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diyAudio group buy Paradise R3 phono stage boards

sq225917 said:
I get 93mv and 93.5mv across those two resistors, r6and r11, the 2.2ohm parts.. Each time you redial the calvin board you'll need to adjust the trim pots on the main board. Eventually it should all even out.
Click to expand...

Si,

'cos I'm stupid...

The aim is to get the voltages across R6 and R11 the same by adjusting the trimmer on the Calvins. Then check the PSU voltages and trim them to be equal at +/-18V. Back and check the voltages on R6 and R11, trim the Calvin to get the voltages equal. Then back to equal out the PSU voltages, rinse and repeat.
 
I removed the Calvin board on one channel and made up some power extender leads so I can get at the shunt trimmers. With Calvin board disconnected I checked my raw dc to the shunt ip and it's still 5V higher on the negative.
I can trim the outputs easily for +/- 18V. The current for the neg rail is circa 175mA and the pos rail 216mA. The readings are the same as when I checked previously with the Calvin boards connected.

Now with Calvin connected I get 175.5mA neg and 220mA pos. Strange as the Calvin's supposed to add 30mA.
 
It looks to me like an error that's been repeated on both boards. What I'm unsure of is whether the neg rail or the pos rail is wrong. Looking at DIY audio notes I think the neg rail current is nearer the design spec. I assume comparing test point voltages will help me.
 
Avinunca, remove the links between the front and back end of the boards, so you can test the shunt in isolation. I doubt it is the shunt, but always best to check.

I've built a fair few of these now, and fixed even more for other builders. The most common mistakes are poor matching and solder bridges on the smt caps beneath the boards.

Take some hires pics of top and bottom of boards and lets see if we can spot any obvious errors.
 
Ok will do Simon. The soldering looks very competently done. though I haven't seen the backs of the boards yet.
 
Simon,
Pulling the links to the amplifier section makes no difference. I've had a look at the psu section with a magnifier. Nothing obvious. Will get some good images tomorrow,

Michael
 
Avinunca said:
Ok will do Simon. The soldering looks very competently done. though I haven't seen the backs of the boards yet.
Click to expand...

Ok then you at least know that it is your shunts.

Do you know if they are built to exact BOM spec. As an upgrade before anything else Swap the J310s and the associated 3k resistors for J113 and 1k resistors. Better parts, faster tracking in the shunt.

After that it's voltage test time. Good luck.

I'd still like to see some pics.
 
Avinunca said:
Just checked my voltages so that I can order some new dropper resistors. The +V are both +26.7V which I assume is fine. The -V however are both -32V. Is it normal to have less current demand on the negative rails?
Click to expand...

Am I being thick here, but are the voltages above coming from the PSU, into the shunt on the Paradise boards? If they are then isn't the problem upstream of the Paradise boards, the transformer, diode bridge and the cap bank...maybe a resistor too high/many in the cap bank?
 
Offload, the raw dc from the pre-reg is the same voltage for neg and pos. The shunt reg is loading the positive rail more than the negative rail.
 
Here are some images
V0a63z

https://www.flickr.com/gp/140505027@N03/V0a63z
V0a63z

Edit Post by Avinunca


I tried powering up with my Lab PSU set to 26V and current limiting at max.
It draws 144mA neg rail and 183mA positive rail.
I assume the neg is what the shunt psu should draw (no Calvin conn) and that the pos side is drawing too much current.
I haven't seen details for the mod you mention Simon. Will look for it on DIY Audio
 
Do you have a link for those connectors you have used for the loading resistor/input/output leads etc, they look useful.
 
I bought the Paradise phono already assembled as a stopgap until I could assemble my own box of parts so I don't know anything about the connectors.
 
Check the pinout and the underside of whatever is in the j310 slot on the shunts. Also check those smt caps. Clean up that blob on the underside of the 4.7ohm resistor on the output, in fact just remove it entirely. If that doesn't do it then its time to strip the shunt.
 
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