Electron Kinetics Eagle 2C amplifier problem

[budm]

Re: Electron Kinetics Eagle 2C amplifier problem

The thread is long so I do not remember if you already test that Transistor already or not and compare it to the working channel. You have one working channel so you can always do the comparison test against working channel.

[Gammaray]

Re: Electron Kinetics Eagle 2C amplifier problem

Sorry for the lengthy thread! Here are the voltages from the transistors I measured from each side:

(CHANNEL A) Top Transistors
#1 Sanken (2SC2774) B=.631 DCV/ C=48.0 DCV/ E=.018 DCV
#2 Sanken (C2168) B=1.22 DCV/ C=47.7 DCV/ E=.627 DCV
#3 Sanken (2SC2774) B=.626 DCV/ C=48.0 DCV/ E=.017 DCV
#4 Sanken (A958) B=46.4 DCV/ C=1.22 DCV/ E=47.3 DCV

(CHANNEL A) Bottom Transistors
#1(2SA1170) B= .603 DCV/ C= -46.55 DCV/ E= -.012 DCV
#2(A958) B= -1.22 DCV/ C= -46.33 DCV/ E= -.600 DCV
#3(2SA1170) B= -.593 DCV/ C= -47.3 DCV/ E= -.002 DCV
#4(2SC2168) B= -44.7 DCV/ C= -1.20 DCV/ E= -44.8 DCV


(CHANNEL B) Top Transistors
#1 Sanken (A958) B= 47.8 DCV/ C= -40.0 DCV/ E=46.1 DCV
#2 Sanken (2SC2774) B= -21.0 DCV/ C= 46.8 DCV/ E= -19.6 DCV
#3 Sanken (C2168) B= -18.8 DCV/ C=46.8 DCV/ E= -18.9 DCV
#4 Sanken (2SC2774)B= -18.75 DCV/ C=46.9 DCV/ E= -19.4 DCV

(CHANNEL B) Bottom Transistors
#5 (2SC2168) B= -44.8 DCV/ C= -2.27 DCV/ E= -44.8 DCV
#6 (2SA1170) B= -1.15 DCV/ C= -45.9 DCV/ E= -.63 DCV
#7 (A958) B= -1.9 DCV/ C= -46.7 DCV/ E= -1.22 DCV
#8 (2SA1170) B= -1.42 DCV/ C= -46.1 DCV/ E= -.75 DCV

[budm]

Re: Electron Kinetics Eagle 2C amplifier problem

If you suspect that E-B junction is shorted then you should be able to use Ohm meter to check the resistance between E and B pin if the suspect transistor.

[Gammaray]

Re: Electron Kinetics Eagle 2C amplifier problem

If you suspect that E-B junction is shorted then you should be able to use Ohm meter to check the resistance between E and B pin if the suspect transistor.

OK, I will do that and post the resistance. Should I discharge the caps before I take a measurement of the transistor's resistance?

Thanks!

[budm]

Re: Electron Kinetics Eagle 2C amplifier problem

OK, I will do that and post the resistance. Should I discharge the caps before I take a measurement of the transistor's resistance?

Thanks!

Yes! discharge the caps and then take the Voltage reading on the discharged caps to make sure it is discharged.

[Gammaray]

Re: Electron Kinetics Eagle 2C amplifier problem

I measured that transistor (2SC2168) from B to E and got 1.292 M ohms..Does this seem bad?

[R_J]

Re: Electron Kinetics Eagle 2C amplifier problem

Not really, but
Read post #61 again. and check other parts the same way, you may be suprised at what you will find that way.

[budm]

Re: Electron Kinetics Eagle 2C amplifier problem

Not really, but
Read post #61 again. and check other parts the same way, you may be suprised at what you will find that way.

Also in post #4.

[Gammaray]

Re: Electron Kinetics Eagle 2C amplifier problem

Would it be ok to take the pcb off from the amp chassis and do some resistance comparisons? I mean is this a good way to find faulty components without worrying about if I may accidently touch some live/hot and zap me or something else?

