@sg97 - You're getting some exceptional advice including direct instruction from one of the best.
My first advice (after Mooly gets you moving) is to post your location in your profile. You may be surprised to find if someone with excellent skills is near you and could help you more directly either with a phone call / video chat or maybe you bring them the board, and they can help you fix it and/or modify it as needed to get it working.
Welcome, and Good Luck!
My first advice (after Mooly gets you moving) is to post your location in your profile. You may be surprised to find if someone with excellent skills is near you and could help you more directly either with a phone call / video chat or maybe you bring them the board, and they can help you fix it and/or modify it as needed to get it working.
Welcome, and Good Luck!
thanks, i want to fix it my self its something i want to do for some time, as i said in my first post me any my grandpa worked on this and he died this year and i want to fix this in his honor i know that i can pay someone to do it, but also this way i will learn a lot about how those circuits work.
Well...
Although we would replace both, the one getting hot could well be OK and the one that is cold could well be short circuit. So that is something you could measure with the amp OFF and using the diode check range on a meter. See if either of the 2N3055's read short circuit from the metal case to either of the other two legs.
The 2N3055's are probably mounted on insulating washers (mica) and will have insulating bushes through the bolt holes. Mica is super brittle and easily damaged. We would normally replace with more modern synthetic materials but its not necessarily essential to do that.
One thing we always recommend is using a DBT or dim bulb tester as it can save parts failing if there are problems. It consists of a low wattage mains filament bulb in series with the mains supply to the amp to limit current.
You could also try and accurately measure those wire resistors and see if they have been damaged. They probably are in the 0.33 or 0.47 ohm region. Because they are so low in value you need to subtract the meter lead resistance from the measured result. That is the reading you get just shorting the meter probes together.
Although we would replace both, the one getting hot could well be OK and the one that is cold could well be short circuit. So that is something you could measure with the amp OFF and using the diode check range on a meter. See if either of the 2N3055's read short circuit from the metal case to either of the other two legs.
The 2N3055's are probably mounted on insulating washers (mica) and will have insulating bushes through the bolt holes. Mica is super brittle and easily damaged. We would normally replace with more modern synthetic materials but its not necessarily essential to do that.
One thing we always recommend is using a DBT or dim bulb tester as it can save parts failing if there are problems. It consists of a low wattage mains filament bulb in series with the mains supply to the amp to limit current.
You could also try and accurately measure those wire resistors and see if they have been damaged. They probably are in the 0.33 or 0.47 ohm region. Because they are so low in value you need to subtract the meter lead resistance from the measured result. That is the reading you get just shorting the meter probes together.
Do you have a DVM (digital volt meter)? You will need one. I like the Tenma sold by Farnell but there are many others.
About $30.
This is very simple. It should not be hard. I fixed my first transistor amp without a schematic. No internet then. I drew a schematic by testing with the DVM. The schematic posted first is likely very close. First is there a speaker cap between the output transistor (2n3055) and the hot speaker terminal? The schematic has one. If not there will likely be two power supply capacitors and three power terminals to the output board, instead of 2.
Shorted speaker terminals blow output transistors, many emitter resistors, and likely the driver transistors and resistors before that. Sometimes also the VAS transistor , the one before the drivers.The emitter is the one with the arrow on it in the diagram. Download 2n3055 datasheet from datasheetcatalog.com On TO3 package (the big ones) if you look at the bottom from the long end, the emitter is the pin on the right, the base on the left. On diode scale of dvm there should be 0.6 volts (or 600 on a 1999 scale) from base to emitter, red to base, black to emitter. Same from base to collector, which is the case. 9999 backwards.
On the TO5 transistors, the base is the one in the middle. From the bottom the emitter has the tab between it and the base. The collector is the other. NPN will be positive 600 from base to emitter, pnp will be positive from emitter to base. Same with collector.
I'll post another likely schematic if your board has two power supplies and no speaker capacitor.
About $30.
This is very simple. It should not be hard. I fixed my first transistor amp without a schematic. No internet then. I drew a schematic by testing with the DVM. The schematic posted first is likely very close. First is there a speaker cap between the output transistor (2n3055) and the hot speaker terminal? The schematic has one. If not there will likely be two power supply capacitors and three power terminals to the output board, instead of 2.
