Soundstream 405 sub-channel Problem,plz help!

[cgpeanut]

Hello Everyone,

I have an Soundstream Reference 405, The sub channel keeps blowing woofers, literally it smokes them

I measured the output comming from the speaker terminals and it measured 30 volts.

I opened the soundstream 405 540-621 rev 6 amp this weekend looking for signs of burned components but found non, I then removed the silver screws out and fliped the board to check for burned transistors they all appeared clean no "physically" burned components I could find.

I called soundstream and they promptly emailed me the schematic diagram for both the sub-channel and power supply.

Could someone please post me instructions on how to properly check if the transistors are good using a multimeter? I was planning on replacing all the transistors at the power supply side to start but thought maybe someone here can point me to the right direction to take. Thanl you!

--Roberto


p.s: soundstream wanted $125 just to look at it.

[swordfish689]

There's an excellent web page for newbies like yourself , http://www.bcae1.com/ on the side panel goto number 97 "output transistor faliure". It shows you how to check them. IF your getting that much dc on the output then you have a bad transistors.

[cgpeanut]

swordfish689, thanks for the info I'm reading that page now and will try to diagnose tonight.

I think it's best to replace all SIX TIP102 transistors which are Q607, Q608, Q609, Q610, Q611, Q612 as well as all SIX TIP107 transistors which are Q613, Q614, Q615, Q616, Q617, Q618 as seen in this schematic I'm attaching.

I'm also planning on replacing the following FED16BT components D103, D104, D105, as D106 depending on what I find when I do my diagnostics tonight.

I'll also do a resistance check on all the resistors near the output section especially
the lower ohm values.

I think this amp is worth the effort and cost to fix. I like the clean sound it produces and the one amp solution setup it provides.


--Roberto

[swordfish689]

The only transistors you should be checking are the ones used for the sub. The rest should be okay. Usually the sub channel on five channel amps, are not very good. People try to run 2 10's or 12's. I think there only good for one ten inch and that's it.

[cgpeanut]

Thanks again swordfish689,

I checked for gate leakage or short using the website you graciously provided

http://www.bcae1.com/

and here's what I found out. Just to be safe I used a fluke 81438 and my old trusted fluke 73 multimeter.

All the motorolla TIP120 519 have gate leakage or short no matter which fluke I use



All the motorolla TIP107 520 also have NO gate leakage on G + D but have leakage on G+S so they still fail.



Ordered all the TIP102 and TIP107 from digikey last night part #: 497-2546-ND, 497-2606-ND respectively,

I also tried checking all the caps on the ultra-low esr capacitor bank (1000UF 16 volts) and they don't seem to charge up.



they are yellow right side below the coil. I will have to replace all of them as well.

There's also gate leakage or short with these

GIFED16BT
FA277FEP16BTD
GIFED16BT 9508
Motorolla mc T7815CT
Korea 436 KA7915
TP50N0SE 527

I'm not sure if these are NPN Darlington power transistors I will try and ask soundstream today for more information, Can someone please inform me what kind of transistors these are?

Aghain thanks for the information.

--Roberto

[Perry Babin]

Unless the capacitors show signs of distress (leaking, burst vents on top...), they are likely OK.

The TIP107/102s are not FETs They are BJT darlingtons. They have internal resistors so they are not easy to check with 100% accuracy with a standard meter. If they are not shorted, they are likely OK.

The following are:
GIFED16BT --- Dual rectifier
FA277FEP16BTD --- Dual rectifier
GIFED16BT 9508 --- Dual rectifier
Motorolla mc T7815CT --- Positive 15v regulator
Korea 436 KA7915 --- Negative 15v regulator
TP50N0SE 527 -- Likely an MTP50N05 Mototrola MOSFET

[cgpeanut]

Thank you Perry for the info.

All qty (10) TIP107 and qty(10) TIP102s all have the same readings when I used my fluke G+D=-.487 G+S=-.504 so I thought they could not all be shorted. I have a velleman 10mhz portable oscillosope can that be used to determine if these parts are bad?

I think the only way to tell is to remove them and test again but once I remove them, might as well replaced them all since these are old and get hot alot.

so, now I'm thinking maybe the qty (5) GIFED16BT 9505 dual rectifiers diodes might be defective. I'm attaching the schematic diagrams of bothof the power supply and sub channels in pdf format maybe someone can help.

[cgpeanut]

Here's the Ref_405_Channels schematic as well

[Perry Babin]

The TIP102/107s have Base, Collector and Emitter terminals. That's very different than FETs which have Gate, Source and Drain terminals. The test procedure is very different for BJTs and FETs.

The transistors you have are darlington BJTs with internal resistors and a reverse diode so they don't check like FETs or standard BJTs.

I don't know of any way to check the transistors with a scope unless you have a curve tracer like the one shown on this page:
http://www.fullnet.com/u/tomg/gooteect.htm

Generally, if the diodes fail, they fail shorted and destroy the power supply or blow the main power fuse.

If you found a shorted 102/107, that could cause the rail voltage to be applied to the speaker leads. For this to happen, you would have to have had some open emitter resistors or open complementary transistors (complement to the one that shorted).

If none of the outputs were defective, you could have a problem with bad connections on the driver board or a defective driver.

[cgpeanut]

Perry Said:

If you found a shorted 102/107, that could cause the rail voltage to be applied to the speaker leads. For this to happen, you would have to have had some open emitter resistors or open complementary transistors (complement to the one that shorted).

---

I will check for burned or shorted resistors especially near the speaker terminals maybe there's something I missed.

There's no signs of burned components that I could see fron and back.





Back side:




I will resolder the daugther card and the terminals until my part from digikey comes.

Perry, Digi-Key part #: 497-2546-5-ND and 497-2606-5-ND are NOT darlington BJTs? so it the wrong part that I ordered?

--Roberto