i'm on a roll... the kgsshv

[mwl168]

you can use 71-RN60D1743F for the 174K positions. This part has proven to work for many and is in stock at Mouser. 

[sorenb]

 

Yeah, definitely wanted to go over this thing with a fine tooth comb before putting any power through it. This was one of those projects that was 80% done that I picked up because I figured it would be easier than starting from scratch, especially with the case stuff almost all done already. I just need to tap holes for the case feet and enlarge the tap for the volume pot a hair.

 

Also, looking closer at the transformer and comparing to the website specs, this is the 500v version after all, not the 450v. The amp boards look to have the correctIXTP01N100D for it installed as well. I think 500v means I need a jumper in place of one of the missing film caps? I'm still trying to puzzle out the rest.

 

I'm getting a mouser order together for what I lack. So far I know I still need 8 STM STTH512FP to replace the Vishay ETF12's in the rectifier bridges.

Did you buy it off someone at Head-fi?

Edited October 15, 2015 by sorenb

[Tinkerer]

 

Did you buy it off someone at Head-fi?

I traded for it, but yeah.

[insanity]

Ok I need to correct myself. The 4686 is fine for 500V. It's indeed just the 1986 (which you don't have anyway) that is not suited for 500V. 

[Tinkerer]

Just finished going through the amp boards part by part and other than a couple of 7.1k resistors in place of 5.1k that need to be replaced, I had two things that needed checking out.

 

First is that there is a slot for an extra pair of 1k resistors that aren't in the current revision. Second is that there are a pair of 250 ohm resistors installed and the PCB matches that value, when the latest revision is 180 ohm. So would it be better to follow the original board or to put jumpers over the 1k and swap the 250 for 180 to bring it up to current?

 

 

Will go over the PSU next.

Edited October 16, 2015 by Tinkerer

[Pars]

I'm certainly no expert, but the production kgsshv schematic I have shows a pair of 1k resistors R3/R4 feeding the bases of Q1/Q2 (2sc4686a). 180R resistors (R5/R6) hang off the emitters of Q3/Q4 (2sc4686a). Not sure if the 1K resistors you are seeing are R3 and R4 in the schematic? If so and if the current boards match the schematic I have, you don't want to jumper them. Hopefully Birgir or Kevin or someone else more knowledgeable will weigh in here

[insanity]

The resistors / resistor value labeled "I" are for the version that uses the IXYS parts as output devices (upper right heatsinks of the board). Since you have the 4686 you don't need to populate the 1k and leave it open. Furthermore you need to use 180R and not 250R. On other versions of the board instead of "I" = IXYS, the designation "M" = mosfet was used.

Since you are using the IXYS as the current source (lower left heatsinks of the board), you need to populate the resistors labeled "I" in this section, and leave the ones labeled "A" = sanyo parts open. This also applies for the LED in this section.

Edited October 16, 2015 by insanity

[mwl168]

R5 and R6 set the current of the 4686 output devices. I have the off-board heatsink version and I use 100R in those positions which sets the current to about 10mA. With the on-board heatsink, the current needs to be reduced to prevent overheating.

 

Edited October 16, 2015 by mwl168

[sorenb]

 

Just finished going through the amp boards part by part and other than a couple of 7.1k resistors in place of 5.1k that need to be replaced, I had two things that needed checking out.

 

First is that there is a slot for an extra pair of 1k resistors that aren't in the current revision. Second is that there are a pair of 250 ohm resistors installed and the PCB matches that value, when the latest revision is 180 ohm. So would it be better to follow the original board or to put jumpers over the 1k and swap the 250 for 180 to bring it up to current?

 

the two resistors pointed out as 250ohm is governing the current in the output stage, at 250ohm you'll have 4.5mA ....at 180ohm you'll have 6.5mA ....the transistor can go to 10-12mA but then you need bigger heatsinks.

[spritzer]

All of this is true and don't forget the small jumper marked B in the upper right hand corner.  That needs to be connected. 

All in all this shows what a terrible idea it is to take over someone else's project. 

[sorenb]

 

All in all this shows what a terrible idea it is to take over someone else's project. 

