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Realistic STA 2100D amp layout

Stereoboy70

Stereoboy70

Active Member
Hello All. Question..... I’m replacing the transistors on both amps in my 2100D. The service manual shows different layouts for the 507 and 508 transistors. The pic of the L amp shows. B C E but the right shows E C B
I’m replacing with MJE 15032 and 15033 which are B C E. The actual amp board shows. E C B. So do I put these new ones in backwards ???? If I do the heat sinks will not be in a position to accept the screws that hold them to the board. A little confused.
 
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Yes. The old transistors are obsolete. The modern equivalent from what I’ve found on here is the MJE 15032 and 15033. They are PNP and NPN bit the pin out is B C E not E C B. I’m just confused because the service manual shows two different orientations. One amp shows BCE and the other shows ECB. I’m pretty confident the ECB is correct meaning the transistors I have will go in backwards.
 
It looks like the service manual PCB illustrations (pgs. 42, 43) are buggered up between the L and R channel PCBs. By comparing the PCB traces to the schematic (Manual 31) Schematic), the pins are ECB as shown on the Right PCB. The bases of 507, 508 are connected to 505, 506, respectively. The emitters are connected to R523, 524. The manual for 16) Main Amp PCB (Right) top and bottom views match the schematic. The left channel views are incorrect. Since the PCBs are shown to have identical tracings and the components also have identical placement, then the pinouts are identical between channels.

I suggest verifying this on the actual unit (my STA-2100D is running fine and is closed up).
 
I was thinking of the KSA1220A and KSC2960A but it looks like the current spec is lower.

Rob
 
RTally said:
It looks like the service manual PCB illustrations (pgs. 42, 43) are buggered up between the L and R channel PCBs. By comparing the PCB traces to the schematic (Manual 31) Schematic), the pins are ECB as shown on the Right PCB. The bases of 507, 508 are connected to 505, 506, respectively. The emitters are connected to R523, 524. The manual for 16) Main Amp PCB (Right) top and bottom views match the schematic. The left channel views are incorrect. Since the PCBs are shown to have identical tracings and the components also have identical placement, then the pinouts are identical between channels.

I suggest verifying this on the actual unit (my STA-2100D is running fine and is closed up).
Click to expand...
Thank you I will verify.
 
RTally said:
It looks like the service manual PCB illustrations (pgs. 42, 43) are buggered up between the L and R channel PCBs. By comparing the PCB traces to the schematic (Manual 31) Schematic), the pins are ECB as shown on the Right PCB. The bases of 507, 508 are connected to 505, 506, respectively. The emitters are connected to R523, 524. The manual for 16) Main Amp PCB (Right) top and bottom views match the schematic. The left channel views are incorrect. Since the PCBs are shown to have identical tracings and the components also have identical placement, then the pinouts are identical between channels.

I suggest verifying this on the actual unit (my STA-2100D is running fine and is closed up).
Click to expand...
Checked the transistors They are in correct.
when I hook up to a DBT the light is super bright. None of the transistors are shorted. Even the main output ones. All is good with the protection circuit. Green light. But when I start plugging in the wires in the amps it all goes south. I had this running two weeks ago. But after 3 days the resistor 524R blew up when I powered up. I replaced it along with several transistors that shorted but now something else is wrong. Power supply is good.
 
RTally said:
It looks like the service manual PCB illustrations (pgs. 42, 43) are buggered up between the L and R channel PCBs. By comparing the PCB traces to the schematic (Manual 31) Schematic), the pins are ECB as shown on the Right PCB. The bases of 507, 508 are connected to 505, 506, respectively. The emitters are connected to R523, 524. The manual for 16) Main Amp PCB (Right) top and bottom views match the schematic. The left channel views are incorrect. Since the PCBs are shown to have identical tracings and the components also have identical placement, then the pinouts are identical between channels.

I suggest verifying this on the actual unit (my STA-2100D is running fine and is closed up).
Click to expand...
I noticed that my amp center voltage is 5+ V
It’s supposed to be around 15Mv. This is what is making my protection relay open. I’m not an expert at reading schematics but pin 15 on my amps is the culprit. This is where the 5V is coming out. What would produce 5v here ? Apparently some issues in the main amp.
 
What happens when you pull out the outputs?

The 2100D is pretty well known to take out emitters when it dies along with a shorted dual diode setup. If I remember correctly the amps are interchangeable on these units. It could be a damaged output as the I remember the output stage can oscillate if there's leakage on the Zeners. Check your resistor network as well because the resistors can go open or change value when it opens. Compare with the good amplifier.
 
Porkbuns said:
What happens when you pull out the outputs?

The 2100D is pretty well known to take out emitters when it dies along with a shorted dual diode setup. If I remember correctly the amps are interchangeable on these units. It could be a damaged output as the I remember the output stage can oscillate if there's leakage on the Zeners. Check your resistor network as well because the resistors can go open or change value when it opens. Compare with the good amplifier.
Click to expand...
It’s both. When I plug in one amp it’s fine. When I plug in both amps is when it opens the protection relay. Either amp is fine by itself it’s only when both outputs are plugged in
 
Stereoboy70 said:
It’s both. When I plug in one amp it’s fine. When I plug in both amps is when it opens the protection relay. Either amp is fine by itself it’s only when both outputs are plugged in
Click to expand...


That's... very very weird. Can you measure the pins on the relay or from the amps?

What's the DC offset on the relay?
 
Porkbuns said:
That's... very very weird. Can you measure the pins on the relay or from the amps?

What's the DC offset on the relay?
Click to expand...
I’ll do it today. Yes it is weird. If only 1of the out puts is connected my relay stays closed. As soon as I connect the other amp it opens. Doesn’t matter which channel. I do have a solid 5.2V dc at pin 13 on each amp (out). It’s supposed to be around 15Mv
 
Dc off
Porkbuns said:
5.2VDC...

Wait both amps are 5.2V??
Click to expand...
DC offset is dialed in. Idle current should be 9mv. I have 0mv. When I adjust VR 502 I can get it to go negative but all the way L it just goes to zero. Will this be a problem?? I have replaced D 502 with 2 1N4148 diodes in series. R 522 checked good but did not replace. The trim pots have also been replaced with Bourns equiv. Sorry to ramble on. This unit has been a real problem for me.
 
Stereoboy70 said:
Dc off

DC offset is dialed in. Idle current should be 9mv. I have 0mv. When I adjust VR 502 I can get it to go negative but all the way L it just goes to zero. Will this be a problem?? I have replaced D 502 with 2 1N4148 diodes in series. R 522 checked good but did not replace. The trim pots have also been replaced with Bourns equiv. Sorry to ramble on. This unit has been a real problem for me.
Click to expand...
Got it. Found a bad couple of solder joints on T507. Got idle current to 9mv. Thanks for making me jog my brain.
 
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