I'm having the same problem with my Rubicon 1002. It's runs hot at 4 ohms mono and seems to draw more current then it should from my overkill 240 amp alternator. Did they mess them up at the factory and put in an incorrect part on the board and it's a must that it be corrected?
I have a Rubicon 502 at 4 ohms stereo running my components and it stays ice cold, I guess because it's doing less work then the 1002 on subwoofer duty.
Reading other threads it seems like less than ideal or possibly even the wrong components were used on the 1002 board that causes thermal runaway and excessive current consumption.
These amps are new, just took them out of the box for my 2020 build.
Since nothing blew yet and they appear to be functioning normally, can I just take the amp to some electronics repair and have the bias turned down, or does something more drastic need to be done like replacement of less than ideal board components?
I have a Rubicon 502 at 4 ohms stereo running my components and it stays ice cold, I guess because it's doing less work then the 1002 on subwoofer duty.
Reading other threads it seems like less than ideal or possibly even the wrong components were used on the 1002 board that causes thermal runaway and excessive current consumption.
These amps are new, just took them out of the box for my 2020 build.
Since nothing blew yet and they appear to be functioning normally, can I just take the amp to some electronics repair and have the bias turned down, or does something more drastic need to be done like replacement of less than ideal board components?
The bias setting could just be off a bit. What experience do you have with amp repair?
You'd need to pull the bottom cover and make some accurate voltage measurements to see where the problem is.
You'd need to pull the bottom cover and make some accurate voltage measurements to see where the problem is.
I'm good with a multimeter, however I heard the problem with these amps is either the Darlingtons or some other board components that need to be upgraded. 90scaraudio just fixed this same amp, hoping he will chime in.
Quoting what someone else said:
"Pretty much all Soundstream amps using Darlington output devices will fail if biased "correctly". The TIP142/147 and the TIP102/107 have serious thermal issues.
If these devices are biased with the Vbe generator set to 2.25v (A good value when a double Darlington DISCRTETE pair of devices are used) they will blow up."
Quoting what someone else said:
"Pretty much all Soundstream amps using Darlington output devices will fail if biased "correctly". The TIP142/147 and the TIP102/107 have serious thermal issues.
If these devices are biased with the Vbe generator set to 2.25v (A good value when a double Darlington DISCRTETE pair of devices are used) they will blow up."
According to the diagram I have (can't post it) this doesn't use the Darlington outputs. It uses the 2SC3281/2SA1302. Post a photo of your board if you think you have a Darlington amp.
If you have the mini-grabber clips, use them to prevent slipping when measuring the following.
You need to measure the DC voltage (no load, no signal) across the large emitter resistors in the output stage. Post a general average of the voltages in each channel. None should be significantly higher than the others. You'll need to give the full reading displayed by the meter. a few thousandths of a volt difference could be important.
If you have the mini-grabber clips, use them to prevent slipping when measuring the following.
You need to measure the DC voltage (no load, no signal) across the large emitter resistors in the output stage. Post a general average of the voltages in each channel. None should be significantly higher than the others. You'll need to give the full reading displayed by the meter. a few thousandths of a volt difference could be important.
By the diagram you mean the Rubicon 1002 schematics? I have a copy already somewhere, the amps are still in car right now but I know they have the red circuit board, not the blue.
Username MOAR on here said they were Darlingtons, I was unable to PM any of these guys as I am a new member.
Username MOAR on here said they were Darlingtons, I was unable to PM any of these guys as I am a new member.
I used NOS 2sc5200/a1943. The Darlington pairs that I've seen were used in the Reference series, r405, r300, r500, r500s, r1000s, ect...
You say they are new? Been sitting around for a bit. I'm not sure but I think some of the electrolytic capacitors do have a shelf life.
Someone can chime in if I'm wrong.
You say they are new? Been sitting around for a bit. I'm not sure but I think some of the electrolytic capacitors do have a shelf life.
Someone can chime in if I'm wrong.
