Soundstream 705S DC output...

[1moreamp]

Originally Posted by KilroyNo1

Jaime replied to my email and said that he closed his repair business in 2008 and he now only sells components that he has left over. He does have the FEB boards (50-60 of them!) for this amplifier, but I haven't ascertained that the FEB board on this speaker channel is the issue. I'm thinking it might be prudent to purchase a few of them for future repairs as I don't imagine SoundStream makes them anymore.

"The other 4 channels typically used for the four corners of a car have circuit breakers on the outputs soldered to the board. I would test there for your DC voltage IF the amp was still in its sink... But since its already out now simple ohm meter testing should find open emitter resistors and shorted outputs for the bad channel in question."

So you are saying to hook up the amplifier again and check across the circuit breaker (I've traced the path back from the bad channel and found the circuit breaker) for DC voltage?

I'm not giving up yet, I'm planning on doing more reading on Perry's website tomorrow night!!

As for checking the circuit breaker well if you were to power the amp up for a few seconds you could test for the rail voltage at each breaker, that you say is present on one of your channel and then you would know exactly which outputs and FEB could be damaged.
You do enough of these and one tends to get into a rhythm about doing repairs to each brand of amp. SoundStream was prone to a typical set of failures so simple test methods while in the sink to localize troubles were my norm when dealing with one of these.

Simple DVM testing while powered up on a current limited variable power supply was first step and detection of errant voltages and DC offsets was number one. Switch testing was number two on the list, along with gathering of a set of replacement switches. Bad solder joints on the FEB boards was three. Once localized then board removal from sink was next so the repair could be completed and the re-assembly and test to SS procedures list.

Switch cleaning:
Well yes I have done this before, and found the old switches to be erratic in behavior, work sometimes and not another. I found them to need cleaning and also the bodies had loosened up and the contacts were intermittent. Now unless you enjoy removing and the tearing down and cleaning and reassembling these old switches I suggest you get Jaime to sell you a whole set and replace them and be done with them as possible rework issues. Yes switches can be saved but unless your use to repairing switches and the time sink of removal and re-install and retest, and sometimes repeat of this
step, then I say just buy new switches and replace them once, and hit the ground running not having second guess thoughts about any pesky little switch.

To be completely honest and up front to do the best job in as little time loss as possible just plan on gutting the defective channel by replacing the FEB card and all the outputs with same date code devices, and the MPSA13 Thermal bias transistor, and any out of tolerance emitter resistors. Once you have completed this simple and quick repair then you can concentrate on final test. This is where you find out if you missed something < very unlikely if you do a complete channel rebuild> and your back to some simple DC offset tests and voltage checking.

A complete FEB board and all new outputs will likely cost you around $20.00 to $30.00 US and you should have LIKE NEW operations without all the headaches of teching out each component, and possibly missing something. The latter will haunt you very shortly after you try to run the amp in real world.

Perry's tutorial, IMHO has to be the best training tutorial you will likely ever come across. But if your a one timer at this and want the job done quickly and completely correct then the simple method above might be for you. The parts are cheap enough, and the work simple enough requiring on simple soldering skills and some rudimentary DVM work. On the other hand if your educating yourself for the long term use of this sort of electronics tech level craft then please do not use the fast tech way above as this method is what experienced tech's working production level do for high speed and low rework situations, where Time Is Money....

[JLH]

Originally Posted by 1moreamp

To be completely honest and up front to do the best job in as little time loss as possible just plan on gutting the defective channel by replacing the FEB card and all the outputs with same date code devices, and the MPSA13 Thermal bias transistor, and any out of tolerance emitter resistors.

I thought this was a MPSA14 in most of the Reference series? Are the schematics wrong?

Rgs, JLH

[1moreamp]

Originally Posted by JLH

I thought this was a MPSA14 in most of the Reference series? Are the schematics wrong?

Rgs, JLH

My bad I stand corrected, I was using my tired old memory instead of my 705S documents. It is a MPSA14