Soundstream Reference 300sx

[Dr Zeus]

Pin outs are slightly different.

FEB1 has the 3067. FEB2 has the C3381

 

[Perry Babin]

The diagrams I have marked FEB1 have the 3381.

Is the -15v going to the driver board dropping more than the -15v going to the op-amps?

Is the problem different between high power and high current?

 

[Dr Zeus]

So the regulated voltage is dropping to +/-10. voltage at 12.2vdc ps. At 14v it’s at +/-15v. Voltage on the driver boards are between +-9v and +-14v.

I think these lme opamps may be drawing more from the regulation than the Tls were.

R89/r90 get pretty warm but not unreasonably so. I see a 5 volt drop on those as well.

 

[Dr Zeus]

Wait I think that might be it. R89/R90. They're 380ohm 2w resistors look like they've been replaced too. They're supposed to be 220ohm. You think? I actually mentioned this also back in Post #19.

 

[Perry Babin]

Is the problem different between high power and high current?

The temperature of those resistors isn't an issue. They will likely only overheat if the Zeners short.

You stated that the problem was present with no load. Do any of these voltages change with no load?

 

[Dr Zeus]

The problem happens probably slightly worse in high current mode. Still regulated voltage drops by 5v. Rail voltage too but that is at least staying about +-30vDC.

All the recent voltage measurements are with no load.

I think the amp is starving for regulated voltage. I'm looking for some 220ohm resistors. Something tells me the zeners (D17/D18) may not even be seeing more than 16v. I may pull them to test, and also try dropping R89/R90 to a lower value.

 

[Dr Zeus]

OK I believe Ive fixed this with modifying R89/R90.

First I verified that D17/D18 were testing ok lifted. Resoldered. Then I jumped the current 380ohm resistors with a set of 320ohm resistors; effectively making R89/R90 about 180ohms by my meter. Its all I had in order to get close to 220 in 1w/2w configuration (Used 320o resistors off an old parts board).

The LME49740/20 OpAmps are rated for +-17vDC. As stated previously I think these beasts like to draw a lot more than TL07x opAmps.

Now the amp holds regulated voltage between +-16 and +-17vDC at all voltages between 12vDC-15vDC in both High Current and High Power operation. Driver boards are seeing much higher/better regulated voltage up to +-17vDC at 15vB+. Output is no longer cutting out like it was before. I'm going to put some 4-ohm loads on next to be sure this is working fully.

Thank you

 

[Dr Zeus]

Yup. 4-ohm and 2-ohm loads passed now. Figure this one is fixed. I'm going to be using this in my own vehicle for rear stage and so Very happy. Also I'm going to leave out the modified drive circuit seeing as the stock SG with 10ohm and IRF3205 seem to be carrying on OK at 4-ohm load to clipping. I'll try 2-ohm now.

 

[Perry Babin]

Are you going to leave the 3205s with only the 150 ohm pulldown resistors?

 

[Dr Zeus]

I think so. I did have the 1k pulldown resistors in there when I modified the PS drive circuit and they won't work without the drive circuit hence that is why I went back to 150ohm - Amp drew excessively with the 1k pulldowns.

I just ran this amp at 2-ohm hard on the bench with resistor packs. It pulled 30A and popped a 20A fuse but it requires a 30A. Rough calculation is it made about 150watts at 35vAC * 4.3A at speaker terminals. It might have some more in it but but I didn't test with a 30A fuse. The wattage figure was while it was pulling 20A off the bench.

The whole amp got up to about 115F on the bench after running it at 20A pull for about 10 minutes while I constantly varied input voltage between 12v and 14.4v. I think it will be absolutely fine in my truck at the 4-ohm load I'm planning for it; running 2x 6.5" speakers for rear soundstage.

Do you recommend a different pulldown resistor?

 

[Dr Zeus]

Hey Perry, Im confused about FEB1 vs FEB2. Not that it matters since I fixed this amp, but its the way Jaime is selling them that I think either he or you may be confused.

Take a look at this; FEB1. Its got the 3067. When I ordered these they came in a bag also marked FEB1.

Soundstream replacement FEB1 Driver PCB for first Reference generation amps | eBay

 

[Perry Babin]

I never referred to them as FEB 1 or FEB 2. If I had to differentiate between the two, I used the number on the differential transistor. When I searched for the board diagrams, I found the attached PDF file. He's probably right. The document could have been incorrectly renamed.

Wasn't the drive waveform really bad and that's why you wanted to try the emitter follower pair, initially?

 

[Dr Zeus]

Yes the drive waveform from SG to 3205 through 10ohm resistors looks like this.

Still though, the amp seems to be holding itself together.

 

[Perry Babin]

Without an input inductor on the 12v line, that much deadtime may be tough on the primary caps.

Can you get to the terminals of TS1 where they come through the board to confirm that it's closed?

 

[Dr Zeus]

Yes TS1 is closed circuit.

I may put the modified drive back in tomorrow. It wasn't that difficult to do. Goodnight

 

[Dr Zeus]

I believe that feb_1 pdf is actually for Rubicon series amplifiers. Link to where Wadest attached that file and said it was for Rubicons. The thing about Ruicons is I think the driver boards are again different than the older amps using FEB1 or FEB2 boards. Different look by the pictures.

soumdstream old school amplifiers

 

[Perry Babin]

Are the driver boards for the rubicon amps no longer available?

If Jaime has them, what is their FEB number?

 

[Dr Zeus]

I don't see Jaime selling Rubicon driver boards so not sure if they are available.

From the look of things there are more electrolytic caps on the Rubicon driver boards; which seems to match that FEB_1.pdf. The FEB1/FEB2 boards only have by 1 Electrolytic cap on them. Looks like the Rubicons maybe have about 3.