# Overheating Resistors on Continuum, any ideas?



## Audiophyle (Aug 8, 2009)

I have an SS Continuum amp that has been under the knife for a while now and I cannot seem to get it to play nice.

It blew up half of the rail caps, and burnt out all 4 large resistors on channel 3.

I have since replaced all 6 rail caps, all 4 resistors, and replaced the PNP & NPN transistors on that channel, as well as resoldered the vertical daughter boards as discussed in the other Continuum thread. 

All 4 of the resistors I replaced are getting very hot, and the new transistors are also heating up (not as hot, but can be felt through the board). I have no ideas where I should look to find the problem. The amp is fine with power & ground applied, but as soon as the remote terminal sees power the resistors on channel 3 begin to warm up, and within a minute or two they are too hot to touch. The old transistors did not pass testing when replaced, and the new ones meter very close to the other 3 channels so they should be functioning fine.


This is with no signal being fed into the amp, or speakers connected, and it is being run off a 10a 12vdc power supply. The front LEDs indicate the correct settings (HP or HC) and the fault LED does not illuminate.
Any advice or ideas would be greatly appreciated.


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## IBcivic (Jan 6, 2009)

Contact member envisionelec. He knows a thing or two about amps. (understatement)
DIYMA Car Audio Forum - View Profile: envisionelec


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## MarkZ (Dec 5, 2005)

Which resistors are you referring to? The really low value ones at the output (usually less than a couple ohms each)? Those are heating up in only a single channel, right? Could you begin by measuring the DC voltage at the junction of those two (or four) resistors?


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## Audiophyle (Aug 8, 2009)

Envisionelec is very knowledgeable yes, however Im sure he is busy & if I remember correctly charges money for repairs. If he is gracious enough to stop by & give some advice that would be awesome, but Im sure there are many people on here familiar with repairing these old amps.

MarkZ
Ill check out the DC voltage at the resistors, and yes they are the primary resistors on the output path.
Do I test the DC by metering the Resistor & using the ground terminal at the amp for reference, or the neg speaker terminal?

All four transistors each run through a large (low value) resistor and then combines after the resistors, which then runs through a circuit breaker (grey box?) and straight to the speaker terminal. (pos terminal I believe, cannot remember)


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## chad (Jun 30, 2005)

Audiophyle said:


> if I remember correctly charges money for repairs.


Reminds me of a co worker at the old shop. We repaired pro audio gear, and if you like live music and go see live music you WILL be pestered about looking at someone's twin that "just needs cleaned up" that has drank a case of Killian's Red and been found as the only thing that resembles itself after a house fire.... As a favor.

Well, he had enough, stood up in a bar and proclaimed...... "The repair business is NOT a community service, I've done PLENTY of community service and I'm FINALLY off probation for.. You guessed it... Ask again, ask me about your amp ONE MORE TIME."

Exactly one second later I literally fell off a bar stool.


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## MarkZ (Dec 5, 2005)

Audiophyle said:


> Envisionelec is very knowledgeable yes, however Im sure he is busy & if I remember correctly charges money for repairs. If he is gracious enough to stop by & give some advice that would be awesome, but Im sure there are many people on here familiar with repairing these old amps.
> 
> MarkZ
> Ill check out the DC voltage at the resistors, and yes they are the primary resistors on the output path.
> ...


Yes, spkr neg for reference.


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## Audiophyle (Aug 8, 2009)

Thanks MarkZ, will check it out now.

For reference, this is the CH3+4 section of the amp









& this is the offending channel 3. The damage to the board was exclusively from the resistors failing, the bottom side looked just fine.


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## chad (Jun 30, 2005)

Just for ****s and giggles, check the integrity of all the connections on that daughter board.

Is anything on that daughter board getting hot?


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## Audiophyle (Aug 8, 2009)

I have already gone over all of the daughter boards connections since I guess its a common place for issues. The one on ch3 does not show any signs of warming, something I had checked already.


The DC voltage between the pos & neg terminals at ch3 is 27mv, and the voltages on the other side of the resistors range from 200mv (at PNP base pin) to 260mv (at NPN base pin).

