As you can see from the 440 posts, we all try to help.
Your part of the job is to try to grasp the given info the best you can. 🙂
I'm sure we will get there in the end.
Your part of the job is to try to grasp the given info the best you can. 🙂
I'm sure we will get there in the end.
We will know what current flows when we got the measurements.
Keep using the bulb for now, it's a nice one. 🙂
Keep using the bulb for now, it's a nice one. 🙂
i will do it. btw today i can work on this project but in next few days i will not be able to because of some thing i have to do. so today i will do it and you can tell what is going on 😀
Try a bigger speaker? Make sure the distortion is not caused by the speaker been over driven.
please post the voltage of the following point:
It should be around half of the power supply voltage = 27.5V, if not, adjust the potentiometer to get the voltage as close to 27.5V as possible. It will increase power and reduce distortion.
please post the voltage of the following point:
It should be around half of the power supply voltage = 27.5V, if not, adjust the potentiometer to get the voltage as close to 27.5V as possible. It will increase power and reduce distortion.
maybe capacitorts are bad maybe some of them. i dont have option on my meter to test caps so they are maybe bad at least some of them
Got suspect capacitors? You can do very crude tests with almost nothing at all. Charge it on a 9 volt battery and see if it even holds a charge for a few seconds. Charge it, let it sit for a bit, measure with your cheapo meter. ESR test? Discharge it through a speaker (charged on the 9 volt) and see if there is a healthy pop. No, you cant tell if it’s in spec or not. But you can tell if it will prevent your amp from working. Theres mildly bad that can use replacement but not the end of the world bad, and very bad where it won’t even pass a signal bad. Those you have to change out. Got a big cap you wouldn’t trust discharging thru a speaker because it might fry it? Discharge it thru the dim bulb (at full or almost full voltage). If it doesn’t light for a second at all, its got too much internal resistance to work properly.
You can make do with what you have. You just have to think about things and how they should behave.
You can make do with what you have. You just have to think about things and how they should behave.
big cap one for power or on speaker ? one on speaker does not have any voltage i think i am not sure 100% but it looks like it
The big cap on the power supply is easy to test. Just plug in the power supply without the amp hooked up to it. Monitor the output voltage. It should only down SLOWLY with no load after switching off power. Discharge it into a 60 watt light bulb. You should see a momentary flash. Won’t be full brightness because it’s only 55 or so volts but it will light up for a second or so. If the cap voltage falls instantly when you switch off power, or if the bulb won’t come on it all when discharging it’s unhealthy enough to cause trouble. The one in series with the speaker may be too small to hold enough charge to tell much with a dim bulb, but probably ok to unhook, charge with a 9 volt battery, as discharge into a speaker. You could discharge it with a screwdriver and look for a good spark, but it’s not good for the capacitor to do that. It was however, a great source of entertainment back in middle school, with expendable capacitors. Smaller 10-100 ish uf capacitors still produce a solid pop in a loudspeaker if healthy.
If the amplifier had enough oomph to blow up the output transistors when the speaker got shorted the cap probably has a low enough resistance not the be a problem in normal operation. If the cap was excessively lossy it might have heated up and blown the cap not the transistors. Or might not have been able to pass enough current to do any damage. They can get THAT bad.
If the amplifier had enough oomph to blow up the output transistors when the speaker got shorted the cap probably has a low enough resistance not the be a problem in normal operation. If the cap was excessively lossy it might have heated up and blown the cap not the transistors. Or might not have been able to pass enough current to do any damage. They can get THAT bad.
i am not sure if all caps work, i am not a pro when it comes to this but if resistors are all working transistors are working what else is there? caps i dont have equal voltage on both 2n3055 so one comes hot really fast and other one is mildly hot after a few minutes so the voltages confirm that. adjusting trim does almost nothing to equalize that voltage. so my suspects are caps. i will test them but i am sure that one of them may be bad ones on board probably.
i may have time to test it in the evening. but voltages that i already tested are 26v for one transistor and 7.5 for other one. they should be equal ? i will test what you told me last time but i am just giving suggestions now what problem could be.
Hot transistors does not point to defective caps. Defective caps are when the amp comes up seemingly normal (with low heat, normal voltages) and you get a lot of hum or very low audio.
Hot transistors - what is the voltage between the bases of Q3 and Q4? Does the heat GO AWAY if you short those two points?
Hot transistors - what is the voltage between the bases of Q3 and Q4? Does the heat GO AWAY if you short those two points?
sg97, you keep giving us the same measurements across the transistors, but that does not help us.
Yes, please start with the measurement asked for in post #446. If we don't get that information, we cannot help you.
A wild guess would be 7.5 V.
https://www.diyaudio.com/community/...ing-after-shorting-output.406712/post-7559608
But the top transistor should measure 55V, not 26V if the schematic is correct and if sg97 measured the collectors to ground.
Much if's...
https://www.diyaudio.com/community/...ing-after-shorting-output.406712/post-7559608
But the top transistor should measure 55V, not 26V if the schematic is correct and if sg97 measured the collectors to ground.
Much if's...
Why we need to guess? Is it that hard for OP to get the measurement that everybody asking for?