90scaraudio
What did you use for the final bias setting?Caps vary greatly. Some failed (during capacitor plague) on the shelf. I've checked others that were 30 years old and they were within tolerance. I didn't check a lot of caps for many years but saw how many people were claiming that not changing caps, blindly, made a tech an idiot/incompetent. I checked caps for about 20 years and found VERY few that were out of tolerance. I feel sorry for all of the people who removed perfectly good caps and installed plague caps, only to put the amps in storage and come back to see irreparable damage.
There are some caps that tended to fail after some years. In early Rockford amps, there were a few small caps that would leak electrolyte and turn pink. Most all of the other caps were good for MANY years.
Orion used a lot of caps that failed and they all need to be replaced in some series amps. Phoenix Gold and Zapco also had problems.
I think much of the problem with caps could be the heating during flow soldering. The heating curve may have been too aggressive. Other times, it was poor quality and sometimes, maybe a combination of the two.
I don't recommend blindly replacing perfectly good caps.
I remember one of the techs at soundstream said to check for current hogs... check dc voltage across each emitter resistor, they should be close to each other. The one that is a higher voltage is a current hog (That would be the output transistor). But, I cant remember if this was for the Reference series but the theory should work, I think.
Scott
Scott
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What did you use for the final bias setting? 1.5mV Pretty sure. from the final alignment section. I think you have this...
Scott
I do but what I don't understand is whether these amps actually have a thermal runaway problem and if that setting caused it.
Yes, the amps were brand new, just took them out of the box in 2020. I'll check for leaky caps, but the bigger issue is I have overkill on alternator and my headlights still dimm and the amp runs too hot IMO for a 4 ohm mono load, something's wrong. I want to see if it's just a simple bias adjustment before it burns up or fry's itself or my alternator.
Only one way to find out. I need someone reputable to send them to be gone through and checked. I doubt capacitors are my problem.
The voltage only has to drop a fraction of a volt for incandescent lights to dim, especially at higher voltages.
The voltage readings from the emitter resistors should tell us a lot.
Thermal runaway from bias settings ()for amps with design flaws) are typically an avalanche where the amp starts to heat up and the hotter it gets, the greater the rate of heating. Simply over-biasing (for an amp with a good design) makes it heat up but the idle current shouldn't avalanche. The bias transistors must track thermally with the output transistors. There have been designs where they were too far from the outputs and that caused (minor) problems. Other times, the bias transistors are not well mated to the heatsink, thermally.
The voltage readings from the emitter resistors should tell us a lot.
Thermal runaway from bias settings ()for amps with design flaws) are typically an avalanche where the amp starts to heat up and the hotter it gets, the greater the rate of heating. Simply over-biasing (for an amp with a good design) makes it heat up but the idle current shouldn't avalanche. The bias transistors must track thermally with the output transistors. There have been designs where they were too far from the outputs and that caused (minor) problems. Other times, the bias transistors are not well mated to the heatsink, thermally.
I know what your talking about. Mine would get so hot, it was frightening. But like I said in the post I did, It was abused by who knows and for how long so could have been lots of damage.
I know there are checks you can do that soundstream performed after assembly. I'm not sure if Perry has this, if not, PM me and I'll send one to you.
Scott
I know there are checks you can do that soundstream performed after assembly. I'm not sure if Perry has this, if not, PM me and I'll send one to you.
Scott
Thanks, I already have the schematics, I think I know the test document you are referring to, having that would definitely help whoever checks these amps for me.
If the bias isn't holding, it's a design flaw. It could be a physical problem or a flaw in the circuit. That said, you need to take readings, set the bias and see what happens.
As far as the spec bias setting, 1.5mv may be too high. If the bias holds when everything is right, physically, I think I'd set the bias to where the amp produces clean audio across the audio spectrum and not any higher.
As far as the spec bias setting, 1.5mv may be too high. If the bias holds when everything is right, physically, I think I'd set the bias to where the amp produces clean audio across the audio spectrum and not any higher.