Shorted speaker terminals blow output transistors, many emitter resistors, and likely the driver transistors and resistors before that. Sometimes also the VAS transistor , the one before the drivers.The emitter is the one with the arrow on it in the diagram. Download 2n3055 datasheet from datasheetcatalog.com On TO3 package (the big ones) if you look at the bottom from the long end, the emitter is the pin on the right, the base on the left. On diode scale of dvm there should be 0.6 volts (or 600 on a 1999 scale) from base to emitter, red to base, black to emitter. Same from base to collector, which is the case. 9999 backwards.
On the TO5 transistors, the base is the one in the middle. From the bottom the emitter has the tab between it and the base. The collector is the other. NPN will be positive 600 from base to emitter, pnp will be positive from emitter to base. Same with collector.
I'll post another likely schematic if your board has two power supplies and no speaker capacitor.
indianajo thanks for the info, i will get multimeter that is good i have one but is not working as it should, so i will get new one. btw there are two big caps. they are not in the pic. i dont knwo the values because they have some kind of clamp over them to hold them, so one is for power if i understand and second one is for output. i dont know if they may also be a problem. but with all info that you people told me, i am sure that those transistors are issue and resistors so i will try to replace them with same ones. or similar.
i will measure them for shorts, but i will replace both 2n3055. i had 4 of them somewhere i dont know if they work if i find them i may put those if they work.
If one of the wires from a big cap goes to the speaker hot terminal, then there is one power supply capacitor and one speaker cap. The speaker wire may go though a coil on the way to the speaker hot terminal. If wires from both big caps go the power rectifiers (diodes) and then to the board, then it is a split supply amp. Requires no meter to observe this.
You can check your spare 2n3055 with diode scale of DVM. If read 600 forwards 1999 backwards, not a complete test, but likely they are good.
Basic safety. Never measure anything with two hands with the power on. >25 v from one hand to the other can stop your heart. Use an alligator clip lead to connect the black lead of the DVM to speaker ground. Keep one hand in the pocket if you are impulsive.
Never wear jewelry on hands wrists or neck. 1 v at high current through a ring can burn your flesh to charcoal.
Wear safety glasses unsoldering or testing with AC power on. Solder can splash in you eyes, parts can explode.
What country are you in? We can recommend a supply house where every transistor is not counterfeit. Farnell operates nearly everywhere, but country determines what others are good. Also what transistors might be in stock.
You can check your spare 2n3055 with diode scale of DVM. If read 600 forwards 1999 backwards, not a complete test, but likely they are good.
Basic safety. Never measure anything with two hands with the power on. >25 v from one hand to the other can stop your heart. Use an alligator clip lead to connect the black lead of the DVM to speaker ground. Keep one hand in the pocket if you are impulsive.
Never wear jewelry on hands wrists or neck. 1 v at high current through a ring can burn your flesh to charcoal.
Wear safety glasses unsoldering or testing with AC power on. Solder can splash in you eyes, parts can explode.
What country are you in? We can recommend a supply house where every transistor is not counterfeit. Farnell operates nearly everywhere, but country determines what others are good. Also what transistors might be in stock.
i never measure things while its on , if i must i try to not touch anything with my hands, i fixed few things before like my tv mostly replacing caps, but also few radios , but those are simple things, nothing in this scale. so that why i posted here, i cant read schematics well , this amp board seems simple in constrution but yet gave me a lot of trouble mostly because i am not professional so i dont know how to identify components , like those small transistors and resistors. all of them look the same so its confusing to me i may put inapropriate resistor or transistor and blow up something xd
Resistor color code is on wikipedia.
Small transistors, the numbers Mooly posted are for Europe or Asia. In western hemisphere the only surviving small transistors that are EBC pattern are 2n5320-2n5322. Sometimes farnell has an odd number TO39 which can replace 2n5320/22 but I have to search for them. All the other mid-sized replacements are BCE which when I twisted the leads around to fit, broke one lead, and lifted the land off the board in another case.
Post 1980 the unmarked big transistor could be MJ2955 or some other PNP, you will have to measure emitter polarity with the meter or look at the date codes. Date code is YYWW where year is first 2 digits from 46 to 99 and week is 2nd 2 digits, from 01 to 53.
Small transistors, the numbers Mooly posted are for Europe or Asia. In western hemisphere the only surviving small transistors that are EBC pattern are 2n5320-2n5322. Sometimes farnell has an odd number TO39 which can replace 2n5320/22 but I have to search for them. All the other mid-sized replacements are BCE which when I twisted the leads around to fit, broke one lead, and lifted the land off the board in another case.
