It is important to realise that the conditions the transistors are tested under makes a big difference to the results. Those Darlington power transistors have an internal 70 ohm resistor across B/E of the 2nd transistor (to speed up and improve switch off time by removing minority carriers from the P/N junction) and something like that resistor may cause a generic all in one tester to give misleading results.
If you are unsure then remove a transistor from the good channels and compare.
Repairing something like this involves a lot more than just replacing transistors in the hope it will work... its good that you are trying but please don't under estimate the skills needed to fault find down to component level.
If you are unsure then remove a transistor from the good channels and compare.
Repairing something like this involves a lot more than just replacing transistors in the hope it will work... its good that you are trying but please don't under estimate the skills needed to fault find down to component level.
I'm using something suggested on this forum at current room temperature of 69°F.
It is giving much more accurate readings than my multimeter.
DROK Transistor Tester, Mosfet Transistor Capacitor Tester, Mega328 NPN PNP Transistor Diode Resistor Inductor Capacitance MOS SCR ESR Meter Automatic Checker Detector https://a.co/d/auEVWlx
Although, I am pretty sure those transistors got fried in the short, I do not want to waste time. Day after day of waiting for another delivery. I may find some cheaper Amazon resistors to put on there just to test if they are going to stop blowing now that I have the problematic transistors out.... They won't have a load on them, just making sure that the component behind them isn't causing the fuse blow.
It is giving much more accurate readings than my multimeter.
DROK Transistor Tester, Mosfet Transistor Capacitor Tester, Mega328 NPN PNP Transistor Diode Resistor Inductor Capacitance MOS SCR ESR Meter Automatic Checker Detector https://a.co/d/auEVWlx
Although, I am pretty sure those transistors got fried in the short, I do not want to waste time. Day after day of waiting for another delivery. I may find some cheaper Amazon resistors to put on there just to test if they are going to stop blowing now that I have the problematic transistors out.... They won't have a load on them, just making sure that the component behind them isn't causing the fuse blow.
As I have said, if the output transistors are good and you short the vbe multiplier out then you can not get a condition that will bias both outputs on together (which is what causes high current and failure).
I haven't got to the stage of linking them yet because the board keeps blowing fuses.
If I can get the test fuses on without a blow, then, I'll order the transistors, but they are on backorder.
I know the transistors are Sanken. I can get them elsewhere, Sanken has an authorized dealer page. Also, the resistors have a W in a box on them (attached picture). They are not exclusive to Denon, however I can't find much on them, maybe except for the last company to make something that looks like them is Panasonic.
Not to mention, I'm spending 75% more to order the same product from Denon
If I can get the test fuses on without a blow, then, I'll order the transistors, but they are on backorder.
I know the transistors are Sanken. I can get them elsewhere, Sanken has an authorized dealer page. Also, the resistors have a W in a box on them (attached picture). They are not exclusive to Denon, however I can't find much on them, maybe except for the last company to make something that looks like them is Panasonic.
Not to mention, I'm spending 75% more to order the same product from Denon
Attachments
I forgot to mention, way back when I started to work on this issue, the 2560/1647 I was using from a different vendor, they had different ratings than the factory installed ones, not to mention they were also fake. The SK and the model number washed off with a couple exposures to 90% IPA.
That was the reason for the extra heat.
Thanks for keeping up on this thread though @Mooly
If the reason is a bias problem then linking will stop it blowing fuses. In any case it forces zero bias which is a good state to have that channel in while working on it. Fake parts are always a problem 🙁
No, you're right, they don't have the 1647 in stock. The only place I show that does is Verical. They are associated with Arrow (IIRC), and i have bought from them once or twice with no issues. Here is a link to an octopart search. I would trust TME on this list, but not the others (other than Verical).
https://octopart.com/search?q=2SB1647¤cy=USD&specs=0
https://octopart.com/search?q=2SB1647¤cy=USD&specs=0
I'm not going to get any help on this one. Denon/Encompass don't have it in, Denon referred me to Encompass.
I'm on my own here..
One thing I did pledge to make sure I'm not wasting money is getting one channel operational, then moving to another channel (same pair of known good transistors) and on until all are tested and working.
If they are all working, I will order the OEM parts from Denon and start enjoying the thing.
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That sounds like a plan. Fwiw, power transistors usually fail short circuit from C to E but if you have suspected fakes then even they pass that test they would still have other issues.
That's every transistor I have. I'm pretty sure none of them made it through the short.
I will order a pair and see how they compare, but nothing good to compare it with now.
More of this on Wednesday, I guess.
I will order a pair and see how they compare, but nothing good to compare it with now.
More of this on Wednesday, I guess.
These transistors are from DigiKey, a site listed on Sanken.
Still about 300.. nowhere around 5000
Still about 300.. nowhere around 5000
Its down to how they are measured, a generic tester does not make the grade I'm afraid. If they are genuine they will be fine and will meet the published specs if measured under the correct test conditions.
No, if you got them from Digikey they will be genuine parts. You have to accept that the difference between what you measure and what they are supposed to be will down to the tester you have.
If you want to measure the gain of the transistor you will have to rig up a test circuit and calculate the approx gain. You need a suitable current limited power supply and the transistor under test MUST be on a heatsink.
Like this. Calculate the current in R1 and R2 using ohms law. This gives us approximately 190uA in R1 and approximately 416ma in R2. Divide the base current (R1) into the current in R2 and we get approximately 2190 for a basic current gain.
If you want to measure the gain of the transistor you will have to rig up a test circuit and calculate the approx gain. You need a suitable current limited power supply and the transistor under test MUST be on a heatsink.
Like this. Calculate the current in R1 and R2 using ohms law. This gives us approximately 190uA in R1 and approximately 416ma in R2. Divide the base current (R1) into the current in R2 and we get approximately 2190 for a basic current gain.