Electronics > Projects, Designs, and Technical Stuff
Looking for transistor data: ETD41-035
unitedatoms:
There is archived 1987 article on Fuji site about ignition transistors: http://www.fujielectric.com/company/tech_archives/pdf/33-01/FER-33-01-28-1987.pdf
May be the closest device in table 1 is:
ETE41 in TO-3P package 450V 8A 80W 500HFE Darlington, speed unknown, may be in order of 0.5uS
After reading article, it looks like a precursor of IGBTs. The snubber circuit is named "snapper". May be secret of this ignition transistor is an embedded snubber R-C inside the plastic package ?
torch:
--- Quote from: unitedatoms on August 12, 2015, 10:06:52 pm ---There is archived 1987 article on Fuji site about ignition transistors: http://www.fujielectric.com/company/tech_archives/pdf/33-01/FER-33-01-28-1987.pdf
May be the closest device in table 1 is:
ETE41 in TO-3P package 450V 8A 80W 500HFE Darlington, speed unknown, may be in order of 0.5uS
After reading article, it looks like a precursor of IGBTs. The snubber circuit is named "snapper". May be secret of this ignition transistor is an embedded snubber R-C inside the plastic package ?
--- End quote ---
Funny you mention Fuji. The ETD41-035 arrived today. Different from the photo in the ad. This one bears a modern "Fe" Fuji mark instead of the mark identified as Fujitsu by several websites. That is now in question as, while exploring the Fuji website to see if they could have made this, I found Fuji claiming ownership of that mark on their website! They say they used that mark from 1923 to 1978.
However, I still couldn't find the datasheet :(
Anyway, back to the transistor, the Chinese-sourced ones test similar on my $20 transistor tester (early Karl-Heinz type) compared to the 2 de-soldered from a known-good TCI. Hfe around 8. Forward voltage drop is a bit lower -- about 0.9 for these ones, about 1v for the originals. But looking very close at the face under the faint printing, I see fine striations. I wonder if it was sanded and reprinted. If so, the question becomes "by whom?"
unitedatoms:
I think there is no direct replacement from contemporary parts, so it is impossible to get negative spike as on oscillogramm. The negative spike is possibly coming from diode + capacitor in "snapper" circuit. To make an equivalent module it should be high voltage darlington with 2 resistors + avalanche diode + protection slow diode + fast diode + capacitor + resistor. As on Fig 2 and Fig 9 in the paper.
torch:
Actually, that ST901T comes pretty close:
For comparison, here is the original known-good one again:
(The bias is because I forgot to set the coupling the same when looking at the replacement. But the overall waveform is very similar).
mikerj:
Sorry I missed your reply a few days back, it's great to know the replacement worked out ok :-+
One thing that's interesting is that the dwell time appears to be much shorter with the ST901T, about 2ms compared to ~10ms with the original. Presumably this system has an active dwell control based on peak coil current, have you tried looking at coil current?
I'm just wondering if the driver stage before the darlington maybe wasn't providing enough base current to saturate the original transistor, which could both explain it's failure (increased power dissipation) and the longer dwell. The much newer ST901T probably has a higher current gain than the original and requires less base drive.
The RPM is a fair bit higher on the ST901T trace though, so maybe the system (12v) voltage was higher leading to lower dwell time?
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