For comparison, Ch4 is .9mv at the terminals, and range from .5mv (at PNP base pin) to 1.5mv (at NPN base pin) on the other side of the resistors.
Channels 1 & 2 are about the same readings as ch4, and the sub channel is only a little higher around 14mv.


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## chad (Jun 30, 2005)

worth a shot.


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## Audiophyle (Aug 8, 2009)

Yes indeed


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## chad (Jun 30, 2005)

It's evident that the resistors are getting hot because there is potential on one or both sides of that channel. If it's just one then the other will hold fast while the one with potential fights it. Thing is, if it was full rail voltage it would be all over the place like a **** sammich, so the chances of a shorted final are low. Methinks something on that daughter board is leaky and letting one or both sides make "just enough" to heat the works up, but not enough for it to draw ton's of current. Speaking of which, how much current is it drawing when it's doing this?

Also, I'd recommend current limiting at this point, does your supply current limit in case it does decide to go all hero on itself?


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## Audiophyle (Aug 8, 2009)

No, its a pretty basic power supply however it is only a 10a supply. The amp is pulling 6-8amps from the power supply while at idle.


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## ATOMICTECH62 (Jan 24, 2009)

The idle bias is too high on that channel.Whenever outputs are replaced the idle bias needs to be adjusted to match the beta of the new transistors,however I dont see an adjustment pot in the pictures so it must be the servo type that doesnt have the pot.This means there must be a bad driver or predriver transistor on the vertical board.I would rebuild the driver board.It would cost less than $10 in parts.Also look for a bad feedback resistor on the bad channel.They sometimes burn out with the channel also.


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## chad (Jun 30, 2005)

ATOMICTECH62 said:


> This means there must be a bad driver or predriver transistor on the vertical board.I would rebuild the driver board.It would cost less than $10 in parts.Also look for a bad feedback resistor on the bad channel.They sometimes burn out with the channel also.


I'm thinking the same thing.


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## Audiophyle (Aug 8, 2009)

So the high idle bias is causing the heat? 

Here are a couple pics of the driver board.

















Is there anything specific I should be looking at on that board, or do I need to just replace every component on it?


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## ATOMICTECH62 (Jan 24, 2009)

The 4 black transistors and the 6 pin dual transistor at the center,also the 1 diode.Check the resistors with the transistors removed from the board to see if their within tolerance.
The dual transistor will be the hardest to find.


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## MarkZ (Dec 5, 2005)

The cool thing about working on audio amplifiers is that when you have a bad channel you can compare it to the good channel. You can probably do a first pass of measuring without removing the components from the board. See if you can find some inconsistencies in resistance and (if possible) operating voltage between the bad channel and good channels.


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## djtsmith007 (Sep 21, 2010)

If you need actual circuit schematics let me know. I have the ones for the Reference 705 and Continuum which are the same. 

OT: I sold my SS ref 705 couple months ago with extra parts, including the FEB's your having an issue with


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## Audiophyle (Aug 8, 2009)

djtsmith007 said:


> If you need actual circuit schematics let me know. I have the ones for the Reference 705 and Continuum which are the same.


That would be great to have a copy of, PM'd email address.


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## Matt K (Mar 4, 2010)

I'm the amp's owner...he finally decided to call it quits trying to figure it out. Is anyone else out there willing to try? I've got plenty of time... Feel free to email me at [email protected]


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## daveds50 (Jun 10, 2011)

Matt K said:


> I'm the amp's owner...he finally decided to call it quits trying to figure it out. Is anyone else out there willing to try? I've got plenty of time... Feel free to email me at [email protected]


 heh, iv'e worked on so many Soundstreams, including about 20 Continuums, that they hurt my head.  
i could take it on... i have all the parts needed in stock.


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## Matt K (Mar 4, 2010)

daveds50 said:


> heh, iv'e worked on so many Soundstreams, including about 20 Continuums, that they hurt my head.
> i could take it on... i have all the parts needed in stock.


Emailed you, thanks!


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