mwl168

All boards are here and I am ready to start shipping the boards to the GB participants. I'll be using USPS Priority Mail for all US participants. All US GB participants please PayPal me $8.40 for the shipping charge. For international participants I will PM you the shipping charge after I have the package weighted at the post office. I have used first class mail without insurance and tracking in the past. Please let me know ASAP if you want to add tracking and/or insurance but be warned they are quite expensive options. I'll ship the package when I received your shipping payment. When you PayPal me, PLEASE INCLUDE YOUR SHIPPING ADDRESS and HEAD CASE ID if you have not done so when you PayPal'ed me the cost for the boards.

470uf/400V

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.

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

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

I am starting a new build thread for the PSU (GR78, GR79, GRHVxxx and the main board) so all can share and exchange experience.

This whole thing is just odd - less than 24 hours after getting a call from FedEx to inform me that the "shipper" in Taiwan had sent FedEx the wrong item to ship and the correct item has not been shipped and I should contact the shipper directly, the boards showed up yesterday (I know that PCBnet has some of their boards fabricated in their Taiwan facility). As expected, these 2mm boards look and feel great! Going to start packaging boards for shipment and I should receive the GRHVxxxx bare boards next week.

The latest FedEx tracking shows our boards are "in transit" in Japan I don't know if to laugh or cry!

FedEx was supposed to deliver the re-manufactured PSU main boards yesterday. FedEx messed up the delivery (long story), I ended up calling FedEx customer support to straight things out. Wes put on hold for 40+ minutes, finally talked to a rep and confirmed address and contact info. Then, nothing - tracking info still shows "pending" due to incorrect address today. Called customer support again just now, went through the same routine. Let's see what happens next. It shouldn't be this hard!

Belated Happy Birthday Chris!

Just got these in...

What? No love for the Pioneer 8 Track player? I grew up with those things!

I also recall the terminal blocks shorting issue also had to do with too much solder being applied.

Some bending but no twisting...

The board I will be building has 2SC3381. I don't have the board in hand yet. Looking at the 2SC3381 and MPSA06 pinout, one should be able to mount the 2 MPSA06 into the 2SC3381 position without twisting the pins by positioning them in different orientation therefore not possible to bond the two MPSA06 together.

Thanks JoaMat. I am thinking of using 2 MPSA06 mounted on the same side without bounding them together. No twisting and no dancing

Kevin has mentioned that the 2SC3381 can be replaced by a pair of MPSA06 as well. Has anyone tried that? Also, why do you put one of the KSC1008 on the opposite side?

Got good news from PCBnet - they will remanufacture the PSU main boards to the spec'ed 2mm thickness. Expect to be shipped next week. PCBnet has truly been a top notch company to do business with. Their product quality and customer service have both been excellent!

yes, the technology has existed for some time but I am hoping for the technology to be more accessible (cost, size, etc.) and better usability.

There is no way for me to prove this but I am willing to bet big dollars that the reason some times the same gears of mine sound much better (or worse) than other times has to do with the quality of the AC power from the grid at the time. Would be great if someday the battery technology is such that we can power our audio gears from DC supply that's totally isolated from the AC grid.

More goodies showed up last night but with some bad news. The PSU main PCB came in 1.6mm/3oz copper instead of 2mm/3oz copper specification. There was a miscommunication that neither I or PCBnet caught until now - the order submitted specified 2mm thickness an 3oz copper but the quote was for 0.62' and 3oz copper and manufactured accordingly. I noticed this discrepancy when I took the PCBs from their wrapping to take some photos. The mini T2 boards are 2mm/3oz copper as ordered. All the PCBs look great with a nice heavy feel to them and are very good quality as can be expected from PCBnet. I have contacted PCBnet to see what can be done to resolve the issue.

Updated GR78 and GR79 BOM in the first post to correct the C5 (47 pf) part number from 1206 to 0805. The 1206 package may fit but more difficult to solder.

R5 and R6 set the bias current of the C4686A output devices. The voltage drop across them divided by their resistance is the bias current. IIRC, the position of these two resistors varies depending on the version of the board. You’ll need to trace the board to locate them.

What's supply rail voltage and the bias current of your KGSSHV? It's probably not healthy for the active devices on the amp longterm if the heatsinks are so hot that you can barely touch it. May want to consider either reduce the voltage and/or the bias current.

Look what I just found at my door step...