All 4 channels are working on the bench now. I notice when I flip Channel 3/4's bridged switch I then only get gain controllability from Channel 4. its almost like Channel 3's gain gets taken out of the loop. On the other hand Channel 1/2's gain work together in Bridged mode.
Channel 2 also has some audible dirt on it. I checked the NE5532 opAmp and it seems -ok-. Enabling Channel 2's LP crossover reduces the noise considerably. If I ground the input RCA shields the noise is eliminated completely.
Scope set to .5v Div and 20uS.
Heres with no RCAs connected:
Here is with RCAs connected and frequency generator pushing a 20,000hz frequency
The noise -is- audible.
opAmp datasheet
http://www.datasheetcatalog.org/datasheet2/5/0q263do8iq991qftdprcsxqcjsky.pdf
Channel 2 also has some audible dirt on it. I checked the NE5532 opAmp and it seems -ok-. Enabling Channel 2's LP crossover reduces the noise considerably. If I ground the input RCA shields the noise is eliminated completely.
Scope set to .5v Div and 20uS.
Heres with no RCAs connected:
Here is with RCAs connected and frequency generator pushing a 20,000hz frequency
The noise -is- audible.
opAmp datasheet
http://www.datasheetcatalog.org/datasheet2/5/0q263do8iq991qftdprcsxqcjsky.pdf
Well I think I'm just going to leave this noise well enough alone. I've been running this amp for the past ~20 minutes or so on the bench and it seems to be pretty stable. The gain controls are a little bit lop-sided between the 4 channels but I guess thats what I'll have to accept for the most part. Seems for channels 1&2 I have to raise the gains together, while Channel 4's gain controls both 3&4 in bridged mode. If I turn the gains up the same on all 4 dials in Stereo; I get different level of voltage outputs on the speaker terminals.
I'm thinking of buttoning this amp up and giving it another whirl in my car in place of my PC275.
I'm thinking of buttoning this amp up and giving it another whirl in my car in place of my PC275.
I also think I know why I blew channel 3 up the first go-around. Running this amp in bridged mode only requires one RCA per pair of channels.
Page 17 shows the HU RCAs split one left, one right. I told you this amp was finicky!
http://www.soundstream.com/manuals/AMP/sa_mc_d_class%20a/mc140245/mc140245.pdf
Page 17 shows the HU RCAs split one left, one right. I told you this amp was finicky!
http://www.soundstream.com/manuals/AMP/sa_mc_d_class%20a/mc140245/mc140245.pdf
Went ahead and put this amp in my car. Is sounds so crisp and clean! Beats my PC275 to pieces in terms of clarity AND strength. For the minutes I played it with the car off I thought I had a show/sq winner.
I'll keep it in the car for a little while; but unfortunately the amp suffers from vehicle electronic whine. The amp picks up everything it seems, to a softness which I can hear under about the first 15% of my music volume. Changing tracks makes the noise more pronounced. My PPI amp does not do this so I'll likely pull this Soundstream 140x for additional service if more can be done.
Both bridged channels do this.
Thanks for hanging in there folks!
I'll keep it in the car for a little while; but unfortunately the amp suffers from vehicle electronic whine. The amp picks up everything it seems, to a softness which I can hear under about the first 15% of my music volume. Changing tracks makes the noise more pronounced. My PPI amp does not do this so I'll likely pull this Soundstream 140x for additional service if more can be done.
Both bridged channels do this.
Thanks for hanging in there folks!
BAAAAAHH. Channel 4 poped another 5A fuse. This time it took out the fuse and both the TIP101 & TIP106 output transistors. Bollocks! The fuse and transistors blew out at high volume. The amp was running CH3 & CH4 bridged. Maybe its because they got hot too many times before or maybe there is something else wrong with CH3/CH4. So sad too bad. She sounded really good until the end.
In better news I think I figured out the ground loop noise. Seems my RCA cable shields were touching the chassis which is directly connected to amp ground. Unfortunately I was unable to verify after fixing it because CH4 blew.
Now I've gotta order parts.
In better news I think I figured out the ground loop noise. Seems my RCA cable shields were touching the chassis which is directly connected to amp ground. Unfortunately I was unable to verify after fixing it because CH4 blew.
Now I've gotta order parts.
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In bridged mode, one gain control is disconnected from the circuit. I don't know if 1/2 and 3/4 have an identical configuration. Does the bridge switch have any effect on channels 1 and 2 if they're bridged?
If the amp is configured like other old models, having the RCAs plugged into both RCA jacks won't cause any problems.
Have you noticed if the amp is more likely to blow the fuse if it's in bridged or in stereo mode?
If the amp is configured like other old models, having the RCAs plugged into both RCA jacks won't cause any problems.
Have you noticed if the amp is more likely to blow the fuse if it's in bridged or in stereo mode?
For CH1/CH2 I must have the switch set to bridged for bridging to work, and then both CH1/CH2 gain pots work in tandom with each other.
