mwl168

I think I have a minor success to report on my kgsshvpsminifinalstn9360 PSU build. After replacing the rectifier diodes with the correct STTH512FP parts, using my freshly arrived variac, I powered up the PSU successfully, and I measured -406V, +408V and bias voltage 560V (from test point) after about 15 minutes. These are the correct numbers I was expecting based on my setup. I did not notice any smoke, spark or abnormal temperature during this brief testing. The +/- output voltage was very stable, varying around 1V from start up till the end of the 15-min testing period. The bias voltage raised about 10V during the same time. I do not have the equipment to measure noise and such but I hope this is enough evidence that the PSU board is fine. If so, this is good news for the GB participants who have received this board. I have some work to do to complete the amp boards (kgsshvampv16mini) and start testing them. Please let me know if there are additional testing I should and can run with my Fluke 112 meter to make sure the PSU is functioning as designed. Many thanks again to all that came to my rescue with my problem. P.S. A word of caution for safety - the bias voltage sustained much longer than the +/- outputs after powering down the PSU. When the output voltage dropped to below 1V after a couple of minutes the bias voltage still measured well over 100V!!!

Sorry, using my Chinese combined with long-forgotten and very limited Japanese, I was not able to find out if the pinout on the datasheet Laowei attached was bottom or top view. All I can say is that the datasheet did not state one way or the other. I did find another 6ra6 pinout diagram which looks exactly the same but with "T7C" text below it. Not sure if this means anything. I could not find any information relates to "T7C". FWIW, couple of Japanese sites on tube history state that the 6ra6 was created as an "improvement" or "alteration" of the 6s4a tube.

Sorry, please ignore my post from 30 minutes ago (deleted). Got myself confused between 6ra6 and 6ar6.

Thanks Birgir!

Thanks Pars. I was typing my response while you posted your response. I will check out those RN65 178K resistors.

Thanks John. Glad I checked. I am sorry, I am not knowledge enough to know what spec parts are needed by reading the schematic. IIRC, Kevin's original KGSS article mentioned that some resistors can be 1/4W rated. But these resistors appear to be part of the CCS, I figure I better check. I cannot find 1/2W 174K or 175K resistor in stock at Mouser. So I am going to order Vishay CMF60 1/2W 348K resistors and parallel two to get the desired resistance to be safe. Vishay CMF60 is rated at 500V.

So I am a bit paranoid now after my mess-up with the diodes. I have a part spec question on the amp board KGSSHVAMPV16MINI. I could not find 175K 1/2W resistor for R14 and R29. I used 1/4W, 174K Xicon instead (Mouser part# 271-174K-RC). Is this OK? Or do I need to find 1/2W resistors for these positions? I am using ixtp01n100d for CCS, so not populating R10 and R11 which are also 175k. Thanks!

Thanks guys. Point taken. Will order the correct part tonight. It came back to me now how I ordered those incorrect diodes. The screen says STTH512FB ( should be STTH512FP ) which is not found at Mouser. I then proceeded to find insulated TO220 rectifIer diode and picked the one with high current rating but did not know the need to spec for high reverse voltage rating. I learnt something today. The reason I asked about using the 600 v diodes is simply because I have like 80 of them on hand and can replace them tonight and continue with my testing without further delay. I was impatient to wait 4 - 5 days to have Mouser order delivered to me and, on top of that, pay $5 shipping for $10 worth of parts. Thanks all again for your help!

Thanks Kevin and Pars. I assume by 1kv diodes you mean diode rectifiers with 1kv reverse voltage rating? Would 600v diodes work?

Tried the 5A fuse. Upon flipping the switch, the two thermistor started smoking, no output voltage registered. Shut down, visually inspected everything and noticed the transformer was warm to the touch and the STTH802FP rectifiers were very hot to the touch. Measured the rectifiers and the two on the back for the - rail were shorted. Did I make a dumb and ignorant mistake ordering the wrong rectifiers? STTH802FP (Mouser part # 511-STTH802FP) is rated at 8A continuous forward current but only 200V reverse voltage. I have ordered two extra STTH802FP. I also have many uninsulated HFA2TB60PBF and HFA08TB60 at home but decided to be safe and ordered the insulated part. I assume the reverse voltage of the rectifier needs to be above the 400 v + working voltage. Is 600v reverse voltage rating safe to use? Thanks! Edit: A further thought; this may explain why the PSU seemed fine when being fed 15v secondaries but failed when fed the 350v secondaries. I wonder if any further damage was done other than the toasted rectifiers. I visually inspected the PSU but did not see any obvious problem like charred resistors or cracked transistors. I am guessing those rectifiers were fried on my first attempt with the 3.15A fuse. On the second try with the 5A fuse and, presumed fied rectifiers, the 680uf capacitor did not appear to be charged at all. Another question, how do I check if the thermistors are OK?

Thanks all for your responses. I am in US hence working with 110v AC. The 3.15A fuse is a slow blow. I chose it based on information I collected reading the thread. I was testing the PSU alone without load. Don't have 4A fuse but do have 5A ones. I thought about trying the 5A fuse soon after I blew the 3.15A but hesitated because I worry if there was something wrong with the PSU the 5A fuse may allow catastrophic damage to take place. Just got home from driving around town looking for a variac. Search was in vein - did not realize many stores are closed for Easter and Home Depot, which is open, did not carry one. I am surprised no one I asked, including the Home Depot guy, know what a variac is, let alone owning one. The reason I skipped the variac test is because the one I managed to borrow was defective and I was hopping to get this test done this weekend to verify if the PCB is correct. May just bite the bullet and buy the one I found on Amazon that's rated at 3A. Edit: To be sure, the fuse is Digikey part # 507-1251-ND. MFG P/N says " 5ST 3.15 -R".

