I stumbled across this site via a search.
Nice to see folks are able to fix these fine amps!
My problem, however, is that I need someone to fix my Ampzilla that I have had for longer than I can remember. At one time James Bongiorno had recommended a couple shops but I was never able to get email thru to them so I am still looking to get it repaired. Any information would be appreciated!
Nice to see folks are able to fix these fine amps!
My problem, however, is that I need someone to fix my Ampzilla that I have had for longer than I can remember. At one time James Bongiorno had recommended a couple shops but I was never able to get email thru to them so I am still looking to get it repaired. Any information would be appreciated!
GAS pre-drivers
I have a GAS grandson in need of (2) MPSU 06 and (2) MPSU 56 pre-drivers to get it running again.
Anyone know of some good parts that are available?
(Is GASWORKS still around, in Idaho?)
Thanks.
I have a GAS grandson in need of (2) MPSU 06 and (2) MPSU 56 pre-drivers to get it running again.
Anyone know of some good parts that are available?
(Is GASWORKS still around, in Idaho?)
Thanks.
Hi everyone!
I need new power output transistors for my GAS Son of Ampzilla. Where can I purchase these?
Best regards
I need new power output transistors for my GAS Son of Ampzilla. Where can I purchase these?
Best regards
induplo said:
I just replaced all of the outputs in my SonofA with MJ15003/MJ15004. I purchased matched pairs from Jack Walton at Tech-Diy. Various devices are recommended as correct replacements for the original GAS outputs. I chose these because they appear on the GAS device substitution sheet, had ratings within the circuit's requirements and were inexpensively available matched. Other devices may work as well or better. I also had to replace the input differential pairs to get the channels to DC balance correctly. While I was in there I changed all of the electrolytic caps, as they're 30 years old and some had been hot. The amp powered up perfectly the first time and has run like a charm driving my Linn Isobarik DMS speakers, a 'difficult' load. Just for the heck of it I bought another SonofA yesterday. I guess that makes me a 'collector' again
(edited 10/27/08 for speling)
So i have been trying to make heads and tails of the PDF version of the Son of Ampzilla schematic but the fact that some of the values are X'd out is making it difficult to order parts. Does anyone know the values for the C125 and C108 Caps? The C108 cap says .001 so im guessing thats .001uF? And the C124 Cap says 10K. Also the capacitor on the bottom board reads 1K 100, i know its 100V but not sure what the 1K means, 1KuF maybe? If anyone could help me out i would greatly appreciate it. Thanks! -Ryan
If you replace the output transistors it is important to set up the output DC offset and the bias current.
If these arent right you might continue to blow up output transistors.
If these arent right you might continue to blow up output transistors.
C122 & C125 are 10pf, C104 & C108 (there are two C105s on the schematic, one is supposed to be C108) are 1000pf, 1k as you mentioned. I don't see a C124, what is it close to? Also if the caps are film/ceramic the values could be in uf or pf, so if you see one with 10k it's probably pf, .01 in uf. Electrolytics are usually always in uf.
Craig
Craig
Thanks for the reply Craig, i just put the amp back together and i don't remember off the top of my head which Cap is C124 but i am confused by the capacitor on the bottom transistor board. It's large, white, and square and says 1K 100 on the top. Like i said the schematic says its 100V but doesnt list the capacitance. It's seems odd though that it would be so large for only a .001uF cap.
If it says 1 it's a 1uF cap not a 0.001uF one. If it says .1 (note the dot in front of the 1) then it's a 0.1uF. Old caps were a lot larger than current ones, technology has evolved quite a bit in fitting capacitance in smaller packages.
That's C202, part of the Zobel network on the output of the amp. It's 1uf/100v,
that's what's on the schematic and the board that I'm looking at.
Craig
that's what's on the schematic and the board that I'm looking at.
Craig
Forgot to say mine reads "1 J 100". The "1" is the value, the "J" is the tolerance, and the "100" is the voltage rating.
