Hello everybody,
i'm new here on this forum. I was recommendid this forum through members of audiokarma.org.
i'm a marantz collector and repair man for audio. I usually make everything in good working order and i rebuild with original components and high quality like panasonic FM and FC caps motorola/onsemi/toshiba transistors and the original types of casing, But i bought a GAS son of ampzilla, and it died on me last week. and it is quiet a different amp that i'm use to, all the transistors have patent GAS XXX number. you MUST need the manual to decode the numbers
problem is that the bias IC is broken and i do not know wich one i need to replace this broken one.
could anyone help me with the specs on this bias IC.
hear is a picture of the gas (hour later it died.....)
i usually repair different stuff
well i hope to get any reply.
thanks in advance,
Jon
i'm new here on this forum. I was recommendid this forum through members of audiokarma.org.
i'm a marantz collector and repair man for audio. I usually make everything in good working order and i rebuild with original components and high quality like panasonic FM and FC caps motorola/onsemi/toshiba transistors and the original types of casing, But i bought a GAS son of ampzilla, and it died on me last week. and it is quiet a different amp that i'm use to, all the transistors have patent GAS XXX number. you MUST need the manual to decode the numbers
problem is that the bias IC is broken and i do not know wich one i need to replace this broken one.
could anyone help me with the specs on this bias IC.
hear is a picture of the gas (hour later it died.....)
An externally hosted image should be here but it was not working when we last tested it.
i usually repair different stuff
An externally hosted image should be here but it was not working when we last tested it.
well i hope to get any reply.
thanks in advance,
Jon
While I can't help you with the IC itself, I can point you to the schematic which should help you to find a substitute:
http://www.audio-circuit.dk/Schematics/GAS_Son_Of_Ampzilla.pdf
Have fun, Hannes
http://www.audio-circuit.dk/Schematics/GAS_Son_Of_Ampzilla.pdf
Have fun, Hannes
Hi,
The bias IC is an MPQ6001. It is essentually two NPN transistors and their complementary PNP transistors in a 14 pin DIP package; with the IC package located and touching the heatsink between the output transistors.
You should be able to find a schematic on the SAE_Talk forum on Yahoo. I haven't looked recently so I'm making an assumption there. I can post one if necessary.
Regards, Mike.
The bias IC is an MPQ6001. It is essentually two NPN transistors and their complementary PNP transistors in a 14 pin DIP package; with the IC package located and touching the heatsink between the output transistors.
You should be able to find a schematic on the SAE_Talk forum on Yahoo. I haven't looked recently so I'm making an assumption there. I can post one if necessary.
Regards, Mike.
Wow, some classic gear in those pictures. Brings the memories flooding back.
I think you will struggle to find a repacement part, and may need to make some adaptions to solve your problem - I'm wondering if something like a CA3083 (its a 16 pin device unfortunately) might not do the trick
http://www.intersil.com/data/fn/fn481.pdf
There are bound top be some Ampzilla experts somewhere on the forum - hopefully they can help steer you in the right direction.
Man, that Marantz looks good.
Reminds of when I was wondering around Buiwerwijk (I think I got the spelling right) a few years ago. There wa s one section where they had loads of 70's vintage amps and stuff. I wasn't able to buy anything - but some of th e stuff sure looked interesting.
I think you will struggle to find a repacement part, and may need to make some adaptions to solve your problem - I'm wondering if something like a CA3083 (its a 16 pin device unfortunately) might not do the trick
http://www.intersil.com/data/fn/fn481.pdf
There are bound top be some Ampzilla experts somewhere on the forum - hopefully they can help steer you in the right direction.
Man, that Marantz looks good.
Reminds of when I was wondering around Buiwerwijk (I think I got the spelling right) a few years ago. There wa s one section where they had loads of 70's vintage amps and stuff. I wasn't able to buy anything - but some of th e stuff sure looked interesting.
Ampzilla bias problems
I have repaired many Ampzillas from the early 70's and onwards. I always have replaced the bias IC with discrete parts. There is nothing fancy about the bias circuit. An NPN/PNP compound pair does as well. There is nothing fancy about the output stage. Simple darlington pair with 4 x Vbe drops in the bias path.
The new bias circuit lives between the two collectors of the VAS complementary stage.
Take any PNP capable of a few hundred mA collector current and connect its emitter to the positive VAS collector. Connects its emitter to the collector of the negative VAS collector.
Then solder a 620 ohm resistor Base to emitter of this PNP.
Then take an NPN TO-220 transistor (Beta >100) and connect its collector to the base of the PNP. Then connect the emitter of the NPN to the collector of the PNP.
Next solder a resistor of 1K6 between the emitter of the PNP and the base of the NPN.
Lastly connect a 220 ohm trimmer in series with a 430 ohm resistor between base and emitter of the NPN.
The thermal tracking of this circuit works well on the double Darlington output stage where you have 4 x Vbe drops.
Steve Mantz
Zed Audio Corp
I have repaired many Ampzillas from the early 70's and onwards. I always have replaced the bias IC with discrete parts. There is nothing fancy about the bias circuit. An NPN/PNP compound pair does as well. There is nothing fancy about the output stage. Simple darlington pair with 4 x Vbe drops in the bias path.
The new bias circuit lives between the two collectors of the VAS complementary stage.
