Hello:
I have a Crown UT2020 = CE2000 that has no output on both channels but no fault LEDS on, amp cycles to turn on power LED and with signal applied signal LED turn on and blinks. Actually on channel 2 can barely hear some output not affected by volume pot. Board PWA 137557-3. Date of production 0055=5 of 2005? Any suggestions on repair.
Thanks in advance
Nicolas
P.S. Here the schematic etc...http://elektrotanya.com/crown_ce1000_ce2000_ce_series.pdf/download.html
I have a Crown UT2020 = CE2000 that has no output on both channels but no fault LEDS on, amp cycles to turn on power LED and with signal applied signal LED turn on and blinks. Actually on channel 2 can barely hear some output not affected by volume pot. Board PWA 137557-3. Date of production 0055=5 of 2005? Any suggestions on repair.
Thanks in advance
Nicolas
P.S. Here the schematic etc...http://elektrotanya.com/crown_ce1000_ce2000_ce_series.pdf/download.html
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Finally obtained the correct schematic for board PWA 137557-3 from bmamps.com...look under TECH tremendous listing of schematics there...look for Crown CE2000A. So started to look at the amp no obvious external or internal damage. Got the cover off and turned it on. It cycles normally without fault lights but after a while the heat sink for output transistors Q114 to Q119 heated up and current could be felt on touching it. Full output voltage of 91 VDC was measured between that heat sink and chassis! No voltage to chassis from the other heat sinks Yet no output from both channels. Will pull out main board and continue.
What happened before the fault?
A party where the amp was moved and wiring was temporary?
A band on stage? Are you a pro in the repair business?
A home where speaker wires were stable then poof?
Sounds as if the insulator between one or more output transistor and heat sink is faulty. That event possibly took out some output transistors. If case 1 or 2, the wiring change probably did it, you don't need to look for a root cause.
A party where the amp was moved and wiring was temporary?
A band on stage? Are you a pro in the repair business?
A home where speaker wires were stable then poof?
Sounds as if the insulator between one or more output transistor and heat sink is faulty. That event possibly took out some output transistors. If case 1 or 2, the wiring change probably did it, you don't need to look for a root cause.
Hello Indianajo:
History on the amp is limited...Church had it in storage for a long time wants to sell it so a friend of the church brings it over for me to check and possibly buy. Apparently no speakers were blown as DC offset at Speakon speaker terminals was not measurable by me. I am an "Audiophile" not a pro at repairs but have some basic knowledge of schematics and parts. The flyback diodes for that channel measure shorted so likely output transistors are bad. It´s christmas but I´ll get to check them soon. The serv manual recommends using matched output devices. Is this really necessary ?
Thanks for the input and interest
Nicolas
History on the amp is limited...Church had it in storage for a long time wants to sell it so a friend of the church brings it over for me to check and possibly buy. Apparently no speakers were blown as DC offset at Speakon speaker terminals was not measurable by me. I am an "Audiophile" not a pro at repairs but have some basic knowledge of schematics and parts. The flyback diodes for that channel measure shorted so likely output transistors are bad. It´s christmas but I´ll get to check them soon. The serv manual recommends using matched output devices. Is this really necessary ?
Thanks for the input and interest
Nicolas
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Amps installed and removed by amateurs can have had wiring problems, then the output transistors were at risk. Worth measuring. Ones that sat around and went dead more have input problems, oxidized select switches, pots, or connectors, especially punchdown connectors. Dried up input caps, etc. over 15 years on a crown (known for longer life than many brands).
Blown amps for me are about a $60 item. The heatsinks are worth >$30 each retail in USA. Maybe $100 if you're feeling generous. Working ones of that class are about $300.
If emitter resistors on output transistors are 0.5 ohms or above matching is not required, says Peavey. Most amps use more like 0.22, matching is very cheap at a factory. Individuals have to buy more transistors than they need, then do a test. I use a 12 v power supply (car battery charger + parallel filter capacitor) a 10 ohm resistor and a 100 ohm resistor. 100 P.S to base, 10 to collector, measure Vce, mark with sharpie. Outlier values go in the parts bin. Using ON semi G suffiz parts I only had 2 outliers out of 22 transistors, used 20 of them.
If ordering OT's, check emitter resistors too, are usually blown. Also check driver transistors, and further back. I had 124 parts blown in my 1.3kw amp, most cheap 1cent diodes or .22 ceramic bypass capacitors. I did have to buy a couple of op amps and TO92 transistors too, but most parts were salvaged from dead PCAT power supplies.
I'll be more help to a newbie if necessary keep posting. Only a DVM and maybe an analog VOM with 20vac scale are necessary, no scope.
See this thread, too: vintage amplifier repair/upgrade manual - diyAudio
Have fun with this. Great learning experience.
Blown amps for me are about a $60 item. The heatsinks are worth >$30 each retail in USA. Maybe $100 if you're feeling generous. Working ones of that class are about $300.
If emitter resistors on output transistors are 0.5 ohms or above matching is not required, says Peavey. Most amps use more like 0.22, matching is very cheap at a factory. Individuals have to buy more transistors than they need, then do a test. I use a 12 v power supply (car battery charger + parallel filter capacitor) a 10 ohm resistor and a 100 ohm resistor. 100 P.S to base, 10 to collector, measure Vce, mark with sharpie. Outlier values go in the parts bin. Using ON semi G suffiz parts I only had 2 outliers out of 22 transistors, used 20 of them.
If ordering OT's, check emitter resistors too, are usually blown. Also check driver transistors, and further back. I had 124 parts blown in my 1.3kw amp, most cheap 1cent diodes or .22 ceramic bypass capacitors. I did have to buy a couple of op amps and TO92 transistors too, but most parts were salvaged from dead PCAT power supplies.