Post 1980 the unmarked big transistor could be MJ2955 or some other PNP, you will have to measure emitter polarity with the meter or look at the date codes. Date code is YYWW where year is first 2 digits from 46 to 99 and week is 2nd 2 digits, from 01 to 53.
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thanks 😀 i just want to fix this and to learn some stuff, maybe one day i will be able to build amp from scratch but for that i need to learn a lot xdd but for now i will be satisfied with this xdd
i am from europe so i think that i will be able to find all components i would need for that. btw 2n3055 are were made here by company EI so i can find new old stock of them , its under 1$ but those small ones i have to indentify first xd
i wanted to say that those 2n transistors were made here before like 30 years from one company called EI and they made a lot, people sell new old stock, for cheap because it was domestic production.
The TIP31/32 that are in the schematic mooly posted are TO220 package, BCE pattern. BLack plastic case with a heat tab. I don't like twisting the leads around bacause of the damage I caused by doing that.
Measure your other big transistor on diode scale and see if it is plus forward base to emitter (2n3055 npn) or minus forwards base to emitter (MJ2955 pnp)
Thare much better TO3 transistors than 2n3055 since 1976. MJ15003/4 is popular here.
So do you have a big speaker cap? or two P.S. caps? no meter required.
I'm headed out to rake leaves while the sun shines, back evening.
Measure your other big transistor on diode scale and see if it is plus forward base to emitter (2n3055 npn) or minus forwards base to emitter (MJ2955 pnp)
Thare much better TO3 transistors than 2n3055 since 1976. MJ15003/4 is popular here.
So do you have a big speaker cap? or two P.S. caps? no meter required.
I'm headed out to rake leaves while the sun shines, back evening.
https://be.farnell.com/multicomp-pr...-60v-15a-to-3/dp/3378898?MER=sy-me-pd-mi-alte
You'll need a VAT number or someone who has one.
You'll need a VAT number or someone who has one.
FIrst things to order 1 good DVM like Tenma ~Euro30.
2. pack alligator clip leads, or roll wire and pack alligator clips to make some
3. light bulb base to make series bulb tester, ~60 w tungsten light bulb. Case to put it in. Cord grips & AC socket. luxury, fuse or circuit breaker. Hardware store or electrical supply
4. Pack TO3 mounts with new mica washers Or silicon substitutes. Heat sink compound.
5. Safety glasses. hardware store
6, emitter resistors. I recommend .47 ohms 5 watts even if originally .33 ohms or .22 ohms
7 any burned resistors.
8. pack fuses.
If don't have 2n3055, some substitute. 2n5629/30/31 are better as are MJ802, MJ15003, MJ15024. For small round transistors, use farnell search function for TO39 transistors. You'll need NPN & PNP with Vce >50 volts, wattage >10.
Mail/internet order distributors require a debit or credit card. Storefront distributors sell a lot of counterfeits & rejects, even here in the USA. In Europe, besides farnell, there is digikey, RS, Reischelt. You can order from another country in Europe, there should be no customs. Make sure there is local stock, you do not want parts going through customs from UK or USA.
2. pack alligator clip leads, or roll wire and pack alligator clips to make some
3. light bulb base to make series bulb tester, ~60 w tungsten light bulb. Case to put it in. Cord grips & AC socket. luxury, fuse or circuit breaker. Hardware store or electrical supply
4. Pack TO3 mounts with new mica washers Or silicon substitutes. Heat sink compound.
5. Safety glasses. hardware store
6, emitter resistors. I recommend .47 ohms 5 watts even if originally .33 ohms or .22 ohms
7 any burned resistors.
8. pack fuses.
If don't have 2n3055, some substitute. 2n5629/30/31 are better as are MJ802, MJ15003, MJ15024. For small round transistors, use farnell search function for TO39 transistors. You'll need NPN & PNP with Vce >50 volts, wattage >10.
Mail/internet order distributors require a debit or credit card. Storefront distributors sell a lot of counterfeits & rejects, even here in the USA. In Europe, besides farnell, there is digikey, RS, Reischelt. You can order from another country in Europe, there should be no customs. Make sure there is local stock, you do not want parts going through customs from UK or USA.
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thanks i will do all of that and post it here with the results , i hope that i will do something 😀
Farnell has a 3055 but they only sell to companies or people with a VAT number.
But as indianajo said MJ15003 will work very well.