CH3/CH4 seems to remove CH3's gain pot from the circuit while bridged. Compairing CH1/2 with CH3/4 bridged - the gain pots get into grosely different arrangements. I have to set the gain via the amp's output with 60hz and a volt metter to get the two sides to match. I mean the difference is very substantial - like twice the amount of rotation on CH3/CH4 vs CH1/CH2 gain pots. Very Finicky.
Unfortunetaly I've only had fuses pop when operating in bridge-mode, but thats not to say stereo mode doesnt have the same problem - I just didnt try it for long enough I guess. I wish now that I tried un-bridged. Now that CH4's TIP101/TIP106 are shorted (Pin2 to Pin3) I'm stuck with ordering some parts.
I did some searching and saw some posts about the MC series getting out of tune. All the other amps I've worked with have Bias control - this one doesnt. Seems some people actually add a bias pot somehow to these little amps. Maybe I should have checked voltage across the emitter resistor before putting the amp in my car.
That being said, I didnt want to put the PPI PC275 back in the car, so I decided to test the Punch 60x2 DSM. I continually underestimate those DSMs. It sounds great.
CH3/CH4 seems to remove CH3's gain pot from the circuit while bridged. Compairing CH1/2 with CH3/4 bridged - the gain pots get into grosely different arrangements. I have to set the gain via the amp's output with 60hz and a volt metter to get the two sides to match. I mean the difference is very substantial - like twice the amount of rotation on CH3/CH4 vs CH1/CH2 gain pots. Very Finicky.
Unfortunetaly I've only had fuses pop when operating in bridge-mode, but thats not to say stereo mode doesnt have the same problem - I just didnt try it for long enough I guess. I wish now that I tried un-bridged. Now that CH4's TIP101/TIP106 are shorted (Pin2 to Pin3) I'm stuck with ordering some parts.
I did some searching and saw some posts about the MC series getting out of tune. All the other amps I've worked with have Bias control - this one doesnt. Seems some people actually add a bias pot somehow to these little amps. Maybe I should have checked voltage across the emitter resistor before putting the amp in my car.
That being said, I didnt want to put the PPI PC275 back in the car, so I decided to test the Punch 60x2 DSM. I continually underestimate those DSMs. It sounds great.
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Is this amp really a Class B? I wonder how good or bad that makes it?
To be honest; no switch makes a difference in the relay's operation. The relay always activates with remote regardless of switch positioning. From the look of it, theres a few components in-between but the relay is actuating off Pin 15 of the SG3524
To be honest; no switch makes a difference in the relay's operation. The relay always activates with remote regardless of switch positioning. From the look of it, theres a few components in-between but the relay is actuating off Pin 15 of the SG3524
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If it's indeed class B, it will have 0.000v DC across the emitter resistors.
There was at least 1 SoundStream amp that was supposed to be class AB (A at low power) and had no bias pots. It was the Class A 50. It had 1 ohm emitter resistors in parallel with diodes in place of the 0.1 ohm resistors. With 1 ohm resistors, the biasing isn't quite as critical so they may be able to have bias current without needing bias pots. Yours is almost certainly class B.
Class B amps can sound as good as other classes if properly designed.
Do the relay contacts have audio or only DC? If you don't know, don't bother checking.
There was at least 1 SoundStream amp that was supposed to be class AB (A at low power) and had no bias pots. It was the Class A 50. It had 1 ohm emitter resistors in parallel with diodes in place of the 0.1 ohm resistors. With 1 ohm resistors, the biasing isn't quite as critical so they may be able to have bias current without needing bias pots. Yours is almost certainly class B.
Class B amps can sound as good as other classes if properly designed.
Do the relay contacts have audio or only DC? If you don't know, don't bother checking.
I think the relay only has DC voltage.
I think I found a missing component on this amp's PCB. Its either a resistor or a diode; but it looks like someone previously chopped it off. I believe this missing component has something to do with the relay's circuit but I dont know what its designed to specifically do. I'll likely search around for some old pics of Soundstream amps to get a better idea.
This missing component is in the center of this photo - the two pads down from the larger yellow cap. The component basically connects from the 3524 Pin1 on one pad and then up to the top of the PCB where the little transistor and wierdly installed resistors live. This small transistor seems to control the relay's operation. Again, this connection is lost because this component may be missing.
Something else was done to this amp; perhaps I should have mentioned this earlier but I really dont have problems with CH1/CH2. Either the factory or someone put this black wire going from the RCA shields to CH1/CH2's Stereo/Mono switch's 'shield' or output post. Also in this photo CH1/CH2 RCA shield trace connection has been severed. By comparison; CH3/Ch4 does not have this configuration and shield is instead running through resistors and on to different things.
I think I found a missing component on this amp's PCB. Its either a resistor or a diode; but it looks like someone previously chopped it off. I believe this missing component has something to do with the relay's circuit but I dont know what its designed to specifically do. I'll likely search around for some old pics of Soundstream amps to get a better idea.
This missing component is in the center of this photo - the two pads down from the larger yellow cap. The component basically connects from the 3524 Pin1 on one pad and then up to the top of the PCB where the little transistor and wierdly installed resistors live. This small transistor seems to control the relay's operation. Again, this connection is lost because this component may be missing.