I'll be more help to a newbie if necessary keep posting. Only a DVM and maybe an analog VOM with 20vac scale are necessary, no scope.
See this thread, too: vintage amplifier repair/upgrade manual - diyAudio
Have fun with this. Great learning experience.
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Hello Indianajo
Thanks for all the info. The flyback diodes, driver transistor and all the OTs in that shorted channel diode measure bad. The other non functioning channel measures good. Dont think owner is interested in a repair since it looks to be expensive. Will offer to buy at a deep discount and make the learning experience less expensive. Purchase decision is to quantity buy unmatched OTs MJ21194 from Chinese seller vs matched OTs from Crown vs unmatched OTs from American seller??
Will check to see what seller wants to do and proceed from there.
Thanks again
Nicolas
Thanks for all the info. The flyback diodes, driver transistor and all the OTs in that shorted channel diode measure bad. The other non functioning channel measures good. Dont think owner is interested in a repair since it looks to be expensive. Will offer to buy at a deep discount and make the learning experience less expensive. Purchase decision is to quantity buy unmatched OTs MJ21194 from Chinese seller vs matched OTs from Crown vs unmatched OTs from American seller??
Will check to see what seller wants to do and proceed from there.
Thanks again
Nicolas
I recommend unmatched OT's, from known distributor like farnell, mouser, digikey, RS (UK & commonwealth) If the warehouse is in your country, they take the risk of getting parts through customs & mail/freight without being substituted with counterfeits by the customs/freight workers. Farnell operates in the most countries IMHO, I buy from their US distributor because he is closer than the others by one day surface freight.
There may be reputable vendors in C**** but there are a lot of counterfeiters. Check local knowledge on another forum which vendor is reputable. E-bay US is known for counterfeiters, except for a couple of guys that post on here.
Buy about 20% extra OT's IMHO. I bought 22 transistors, needed 18, most were 0.12 or 0.13 Vce, three were 0.11 Vce (better gain really but minority) and went in the parts bin. There are a lot of amps you can build with only two OT's when you get done. I listen to one in my living room, 1/4 watt average, 180 W peak on 1812 overture.
Crown parts are exellent but it depends on the customs/mail/freight practices of your country whether you would actually get them. Some countries those workers actually would buy counterfeit parts to put back in your box. I don't recognize your flag, no experience there but there are horror stories from Africa.
See this thread about matching OT's. http://www.diyaudio.com/forums/parts/43304-matching-mj15024-25-other-output-transistors.html
While some poster told me Vce under load was important, these guys think Vbe is a good enough predictor of matching. Gain matching over temperature is ideal, but it is very expensive to do. I'd rather up the emitter resistor value and lose a little peak power & efficienty. About 1/2 my emitter resistors were blown anyway. But the 0.5 ohm my amp had is pretty extremely high when it comes to emitter resistors. I won't be running 2 ohm loads anyway, which the amp is rated for. If your speaker load is close to the amp minimum rated ohms and the power you run is close to the maximum (think beach bar service) then matching is more important. I subbed MJ21193/94 for OEM MJ15024/25 because they were cheaper, and turns out they have better SOA at higher voltage than the originals. Good because my amp has +-85 v rails.
Enjoy the learning experience, I certainly did. At home I have better parts availability than physics lab at college. There all the wire was cut up into 1" pieces. Scout around for blown switcher supplies or even TV's to cut up, will save a lot of freight bills on parts. Those with leaded parts, mid oh-ohs or earlier. I don't get much thrill out of surface mount parts. The marking is fairly useless. Baggies and a spirit marker (sharpie here) are useful inventory control devices.
There may be reputable vendors in C**** but there are a lot of counterfeiters. Check local knowledge on another forum which vendor is reputable. E-bay US is known for counterfeiters, except for a couple of guys that post on here.
Buy about 20% extra OT's IMHO. I bought 22 transistors, needed 18, most were 0.12 or 0.13 Vce, three were 0.11 Vce (better gain really but minority) and went in the parts bin. There are a lot of amps you can build with only two OT's when you get done. I listen to one in my living room, 1/4 watt average, 180 W peak on 1812 overture.
Crown parts are exellent but it depends on the customs/mail/freight practices of your country whether you would actually get them. Some countries those workers actually would buy counterfeit parts to put back in your box. I don't recognize your flag, no experience there but there are horror stories from Africa.
See this thread about matching OT's. http://www.diyaudio.com/forums/parts/43304-matching-mj15024-25-other-output-transistors.html
While some poster told me Vce under load was important, these guys think Vbe is a good enough predictor of matching. Gain matching over temperature is ideal, but it is very expensive to do. I'd rather up the emitter resistor value and lose a little peak power & efficienty. About 1/2 my emitter resistors were blown anyway. But the 0.5 ohm my amp had is pretty extremely high when it comes to emitter resistors. I won't be running 2 ohm loads anyway, which the amp is rated for. If your speaker load is close to the amp minimum rated ohms and the power you run is close to the maximum (think beach bar service) then matching is more important. I subbed MJ21193/94 for OEM MJ15024/25 because they were cheaper, and turns out they have better SOA at higher voltage than the originals. Good because my amp has +-85 v rails.
Enjoy the learning experience, I certainly did. At home I have better parts availability than physics lab at college. There all the wire was cut up into 1" pieces. Scout around for blown switcher supplies or even TV's to cut up, will save a lot of freight bills on parts. Those with leaded parts, mid oh-ohs or earlier. I don't get much thrill out of surface mount parts. The marking is fairly useless. Baggies and a spirit marker (sharpie here) are useful inventory control devices.
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