Craig
Craig
Great, thanks everyone. I appreciate all your help. One last thing though, my front Watt meters read 3.2 and .8 when the amp is idling. I adjusted the pots on the meter boards but that won't move it down to zero. Does anyone else experience this much power draw at idle or are my meters just fubared?
With no power applied use the mechanical adjustment, front bottom, on the "meter" itself to zero it out, to the far left. This adjustment is directly behind the faceplate. The electronic adjustment is used to adjust for "0 db" or 80 Watts into an 8 Ohm load. With power on and no signal the meter should have no reading at all, far left again. If your meters move while music is playing the meters "should" be OK.
Craig
Craig
I adjusted the front two pots, the right one all the way clockwise, the left one all the way counter clockwise but they still read .8 and 3.2. I am running 4 ohm speakers though and the meteres don't seem to move too much when being used, that is they dont move much more than a tick or two at the most.
Son Of Ampzilla Driver transistors
Hello all,
Im trying to revive a Son Of Ampzilla, Does anyone know what the 4 driver transistors are Q101,Q102,Q105,and Q106 are? Looks like they have GAS numbers on them which I`m sure are no longer available. Does anyone know what the actual number is? Any help would be appreciated
Ron
Hello all,
Im trying to revive a Son Of Ampzilla, Does anyone know what the 4 driver transistors are Q101,Q102,Q105,and Q106 are? Looks like they have GAS numbers on them which I`m sure are no longer available. Does anyone know what the actual number is? Any help would be appreciated
Ron
What are the GAS numbers? 116 and 117 were the problematic Fairchild FT317 and FT417, those need to go if not already gone. James Bongiorno recommended a Toshiba part but those are all plastic case and since the normally metal tab of the TO220 case is used it makes it messy to use the Toshibas. I usually use ONSEMI MJE15030/31 in the top position and MJE15028/29 in the bottom position.
Craig
Craig
Continuing education on the Son
Hi all🙂,
First time post on this great forum!
I have read exhaustively through the diy, and audiokarma forums looking for specific info regarding repairing my son of AMPZILLA. After working on it quite a bit, I have so many questions.
I acquired the amp years ago (free) and it has sat on the shelf. I brought it up on the variac and it came up with some distortion on one channel. After a while one of the caps on a driver board overheated and popped. So to insure a clean start I rebuilt the PS board and upgraded the filter caps and bridge. I also installed the recommended bypass caps on the filters to insure clean power. I then replaced the lytics on the driver board. Presently I am working on one side of the amp because I am experimenting with the changes in the schematic.
I am getting 30mV across the emitter resistors just fine but when I was testing with an 8ohm load and a 1kHz sine wave, one of the fuses (#3) blew at about 23 volts p/p, it was the correct amperage (8). I replaced it and the amp seems ok. Funny though, the meter did not deflect at all. I read they are not the best design, but they should still move more than a little. I re-soldered the meter board and got the lights on nice and steady, but still little deflection. Back burner for now😉
Seems like the differential amp xsistors are getting a little warm compared with other components. I replaced their emitter resistors with 1% matched to see if that helped but they still seem a little too warm. Is that normal for this amp? It looks like the IC (MP6001?) might fit in those sockets on the driver boards, should I perhaps get some and put them in? The IC's are still in the output boards and are working fine.
I have looked at many schematics, but can only find one that is read-able and the schematics are modified and not the originals. I am ok with that but Mr. Bettenger and Burnedfingers say that except for some bypass caps, to leave them as is as much as possible. I am curious about thoughts on those mods? Who made them on the schematic? Has anyone done them and lived to tell the tale😱? If so, the schematic is a little too fuzzy where they took out C109 220pF and inserted a diode. There are numbers next to it that I can't read and it doesn't look like a Zener either. I am a little concerned about doing that without knowing what that is all about. Also, my output boards also have the cap and resistor soldered across the driver board connector. Must have been advised at one time.
So after reading all the replies to others, I am guessing folks will make the same recommendation to me but I was just wondering about all those mods and the lack of un-changed schematics out there.
