For UDP3 capacitors C1 and C2, you want extra safety margin because noise on the AC mains gets transferred from transformer primary to transformer secondary, and that gets directly applied to C1 and C2. So you want capacitors rated at least 100V DC and at least 63V AC. Take a look at the attachments.
_
Attachments
Last edited:
22VAC is specified for the transformer, but the split bobbins have 18v and 24v secondaries in 12va and 20va. I like the Triad C2 trannies, any recommendations?
Mouser listings
Mouser listings
The only split bobbin transformer I can find, which will work correctly with an unmodified UDP3 using all of the recommended Parts Lists components with zero changes, is the Hammond 229B840. (It is sold at Newark) and perhaps elsewhere. All the other split bobbin transformers I found, either have the wrong voltage, the wrong VA rating, or both.
However if you want to re-engineer the UDP3 to make it work with a different transformer, changing component values and wattage ratings and voltage ratings as you deem necessary: please feel free to go right ahead, however you are on your own. You may decide to use a taller heatsink, which means your UDP3 will no longer fit in a "standard 1U height" chassis like the Pearl3 chassis's sold in the Store.
However if you want to re-engineer the UDP3 to make it work with a different transformer, changing component values and wattage ratings and voltage ratings as you deem necessary: please feel free to go right ahead, however you are on your own. You may decide to use a taller heatsink, which means your UDP3 will no longer fit in a "standard 1U height" chassis like the Pearl3 chassis's sold in the Store.
Hi Mark,
Maybe I'm confused, I thought you suggested a split bobbin transformer for this project or is that only for the CRCRC from @rhthatcher?
I have the UDP3 board, ready to pull the trigger on BOM at Mouser and put it in a taller chassis.
Wouldn't the Triad give +/-19V output also? Please forgive my ignorance - i can see I'm missing something basic here. Why would different transformers work with the CRCRC but not for the UDP3?
Best, Bill
Maybe I'm confused, I thought you suggested a split bobbin transformer for this project or is that only for the CRCRC from @rhthatcher?
I have the UDP3 board, ready to pull the trigger on BOM at Mouser and put it in a taller chassis.
18v secondaries feed Q3 about 25vdc, 22v secondaries give a higher rectified voltage?
Wouldn't the Triad give +/-19V output also? Please forgive my ignorance - i can see I'm missing something basic here. Why would different transformers work with the CRCRC but not for the UDP3?
Best, Bill
@6L6 I see the italics.. but it's over my head the distinction you're trying to make. I'm confused why different voltage inputs from different transformers are not possible, as the clamped output is 19v regardless?
If Mark is saying the UDP3 circuit accepts only 22VAC input, OK i get it. Would it follow to just get one of the two encapsulated transformers the Quasimodo designer so kindly listed on thread with measurements as the most appropriate?
Thank you for the previous responses and transformer recommendations!
If Mark is saying the UDP3 circuit accepts only 22VAC input, OK i get it. Would it follow to just get one of the two encapsulated transformers the Quasimodo designer so kindly listed on thread with measurements as the most appropriate?
Thank you for the previous responses and transformer recommendations!
I mentioned split bobbin power transformers on 09 October 2023 in Pearl3 post#87. At that time, I didn't know that split bobbin transformers were not available in very many different output voltages, and it wasn't till three days ago that I learned a split bobbin with 2x22VAC secondaries at 10-30VA isn't available from any supplier at all. That's unfortunate and I am sorry it turned out this way.
The good news is, if someone is determined to use a split bobbin transformer with UDP3, the Hammond 229B840 (2 x 20VAC) will work. The other good news is, both Talema and Amgis sell non-split-bobbin transformers with 2x22VAC secondaries, that are short enough to fit in a 1U chassis. Perhaps even Block Transformers in the EU has one too, but their catalog mystifies me. Other voltages and/or other VA ratings, will require the builder to re-engineer UDP3 and that's not a trivial task.
The good news is, if someone is determined to use a split bobbin transformer with UDP3, the Hammond 229B840 (2 x 20VAC) will work. The other good news is, both Talema and Amgis sell non-split-bobbin transformers with 2x22VAC secondaries, that are short enough to fit in a 1U chassis. Perhaps even Block Transformers in the EU has one too, but their catalog mystifies me. Other voltages and/or other VA ratings, will require the builder to re-engineer UDP3 and that's not a trivial task.