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Started by dlbraly, July 16, 2018, 10:51:25 PM

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What is your favorite website to order parts from?

I found some parts on utsource.net, but I was not ready to check out. I knew I wanted to get some more parts.
The next day they emailed me (copied email below). now Im afraid to purchase from them.
Seemed weird to me.

Dear my friend
Wish you have a nice day !
We noticed that you add the parts:2SK30A-GR etc.to shopping cart from our website ,but we still did not get your any payment ,May i know the reason ?

Could you please inform us when do you complete the payment ? We will arrange the shipment for you in advance, any questions pls mail us.

In order to have more cooperation,
If you are new customer, You get an opportunity to redeem $14 free shipping coupon.


I did a search and did not see a post on places to get parts.
Is that a faux pas to ask on the forum?


No problem asking, most folks already have parts sources.   I have not heard of the one you linked, I know nothing about them.  I note they are not a USA company.

We generally use large parts houses like Mouser or Digikey.   But your 2SK30 is an old obsolete part they won't have.

Companies like AES - www.tubesandmore.com - sell a variety of parts specifically for teh old amplifier market.  They sell tubes and sockets, jacks, pots, etc.  But I don't see 2SK30 there.

Small Bear Electronics has a bunch of interesting parts, and they list the 2SK30, though they say out of stock at the moment.

I see 2SK30 on ebay, but I personally never buy parts from ebay.


Is there a replacement transistor I could use instead of a 2SK30?

yeah I won't be using the one I linked.


Let me rephrase that
Please teach me how to figure out a replacement part.
Do I look at data sheets?

quick google someone said 2n5457 - so I guess I need to compare data sheets on those.


Is this about your Yamaha?

That amp is full of 2SK30 JFETs.  WHich one is your bad one?  And what is it doing?

See TR206,207?  On the power supply board, near the speakers on the drawing.  They are almost in parallel, but both work together to act as a power up mute.   If you carefully remove them, you can use them elsewhere in the circuit.   If the bad one IS one of those, then just remove it.

TR301,TR302 are the diffy pair at the power amp input.  If one is bad, swap it for one of the mutes.

Likewise the preamp has several.  Tr101 on each channel board is its output and can be swapped for a mute.  TR102 on each preamp board is a mute used for channel switching.  WHen it turns on the mute that channel goes off.  Again, any of those can be replaced by one of those main mutes.

So what I am saying is you have two "spare"2SK30's on the power supply board.  Determine where you need one and use one of those. 


Quote from: dlbraly on July 17, 2018, 10:50:51 PM
Let me rephrase that
Please teach me how to figure out a replacement part.
Do I look at data sheets?

quick google someone said 2n5457 - so I guess I need to compare data sheets on those.

The 2SK30 is an N-channel MOSFET, not a JFET like the 2N5457.

I would go to Mouser.com, do a search for N-Channel MOSFET and plug in all the details you can from the 2SK30 datasheet in their search filter.

As far as suppliers, I tend to order a lot of parts from Tayda Electronics, but I've used Futurlec and Mouser a few times as well.
Tayda keeps up on what's in stock and available, and their shipping is reasonable.  Futurlec can have stuff you won't find anywhere else, but there are complaints all over the net about their shipping time, mostly because they will hold up your entire order for one item that's out of stock. 


Tayda says 2SK30 are out of stock, Futurlec says they have them in stock, but don't believe them until you get a positive response.  Their "Contact us" page has phone numbers and email addresses.


The Schematic states 2SK30A which is a FET ,, while 2SK30 is a mosfet.  It's easy to get them mixed up ;)
And yes likely getting harder to find.

NTE458 might work but reading says the pinout is reversed


Yes - it is the Yamaha G100-112 first series amp.

Thanks for all the comments. Thanks you for being patient with me. I am new at that this and want to learn for a hobby. late in life to learn, but fun.
I will take a better look tonight when I get home.
BUT I'm pretty sure someone may have changed out the FET transistors on the MA board with a different ones. I took lots of pictures on my cell phone.
Looks like 2 on the MA Board are:
8 .IN

transistors on the MA board looked backwards, so being different might explain that. the pin out might be different on those parts.

Yes the bad transistor found was on the DC board.

Problem - the amp was not amplifying the clean channel like you would expect a 100 watt amp. you would have to turn it up past 5 on the clean channel.
The distortion channel was even worse and sounded terrible. had to turn the distortion channel up to 10.

So far I have found some bad solder joints, the boards were caked with flux and grime, a 47k ceramic capacitor that reads 43, a cracked input jack, and that bad transistor 2SK30A on the DC board.

what I've done - I'm learning, I probably did not have to do all this. Fun hobby for me.
Ive been cleaning the boards with  isopropyl alcohol and a toothbrush, removing parts checking them on a LCR T4 tester, cleaning the hole if a drill bit, and putting them back on.

I'm at work, do you want to see pictures? I can post them when I get home.


There are two of them on the power supply board.  I mentioned they are power up mutes.  If they short or get leaky, then the amp remains muted.   SO just remove the bad part and see if the amp wakes up.

Ever try to drive your car with the parking brake on?  It usually goes, but the car feels weak and sluggish.   If you then kick off the brake, the car comes back alive.   This is similar, I suspect your amp is being muted - like a parking brake -  and removing that "brake" might wake it up.

MOSFET?  I can't find a data sheet for the plain 2SK30, it was always a JFET to me.  The schematic shows JFET 2SK30A anyway.


yes one of the bad transistors was TR206 or TR207

Whats written on the transistors in TR301 and TR301 is
(triangle) N


So did you try just simply removing that bad one and trying the amp without it?

I assume they used a 2SK127 there then.


I want to, but I don't have any thermal paste for Transistors that I took off.


Goes by various names, all similar to:  silicone thermal heatsink grease, or thermal compound.  Electronics parts houses like Mouser or Digikey sell it.   Radio Shack used to, maybe still does if you still have a Radio Shack around.

NEVER fire up the amp without the transistors mounted properly on a heat sink.  To do so would be like running your car motor with no water in the cooling system.


I figured as much, We have a Fry's Electronics not too far. I may pick some up tonight.