i'm on a roll... the kgsshv

[nopants]

I think if I was going to stand off the resistors like that I'd probably have use some teflon tubing, otherwise I'd never get anything to line up. Great job, needs a (solid) platinum knob. Is there a switch built into your power inlet?

 

What are the specs on your R-core? Very compelling if you got both the LV and HV windings in one package.

[kevin gilmore]

actually WAY back then there were ceramic spacers for doing that.

speaking of knobs, got in a piece of ebony, completely coated in

wax. took the wax off and turned it round. completely black.

then 3 days later 4 major cracks due to the wood being very

wet. so pissed off.

a piece of kiln dried ebony on the way. another vendor says

there is no such thing as kiln dried ebony.

precious metals are so much easier...

want r-core transformers so bad...

Edited May 14, 2015 by kevin gilmore

[spritzer]

 

Even includes Kevin's toes!!! 

[johnwmclean]

Looks like it was use as a target in a pistol range.

[kevin gilmore]

there is no way he could have been that good of a shot.

[nopants]

Some rifling through ebay:

 

 

R80-56 0-6.3 X1 (2A), 320-0-320(80MA), 0-18 X2 (2A), 0-5（2.5A）

 

Can the input stage work off 12V? Might have a few more options if so

[kingofsnake]

wow, all the holes on the bottom in a straight line.

 

 

Those holes took me a whole 45 mins to drill out. Downloaded some dot paper, printed it onto sticker paper, slapped it on and drill drill drill remembering not to put a hole where you have a pcb fixing.doh!!

[kingofsnake]

 Is there a switch built into your power inlet?

 

 

Yes the switch is built into the power socket. I really couldn't face drilling another big hole through that thick aluminium front panel. As it is i made a bit of a mess drilling the hole for the headphone output. Thick aluminium faceplates are nice until you have to make big holes in them...20mm+ is my idea of a big hole.

 

 

 

What are the specs on your R-core? Very compelling if you got both the LV and HV windings in one package.

 

This is what i bought. Unloaded it outputs 2x320vac/2x18vac.

 

Thanks for the comments chaps. Im still waiting for someone to ask why i used spring loaded connectors!

[nopants]

Oh you're running it at 350V. What did you dial in the current at?

 

Why did you used spring loaded connectors!

[nopants]

Well I can't seem to find your item (not to mention in 115V), but I did come across this:

http://www.ebay.com/itm/280W-Custom-spec-high-quality-R-Core-Transformer-any-voltage-/271865288825?pt=LH_DefaultDomain_0&hash=item3f4c6f1879

[mwl168]

Thanks mwl168. These are of course the boards from your group-buy. May i ask how your build is shaping up regarding the temperatures you were experiencing. what would you say is the maximum temp the heat-sinks reach?

I still don't have a device to accurately measure the heatsink temprature yet. To speak in general terms, in open air, the heatsinks never get more than slightly warm to the touch even after hours of driving my 007. The heatsinks do get appreciably hotter ( I can still put my hands on them with no worry of getting burned ) when I put the cover on so the heatsinks are entirely enclosed inside the chassis.

The offset does rise quite a bit with the higher heatsink temprature.

Your heatsinks are much larger than mine and exposed to open air. I would be very surprised if they get more than warm to the touch. This is assuming you are running the stock 120R in R5 and R6.

No sure if this answers your question.

[mwl168]

Those holes took me a whole 45 mins to drill out. Downloaded some dot paper, printed it onto sticker paper, slapped it on and drill drill drill remembering not to put a hole where you have a pcb fixing.doh!!

How did you get the edge of the holes so clean-cut? All the holes I drill on aluminum plate leave rough edges on at least one side.

[wink]

You de-burr them with a de-burring tool or a larger drill.

[kingofsnake]

Oh you're running it at 350V. What did you dial in the current at?

 

 

I populated the pcb's with their stock values printed on the pcb's themselves. I knew the build was going to be tight and pretty toasty in there hence the holes drilled in the bottom. I have 120ohm resistors in R4/R5.Are these the resistors responsible for setting the current output? Excuse my ignorance for not knowing, I'm on a very steep learning curve here.

 

I used spring loaded connectors believing they would make connecting the wires up would be made easier!...well it didn't. Despite testing every connector prior to soldering it onto the pcb's when it came to connecting the wires up two of the connectors just would NOT accept wire into them!

   I must have fannyed around for 20 minutes before having to remove one of the heat-sinks from the main enclosure, just to attach 2 wires.

  

  I was so sure that spring loaded connectors were the way to go that whilst waiting for some parts to arrive to complete this build i started to populate a KGSSHVMINISTEREO pcb with the said connectors. If it wasn't such a pita i would desolder them and install something else. As my desoldering skills are very limited at the moment i think i'll leave them in for now and just prey they work as i expected .