[Gammaray]

Re: Electron Kinetics Eagle 2C amplifier problem

bump

[budm]

Re: Electron Kinetics Eagle 2C amplifier problem

You are taking the resistance reading so the unit should not be powered in the first place so I do not see how you will be zapping anything once the filter caps are discharged and the unit is not plugged in.

[redwire]

Re: Electron Kinetics Eagle 2C amplifier problem

If you pull the board out, a schematic can get drawn up given some good pictures of the back side. The front pics have some areas I can't see.
Sometimes it's easier to sketch it one and then troubleshoot.

[Gammaray]

Re: Electron Kinetics Eagle 2C amplifier problem

You are taking the resistance reading so the unit should not be powered in the first place so I do not see how you will be zapping anything once the filter caps are discharged and the unit is not plugged in.

OK, I see. So would I have to de-solder these components to check for resistance, or can I leave them mounted to the pcb and check resistance?

[Gammaray]

Re: Electron Kinetics Eagle 2C amplifier problem

If you pull the board out, a schematic can get drawn up given some good pictures of the back side. The front pics have some areas I can't see.
Sometimes it's easier to sketch it one and then troubleshoot.

Thanks, but not sure how I could draw up these traces for the schematics. Seems to be a little out of my noob hands..LOL

[electricboyo]

Re: Electron Kinetics Eagle 2C amplifier problem

What we need are very sharp clear photos of both side of the PC board. If you remove the mounting screws from all the power transistors and the input and output jacks then you should be able to lift the PC board from the heat sinks so that both front and rear of the PC board can be seen.
The circuit design of this amplifier is somewhat unusual. Some of us who have worked on audio amplifiers for years might be able to tease out its schematic from looking at a really good set of photos of this PC board.
Because you have one channel that works it should be feasible to fix the other channel. The problem could be that just 1 component is bad.

[electricboyo]

Re: Electron Kinetics Eagle 2C amplifier problem

I suggest checking the value of all resistors on the PC board. Do this with power off and with an ohmmeter. Resistors can fail in the "open circuit" state without looking burnt or damaged.

Because there are unusual DC voltages on the faulty channel I recommend that you should only apply AC mains power to the amplifier through a "dim bulb" tester. This is a conventional incandescent 120V light bulb either 60W or 100W which is wired in series with the AC power source. This can be made with a light bulb socket and an old extension cord. Cut the hot wire of the extension cord and connect the cut ends to opposite sides of the light bulb socket. Typically the light bulb will be bright when the amplifier is first powered up and then it should get dim after the large power supply capacitors charge up. there are other postings on the forum for ''dim bulb tester" that will provide more detail about constructing and using it.

-EB

[electricboyo]

Re: Electron Kinetics Eagle 2C amplifier problem

Based on your previous voltage measurements I suggest checking all 4 of the large power resistors connected between the emitters of the channel B output transistors. One or more of these resistors is open. Or else there is a bad solder connection or broken foil on the PC board.

Under normal conditions the emitters of all 4 large power transistors should be within +/- 50 mV of each other, and this should also be very similar to the DC voltage appearing at the red output terminal post on the rear of the panel for this channel.

Ideally the DC voltage on the red output terminal post should be less than +/- 10 mV.

EB

[electricboyo]

Re: Electron Kinetics Eagle 2C amplifier problem

After looking at your photos of the PC board again up-close I am thinking perhaps some of the power transistors for the bad channel aren't actually soldered to the PC board. Or rather, their solder connections broke off. As far as I can tell there isn't much of anything mechanically holding the PC board except for the soldered pins of the large power transistors and the speaker output binding posts. I don't see any bolts or screws holding the PC board.

So, seriously, as suggested by an earlier post, it is really important to unbolt all of the power transistors from the heat sink and the pull out the PC board so you can inspect the back side of it. You may have to unbolt or unsolder the 4 speaker ouput binding posts in order to remove the PC board.

EB