At least it shows that one might spend at least as much time figuring out whether the stuff has been assembled correctly as one would spend building the stuff from scratch ... 

BTW doesn't the LV rectifier look a bit odd?

Would be interesting to see the bottom side of the boards as well ... 

 

Edited October 16, 2015 by sorenb

[Tinkerer]

Soldering actually looks good on the bottom. It's just none of the flux has been cleaned off so the board bottoms are ugly as hell at the moment. I'll get it all prettied up and probably reflow everything just to be safe. At the least though, for what cost me about $700+ shipping (trade was worth a lot more but that's what I paid for what I traded), I don't mind spending a little time to fiddle with things.

 

Edit: Looking over the BOM for the amp boards here again https://docs.google.com/spreadsheets/d/1tQvwqsARXGge6Tw6edqicCDti6Mite2F24T5YddyEEc/edit?pli=1#gid=0

It has the 250 ohm R for the IXYS parts build. But I can use 180 ohm R in an IXYS current source 500v build as long as the onboard sinks dissipate the heat? Otherwise, it seems most of the parts I thought were missing have the A designation so should be left alone right?

The mentioned jumper in the upper right is also marked A instead of I. So it should also be left alone?

I also needed to ask again about the local vs. global feedback jumper. What's the standard everyone uses in their builds?

 

Edited October 17, 2015 by Tinkerer

[JoaMat]

/

Edited November 11, 2015 by JoaMat

[Tinkerer]

Great. That squares with the schematic only showing the alternate current source in the lower left as different parts. So the only questions on the amp boards left is do I put in the '1K I' labeled resistor spots in the upper right and what do I set the G/L jumper to in the center of the board. Oh, almost forgot, what's the size for the nylon screws/washers that will fit the heatsinks?

 

Other than that, went through the psu and listed the discrepancies where they seemed like they might be important. So stuff like a couple of the smaller caps having more than minimum capacitance values I left out. Also not quite sure if the zener strings are correct as the schematic reads 150/150(200)/200 and the PCB reads 150/150(200)/150. Might just replace them all to be positive.

 

 

Seems like the 680uF 450V caps are bit of a pain to come by too as there's a group buy going on and the one in the BOM is OOP.

[sorenb]

Great. That squares with the schematic only showing the alternate current source in the lower left as different parts. So the only questions on the amp boards left is do I put in the '1K I' labeled resistor spots in the upper right and what do I set the G/L jumper to in the center of the board. Oh, almost forgot, what's the size for the nylon screws/washers that will fit the heatsinks?

 

 

Other than that, went through the psu and listed the discrepancies where they seemed like they might be important. So stuff like a couple of the smaller caps having more than minimum capacitance values I left out. Also not quite sure if the zener strings are correct as the schematic reads 150/150(200)/200 and the PCB reads 150/150(200)/150. Might just replace them all to be positive.

 

 

Seems like the 680uF 450V caps are bit of a pain to come by too as there's a group buy going on and the one in the BOM is OOP.

http://www.aavid.com/product-group/accessories/washers (you need to make sure that the washer goes into the alu pad so not metal is exposed.

As for the Zeners, it doesn't matter as long as the total sum is the same: 500V (DC450V) or 550V (DC500V) [As per comment by Spritzer below]

if you are really kean on getting those 680uF/450V I can supply you some, pm me - wouldn't do it my self though ... those are in series and thus can withstand the 500V no prob

As for the 2200uF/50V ....no big deal ....you might hear some strange noise when powering off the amp and have the headphone connected ...nothing to worrie about ....should you consider changing to 3300uF go for 35V rather than 25V ...

and please change the rectifiers for the STTH512F as pointed out by several good people in here

 

A general advice; please read this thread ...yes, all of it ... you might find yourself much better equipped afterwards....and answers to all your questions as well :o)

Edited October 19, 2015 by sorenb

[spritzer]

The zener has to be 550V for 500V use and don't jumper that cap.  The only thing that will do is connect the HV directly to ground.  That isn't the best idea... 

[sorenb]

The zener has to be 550V for 500V use and don't jumper that cap.  The only thing that will do is connect the HV directly to ground.  That isn't the best idea... 

Correct my posting, thanks.

