Kerry Design PSU Build Thread

[mwl168]

Hi All:

This is the build thread for the Kerry design PSU. I posted BOM and schematic with Kerry's permission here and will be posting more information including photos of my test build.

My test build use the partially-assembled GRHV boards. I soldered in the the pass transistor and the resistors to set up my desired output voltage. The voltages, timer all tested as expected without load. 

Fire up your soldering irons and happy building!

 

 

GRHVBase-v2-production.pdf

GRHVBase-BOM - V2 production.xlsx

Edited May 25, 2020 by mwl168

[mwl168]

Here are a few pics of my test build. GR78/GR79 are set for +/-15VDC, GRHV set for +237VDC/-247VDC. I did not build out the bias supply on this board. I use 182K for R22 and 330uF for C17 which results in timer delay of about 75 seconds. I also tested a 500K/100uF setup which results in about 55 seconds delay. The 100K/470uF combination in the BOM provides about 50 seconds delay. Not these numbers will vary a bit mostly due to the tolerance of the capacitor (see more details in the next post).

The PSU main board is of a modular design (see the schematic). It contains the following circuits:

1. A set of GR78/GR79 low voltage regulators.

2. A set of GRHVxx high voltage regulators (B+ and B-).

3. A CD4093BM trigger based timer control (need to provide aux-power, see my posts below).

4. CPC1117N based soft-start for the GRHV.

5. A configurable headphone bias supply (2 outputs are provided  - Bias H and Bias L). 

Note that C1, C2, C3, C4 are pre and post regulation filter capacitors and their values and voltage rating need to be picked based on your needs. The pitch for the pins are all 10mm. C1, C2 diameter need to be 35mm or less and C3, C4 need to be 22mm or less.  Pick caps with smaller diameters if you don't like the caps physically touching each other when installed.

I mounted the pass transistors of the GRLV in a goofy way and it's not what Kerry has intended. For a normal person, the pass transistors should be behind the PCB 

 

Edited May 26, 2020 by mwl168

[mwl168]

This post is about the auxiliary power supply for the timer circuit.

Kerry designed the board to accept an external +5VDC supply for the CD4093BM based timer. After Kerry and I discussed we agreed that there are 3 options:

Option 1: For the purist, use an external +5V supply as designed. Note that C17 will see almost the entire voltage drop of the supply so it needs to be rated for 5V or higher. 

Option 2: Jumper a wire directly from GR78 output to the +5V pin of the Aux - Pwr pads. If you do so, make sure C17 is rated for the GR78 output voltage AND change R1 and R2 from 3K to 10K. For this option, the highest value we could find for C17 in 1210 package is 100uF/16VDC. Combined with 500K for R22, the delay is about 55 seconds give or take a few seconds. I tested this option by rigging in through-hole parts for C17 and R22 and it worked fine. I also added a 12K resistor in series to the LED indicator but this may or may not be needed. 

Option 3: Solder a 7805 regulator directly in the Aux-Pwr pads and feed theGR78 output to it. I came up with this option mostly because the parts I happened to have on hand and it's what's shown in the pic below. You'll need some capacitance between the Vout and GND pins of the 7805 for it to work (I use a 47uf cap). I also soldered in a 1N4007 zener between Vin and Vout pins to protect the 7805 regulator.  I use 330uF/6.3V tant capacitor for C17 and 182K for R22 and the delay is about 75 seconds (I prefer a longer HV delay). You need to jumper a wire from the Vout of the GR78 to the Vin pin of the 7805 (the purple wire in the pic).  

Options 2 and 3 are easy to do because there is extra hole for the GR78 Vout on the board.

 

Edited May 26, 2020 by mwl168

[thuytn]

Great guide, thanks!

What's the value of C1,C2 are you using? 

[mwl168]

10 hours ago, thuytn said:

Great guide, thanks!

What's the value of C1,C2 are you using? 

470uf/400V

[Vintage12]

Apologies for the noob questions in advance. Specifically for the Mini T2 PSU, are there recommended off the shelf 120VAC toroidals for use with this project? Or is everybody custom ordering, if so what exact specifications and suppliers recommended? 

I assume folks are building a separate boxed PSU with two toroidals for high/low voltage. If that’s the case, will you be potting them or not necessary? Anybody planning a single box solution for PSU and Amp or best practice not to do this, mitigate hum/noise etc.

Many Thanks.

[tomislavkufrin]

18 minutes ago, Vintage12 said:

Apologies for the noob questions in advance. Specifically for the Mini T2 PSU, are there recommended off the shelf 120VAC toroidals for use with this project? Or is everybody custom ordering, if so what exact specifications and suppliers recommended? 

I assume folks are building a separate boxed PSU with two toroidals for high/low voltage. If that’s the case, will you be potting them or not necessary? Anybody planning a single box solution for PSU and Amp or best practice not to do this, mitigate hum/noise etc.

Many Thanks.

you can find some more info in this thread:

about trafo specs: 

 

[audiostar]

Linking here as well James' build notes on the GR78xx and GR79xx

https://www.head-case.org/forums/topic/13533-kerry-design-mini-grhvgrlv-and-joamat-mini-t2-group-buy/?do=findComment&comment=828728

Edited December 27, 2023 by audiostar