I can't seem to find any reliable info on adjusting the pos and neg protection trimmers (which I changed out). I can't even find much info on their purposes. Perhaps you can shed some light on that too. (I said above I am an amateur 🙄) I am concerned about the initial power up settings like a default voltage across the trimmers to insure I don't blow it up. Perhaps it is not an issue and I should do as noted elsewhere in this thread. I at least set them to the same voltages at the start.
I am sorry for so many questions, but perhaps it will save time getting all the ones I can think of now, out there in one message.
I hope you can address my questions without too much pain and hassle. I am really looking forward to hooking this amp up!
Thanks up front for any help🙂
Hi all🙂,
First time post on this great forum!
I have read exhaustively through the diy, and audiokarma forums looking for specific info regarding repairing my son of AMPZILLA. After working on it quite a bit, I have so many questions.
I acquired the amp years ago (free) and it has sat on the shelf. I brought it up on the variac and it came up with some distortion on one channel. After a while one of the caps on a driver board overheated and popped. So to insure a clean start I rebuilt the PS board and upgraded the filter caps and bridge. I also installed the recommended bypass caps on the filters to insure clean power. I then replaced the lytics on the driver board. Presently I am working on one side of the amp because I am experimenting with the changes in the schematic.
I am getting 30mV across the emitter resistors just fine but when I was testing with an 8ohm load and a 1kHz sine wave, one of the fuses (#3) blew at about 23 volts p/p, it was the correct amperage (8). I replaced it and the amp seems ok. Funny though, the meter did not deflect at all. I read they are not the best design, but they should still move more than a little. I re-soldered the meter board and got the lights on nice and steady, but still little deflection. Back burner for now😉
Seems like the differential amp xsistors are getting a little warm compared with other components. I replaced their emitter resistors with 1% matched to see if that helped but they still seem a little too warm. Is that normal for this amp? It looks like the IC (MP6001?) might fit in those sockets on the driver boards, should I perhaps get some and put them in? The IC's are still in the output boards and are working fine.
I have looked at many schematics, but can only find one that is read-able and the schematics are modified and not the originals. I am ok with that but Mr. Bettenger and Burnedfingers say that except for some bypass caps, to leave them as is as much as possible. I am curious about thoughts on those mods? Who made them on the schematic? Has anyone done them and lived to tell the tale😱? If so, the schematic is a little too fuzzy where they took out C109 220pF and inserted a diode. There are numbers next to it that I can't read and it doesn't look like a Zener either. I am a little concerned about doing that without knowing what that is all about. Also, my output boards also have the cap and resistor soldered across the driver board connector. Must have been advised at one time.
So after reading all the replies to others, I am guessing folks will make the same recommendation to me but I was just wondering about all those mods and the lack of un-changed schematics out there.
I can't seem to find any reliable info on adjusting the pos and neg protection trimmers (which I changed out). I can't even find much info on their purposes. Perhaps you can shed some light on that too. (I said above I am an amateur 🙄) I am concerned about the initial power up settings like a default voltage across the trimmers to insure I don't blow it up. Perhaps it is not an issue and I should do as noted elsewhere in this thread. I at least set them to the same voltages at the start.
I am sorry for so many questions, but perhaps it will save time getting all the ones I can think of now, out there in one message.
I hope you can address my questions without too much pain and hassle. I am really looking forward to hooking this amp up!
Thanks up front for any help🙂
The added diodes are FDH400, high voltage signal diodes. I rebuilt mine stock as it came from the factory except all metal film resistors, MJE15028,29,30, and 31s in the VAS and drivers stages. The SanKen output xsistors were still OK so I reused them. I set the VI limiters to the least sensitive position, min. resistance I think, so they are pretty much out of the circuit. If you want to see what they do check out either the Pioneer Spec 2 or 4 service manual. Results should be similar. As far as the meters go they're pretty much useless at the levels I listen, it's my shop amp and can't play too loud.
Craig
Craig
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