Isn't 500V rails on the onboard KGSShv pushing it a bit?

[spritzer]

No, not really.   I don't like doing it because it drifts a bit more but that's it. 

[mwl168]

For my own benefit - do those 680uf caps need to be 450VDC rated? Two each are in series so would 250VDC or 300VDC rated caps work?

I recently changed my KGSSHV PSU to use 1200uf/250VDC caps in the 680uF pre-regulator positions. they are both much smaller in size and much lower cost. I am running 400V for my KGSSHV and the voltage after the STTH512 rectifiers is about 450VDC.   

[kevin gilmore]

no they don't have to be rated at 450V.

the unregulated input caps should be 350v if you are doing a 500v supply.

 

[Tinkerer]

Thanks for all the help so far. I'm up to about page forty of reading the whole thread, about the point when the original battery stuff was getting replaced with the zener string in the layout. Main helpful bit that I picked up there so far is the exact part number needed for the nylon washers and the exact screw sizes if I need any more.

 

Looking up the A1156 sheet and comparing it to the BOM unit, they are only rated to 400V instead of the 600V of the 2SA1486. The extra gain seems nice but I don't know how they'll hold up. I know it's a pain to answer some of these questions. I just really want to only have to make one mouser order for everything, barring doing something stupid and blowing something in the PSU or other such pitfall.

 

Right now the list for parts is:

For PSU

Correct isolating diodes for the HV rectifier bridges

Zener string replacements to guarantee right value (Before that, I'll get them desoldered and identify them. They might be the right values after all.)

Faraday 7815 and 7915 that need to be populated.

 

For Amp boards

Nylon washers for the IXYS parts with isolators

174k resistors that need to be populated (thanks for the alternate part there)

Ceramic caps that need to be populated

5.1k resistors to replace the 7.1K

180 resistors to replace the 250

1k resistors for the "1K I" labeled bits even though I don't know if it's needed

Some LED's

 

But an additional question I had was, could a normal 4 pole 12 pin switch be used to bypass the volume pot the same way you can on an SRM-727? I have a preamp to control the volume to the amp directly and would like to have the option to do that. Best pot is no pot right? I know speaker switches are common as dirt but I don't know how that sort of thing affects SQ at this level, if it does at all.

Edited October 20, 2015 by Tinkerer

[spritzer]

No problem using he 1156 if the 270V zeners are in place.  If not then well it will go boom. 

[JoaMat]

/

Edited November 11, 2015 by JoaMat

[Tinkerer]

Right. Thanks. Reading through again, I understand a lot of the 'I' bits are for if ixys parts are used in other positions besides the current source. Also took a look closer at the psu schematic, saw where the voltage multiplier section was and what traces the jumper should connect. Following it through I discovered the actual real jumper slot I had overlooked. Boy do I feel like a dumbass.

Otherwise, found out the zener strings are correct at 550v, desoldered the stuff that needs to be replaced, put in my mouser order, tapped the holes for the amp feet+ sanded one of the rear ones to use for the chassis ground, and enlarged the attenuator hole to fit. Just waiting on parts to do more now.

EDIT: And confirmed global feedback is the default in the back pages of the thread. I remember reading somewhere a long while back that there was originally just one option, then the second was added and then nobody used it so it was removed again. So that was the case, and it was global in the beginning. Good thing to dig up as the jumpers for that are currently set to local. Still only about halfway through the thread, but I'm getting there. Hopefully I'll be all caught up by the time parts start arriving in force on Monday. It's just a pretty good read anyway, with some great tips on parts and suppliers and how to break ground loops and such that have been very helpful.

I really appreciate you all helping out with my stupid questions as well.

EDIT 2: Just to be clear, I don't hook up the servo until I'm sure everything else is fine on the amp boards and make the initial balance and offset, correct?

Edited October 23, 2015 by Tinkerer

[Tinkerer]

Mouser order came in today. Just tested the power supply after installing the new parts and jumper, and double checking everything. Nothing exploded. +/- 494 on the 500V rails and +/- 14V on the 15V. Feels good, and wouldn't be possible without all the help I've gotten here.

 

Bias at the test point only reads about 520V though.