15lyl

https://www.richardsonrfpd.com/Products/Product/C2M1000170D

They are in China. 86 is China, Hong Kong is 852.

We cannot get these 2SK109 and 2SK389 anymore, they are obsolete for a long time, all of them are fake from AliExpress.

Hi Kevin, Thank you for your message about the bias of the cfa3 amp, I am running the ZF, by disconnecting the 4 600p, I could adjust the bias smoothly to 200mA, no squeak or oscillation any more. What are those 600P for?

I etched the board myself, am running the ZF. I can only stop the oscillation by connecting a 500P to the B, C of the output transistors, smaller than 500P can’t stop the oscillation. I may try to run the SS later to see the negative feedback will help the oscillation.

Thanks, I did so.

Hi Kevin, the 4 transistors around THAT340 are in different orientation, the THAT340 pnp C is to the following Tr E, while the npn is to C. which one is correct? All ON brand MJE15030, 15031 that I used in the power output had oscillation, some Motorola were stable. Is the fT30 too high?

I use this schematic for KGSS +-15V 15V.pdf

ALL my problems are from my very old EI transformer, which produced a big voltage transient surges when switched on and killed 4 of 2sa 1968, now I need to put 2 metal-oxide-type varistors in the secondary. I think I need a toroid transformer to rewire the power supply.

Thank you for your quick response Kevin. 2sa1486 is not available in Australia too. The noise was from the bias voltage. When my probe touched the bias, the noise disappeared, then I put a 5uf cap. after the 4.7M ohm, it has been fixed. Now I need to adjust and listening. Where can I read your KGSSHV the whole article? It is not in the HeadWIze site now?

It takes me almost 8 years to complete the KGSS, because due to the lack of 2sa1968, now I use a 2sa1413 instead and reduce the supply voltage to 345v. When I test the amp with a CRO, there is an about 100 KHz sawtooth wave oscillation, I connect two 560pf caps. between B E of 2sc3675 in the third stage, the sawtooth gone. But when I listen with my Stax SRX mark3, there is still small squall oscillation; even I increase the caps.to 2nf. If I connect the caps. between 2sc2705 base and 2sc3675 collector, all high frequency gone. Will anyone help?