btw, your photos are excellent, very well focused.
We can read the component numbers very clearly.
So clearly, you can afford to zoom out a bit so that we can see more of the board. It would be nice to see what components are removed.

 

I never could understand what would cause R402 to get blown away.

Off hand, the signal originates back in the x3xx section at the push-pull output transistors, An unlikely combination of things could have caused it to blow, like the output transistor in X3xx shorting and the opposite polarity input transistor AND diode shorting would place 120 volts across the resistor resulting in a 200 mA current flowing through a 560 ohm resistor .... and 22 watts later ... we see the results in the picture. But that is my active imagination speaking. I'll have to re-read the thread to see if that type of scenario was possible.

This problem with this set will cause us to be cautious, more so than normal. In the previous 23 pages, I had thought we were making really good progress, but other things popped up in the midst of the repair. Duplicate failures probably should have set us to proceed more cautiously, but I didn't think of it.

I'll do the review tomorrow and try to keep good notes.

I concur, the pictures are the best I've seen in this section of the forum.

 

Okey, i might zoom out a little sometimes, i think pictures are important, so i'm trying to get the most informative of what happens.
I could always take some overview shots of the situation of components at the moment.

I just measured on TP502, i could measure -1,8 V on the - side and 0 V on the + side...

 

Just some overview pics so you guys can see what's removed.

I also got a "new" multimeter.

 

The 1.8V on the negative side is out of tolerance. The 502 test point should be 4mV -7mV

 

The 1.8V on the negative side is out of tolerance. The 502 test point should be 4mV -7mV

So what should we do about it?
New components came really quick...

 

I thought we would hold off on the LEFT channel and work on getting the RIGHT channel working.

 

Sounds good to me. It is noted and it seems different than before.

My only question would be are there enough fets installed to ensure that 1.8 or 0.0 is valid? That pertains to both the left and right channels.

 

What would be our next move on the RIGHT channel ?

 

I would recommend you read page two of the technical manual and follow their recommendations.

 

Working on next step. Reading over all posts.

Make a list of all components not installed.

 

I would recommend you read page two of the technical manual and follow their recommendations.

referring to this JoeJester ?

 

Working on next step. Reading over all posts.

Make a list of all components not installed.

Here is the list

R505
R506
C425
C426

IC401
IC402

Q501
Q503
Q505
Q507
Q509
Q515
Q517

Q423
Q425
Q427
Q429

Q424
Q426
Q428
Q430

R401
R402

 

Yes, specifically the part about doing this before any repairs.

The ICQ adjustments, or misadjustment, can cause excessive current that would exceed the power rating of the R505/R506 resistors.

 

Your photos in the past have been very clear and extremely helpful.
In future there is no need to take pictures unless requested. For now just report what you see.
(When you do take a photo, take a second photo from a different angle because the part identifier is often hidden by a component.)


Apply power and note any indication of the three lamps glowing.
As usual, watch and smell for sparks, smoke or fire.

All voltage measurements are with respect to ground.

Measure voltage at IC401 pin-4 and pin-8.
Measure voltage at IC402 pin-4 and pin-8.
(Just checking. Don't be alarmed if you observe discrepancy.)

Measure voltage at R428 and R430 (both legs).

We are expecting to see
IC402 pin-8 +7.8V
IC402 pin-4 -7.9V
IC401 should not be receiving any power.

 

Your photos in the past have been very clear and extremely helpful.
In future there is no need to take pictures unless requested. For now just report what you see.
(When you do take a photo, take a second photo from a different angle because the part identifier is often hidden by a component.)


Apply power and note any indication of the three lamps glowing.
As usual, watch and smell for sparks, smoke or fire.

All voltage measurements are with respect to ground.

Measure voltage at IC401 pin-4 and pin-8.
Measure voltage at IC402 pin-4 and pin-8.
(Just checking. Don't be alarmed if you observe discrepancy.)

Measure voltage at R428 and R430 (both legs).

We are expecting to see
IC402 pin-8 +7.8V
IC402 pin-4 -7.9V
IC401 should not be receiving any power.

Affirmative about the pictures.

So i turned Power on and off between the measurements.
100W bulb almost no glow, the two 21W no glow.

IC401:
Pin 4: +2.5V
Pin 8: +0.2V

IC402:
Pin 4: -9,4V
Pin 8: +5.6V

R428:
Pin towards heatsink first: -1.2V / +5.6V

R430:
Pin towards heatsink first: -3.8V / -9.4V

 

Yes, specifically the part about doing this before any repairs.

The ICQ adjustments, or misadjustment, can cause excessive current that would exceed the power rating of the R505/R506 resistors.

I checked the adjustments now, we have earlier turned them all fully counter clockwise.
VR401,402,403,404

I rembember you pointed it out

 

It's been a while and it certainly was worth the double check.

 

To avoid reading the whole thread, just arrived. Is it still the same Technics mentioned in the OP in 2017?

 

To avoid reading the whole thread, just arrived. Is it still the same Technics mentioned in the OP in 2017?

Yes it is. Just had a pause in about a year after post 418... time sure flies