3020 FET -any replacement?

Jimvanny

New Member
Got a 3020 a while back that was in pretty sorry shape but have been slowly making some progress on it. After cleaning it up and rebuilding the power supply (new caps and transistors), finally got sound from the aux (and FM) through the pre-amp outputs but the main amp boards are both bad. I have checked the transistors and replaced all the fuse-resistors and now have 45v on the outputs .. odd both left and right have the same problem. One thing is that the FETS (2SK99) seem to be installed backwards... that is the pin 1 'bump' on the IC is not on the same side as the hash-marked spot on the circuit board that I assume means pin 1 goes to that side. I pulled the FETS and the 45v goes to almost zero. I measured them with the diode tester on the DVM and the G-S = 0.62, G-D=0.62, and D-S=0.03. The other side of the same IC is G-S=0.3, G-D=0.3, D-S=0.03.
Is the FET bad on one side or could it have been installed backwards (didnt look like it had ever been unsoldered but I suppose one never knows)? Is there an acceptable modern replacement for the 2sk99 that is available?
 
hmm - not much help on this one yet Jim!

just wondering - what serial number is yours? Not trying to hijack your thread, but so far I haven't seen anyone post one below 1000, and none above 3000. would be interesting to know how many were made, and by that it would seem 2000 or less.

I get mine in a month or so... I'm a wee excited! :D
kudos for tackling a restoration on one. :thmbsp:
 
I believe that you can use a 2SK100 if you can find any of those, they were used in the Yamaha A-1 so they are a bit more recent.
 
Thanks all. Merrylander, I'll keep an eye out for an A-1. The serial number on mine is 02681. Any thoughts on the fact that my 2sk99s' are not reading the same voltmeter checks on both sides of the ICs? I would have expected them to be the same and, if so, the orientation of the chip wouldnt matter.
 
The only hits I come up with are other people asking the same question.
 
If I come up with an answer, I'll be sure to post it. In the meantime, in regards to the serial numbers, is the theory that the serial numbers start at #1000? Seems reasonable since the products I have been involved with have all started their serial numbers at 500.
 
Ca810----2sk99
ca2010--2sk100
c-4------2sk100
a-1------2sk100
 
If I come up with an answer, I'll be sure to post it. In the meantime, in regards to the serial numbers, is the theory that the serial numbers start at #1000? Seems reasonable since the products I have been involved with have all started their serial numbers at 500.

That's my working theory... any searches I've done have not turned up any numbers below 1000 or above 3000... At least not yet. I may start a thread to find out what numbers are out there once I pick mine up next month.
 
3020 serial number

I got my 3020 last summer. It is number 2320. I had a complete restore done - it was not cheap - and it looks and sounds great.
 
I got my 3020 last summer. It is number 2320. I had a complete restore done - it was not cheap - and it looks and sounds great.

:thmbsp: awesome! the restoration must have cost you almost as much as the receiver itself. I'm not sure how much I want to tackle on mine, perhaps just some preventative stuff, replace common problem parts - but a full re-cap/restore I'll leave for awhile. this is not a receiver to screw up!

once I get mine (hopefully in March) I'll start a separate "show off your 3020" thread...
 
Yes, the cost of the 3020 plus the restoration has put this baby over the top as far as resale goes. I will never get my money back, but I don't plan on selling this for many years to come. It is just too good, too beautiful and too rare.
 
Got a 3020 a while back that was in pretty sorry shape but have been slowly making some progress on it. After cleaning it up and rebuilding the power supply (new caps and transistors), finally got sound from the aux (and FM) through the pre-amp outputs but the main amp boards are both bad. I have checked the transistors and replaced all the fuse-resistors and now have 45v on the outputs .. odd both left and right have the same problem. One thing is that the FETS (2SK99) seem to be installed backwards... that is the pin 1 'bump' on the IC is not on the same side as the hash-marked spot on the circuit board that I assume means pin 1 goes to that side. I pulled the FETS and the 45v goes to almost zero. I measured them with the diode tester on the DVM and the G-S = 0.62, G-D=0.62, and D-S=0.03. The other side of the same IC is G-S=0.3, G-D=0.3, D-S=0.03.
Is the FET bad on one side or could it have been installed backwards (didnt look like it had ever been unsoldered but I suppose one never knows)? Is there an acceptable modern replacement for the 2sk99 that is available?
Hey Jimvanny - were you able to figure out your FET problem? I am restoring a 3020, and one channel has a bad 2SK99. Trying to source one or equivalent with no luck. Were you able to find any or equivalent 2SK99?
 
2SK99A and 2SK100 are used in CR3020

I don't understand your mesurement on your double FET
The fact that you are looking for 2SK99A is not a problem but you have to be sure that it is defect for sure .

YAMAHA did use : 2SK99A (IE100770)
2SK99B (IE100700)
2SK100 (IE100600)
2SK100A (IE100900)
2SK100C(IE101130)
2SK100D (IE101140)
 
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2SK99A and 2SK100 are used in CR3020

I don't understand your mesurement on your double FET
The fact that you are looking for 2SK99A is not a problem but you have to be sure that it is defect for sure .

YAMAHA did use : 2SK99A (IE100770)
2SK99B (IE100700)
2SK100 (IE100600)
2SK100A (IE100900)
2SK100C(IE101130)
2SK100D (IE101140)
Do not mean to break in this thread, but I am restoring a Yamaha CR-3020. It has a bad dual FET on main amp board. 2SK99A(IE100770). Can not find any. Seems impossible to find. Considering using discrete FET's as replacement. Is that possible?
 
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