I've let it idle for about 20 minutes,, i really cant see any special hot spot from left to right..

Heat sources are like earlier: Q651-Q654 are about 97 degrees celcius and Q413-Q416 is about 70 degrees celcius... and R671/R673 is pretty hot.
I've felt around everywhere, i can't fint any other very hot components.

 

From the data it appears Q429 is not conducting at all. In fact it looks to be a b-e short.

on second edit: Test the diode D415 (connected to the Q421 collector) for an open.

Test that with your handy dandy tester, test and replace as necessary.

on edit.... added updated voltage chart

 

R671/R673 is pretty hot

That would be a different problem. Use your meter on DC volts and measure the voltage across those two resistors to get an idea of the current being used.

Have you ever measured those supplies before today?

 

Transistors Q651 to Q654 as well as resistors R671 and R674, which are 2w, are on the regulation stage which must lower the rail voltages to +/- 17.8v to supply other sections of the device ( RIAA preamp, tone stage, ...), so yes it gets hard but it's normal.

 

Transistors Q651 to Q654 as well as resistors R671 and R674, which are 2w, are on the regulation stage which must lower the rail voltages to +/- 17.8v to supply other sections of the device ( RIAA preamp, tone stage, ...), so yes it gets hard but it's normal.

Define HOT in numerical terms. He has a thermal camera to check to see if he is within bounds.

on edit ....added charts



I suspect the second graph is in F not C.


on second edit ...

There is a voltage drop of (60 volts to 30.8 volts) across the series resistance of 15 + 150 + 180 (R677, R673, and R671) resulting in 29.2 volts / 345 ohms = about 85 mA. R673 would be dissipating a little over 1 watt and R671 would dissipating 1.3W

Using the chart above that would be about 62 C. Still hot ....

 

From the data it appears Q429 is not conducting at all. In fact it looks to be a b-e short.

on second edit: Test the diode D415 (connected to the Q421 collector) for an open.

Test that with your handy dandy tester, test and replace as necessary.

I tested D415 in circuit with my DMM at diode testing setting.

I can actually measure voltage both ways at this one.. 1.419 Volt one way and 0.620 Volt the other.

For comparison i checked D416, i get a measurement only one way at this one, 0.616 V

Looks like we have found something wrong here!?

I actually don't have a replacement for D415 (MA165)

Would this be the correct one?
https://www.ebay.com/itm/MA165-Pana...843918?hash=item4b7fa1984e:g:kPUAAOSw8gVX98Dl



I also checked voltage at R671/R673

R671: +61.5 V / +50 V
R673: +50 V / +41 V

 

It should be possible to replace an MA165 with a 1N4148.

 

Did you test Q429 as it looks suspicious. Like a e-b short.

On edit .... R671 is dissipating about 3/4 watt
R673 is dissipating about a half-watt

I don't want to get misdirected too much with these new readings.

 

First thing to try is replace D415 with 1N4148.
If you need to purchase (about $0.15 each), get extras (10).
We will replace both D413 and D415 to keep it balanced.

How many 2SA1535 (Q429) do you have in stock?

 

I forgot to say nice job on that diode .... I hadn't anticipated that type of failure with it.

On edit ....

Once you get these operating normally, that would be the time to visit the power supply in the X6 Extend Active Servo section.

 

Did you test Q429 as it looks suspicious. Like a e-b short.

On edit .... R671 is dissipating about 3/4 watt
R673 is dissipating about a half-watt

I don't want to get misdirected too much with these new readings.

I just took Q429 out of circuit and measured it, it turns out to be OK.

About the resistors i measured 671/673 ... the voltage should be +30 volts, no +40 like i measured?
Guess we'll dig in to that later on..

 

First thing to try is replace D415 with 1N4148.
If you need to purchase (about $0.15 each), get extras (10).
We will replace both D413 and D415 to keep it balanced.

How many 2SA1535 (Q429) do you have in stock?

I do have two new 2SA1535, but Q429 turned out to be ok.

I did order new ones (MA165) today for D415/D413.... .... but 1N4148... is that the same as i ordered earlier for D409-D412 ?
I have some new ones of those... so they will do the trick ?

 

1N4148 might not be the same as MA165 but I would go ahead and replace both D413 and D415 with what you have and see if it corrects the problem with VR401.

 

About the resistors i measured 671/673 ... the voltage should be +30 volts, no +40 like i measured?
Guess we'll dig in to that later on..

Yes that is what we will do. Just so you know, at the current that was being consumed, 40V is the normal reading on the collector end of that resistor. But like you said ... we will look it over.

 

The 4148 is one on the replacement list for the MA165.

Thanks for looking into Q429. With what's happened, it's better to be safe than sorry.

 

hmm... looking in to my parts, i have just replaced one type of diode earlier and that was a zener diode... 1N5237B-TR, i have that in stock. No other diode...

So i would have to order the 1N4148 diode!
But i have already ordered Panasonic MA165 diodes i found on ebay... so i need to wait for them to arrive...

 

But i have already ordered Panasonic MA165 diodes i found on ebay... so i need to wait for them to arrive...

No biggie. I'm hoping for it to be done by the third anniversary. We can hang as long as you can..........

 

hehehe, yes we're closing in on the third anniversary

I got the MA165 diodes today. I bought four of them, but it actually was price per pair, so i now got eight.

So i will now replace both D415 and D413 as MrChips suggested above.

 

So here's an update....I took D415 out of circuit, and it measured ok... bummer..
And with the new MA165 in circuit i measure the same as earlier, get a reading both ways, so it must be something else in the circuit causing it.

Since i don't get a reading both ways at D416, there must be something different in the two circuits, right?
And since it seems like RIGHT circuit is healthy... we strive to get similar readings at LEFT..

What component could cause the difference, measuring at D415 ?

 

Just did a little research...I took Q421 and Q425 out of circuit. (Q421 hasn't been out of circuit earlier)

Q425 tested OK.

Q421 did not test OK !
I don't have a replacement for this...need to order again....

Q419 tested OK.