Did you lay those PCBs out yourself? Looks good.Finally the pcbs for the blowtorch arrived
Your preamp looks great! You nearly have me convinced to do 2 encoders instead of 1 w/pushbuttons. Would you have a CAD or FPE file for the front you would be willing to share?
Also, did you do your own layout for the Blowtorch pcb?
Thanks,
Chris
I built up one of the shunt boards yesterday and tested it last night. I did not put in the thermistors yet, but I wasn't really noticing much drift at all, but only ran it for a few minutes testing it. Note I did use the RG Susumus for all (including the 270R) instead of the RR. The glass-encapsulated RGs are supposed to be more stable than the RRs are.
I do wish you would have used 0805 packages rather than the 0603, as those are pretty much at my limit as far as SMD work goes. Putting in 20 270Rs, I only lost 2 🙂 I bought 100 of them, so unless I start losing them at a faster rate, I should be good for doing 4 boards.
Also, the transistors (BC857/BC847) case size of the chosen part numbers (SOT323) in the BOM are nearly too small for the board footprint. I wonder if an SOT23-3 part would fit better?
I do wish you would have used 0805 packages rather than the 0603, as those are pretty much at my limit as far as SMD work goes. Putting in 20 270Rs, I only lost 2 🙂 I bought 100 of them, so unless I start losing them at a faster rate, I should be good for doing 4 boards.
Also, the transistors (BC857/BC847) case size of the chosen part numbers (SOT323) in the BOM are nearly too small for the board footprint. I wonder if an SOT23-3 part would fit better?
Also, what is the min Vin for the shunt boards? I ask because my bench supply only does a bit over 26Vdc per channel. I can series to go higher, but would only be able to test the + or - section at a time. Seemed to regulate at the max for my supply however.
I didn’t share the file with only the encoders because I was thinking to keep it somehow unique(only for me) but if you insist I will send a pm with that one.
The minimum vdrop for the shunt is 6-7v even more. You need at least 5v across the ccs and the rest to account for the mains variations.
With a 26v ps you can set the shunt for 20v.
The minimum vdrop for the shunt is 6-7v even more. You need at least 5v across the ccs and the rest to account for the mains variations.
With a 26v ps you can set the shunt for 20v.
Thanks! It sure seems to be regulating, but I will feed a higher voltage into it (one section +/- at a time) and see how it behaves. The voltage adjust pots were working, etc. and I was able to set both sections to 24Vdc.
Did some more testing at ~30V input, and I see what you guys were saying regarding the thermistors, as I noticed as it was running for a bit the output voltage was dropping (almost a volt). I added the thermistors, so it seems much better now. Those 470R load resistors get rather warm!
Oops, I had missed that post. Good idea, and will keep this in mind instead of cutting traces.
I'm getting a quote on a custom transformer from SumR for this. 4x24V and 2x9V. How do these specs look?
It mostly depends on what you have after the transformer and also mains variation.
For the digital part I used 6v/800ma because I used the smd ldos on the power supply pcb. These are low drop so 6vac can do it.
If you use the through hole ones, these have a higher vdrop so you need a bigger ac voltage and you need also to use heatsinks for them.
Same thing for the analog part, you want your ps to give you at least 31vdc when loaded, 24vout+ 7vdrop for the shunt. If you count in for -10% mains variation you will want to add 2-3v for a total of 33-34v.
If you use the ac/dc pcb from the gb it has some ptc fuses in the secondary of the trafo that will lower a bit the ac voltage.
You want your ac winding current to be 3x the dc current.
Try to make a simulation with psu designer first of ordering the transformer.
For the digital part I used 6v/800ma because I used the smd ldos on the power supply pcb. These are low drop so 6vac can do it.
If you use the through hole ones, these have a higher vdrop so you need a bigger ac voltage and you need also to use heatsinks for them.
Same thing for the analog part, you want your ps to give you at least 31vdc when loaded, 24vout+ 7vdrop for the shunt. If you count in for -10% mains variation you will want to add 2-3v for a total of 33-34v.
If you use the ac/dc pcb from the gb it has some ptc fuses in the secondary of the trafo that will lower a bit the ac voltage.
You want your ac winding current to be 3x the dc current.
Try to make a simulation with psu designer first of ordering the transformer.
Thanks. I would be using the shunts and the PSU that Eric did for the last GB, and not the original PSU from the UGS AI effort.
Do you have 35v or 50v caps on the psu pcb?
For what current did you set your shunt regulators?
For what current did you set your shunt regulators?
I haven't built the PSU yet. The shunt was built with the standard BOM and used the 3R9, so 150mA. I've only built one of the shunts (of 4 for 2 preamps) so can easily make changes.
Still trying to figure out what I need to populate or not on the L & R channel boards when using Eric's new PSU and the shunts. Reading back thru this thread to see if I can figure that out. Doesn't seem like I will need a regulator or two (and jumpers) on the channel boards.
Think I figured out the regulators, etc. from my previous question.
For Eric's PSU, the Schottky rectifiers proposed (MBRS4201T3G) are on extended backorder. I came up with the following Micro Commercial Components SK4200L-TP, which seems to have the same parameters (Mouser 833-SK4200L-TP). Any thoughts, or does anyone have a better sub for these?
For Eric's PSU, the Schottky rectifiers proposed (MBRS4201T3G) are on extended backorder. I came up with the following Micro Commercial Components SK4200L-TP, which seems to have the same parameters (Mouser 833-SK4200L-TP). Any thoughts, or does anyone have a better sub for these?
Those can do the job. Don’t forget to populate also the snubber network after you get the transformer.
I think I am going to use the std. regulators on the Logic Supply board, and go with a 4x24V 2x8V transformer. Any comment? The current limit on the LDOs bothers me a bit.