Something else was done to this amp; perhaps I should have mentioned this earlier but I really dont have problems with CH1/CH2. Either the factory or someone put this black wire going from the RCA shields to CH1/CH2's Stereo/Mono switch's 'shield' or output post. Also in this photo CH1/CH2 RCA shield trace connection has been severed. By comparison; CH3/Ch4 does not have this configuration and shield is instead running through resistors and on to different things.
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By this picture of a SS D100II it sure looks like the missing spot on mine should be a 1N4148 diode...
Soundstream D100II inside - Amp Guts
Soundstream D100II inside - Amp Guts
The pad closest to the yellow cap goes to the non-polar end of the yellow cap and then straight through to the small transistor's pin2. From there it goes straight through again to a small resistor which connects it directly to REM. Basically from REM its a straight shot through the 20k resistor to this pad.
The pad further from the yellow cap goes straight to several pins of the 3524; most notibly Pin1, pin4, and pin5. I also see a trace where it possibly connects to the yellow cap's polar side.
Now I'm almost 100% positive this amp is missing a 1N4148 diode. After looking at a few diagrams I decided to give putting one to the test a try. I did a temporary test of tapping a 1N4148 diode onto the above pads and as I suspected the relay in the center of the amp reacts to the diode. I think everything is OK with this in place of the circuit - basically because nothing turned off or blew up so to speak. I'm tempted to permanently put this diode in its place. Banded side of the diode going closer to pin 1 of the 3524.
There have been amps with diodes and transistors that were used to quickly discharge capacitors when the amp was powered down. These provided more reliable behavior than letting the caps discharge on their own. In some instances, these components failed because they couldn't reliably handle the current that passed through them when the amp was powered off. This caused them to fail and the amp failed to power up properly.
From your description, it appears that the diode may have been feeding voltage back into the IC when the remote voltage was removed. If that's the case, the diode could reverse bias the error amp in the 3524 when the amp is powered down. This could cause it to fail.
Since it's your amp, you can leave the diode. If you're going to sell it, I'd recommend that you not install one there until you find an identical amp with the same or higher revision number that has the diode installed.
If you work on a lot of soundstream amps, you'll see that they make all sorts of circuit modifications. In most cases (for any manufacturer) that means that there were unforeseen problems that needed to be resolved. Your missing diode may be one of those mods.
From your description, it appears that the diode may have been feeding voltage back into the IC when the remote voltage was removed. If that's the case, the diode could reverse bias the error amp in the 3524 when the amp is powered down. This could cause it to fail.
Since it's your amp, you can leave the diode. If you're going to sell it, I'd recommend that you not install one there until you find an identical amp with the same or higher revision number that has the diode installed.
If you work on a lot of soundstream amps, you'll see that they make all sorts of circuit modifications. In most cases (for any manufacturer) that means that there were unforeseen problems that needed to be resolved. Your missing diode may be one of those mods.
This amp's board is revision A, so I guess it was SS's first experiment. I'm begining to think this amp is pretty rare or perhaps they were just too expensive for anybody back in the day. I see more MC24x series for sale, such as one still brand new in the box on eBay going for $500. It makes me think I have something a little special; but alas its just a little amplifier at the end of the day. When it was working it sounded noticably clearer and cleaner than any of the other amps I've worked on.
I instlled the diode but it didnt work out so well. With the diode in place channels 1 & 2 would not work at all - its almost like the relay is required to switch to get CH1/CH2 working properly. I took the diode out and will leave it out as it does not seem to behave with it installed.
Basically, this amp is still toasting CH4, and the output transistors fried and were clipped a few days ago. It seems to only happen in bridged mode, but now that I need to order parts to get it part way working again.
I read somewhere that replacing the TIP101 & TIP106 transistors with TIP102 & TIP107 parts was a good idea (actually suggested from soundstream) so if I do that then I could borrow CH1/CH2's transistors for CH3/CH4 testing. Then replace all 4 with the newer part. Still debating...
I'm not sure if its CH3 or CH4 thats the problem, so hopefully running this amp in stereo mode will point to more compromised components. A few days back it was a pair of CH3's diodes that failed so it could be either side.
I instlled the diode but it didnt work out so well. With the diode in place channels 1 & 2 would not work at all - its almost like the relay is required to switch to get CH1/CH2 working properly. I took the diode out and will leave it out as it does not seem to behave with it installed.
Basically, this amp is still toasting CH4, and the output transistors fried and were clipped a few days ago. It seems to only happen in bridged mode, but now that I need to order parts to get it part way working again.
I read somewhere that replacing the TIP101 & TIP106 transistors with TIP102 & TIP107 parts was a good idea (actually suggested from soundstream) so if I do that then I could borrow CH1/CH2's transistors for CH3/CH4 testing. Then replace all 4 with the newer part. Still debating...
I'm not sure if its CH3 or CH4 thats the problem, so hopefully running this amp in stereo mode will point to more compromised components. A few days back it was a pair of CH3's diodes that failed so it could be either side.
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