Take any PNP capable of a few hundred mA collector current and connect its emitter to the positive VAS collector. Connects its emitter to the collector of the negative VAS collector.
Then solder a 620 ohm resistor Base to emitter of this PNP.
Then take an NPN TO-220 transistor (Beta >100) and connect its collector to the base of the PNP. Then connect the emitter of the NPN to the collector of the PNP.
Next solder a resistor of 1K6 between the emitter of the PNP and the base of the NPN.
Lastly connect a 220 ohm trimmer in series with a 430 ohm resistor between base and emitter of the NPN.
The thermal tracking of this circuit works well on the double Darlington output stage where you have 4 x Vbe drops.
Steve Mantz
Zed Audio Corp
The IC is available from ACK electronics. There were two different IC's used one was marked GAS100 I believe and if memory is correct the other was a GAS101.
Mike feel free to correct me on this.
Please don't cobble the damn thing up with discrete transistors and a cluster farce. The purpose on the IC was to have matched transistors in a package so it would track the heat correctly.
Mike feel free to correct me on this.
Please don't cobble the damn thing up with discrete transistors and a cluster farce. The purpose on the IC was to have matched transistors in a package so it would track the heat correctly.
Bonsai said:Wow, some classic gear in those pictures. Brings the memories flooding back.
I think you will struggle to find a repacement part, and may need to make some adaptions to solve your problem - I'm wondering if something like a CA3083 (its a 16 pin device unfortunately) might not do the trick
http://www.intersil.com/data/fn/fn481.pdf
There are bound top be some Ampzilla experts somewhere on the forum - hopefully they can help steer you in the right direction.
Man, that Marantz looks good.
Reminds of when I was wondering around Buiwerwijk (I think I got the spelling right) a few years ago. There wa s one section where they had loads of 70's vintage amps and stuff. I wasn't able to buy anything - but some of th e stuff sure looked interesting.
this is very helpfull, trhanks!!
Re: Re: Ampzilla bias problems
A better approach if the IC is not readily availible is to take two 2N5551s (NPN) and two 2N5401 transistors, cut the leads short, plug them into the IC socket (obviously following the IC pinout), bend them over over so they will touch the heatsink as you replace the output pcb, apply heatsink compound to improve the thermal connection to the heatsink. If you can match the transistors (without getting too crazy here) better yet.
What you want to look for is proper voltage drop across the output transistor .22 ohm emitter resistors after the amp has warmed up I believe it should be 25mv. Obviously when idling the amp should stay mildly warm and not overheat when pushed hard for an extended time.
I'm doing this from memory so if my suggestion is a bit off use your head, but the concept is correct.
Regards, Mike.
JDRvintage said:which transistors should I use?
A better approach if the IC is not readily availible is to take two 2N5551s (NPN) and two 2N5401 transistors, cut the leads short, plug them into the IC socket (obviously following the IC pinout), bend them over over so they will touch the heatsink as you replace the output pcb, apply heatsink compound to improve the thermal connection to the heatsink. If you can match the transistors (without getting too crazy here) better yet.
What you want to look for is proper voltage drop across the output transistor .22 ohm emitter resistors after the amp has warmed up I believe it should be 25mv. Obviously when idling the amp should stay mildly warm and not overheat when pushed hard for an extended time.
I'm doing this from memory so if my suggestion is a bit off use your head, but the concept is correct.
Regards, Mike.
Son Of Ampzilla
Hi Burntfingers!
Thanks for your reply! Unfortunately I cannot send email at this point (account under moderation).
My email address is: akkabambam@telia.com
Best regards / Lars
Hi Burntfingers!
Thanks for your reply! Unfortunately I cannot send email at this point (account under moderation).
My email address is: akkabambam@telia.com
Best regards / Lars
Re: Re: Re: Ampzilla bias problems
I've been thinking about this and my memory kicked in... To use the TO92 transistors, the socket for the IC is removed and the transistor leads are stuck through the lead holes (but not soldered). A bit of heatsink grease is placed on the top of the transistor package. The output board is remounted and the four transistors are pushed against the heatsink and soldered in place.
I like this because it's clean and effective if the IC is not readily availible.
Mike.
MikeBettinger said:
I've been thinking about this and my memory kicked in... To use the TO92 transistors, the socket for the IC is removed and the transistor leads are stuck through the lead holes (but not soldered). A bit of heatsink grease is placed on the top of the transistor package. The output board is remounted and the four transistors are pushed against the heatsink and soldered in place.
I like this because it's clean and effective if the IC is not readily availible.
Mike.
burnedfingers said:
Hi Joe,
I wasn't paying attention I guess. The GAS 100 is a CA3086, which is an array of 5 discrete transistors all on the same die in a 14 pin package.
The 100A is the MPQ6001 (or 2), which is a 4 transistor array; 2 NPN and 2 PNP transistors on the same die.
I know you know this, I'm just throwing it out for general knowledge.
BTW, I just purchase a couple of blown Ampzilla's to rebuild. I'm looking forward to this.
Mike.
burnedfingers said:
Hi Joe,
The 790001 board (with the wire jumpers to the drive board) uses the CA3086. Off the top of my head I'm not 100% sure of the 790003, but comparing the two might answer your question. I know that circuit uses the 250 ohm trimmer. I can look when I get home later to be sure.
Mike
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