sources so they are all lit.
In the Build guide I state that I've increased B- to -18V. So your readings look fine.
Great!
 

AW

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Got it all together and fired it up, passes audio but no compression, I was going to put my scope across the points in the calibration procedure, but my scope's crt just fried out LOL
I do have a freq counter and I am getting around 275khz at D1 cathode, I am going to take a break on this tonight, any ideas how I can trouble shoot would be great, I only have a freq counter, signal generator and a VOM at present.
 
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Ilya

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Got it all together and fired it up, passes audio but no compression, I was going to put my scope across the points in the calibration procedure, but my scope's crt just fried out LOL
I do have a freq counter and I am getting around 275khz at D1 cathode, I am going to take a break on this tonight, any ideas how I can trouble shoot would be great, I only have a freq counter, signal generator and a VOM at present.
It’s very difficult to know what’s going on without a scope. Ideally, you should look at the base of switching transistor and see if pulses are there. If they are, the unit should compress. You can try whamming the input with +10 db signal, put a threshold down to minimum and check this point with a frequency counter and see what you get. Don’t forget to set a ratio somewhere not 1:1)))
Do meters show anything?
 

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