The KGSSHV stereo mini board has four medium-sized heatsinks, each attached to two transistors (two 2SC4686A pairs and two IXTP01N100D pairs). Any tips or warnings for attaching transistors to both sides of the heatsink? Is there a recommended part number for the sink?

its the same heatsink as the krell klone. (can't find it at the moment)

 

the 2sc4686a parts are insulated, so just thermal washers both sides, screw and nut

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.

 

.......

 

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

I believe there is something wrong with the - rail of my KGSSHVPS8G PS. The zener string on the - rail is only about 2V lower than the rectified output.

I had thought that I was extremely unlucky with the zeners I used. Voltage drop over all three of the 150V zeners measured between 158V and 159V when the PSU was energized. After replacing two of the three 150V zeners with one 140V and another 150V zener which measured within spec, the problem persists. The 140V zener voltage drop actually measured 157V! The + rail measures and works fine.

The regulated output on both rails are correct as configured.

I am at a loss what could be wrong and what I should do next to diagnose and fix the problem?

Any suggestions?

Thanks!

Poking around, I found R19 (650R) in series with 10m90s only measured 19R in situ while R8 on the positive rail measured 650R as spec'ed. I am guessing it's the culprit of my problem.

Can someone confirm and educate me what's the function of R19 and R8 (KGSSHVPS8G schematic):

1. What does it do and what's the significance of its value (650R)? What if I use 604R which I happen to have on hand.

2. What rating should it be - 1/2W or 1/4W? The part I use is CMF649HFCT-ND from Digi-Key.

3. Should I be worried if 10m90s was damaged?

I measured all passive parts before mounting them so have to assume it failed during use.

Thanks in advance for your help.

Edit: I am guessing R19/R8 are Rk used to regulate 10m90s current. Is this correct? Is there a danger going to a lower value which will raise the current according to the datasheet?

Edited May 19, 201511 yr by mwl168

R19 and R8 are the resistor that set the current for the 10M90S. a value of 650 would probably be around 3-4mA, just going from memory of the datasheet. so you can calculate its power would be very low

 

to measure its value the power needs to be off. if you are still measuring 19 ohms then lift one leg of the resistor and measure it. if you now get 650 ohms you probably have a bad 10M90S

Edited May 19, 201511 yr by justin

Many Thanks Justin.

I did measure R19/R8 with the power off. By in-situ, I meant it was measured without taking it off the board.

With power on, I measured 3.15V voltage drop on R8, that's about 4.8mA - very close to your memory. The R19 on the other hand only measured .002V voltage drop.

The CMF resistor I use is rated 1/2W and 250V - should be sufficient in this position.

I'll remove R19 and measure it again. And keep my fingers crossed hoping it's a defective resistor and not a bad or brown 10m90s.

***EDIT:

Well, R8 measured 650R once I lifted one leg off the board. So it's a brown 10m90s after all.

I am guessing when I blew the rectifiers (wrong parts I used by mistake), it also blew the 10m90s. But, thanks to Justin, I at least now know where to start.

Back to work.

Edited May 19, 201511 yr by mwl168

You might also have a blown 80N80C too. Please check.

Sent from my iPhone using Tapatalk

How do I check for blown 80N80C? There are two in parallel on each rail. 

 

Thanks!

Don't check, just replace all the sand on the offending rail. 

Got the PSU running correctly now - the zener string on the - rail now measures around -445V as should be. 

 

In the process I also changed R5/R6 on the amp from 120R to 100R - might as well take advantage of the 290ma current rating of the transformer )  Cannot really say I hear a difference so far with the higher output current. The heatsinks on both the PSU and amp do run slightly warmer now but not by much. 

 

Many thanks to Kerry, Justin and Birgir for your help. 

Has anyone looked into getting the smd carbon boards fabbed? can't find a place that doesn't have an incredibly steep price. Seems to be a little wacky due to the 3 layer affair

 

seeedstudio detects the board as 2 layer, 10x10 cm2. OSHPark doesn't accept the file, cites no outline

Edited May 20, 201511 yr by nopants

I haven't done any investigation into Carbon boards yet, but have you tried contacting iTEAD (http://imall.iteadstudio.com/open-pcb/pcb-prototyping.html)? I've had pretty good luck there. There is no explicit 3-layer option, but there is 4-layer. I would open a support ticket, attach the Gerber zip, and ask if it can be produced as a "prototype" and which checkout option to use.

Edited May 20, 201511 yr by gepardcv

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Edited November 12, 201510 yr by JoaMat

If it´s the kgsshvcarbonleft and kgsshvcarbonright boards - they are two layers.

 

I thought by the exchange between you and kevin it was going to be 3 layers that could be etched by hand or something, I should have checked things myself

some future boards, probably the dynaloss would be 3 or 4 layers if i go completely

surface mount.

 

not really possible on the kgsshv boards

The KGSSHV stereo mini board has four medium-sized heatsinks, each attached to two transistors (two 2SC4686A pairs and two IXTP01N100D pairs). Any tips or warnings for attaching transistors to both sides of the heatsink? Is there a recommended part number for the sink?

This one fits:

http://uk.farnell.com/wakefield-solutions/637-20abp/heat-sink-16k-w-to-220/dp/2295718?ost=637-20ABP

 

This one seems to have a similar footprint but a little taller. Have some on order will let you know if it’s any good.

http://uk.farnell.com/aavid-thermalloy/sw63-4/heat-sink-to-220-218-6-8-c-w/dp/1213458?ost=SW63-4

i used the taller ones on the krell klone, i liked them better because they only had one hole

i used the taller ones on the krell klone, i liked them better because they only had one hole

Swt61 said the same thing once.

I found this one in the meanwhile: http://www.mouser.com/ProductDetail/Aavid-Thermalloy/531302B02500G/?qs=/ha2pyFaduiSqs76HCxkXcUvznuhemcjJ96w0ajgr6U=

 

The fins don't look the same as on the silkscreen, but I can't imagine that matters. The dimensions all look reasonable. If I'm reading the air flow graphs correctly, it has slightly better dissipation performance than the Farnell 637-25ABP at the same height (2.5").

The silkscreen is an approximation at the best of times so this one will work just fine. 

 

Meanwhile...

 

 

I'm interested in what sinks you'll be rolling with this tiny case

i used the taller ones on the krell klone, i liked them better because they only had one hole

 

You mean this one? http://www.mouser.com/ProductDetail/Aavid-Thermalloy/530002B02500G/?qs=sGAEpiMZZMttgyDkZ5WiulSjpO3gDOKQKJpe3qO%2fNp8%3d

 

The hole may not be big enough for Swt61 though...

It lives!! 

 

 

First impressions are positive but I need to play with the bias current a bit. 

Wow!  What voltage are you running it at now?

Very nice indeed ... do you have any carbon boards 4 sale?