thank you all for helping me and also for listening to me xdd this project is gone the long way and i really learned a lot now i can tell npn and npn by symbol for example and all the other stuff that you guys told me 😀 so as i said before when amp is fixed i will put it in custom made box that i already made and it will be custom amp head 😀 btw my initial idea is to use single board amp i have that it rund on 24v it gives 50w but its no fun and those board fail after few years its not long lasting so i decided to go this way 😀 i was thinking i have this old amp from my grandpa why not fixing it it can be good but i did not know that it was this bad xdd
Hi wg-ski,
I have not run into a Leach amplifier. In most amplifiers they would use an output as a driver in high power applications, or a TO-220 device in lower power situations. So the MJ15001 and MJ15002 were completely unknown to me. I have used tons of 2N3773 and 2N6609 outputs.
The Fairchild parts were faster. It was common to have to change the compensation when using them. Mixing those with other brands was a big no-no. In fact, way back we were taught to match outputs and keep to the same brand. It was an excellent rule in practice which I have always followed. RCA parts were also very good, TI was junk back then.
The MJ15015 and MJ15016 were complete garbage transistors. Parameters all over the place and a huge difference between NPN and PNP types. If you look at the data sheet, they state they are "economy grade" devices. I refused to use them even doing warranty service for new product. But back then, transistors weren't that great compared to what we have. I had to pre-sort and grade new parts, buying a lot of them. The culls were used for regulator pass transistors or discarded. Low beta devices hit the trash. Today I don't have to throw any out. Matching yields are very high too, On Semi (Motorola) being the best now. Earlier, the Japanese brands were the best.
If you look at the old beta vs collector current curves (and they were curves!) and compare them to today's parts, you wouldn't use an old output transistor.
I have not run into a Leach amplifier. In most amplifiers they would use an output as a driver in high power applications, or a TO-220 device in lower power situations. So the MJ15001 and MJ15002 were completely unknown to me. I have used tons of 2N3773 and 2N6609 outputs.
The Fairchild parts were faster. It was common to have to change the compensation when using them. Mixing those with other brands was a big no-no. In fact, way back we were taught to match outputs and keep to the same brand. It was an excellent rule in practice which I have always followed. RCA parts were also very good, TI was junk back then.
The MJ15015 and MJ15016 were complete garbage transistors. Parameters all over the place and a huge difference between NPN and PNP types. If you look at the data sheet, they state they are "economy grade" devices. I refused to use them even doing warranty service for new product. But back then, transistors weren't that great compared to what we have. I had to pre-sort and grade new parts, buying a lot of them. The culls were used for regulator pass transistors or discarded. Low beta devices hit the trash. Today I don't have to throw any out. Matching yields are very high too, On Semi (Motorola) being the best now. Earlier, the Japanese brands were the best.
If you look at the old beta vs collector current curves (and they were curves!) and compare them to today's parts, you wouldn't use an old output transistor.
Hi Hugo,
Sir! You are a saint.
Please make sure sg97 knows which pins are which compared to the original parts.
Sir! You are a saint.
Please make sure sg97 knows which pins are which compared to the original parts.
Oh yeah!
Remember when we thought the standard pinout applied to everything? Then we discovered the Europeans had their own ideas (variable at that!), then the Japanese. At least the Japanese were consistent.
No internet then, and I was on my own without older techs to help working in a shop. You sure learned how to figure things out back then.
Remember when we thought the standard pinout applied to everything? Then we discovered the Europeans had their own ideas (variable at that!), then the Japanese. At least the Japanese were consistent.
No internet then, and I was on my own without older techs to help working in a shop. You sure learned how to figure things out back then.
Yes Hugo, we are getting older and recognise what is truly important in life I think.
I tried changing different circuit parameters.
The closest option to what the topstarter said is a leak of the boost capacitor. In my latest diagram this is C1.
If you shunt it with a 1-100 Ohm resistor, then a voltage of +12V or +4V appears at the output, depending on the presence or absence of 2n3055 output transistors.
I don't see any more moves yet.
The closest option to what the topstarter said is a leak of the boost capacitor. In my latest diagram this is C1.
If you shunt it with a 1-100 Ohm resistor, then a voltage of +12V or +4V appears at the output, depending on the presence or absence of 2n3055 output transistors.
I don't see any more moves yet.
That's a good thought Wakh.
I would have replaced those first anyway, then cleaned up the mess once it was working. All those old electrolytic caps go except maybe the main filter cap. Depends on its condition.
I would have replaced those first anyway, then cleaned up the mess once it was working. All those old electrolytic caps go except maybe the main filter cap. Depends on its condition.
i will order them for sure, i will not leave that old caps there but for now i dont think they are main issue
i dont see anything unusual yet. btw i touched one cap by accident and got tiny shock before few days xdd good thing it was not bigger voltage xdd loose connection i take more care now xd
Disconnect C1 in the above diagram and check the DC conditions. We don't care if it passes signal at this point. Disconnect C2 and C9 while you're at it.