Sony amp "protect" issue

[pentium]

Re: Sony amp "protect" issue

Got another one in today with the exact same issue. A blown STK.
this is starting to get annoying.

[shadow99]

Re: Sony amp "protect" issue

Lack of proper cooling no doubt. Install a heatsink, a fan, or both.

[PM650]

Re: Sony amp "protect" issue

Some older STK chips are just notoriously unreliable - you'll find no shortage of projection TVs with dead STK392-110's. My dad's STR-GX900ES reciever had a channel go out one day - intermittent STK350-130A of course. Ended up just using a good chip from the center channel and all has been well for years.

Btw: http://www.acme-sales.net/acmecart/a...&ppinc=search2

ACME sells 100% legit sanyo/toshiba/etc.. parts, no possibility of fakes.

[kc8adu]

Re: Sony amp "protect" issue

thats why i dont care for amps based on stk's.
worse yet they go extinct and you have to work up subs or risk fakes from shady brokers.
as for stk392-xxx i threw out a bucket full of bad ones a while back.projection tv's use a lot of these.just fixed a toshiba at the shop last week.stk's,solder joints,and nicotine.

[Krankshaft]

Re: Sony amp "protect" issue

thats why i dont care for amps based on stk's.
worse yet they go extinct and you have to work up subs or risk fakes from shady brokers.
as for stk392-xxx i threw out a bucket full of bad ones a while back.projection tv's use a lot of these.just fixed a toshiba at the shop last week.stk's,solder joints,and nicotine.

My Toshiba's STK-392-110s went out a year back I upgraded them with STK394-160s.

I read that Sanyo is no longer manufacturing these ICs due to the stupid flatscreen fad (decreased demand). However plenty of these ICs are already in circulation.

Why are these ICs so prone to failure?

Improper heatsinking bad design or both?

[Wizard]

Re: Sony amp "protect" issue

Bad design on IC package itself.

1. Aluminum base not thick enough (1/16") and stamped from aluminum sheet is POOR.
2. Mounting ears outside of the aluminum base (base is raised than the plastic ears) causes bending moment on the Al base with tension of two screws. This makes apply just enough thermal grease diffcult because of this warping and makes you more careful of torque on those two screws, spring straps preferred.
3. Due to thin base, the heat conduction is poorer even the transistor dies are on the copper slugs brazed to the base.

Now you have the formula for blowing STK.

The preferred design is screws THROUGH the base, there are plenty of space for traces to go around the two screw holes.

For this reason, failures with individual transistor on multiple heatsinks much rarer as used in RCA projection units. Yes, those that for convergence. I had hardly having to repair them. All I recall was 2 out of 60 units. That's excellent record.

Cheers, Wizard

[DJCarbine]

Re: Sony amp "protect" issue

I've got a STR-D665 with a similar protect problem.

Only, it will work perfectly fine for a week and then do protect. Cooling it down and trying again it will work for another week.

I've got it apart right now looking for issues, its just a junker amp to me.... I might salvage all the caps from it for electronics experimenting, they are all rubycon

[PM650]

Re: Sony amp "protect" issue

Sounds like a bad solder joint - check any transistors attached to smaller heatsinks. You can download complete schematics here: http://www.eserviceinfo.com/download...-D565_665.html There are no STK chips, so it could be an easy fix.

[cequil32]

Re: Sony amp "protect" issue

I have a Sony STR-D1015 that has gone into Protector Mode. Can anyone tell me how to tell if the STK350-130A is good or bad?

[newbiesat]

Re: Sony amp "protect" issue

Get you voltmeter and put in "continuity" test with your receiver "power off". Measusing Pin 9 (B+) with pin 1, 2, 3, 4, 5, and 6 to check if any short out inside IC. If you can hear the beep sound then you IC is bad. Doing the same with pin 7 (B-) with pin 1, 2, 3, 4, 5, and 6. Good luck

[redwire]

Re: Sony amp "protect" issue

The real Sanyo STK's are reliable but long gone. All the cheap manufacturers like China Co. make a poor product. I found many STK failures were due to the bonding wires breaking.

[multimeter]

Re: Sony amp "protect" issue

also bear in mind there are a lot of fakes on the stk's,so be carefull,check specs etc