A MOSFET can fail even by static but make sure that the non lit LEDs down its way are all correctly oriented and healthy by battery test without removing them first. With different color wires from a 9V you can fast check them one by one for flashing when the (-) goes to cathode side the right way.
Do these look genuine? Are there fakes of these around?
10PCS New 2SA970-BL A970 Low Noise Audio Amplifier For TOSHIBA Good Quality | eBay
10PCS New 2SA970-BL A970 Low Noise Audio Amplifier For TOSHIBA Good Quality | eBay
I have read another thread on this forum, where they compared 2SA970s and a couple of others, in both reel packaged and bulk, which looked quite different. One Chinese poster claimed that the fakes aren't really fakes at all, but a genuine and sophisticated attempt to recreate an out of stock fet. Another poster suggested that RS may have these "fakes" in stock too, judging by appearances. Testing for correct specs is perhaps the best test of all. Counterfeits are not just to fool us DIYers, but designed to fool large companies, even RS, Mouser and Farnell
Apparently, the best way to confirm that the fet is Toshiba is to look for an orangey grey print on the fet, zero exposed copper on the legs (should be well tinned) and shiny not dull plastic case. Testing for specs is important it seems.
I used my brain and decided to use protoboard. I think I have got it figured out. Hope I have enough heatsink. They are about an inch tall...using to-247 mosfets. Got some 2n5457s off of ebay. They are bad fakes...bad printing, sanded down faces. IDSS measures way way low. Once I get some good 2n5457s I should be up and running.
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I have a DIY DAC with quality 2.2uF auricaps at the outputs, and this folded phono stage design also has a 2.2uF cap at it's output.
Is there any good reason not to place a quality 2.2uF DC blocking cap at the input of the pre-amp instead of both sources, and save money on buying pricey high end DC blockers for multiple devices?
I would put the auricaps at the output of the input selectors on the preamp (unless for some reason it's a bad idea.)
I guess when you buy hifi separates that they have DC blockers at the outputs of source devices for safety, and at the inputs of amplifiers for safety, so you end up doubling up and potentially making a mess of the circuit in the form of a high pass filter or bass attenuator.
Is there any good reason not to place a quality 2.2uF DC blocking cap at the input of the pre-amp instead of both sources, and save money on buying pricey high end DC blockers for multiple devices?
I would put the auricaps at the output of the input selectors on the preamp (unless for some reason it's a bad idea.)
I guess when you buy hifi separates that they have DC blockers at the outputs of source devices for safety, and at the inputs of amplifiers for safety, so you end up doubling up and potentially making a mess of the circuit in the form of a high pass filter or bass attenuator.
That's why I recommend dual inputs and/or dual outputs with one of the in/outs bypassing the capacitor.
Then you can choose which capacitor gives better performance.
The body (case) is shiny, the face under the lettering is dull, like it's been sanded down.
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Your protoboard component placement.
Hi Hikari1.
Would you mind upload a drawing of how you place the components on your protoboard?
It would be very appreciated
Regards
Hi Hikari1.
Would you mind upload a drawing of how you place the components on your protoboard?
It would be very appreciated
Regards
OK, now I am worried about my 2sk117GR. I didn't get them from a group buy. Bought they from an online retailer. They appear like the one's Salas describes as fakes above...damn. I checked IDSS, it was in spec...about 4.3. But I didnt test curves. Should I use them?
What the hell is going on the world. This is crazy. I understand the motives for faking these parts but you would think that Toshiba and other big semiconductor manufacturers would be suing the crap out of guys doing these...not to mention the governments of the countries this is happening in. Crazy.
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Hi Hikari1.
Would you mind upload a drawing of how you place the components on your protoboard?
It would be very appreciated
Regards
Turbon,
I will. But don't you want me to get it working first? I don't want to be responsible for a fire in your house. I don't have a transformer yet...But should be soon.
They will probably work sufficiently for now but get better later. Its not clear if they are copies or just an off spec batch from some licensed foundry, one thing is sure, they aren't 100% for curves. Something like 75%.
Would 2sk170bl be a safer choice instead of the suspicious 2sk117gr for q2 and q5? I know my 2sk170 are good. 8.5ma IDDS.
thanks again salas.
Thanks to Tea B I finally got a new mosfet in there,everything light up Now
.now need some adjusting.Now my power supply voltage drop to 37 voltage at DC end when hook up and both fire up? it that normal?lapsan
Could be hotter and driftier until you get genuine 117GR but you will be sure about the noise spec and curves meantime.