Hi all,
This is a noob question I think, but I will ask it anyway 🙂
I have to replace some transistors in a Sony turntable which of course aren't available anymore.
The turntable does not spin although a hum can be heard when engaging the motor. I guess I have to sort out which transistor it will be by eliminating the ones in the specific section that controls the motor. All electrolytics have been swapped with new.
I tried searching on the web and found a website that shows several substitutes for the transistor.
The old transistor is 2SC634A and the site gives multiple possibilities, but the emitter, collector and base are positioned differently compared to the original 2SC634A. Is this a problem? Probably only if it is mounted on a heatsink I guess?
And can you just pick one out of the list shown, or is it still best to compare specs at all time
link;
2SC634a Cross Reference - Electronic Circuits, TV Schematics, Audio
Dan
This is a noob question I think, but I will ask it anyway 🙂
I have to replace some transistors in a Sony turntable which of course aren't available anymore.
The turntable does not spin although a hum can be heard when engaging the motor. I guess I have to sort out which transistor it will be by eliminating the ones in the specific section that controls the motor. All electrolytics have been swapped with new.
I tried searching on the web and found a website that shows several substitutes for the transistor.
The old transistor is 2SC634A and the site gives multiple possibilities, but the emitter, collector and base are positioned differently compared to the original 2SC634A. Is this a problem? Probably only if it is mounted on a heatsink I guess?
And can you just pick one out of the list shown, or is it still best to compare specs at all time
link;
2SC634a Cross Reference - Electronic Circuits, TV Schematics, Audio
Dan
It is a 50v 200ma NPN transistor. TO92 or similar. It is EBC across the front, and any other asian type will have that pinout, so anything with 2SC or 2SD.
Something like a 2N4401 would work, but yes the legs are in different order. One could mount one of those sideways so the legs can be bent to fit the holes. I have done that many times. But really a general purpose NPN 50v part should work. So why not stick with an asian type or one with the same pinout at least.
I am not a fan of using NTE parts, but really, they make an NTE293 as a cross, and it has legs that fit.
Something like a 2N4401 would work, but yes the legs are in different order. One could mount one of those sideways so the legs can be bent to fit the holes. I have done that many times. But really a general purpose NPN 50v part should work. So why not stick with an asian type or one with the same pinout at least.
I am not a fan of using NTE parts, but really, they make an NTE293 as a cross, and it has legs that fit.
Hi!
Why are you not a fan of NTE parts? I do not know them myself. Is it a quality thing?
I am quite new at replacing transistors and electronics altogether, only have some experience with capacitors.
I'd just picked one out of the list in the servicemanual that is in the motor section. I'll have to sort out which one is the faulty component. So therefore I'm learning on understanding transistors and their equivalents.
Why are you not a fan of NTE parts? I do not know them myself. Is it a quality thing?
I am quite new at replacing transistors and electronics altogether, only have some experience with capacitors.
I'd just picked one out of the list in the servicemanual that is in the motor section. I'll have to sort out which one is the faulty component. So therefore I'm learning on understanding transistors and their equivalents.
Hi Dan,
I'm another person who recommends against using NTE, ECG, SK or other replacement brand semiconductors. I've done service for over 40 years and if I see any of the above parts in a unit, they are on the list of parts to be replaced.
When I worked at a Jobbers place where we sold parts to the local service trade, I had to use ECG parts. They were not very good for starters and the cross reference book was so bad I called it "the book of lies". As soon as I switched to "real" parts, my return rate dropped to very low levels from a high level I was getting in trouble for. Most of the other replacement brand companies copied the ECG replacement guide except for the guys at RCA (SK), GE (geic) and Lake Industries (Elcom?).
I see so many bad and incorrect substitutions that I can't trust those brands. So what you want to do is use another Japanese transistor close to the one you have, or use a European or North American transistor. Sometimes the European ones match if you just turn the transistor around. The normal pinout for Japanese signal transistors is ECB whereas in North America we normally see EBC. The European parts can be all over the map, but are most commonly BCE.
Lastly, when you use a replacement brand you haven't a clue as to what part you installed (they remove the original markings and put their own on). Even if you were to use a North American part with the twisting of leads, at least you know exactly what you are installing. Just make certain you buy whatever part from a known distributor, one authorized to sell those parts by the manufacturer.
-Chris
I'm another person who recommends against using NTE, ECG, SK or other replacement brand semiconductors. I've done service for over 40 years and if I see any of the above parts in a unit, they are on the list of parts to be replaced.
When I worked at a Jobbers place where we sold parts to the local service trade, I had to use ECG parts. They were not very good for starters and the cross reference book was so bad I called it "the book of lies". As soon as I switched to "real" parts, my return rate dropped to very low levels from a high level I was getting in trouble for. Most of the other replacement brand companies copied the ECG replacement guide except for the guys at RCA (SK), GE (geic) and Lake Industries (Elcom?).
I see so many bad and incorrect substitutions that I can't trust those brands. So what you want to do is use another Japanese transistor close to the one you have, or use a European or North American transistor. Sometimes the European ones match if you just turn the transistor around. The normal pinout for Japanese signal transistors is ECB whereas in North America we normally see EBC. The European parts can be all over the map, but are most commonly BCE.
Lastly, when you use a replacement brand you haven't a clue as to what part you installed (they remove the original markings and put their own on). Even if you were to use a North American part with the twisting of leads, at least you know exactly what you are installing. Just make certain you buy whatever part from a known distributor, one authorized to sell those parts by the manufacturer.
-Chris
Hi, you wrote you're not familiar with transistors, I would first check that the suspect bipolar transistor is really broken.
If you have a multimeter that can measure transistor beta (shown as "hFE" on the multimeter), measure it. You have to insert all the three transistor legs in the appropriate holes for hFE measurement. (On most multimeters there are 4 holes for NPN and 4 holes for PNP, you have to select the three that fits the order of B, C, and E of your transistor.) For most small signal transistors hFE is somewhere between 100 and 500. If it's zero, very low, or unmeasurable, then the transistor is damaged.
If you don't have hFE check on your multimeter, then at least measure whether the two diode junctions (B-E diode and B-C diode) of the transistor are working.
Select diode drop measurement (shown as diode sign on the multimeter). For NPN transistor put the positive lead to B and negative to E, and measure. The same for the B-C junction: positive to B and negative to C.
If either diode drop is zero, close to zero, or it is "too high" (that is the meter is not capable to display the value) then the transistor is surely broken. If both diode drops are between let's say 500 and 1000 then the transistor is very probably not damaged.
If you have a multimeter that can measure transistor beta (shown as "hFE" on the multimeter), measure it. You have to insert all the three transistor legs in the appropriate holes for hFE measurement. (On most multimeters there are 4 holes for NPN and 4 holes for PNP, you have to select the three that fits the order of B, C, and E of your transistor.) For most small signal transistors hFE is somewhere between 100 and 500. If it's zero, very low, or unmeasurable, then the transistor is damaged.
If you don't have hFE check on your multimeter, then at least measure whether the two diode junctions (B-E diode and B-C diode) of the transistor are working.
Select diode drop measurement (shown as diode sign on the multimeter). For NPN transistor put the positive lead to B and negative to E, and measure. The same for the B-C junction: positive to B and negative to C.
If either diode drop is zero, close to zero, or it is "too high" (that is the meter is not capable to display the value) then the transistor is surely broken. If both diode drops are between let's say 500 and 1000 then the transistor is very probably not damaged.
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