Kinda thought it might be those. I've had a couple now with duff drivers, had a Kenwood TS50 which had got so hot it melted the solder around the drivers and there was an electrolytic cap that had neatly desoldered itself, was rolling around in the bottom of the PA enclosure. Recapped the PA but the client refused to pay for the whole radio to be done.
@@IMSAIGuy Sorry You didn't I look at last video , sorry I am getting old. Still enjoy your channel. I wish you were my neighbour. Cant wait for next video.
I'm no electronics expert, but am I correct in believing the DC supply for the cct is via the centre tap of L10? If so, the DC should go no further than C96 & C97? If for instance C96 went short this would put virtually the supply voltage across both the B-E junction of Q3 and be across R15 and via L7 across B-E Q4 and R14?
$50 EACH!! For a single transistor. Bloody hell, that is absolutely crazy. In the schematic, they are driving centre tapped transformer L10 and L7 is the gate/base driving transformer so its just a switching power supply in push/pull configuration. Check the datasheet and compare the specs to cheaper transistors with the same or better specs. Could they be replaced with FETs?
You can replace those with others, as it is just a class C amplifier, so no real bias issues. 2SC6144 looks like they will fit, and are under $1 each anyway, so even if they blow up cheap anyway, plus are way overkill for this application, using a modern robust power device. looks like they will work here nicely.
@@paulcohen1555 Class C amplifier, so it is switching, and was just a first look at something that was same polarity, similar enough at first look, and lowest in price and in stock. I would then start to look for better matches and something closer then. Transistors are not exactly magic, many part numbers are often the exact same die, just either different package, different pinout and different application. Here not exactly critical, the original part is a pretty old design, and there are plenty of more modern parts that improved on the design that you can use here, that will do the job. It is very rare to have a transistor that cannot be substituted, unless the part was some part that did something, like a GCS, UJT or JFET, or a tunnel diode or backward diode, where the parts are simply no longer made any more for that part. Even germanium transistors can, for the most part, be replaced with silicon with only minor changes, and switching applications there are thousands of transistors that can act as RF amplifiers in the application here, just have to find ones that work with either drop in, or minimal change, though having a non standard pinout is not too much of an obstacle, you just have to either look for a flange mount, or a good insulator for it.
Wow! This is turning into quite an ordeal! Don't you think that there's a chance you'll replace the transistors and they'll just pop again because something else is very wrong?
Kinda thought it might be those. I've had a couple now with duff drivers, had a Kenwood TS50 which had got so hot it melted the solder around the drivers and there was an electrolytic cap that had neatly desoldered itself, was rolling around in the bottom of the PA enclosure. Recapped the PA but the client refused to pay for the whole radio to be done.
I was correct , transistors shorted. Big fan of the channel.
I didn't delete it. at least not on purpose
@@IMSAIGuy Sorry You didn't I look at last video , sorry I am getting old. Still enjoy your channel. I wish you were my neighbour. Cant wait for next video.
Good old Donberg electronics, used them many times.
Two fake transistors on the way.
I'm no electronics expert, but am I correct in believing the DC supply for the cct is via the centre tap of L10? If so, the DC should go no further than C96 & C97? If for instance C96 went short this would put virtually the supply voltage across both the B-E junction of Q3 and be across R15 and via L7 across B-E Q4 and R14?
Indeed.
Please suggest a simple circuit to test RF Power transistors such as 2SC1972.
$50 EACH!! For a single transistor. Bloody hell, that is absolutely crazy. In the schematic, they are driving centre tapped transformer L10 and L7 is the gate/base driving transformer so its just a switching power supply in push/pull configuration. Check the datasheet and compare the specs to cheaper transistors with the same or better specs. Could they be replaced with FETs?
Imsai guy, have you done a vid on your IR camera? What brand/model is it?
ua-cam.com/video/MAZeF4fGRsc/v-deo.html
You can replace those with others, as it is just a class C amplifier, so no real bias issues. 2SC6144 looks like they will fit, and are under $1 each anyway, so even if they blow up cheap anyway, plus are way overkill for this application, using a modern robust power device. looks like they will work here nicely.
wrong pin out
Regardless of the pinout, why you think a SWITCHING transistor can replace an RF POWER transistor?
@@paulcohen1555 Class C amplifier, so it is switching, and was just a first look at something that was same polarity, similar enough at first look, and lowest in price and in stock. I would then start to look for better matches and something closer then. Transistors are not exactly magic, many part numbers are often the exact same die, just either different package, different pinout and different application. Here not exactly critical, the original part is a pretty old design, and there are plenty of more modern parts that improved on the design that you can use here, that will do the job.
It is very rare to have a transistor that cannot be substituted, unless the part was some part that did something, like a GCS, UJT or JFET, or a tunnel diode or backward diode, where the parts are simply no longer made any more for that part. Even germanium transistors can, for the most part, be replaced with silicon with only minor changes, and switching applications there are thousands of transistors that can act as RF amplifiers in the application here, just have to find ones that work with either drop in, or minimal change, though having a non standard pinout is not too much of an obstacle, you just have to either look for a flange mount, or a good insulator for it.
@@SeanBZA Class C doesn't mean it is SWITCHING.
$50 !!! Bloody hell that's expensive.
Intrigued to learn where the permanent 12V is coming from....
All radios of this type have live voltages. It draws 22A at 13.8V so there is no switch big enough. It is important to turn off the external supply.
Wow! This is turning into quite an ordeal! Don't you think that there's a chance you'll replace the transistors and they'll just pop again because something else is very wrong?
yup, that is always a worry