 

  Bet you wished you had never asked now.

[kingofsnake]

You de-burr them with a de-burring tool 

 

Correct. Just pop it into a cordless both sides de-burred in 5 minutes.

[Aive]

Lol at spring connectors - I think they're a nice solution. I quite like using them in my work where there are thousands of terminations (industrial plant). Screwing can get tiring.

[nopants]

if you can swing it I would switch to molex connectors. screw terminals seem to give me problems and they similarly limit the gauge of wires you can use. Not sure how the voltage ratings compare though

[spritzer]

Well I can't seem to find your item (not to mention in 115V), but I did come across this:

http://www.ebay.com/itm/280W-Custom-spec-high-quality-R-Core-Transformer-any-voltage-/271865288825?pt=LH_DefaultDomain_0&hash=item3f4c6f1879

 

I have some of those but haven't tested them yet.  They will go in a BHSE so that will see if they actually work.  The lead wires the use are the worst I've ever come across.  Nasty, cheap stuff. 

[mwl168]

I have a couple of questions about the KGSSHV PSU (kgsshvps8g schematic, kgsshvpsminifinalstn9360 board):

 

I set up the PSU currently to output +/- 400V and configured the pre-reg zener string for 450V (3 150V zeners). The rectified voltage from the transformer secondaries are -479V and +477V measured with load of the amp.

 

It appears I was extreme unlucky picking the zeners - the actual zener string voltage I measured after the amp is fully warmed up is -476.8V and +448.5V. The -476.8V is 6% off, just outside the 5% spec'ed zener part tolerance. The actual output voltage of the PSU is -405V and +408V with load of the amp and has been very stable since the amp was built probably a month ago. 

 

My two questions:

 

1. Should I be concerned about the -476.8V zener string voltage which is almost right at the rectified voltage? Should I start swapping zeners between the two rails to bring it down?

 

2. Given the zener string voltage, how much higher can I safely raise the regulated output voltage? Is it OK to go up to 420V or 430V? If I understand Kerry's post correctly, it seems to indicate I need to give at least 20V headroom for the regulator to work properly.

 

Thanks in advance for your help! 

[Kerry]

You should definitely bring the zener string voltage down by about 25V.  You're basically removing the value of the pre-regulator and passing a bunch of ripple voltage into the error amp.  It will still work, but degrades the performance of the regulator.

 

There tends to be a 10V - 20V variance from cold to warm on the zener strings.  If you bring the zener string down to 450 when warm they will likely be around 430V or so cold.  You'll need 10V - 20V or so above the 400V regulated out so things are getting very close and I wouldn't recommend raising the regulated voltage. 

 

Note that when spec'ing the transformers you should leave about 10% headroom to account for voltage fluctuations in line voltage, so optimally you'd look for 495V or so (also accounts for about 3V-4V of ripple).  That's why Kevin suggests 500V unregulated and setting the zener string to 450V.

 

All these extra tolerances are there because actual electronics are different from what we calculate.

 

I've been playing with some ways to lower the drop out voltage a bit.  They model well, but complicate things a bit.

 

EDIT:  I wouldn't worry too much about your unregulated voltage of 477/479V.

Edited May 17, 2015 by Kerry

[mwl168]

Many thanks Kerry. I'll follow your recommendation.

I forgot to mention the measured transformer secondaries were slightly over 360v with load. I am surprised by the magnitude of the rectifier diodes voltage drop. It seems to be much higher relatively than low voltage applications.

[spritzer]

Diodes have a fixed drop which doesn't change with how much voltage they pass.  Odds are that the meter can't handle the high AC voltage. 

[mwl168]

Thanks Birgir.

The voltage readings are all from a Fluke 112, nothing fancy but I would hope it can handle these voltages.

The foward voltage drop on the STTH512 diodes are rated 1.25V. The transfomer secondaries are rated 350v/290ma. Based on materials I read, with 360v at the input, I was expecting to see the rectified voltage after the smoothing caps to be around 390V 490V.

I am not concerned about the voltage just hoping to learn a lesson in practice.

Edited May 18, 2015 by mwl168

[spritzer]

290ma?  That is a lot so the raw AC is probably much higher than that but it depends on the regulation of the transformer.  You should be getting around 500VDC raw off the rectifiers with that setup. 

[mwl168]

290ma?  That is a lot so the raw AC is probably much higher than that but it depends on the regulation of the transformer.  You should be getting around 500VDC raw off the rectifiers with that setup. 

 

My bad, I meant to say the rectified voltage from the 360vac would be around 490V, not 390V, after deducting the forward voltage drop of the diodes. So I was surprised I was getting less than 480V.

 

The transformer is just a standard Antek 200VA with 350v secondaries ( http://www.antekinc.com/as-2t350-200va-350v-transformer/).