Ampeq SVT7 Pro

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Hi


Someone brought this amp to me to get it fixed. When I first turned ON this amp, It was working as normal. Then after about a minute, the power supply turned off. After a second it turned on again, and then off again. It keeps repeating this constantly, on for a second, off for a second. I left it on for about 5 mins and then it went totally dead. I checked the mains fuse, it is OK, but now it doesn't power up at all. Earlier I realised that IC U2( ICE 2A165) was getting extremely hot within secs when the amp is turned ON. I have checked most of the components on the main board and they seem OK except the front board. What can probably cause this. Please assist.


Thanks
 
The power chopper IC is suffering and shuts down due to excess heat.
Check D9 and the tuning components R49 and C36.
It is similar to the TOP249 range of power supply chips.
 

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The power chopper IC is suffering and shuts down due to excess heat.
Check D9 and the tuning components R49 and C36.
It is similar to the TOP249 range of power supply chips.


I have checked D9,R49 and C36 and they are OK. I have checked even the SMPS transformer and it is OK too. I am having problem getting this ICE2A165 chip, can any of the TOP249 range be used as a replacement. There are actually 3 smps transformers in the circuit. Now I have removed the ICE2A165 chip, because I suspect it has shorted. With this chip removed the amp is totally dead, no indicator, no fan. Is this normal, then what are the other 2 transformers for. I do not understand. Is this chip responsible for starting up the whole power supply. Please advise.


Thanks
 
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I bought one of these blown bass amps cheap and read up on the fix - its the ICE chip.

The newer amps have the higher power version of the chip (ICE2A265?). I purchased a couple off ebay and at the advice of the bass forums, put in a socket.

There is a diode and couple film caps in that area (sorry been a few years) that also blew out on mine.

Anyway, it kept blowing again and again with new chips / diode/caps.

I eventually bought a new amp unit from a company called Compass something in Wisconsin and work perfectly after that. I eventually sold it.. but you, like others on that forum, may have better luck just replacing that chip, mine may have been a knockoff?
 
U2 supplies the low current and start up power, nothing will startup without the +15 supply.
They get hot because there is a tuning issue or they are running at the wrong frequency producing a corrupt waveform.


I was unable to get the 2A165 chip, but instead I got a ICE 2A180z, which has the same specs. After putting in this IC, I turned ON the amp. It started as normal, with a CD input plugged in , it was working normal for about 10mins. Then it suddenly turned off for a second, then turned on for a while and off again. Now it keeps repeating this. After turning off the amp, I realise that this IC is very hot, the smps transformer T3 is also hot. I have checked R49, C36 and D9 and they are OK. What else can possibly be the problem. Please assist.


Thanks
 
U2 supplies the low current and start up power, nothing will startup without the +15 supply.
They get hot because there is a tuning issue or they are running at the wrong frequency producing a corrupt waveform.


Hi


This is what I did today. First I disconnected the J13 connector which carries the 300V, -15V, +15V, GND and other signals from the main board to the preamp board. I left it ON for more than 1hr and the amp did not cut-off. Next I put back the connector but removed the 12AX7, I left it ON for another 1hr and it also did not cut-off. Then I put back the tube, removed the 300V pin from the connector, within 5mins, it started to cut off. Next I put back the 300V pin but removed the -15V pin. It also started to cut-off within 5mins. Lastly I put back the -15V pin but removed the +15V pin. I left it ON for more than 1hr but it did not cut-off. I also inserted a CD signal thru the "power amp in"at the back and it was playing right thru. I suspect that It has something to do with the tube heater circuit, because the heater supply is taken off the +15V rail or some IC on the preamp board. This +15V is also feeding the op-amps in the output circuit on the main board but does not cut off. Its only when the preamp board is connected it cuts off. I also noticed that D1 and D60 on the main board have already been replaced earlier with IN4007s( they are suppose to be 1.5KE200A diodes). Can these diodes be linked to the problem. Please advise.


Thanks
 
Hi


This is what I did today. First I disconnected the J13 connector which carries the 300V, -15V, +15V, GND and other signals from the main board to the preamp board. I left it ON for more than 1hr and the amp did not cut-off. Next I put back the connector but removed the 12AX7, I left it ON for another 1hr and it also did not cut-off. Then I put back the tube, removed the 300V pin from the connector, within 5mins, it started to cut off. Next I put back the 300V pin but removed the -15V pin. It also started to cut-off within 5mins. Lastly I put back the -15V pin but removed the +15V pin. I left it ON for more than 1hr but it did not cut-off. I also inserted a CD signal thru the "power amp in"at the back and it was playing right thru. I suspect that It has something to do with the tube heater circuit, because the heater supply is taken off the +15V rail or some IC on the preamp board. This +15V is also feeding the op-amps in the output circuit on the main board but does not cut off. Its only when the preamp board is connected it cuts off. I also noticed that D1 and D60 on the main board have already been replaced earlier with IN4007s( they are suppose to be 1.5KE200A diodes). Can these diodes be linked to the problem. Please advise.


Thanks




After a week, today I received my order, the replacement ICE2A265. I put in this IC with an IC socket. I plugged in a signal and left in ON for 3hrs. Surprisingly the amp did not shut down at all. I checked the IC and it was very hot indeed, but did not shut down. What I plan to do is, remove the IC socket, apply some heat component under the IC and solder it directly to the PCB, hoping that the PCB will act as a partial heatsink so that it will run a bit colder. I hope the IC will solve the problem and will not breakdown.


Thanks and wishing everyone a merry christmas!
 
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