For the zener string that form the 580V pro bias, what wattage of zener should I get? 

 

I can do , +200, +200, and a +180 to get 580V can't I? 

 

Oh the PCB has 4 zeners on it (3x 150V + 1x 130V), so I guess I will have to short it if I want to have only 3 zeners.

 

Or I could just do 4x 100V + 1x 180V. 

1W is more than enough and any combination will work as long as the end result is 580V.  We chose those values as the board already had a lot of 150V units. 

 

If you jumper a trace, do it on the back to prevent arcing to the ground plane. 

Any other tips and guides, or must-do, for the 500V version, apart from those listed here on Lil Knight's blog?

 

http://tee8tee4388.blogspot.sg/2013/07/kgsshv-amplifier.html

 

Where can I find the LT1021-10? It's a 10V reference isn't it? What are the alternatives?

 

What about this:

http://www.mouser.sg/ProductDetail/Texas-Instruments/REF102CP/?qs=sGAEpiMZZMuBck1X%252b7j9fIs%252ba2gLkdiAHE8B2fyCBAc%3d

 

Datasheet is here:

http://www.ti.com/lit/ds/sbvs022b/sbvs022b.pdf

You can get the LT1021 from digikey.

 

http://www.digikey.ca/product-detail/en/LT1021DCN8-10%23PBF/LT1021DCN8-10%23PBF-ND/891397

You can get the LT1021 from digikey.

 

http://www.digikey.ca/product-detail/en/LT1021DCN8-10%23PBF/LT1021DCN8-10%23PBF-ND/891397

 

Quantity available is shown as 0 for now. If it's just a 10V reference, I can always find an alternative, with the same package (PDIP-8 ) and same pin outs. The pin outs are almost like that of an op amp.

REF102CP (http://www.ti.com/lit/ds/sbvs022b/sbvs022b.pdf) has a min output voltage of 9.9975V to a max of 10.0025V. Not sure how it'd compare to the LT1021-10 (http://cds.linear.com/docs/en/datasheet/1021fc.pdf) though.

 

Also, will it make a difference in sound if I use 12x 2sc4686a vs using all IXTP01N100D?

the ref102 WILL NOT WORK

it cannot operate in 2 wire mode

you cannot use all enhancement mode mosfets

it will go boom

Edited July 20, 201411 yr by kevin gilmore

I meant, for parts where I can put the 2sc4686, can I put that in?

 

http://gilmore.chem.northwestern.edu/kgsshvproductiondualmot.pdf

 

Is the 2sc4686 safe for the 500V version?

 

I like boom, but chips are expensive...

if you have the latest boards with the zener protection you can replace the 3rd stage bottom and top of

the 4th stage with 05n100m (latest on board version)

 

or solder the zeners on the back

schematic was never updated

 

I have never actually seen 2sc4686. only 2sc4686a which is a 1200v part

I've got 1 2sc4686 without the A and collector to emitter voltage is 1000v and the 4686A is 1200v. Compared to the datasheet to death and that's the only difference between the two that I could find. Not sure about the fluxcapacitance though. 

 

Speaking of RK50 pots, is this an RK50?

 

http://www.thevintageknob.org/sony-TA-ER1.html

Edited July 21, 201411 yr by DefQon

1) Yes, that should be the only difference.

 

2) Looks that way.

 

 

//UFN

lots of 2sc4686a on ebay still for cheap. suggest you buy a bunch.

Does this look genuine? http://www.ebay.com/itm/12pcs-Toshiba-New-Original-Genuine-2SC4686A-C4686A-transistor-TO220-/281367004966?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4182c7c726#ht_1352wt_918

 

lots of 2sc4686a on ebay still for cheap. suggest you buy a bunch.

yes it looks real.

 

I have not seen 2sc4686a parts as fake yet.

 

I bought extra parts from many ebay vendors recently

and all test ok.

 

2sa1968 are a different story, most are fake.

Does this look genuine? http://www.ebay.com/itm/12pcs-Toshiba-New-Original-Genuine-2SC4686A-C4686A-transistor-TO220-/281367004966?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4182c7c726#ht_1352wt_918

 

That's where I bought mine from (as shown in ) and I now have some more on the way. However, the batch numbers in the listing picture and the ones I got are (very) different and the available quantity keeps changing. Most likely this is a seller buying up various leftover components from manufacturers in China and so there is some risk that you don't get what you pay for. Also, in my naivity I bought some 2SK389s from the same seller and they were clearly fake (tested as BJTs and not FETs) but the listing very clearly said "genuine Toshiba" so I would not unconditionally recommend this seller.

 

//UFN 

I just bought some 2sc4686a. I will post pictures when they arrive.

if you have the latest boards with the zener protection you can replace the 3rd stage bottom and top of

the 4th stage with 05n100m (latest on board version)

 

or solder the zeners on the back

schematic was never updated

 

I have never actually seen 2sc4686. only 2sc4686a which is a 1200v part

 

So I could replace Q1, Q2 which are 2sc4686a and Q11, Q12 which are 2sc2705 in this schematic, to IXTP05N100M? Is there any merit changing to the IXYS part?

 

http://gilmore.chem.northwestern.edu/kgsshvproductiondual.pdf

 

I haven't received my onboard PCB yet, but since it's from Lil Knight, I'd guess it should be the latest. I will have to check if the zeners are there.

I just returned from local surplus parts shop in Dallas. They are selling NOS 2SC3675 and 2SC4686A for $1.99/$2.75+tax

I didn’t check 2SC3675 but 12pcs left for 4686A.

 

ttp://www.tannerelectronics.com/

http://gilmore.chem.northwestern.edu/kgsshvproductiondualmot.pdf

you replace Q1,Q2,Q9,Q10 with ixtp05n100m

 

I don't think lil-knight has the latest dual transistor layout.

 

the Motorola transistors are a different pinout on the older boards.

 

most of us like the bipolar transistors better.

Thanks.

I have about 15 pieces 2sc4686a coming, should I keep and use 12 of those, or should I replace them with the IXTP01N100D?

 

I guess I will have to measure them and see if I can find matching pairs.

 

In the grand scheme of things, does it even make that obvious of a difference in sound, between using the EOL BJTs, vs the MOSFETs?

There is a huge difference between the mosfets and the BJT's with the latter being far superior.

 

That said I have the newest onboard PCB's should anybody need some. 

What are the differences between the newest onboard PCB and the next-to-newest onboard PCB?

 

I just found that RS-components has most of the BJTs needed. Maybe I should switch my BOM to using BJTs. 

the added zeners for the mosfets and changes in the labeling

also the dual transistor option

Kevin what do you think about using all BJTs (apart for the current source which needs the IXTP01N100D for the 500V ver) vs using all MOSFETs?

that is how I build mine.

For a 450V psu if using 2sa1486, do the unpopulated 270V zeners need to be shorted?

Edited July 22, 201411 yr by johnwmclean