Pin 18 and 17 are swapped on the Sta-2000. It feeds off of shunt regulator TR701. The pcb has pin 18 gnd. Pin 17 is 13.7V - vbe= ~+13V.
Realistic STA-2000D: Turns On but No sound
- Thread starter Juan-Jose
- Start date
Pin 18 and 17 are swapped on the Sta-2000. It feeds off of shunt regulator TR701. The pcb has pin 18 gnd. Pin 17 is 13.7V - vbe= ~+13V.
So you're saying the schematic is wrong?
I am indeed. The red wire is labelled 17 IFB. The black is pin 18 (gnd).
pin 17 is a vbe below the zener diode. I bumped the zener to 14V so pin 17 ends at ~+13V.
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Thank you. I'll stick a note in my files noting this.
There is a muting relay board with a reed relay. That is probably the faint click you hear. It mutes the signal when switching the input selector to avoid "pops". I have found sometimes a diode goes bad. There isn't much on the board, just 4 transistors and a couple of diodes. The SM shows resistors, but mine had diodes instead and doesn't quite match the actual board. There are 2 small electrolytic caps in there too. It is called "FM Muting and switching PCB".I was able to grab this massive Realistic STA-2000D in a gear lot with other stuff.
View attachment 2757317
Unit turns On but there's No sound.
I feel an instant "click" when it turns On (there's no delay like the usual protection relay clicking out - this one clicks right away and the "click" is hardly perceptible).
Unit is currently connected to a Dim-bulb (75W) Tester, the DBT goes into a variac (set to 117VAC). DBT lights up very bright and then goes faint as expected.
View attachment 2757369
Upon initial visual check, nothing seems to be burnt.
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Connected Pre/Main jumpers, same results.
Connected directly into wall outlet, same results.
Tried all inputs (Aux1, Aux2, Phono, AM, FM and Main In, same results. While changing stations in FM, the FM tuning meter seems to change (like it is picking up stations).
Tried all outputs (Channel A, Channel B, Pre Out and Headphones), same results. Power meters never moved.
All fuses tested Ok outside.
Removed all four Output transistors, same results: just an instant but hardly perceptible "click", not the usual relay click. Installed Output transistors back.
Service Manual can be found here.
Schematic diagram can be found here.
Source: Realistic STA-2000D AM/FM Stereo Receiver Manual | HiFi Engine
Any guidance will be much appreciated, PLEASE.
The speaker protection is a louder click and seems it is not engaging. You'll have to check for speaker output _before_ the relay, and coming from the amps. Excessive DC voltage from the amp output can prevent the protection relay from turning the speakers on. Resolve the high voltage problem if that is the case. Zero volume, AUX input and the DC coming from the amp to the relay should be in the mV range. Preferably under 100mV.
The way the amp cards are mounted, burned components can be hidden from view, unless removed.
Removing all output transistors isn't going to determine anything.
cademan
Lunatic Member
But testing them for shorts will.
No testing was mentioned.
Failure of output transistors can cascade back through the amp. Print out that section of the schematic and start testing back toward the input. Mark anything that tests bad on the schematic section. This make it easier to see the path of destruction.The two output transistors to the left tested bad, I have replaced them, but still get the same results: it doesn't click out of protection mode.
View attachment 2840426
Anything I can do/check next? Please, and thanks!