I borrowed a variance for testing but unfortunately it turned out to be defective.

Need help with testing/debugging the KGSSHVPSMINIFINALSTN9360 PSU board. The PSU is set up to deliver around 400 VDC (450 V Zener string, R29/R26 = 432K, R6 = 22.1K, ditto on the - side) Transformer is a 200VA Antek with dual 350v/290mA secondaries. It's overkill I know but they do not have a 150VA option and I thought the 100VA one's current rating is a bit on the low side. I wired one each 10ohm/ 2A inrush current limiter (Mouser part number 871-857153S100M54) on the L and N primaries and use a 3.15A slow blow fuse. I tested the PSU first with 15V secondaries to make sure I did not make elementary mistakes like insert the rectifiers or capacitors out of phase and it tested fine. When I connected the PSU with the 350v/290mA secondaries it blew the 3.15A fuse on start up. I did not see or smell any spark nor smoke and did not see any visible damage to the PSU. The output voltage showed around -170 VDC momentarily before the fuse blew ( I decide to test the PSU one section at a time ). My question; are my inrush current limiters under rated for this application? I did buy extras so would it help if I wire two in series on each primary? Or does this signify some more serious issues? Thanks for any insight or suggestion you can offer.

When I pick the shoulder washer, I purposely picked the ones that the bushing is long enough to extend through the entire thickness of the tab and further into the ceramic pad. Bushing length for 7PPSG is only 0.81 mm according to the datasheet which is not long enough to cover the thickness of the transistor tab. For high voltage application I personally don't fee comfortable using it.

If by isolator you mean the shoulder washer, you want to use 7721-10PPSG. The bushing is 2.41mm which is long enough to extend through the tab of the transistor and some. 7721-3PPSG bushing is 3.81mm but the bushing's outer diameter is slightly larger. In my case, it would not fit through the tab hole of the transistor unless you file and enlarge the tab hole. The ceramic insulator is either AAVID 4170G or 4171G. Both should work fine. 4171G is thicker but smaller in dimension. I use 10PPSG with 4171G and the combination works well. Although I may have used 3PPSG if I had the proper file to slightly enlarge the tab hole of the transistors. Hope this helps.

For my balanced headphone and headphone amps, I use male 4-pin XLR to replace the TRS plug and female 4-pin XLR for the headphone amp's balanced output. I would not call this configuration "standard" but rather it seems to be the "convention" I observe the commercial products seem to adopt. I agree it's controversial. I have been studying the balanced signal wiring scheme recently as well. The way I understand RANE's paper, the cable shield should be connected to pin 1 of the plugs. But pin 1 of both the input and output chassis XLRs should be connected via a short wire to the chassis and NOT to the signal ground. Effectively making the cable shield an extension of the chassis. I hope those with better and more knowledge and experience will chime in. Edit: if I recall correctly, when I re-terminated the Cardas cable of my HD650, the cable is a 4-conductor construction with no shield. I simply soldered each of the conductors to one of the 4 pins of the XLR male plug.

Hi Birgir, any late development or further impression with the 007 Mk3? Have you had the chance to compare it with the 009?

Thanks Kerry!

Thanks Kerry. I am hoping to use an off-the-shelf transformer. Antek has a 100VA transformer with 2 x 350v/120mA and 2 x 6.3v/3A secondaries. Would this provide enough headroom for the KGST? I'm especially concerned about the 120mA current rating. They have another 100VA transformer that has 2 x 300v/170mA secondaries but the rectified voltage is below your 430V minimum. I will have to source a separate transformer for the 15V rails if I go this route.

Thanks Kevin!

Thanks guys! That's really helpful. To be clear; with the stock CCS value (Rk = 300 ohm), each channel of KGST draws 20mA from each of the HV rail. That's 40mA for the two channels combined. That's less than the ~ 52mA (two channels combined) which KGSSHV Consumes. I am trying to understand why it's not recommended to use the more sophisticated kgsshvps8g PSU to power the KGST.

Assuming running the KGST on 350 VDC rails, how much current on each of the HV rails does each channel draw? I searched the posts here but did not find a clear answer. Thanks!

Thanks JoaMat. The LT1021 datasheet does refer to a two-terminal, shunt regulator mode as you stated. I also looked up the older versions of KGSSHV PSU that also used the LT1021 and it was connected the same way (V in pin open).

Hi John: Can you check on your version 1.0 PSU board, where does the V in, V out and GND pins of the LT1021 connect to? On the stn9360 board, the V out pins connect to base of Q3 and Q15, the GND pins connect to ground and -450V. But I cannot figure out where does the V in pins connect to. It seems they don't connect to any thing. Thanks!

Thanks Pars for the kind offer. I may take you up on your offer. I have a few extra transfomers with much lower voltage secondaries. Is it possible to test the PSU by hooking it up to a lower voltage transformer just to test if there are catastrophic problems? If so, what's the minimum secondary needed to test it?