SX-1980 power supply problems

This is my current PS heatsink setup and It works great. Drops the temps down close to 28 degrees from the original heatsinks.
Plus clearance between bottom cover.
Easy to install and close to OEM.

My thread on the subject

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I'm still partial to moving the +/-80V transistors off the board. It helps in at least a dozen ways.

And I prefer this heatsink. Fins facing the right way and all. And you can give the 13V regulator a little help by replacing R202 with a 22 ohm 3W resistor.
 
Nice alternative.
They are the same size as the ones I used and cheaper.
The one advantage to my setup would be the original mounting screw to the PCB. But it may not be needed.
 
I thought the ones you used looked bigger. They are certainly wider, at least. And as far as I'm concerned, the extra screw and a few washers + nut are simply added cooling mass. :tongue:
 
UPDATE.....

The board layout should be completed this week. I'll post pictures of the schematic and layout as soon as they are ready.
 
Need some help....

We are working on the layout and ran into a small snag...

I ordered a service manual from stereo manuals.com and the manual is OK however it's really hard to read all of the part id's on the layout. This would be page 101 or the layout of AWR-154.

If someone has an original manual and can take a hi resolution picture of this page that would be really helpful. Post or PM is fine..

We can power through it by tracing everything out if necessary, it just takes more time.
 
There just a tad blurry aren't they. try taking a picture of it with you cellphone then blow it up . It will give you a little better resolution it will help little
 
There just a tad blurry aren't they. try taking a picture of it with you cellphone then blow it up . It will give you a little better resolution it will help little

I tried to use a nice copy machine we have to blow it up but it was not very good. The original text along with the board traces make it a mess.
 
Help with values

Ran into a small discrepancy....

R210 and R212 are both listed as 5.6 Ohm 1/2w in the schematic and parts list. On the board we are using as a template R210 has a 5.1 ohm 2W and R212 has 22 ohm 1w installed. What is correct? I am assuming they should be the same and match the schematic?
 
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I do not know for sure, without looking and doing some calcs. Most of the low R's are for voltage dropping, to distribute the power or heat between them and the series pass/drop bjt regulator and to add a bit more r/c ripple filtering too.
You should be able to determine the loads and do the calculations to determine what is to be used.
The 5.6 and 5.1 are close but 22 and 5.1 something needs to be checked with the calculations. That is what I'd be doing!!
 
I do not know for sure, without looking and doing some calcs. Most of the low R's are for voltage dropping, to distribute the power or heat between them and the series pass/drop bjt regulator and to add a bit more r/c ripple filtering too.
You should be able to determine the loads and do the calculations to determine what is to be used.
The 5.6 and 5.1 are close but 22 and 5.1 something needs to be checked with the calculations. That is what I'd be doing!!

Do you have one to look at? I just want to understand what was installed from the factory. The board I am working with has been repaired several times from what I can see, and not very well I might add.
 
Most of the pictures I have don't help because R212 is inside a fabric tube. The position of the resistor on the original board is highly distinctive, hidden UNDER the big heat sink plate, and relatively alone, next to the two 3.3k 2w resistors (r102, R308) that drop the relay coil voltages, in an uncomplicated portion of the pattern.

R212 is the -80v power supply (30mA) and then the -34v power supply (64mA). Call it 100mA current.



The WHOLE idea is that those series resistors would act as fuses in serious overload situations, they having an INTENDED 5.6 ohms and 1/2 watt specification. They are not intended nor needed for their voltage drop directly, but rather for their power handling ability and their reaction to an overload (pop).

Thus the WATTAGE changes are the WORST part of substitutions.

hmmm....

original is 5.6 ohms at 0.5 watt and yours is 22 ohms at 2 watts.

p = i*i * R so at 100ma and 5.6 = 0.056 w at 100ma and 22 ohms = .22w

but what current causes rated dissipation?

0.3 amp = square root of 0.5w / 5.6 ohms , while square root of 2w / 22 ohms is 0.3w too.

so we look at the voltage drop.

e = i * r so at 100ma and 5.6 ohms = .56 volt at 100ma and 22 ohms is 2.2 volt

hmmm.. a drop in the bucket so to speak...

Thus we have to look at the resistor types. the 5.6 is a carbon comp, what is yours. if it is a wire wound, it is FAR more tolerant of an overload, which is BAAAAD.

The detraction would seem that the 22 ohm would be contributing to the heat load, but it's only shifting it slightly away from the pass transistor...

DOES IT LOOK LIKE A FACTORY PART INSTALLATION???
 
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Most of the pictures I have don't help because R212 is inside a fabric tube. The position of the resistor on the original board is highly distinctive, hidden UNDER the big heat sink plate, and relatively alone, next to the two 3.3k 2w resistors (r102, R308) that drop the relay coil voltages, in an uncomplicated portion of the pattern.

R212 is the -80v power supply (30mA) and then the -34v power supply (64mA). Call it 100mA current.



The WHOLE idea is that those series resistors would act as fuses in serious overload situations, they having an INTENDED 5.6 ohms and 1/2 watt specification. They are not intended nor needed for their voltage drop directly, but rather for their power handling ability and their reaction to an overload (pop).

Thus the WATTAGE changes are the WORST part of substitutions.

hmmm....

original is 5.6 ohms at 0.5 watt and yours is 22 ohms at 2 watts.

p = i*i * R so at 100ma and 5.6 = 0.056 w at 100ma and 22 ohms = .22w

but what current causes rated dissipation?

0.3 amp = square root of 0.5w / 5.6 ohms , while square root of 2w / 22 ohms is 0.3w too.

so we look at the voltage drop.

e = i * r so at 100ma and 5.6 ohms = .56 volt at 100ma and 22 ohms is 2.2 volt

hmmm.. a drop in the bucket so to speak...

Thus we have to look at the resistor types. the 5.6 is a carbon comp, what is yours. if it is a wire wound, it is FAR more tolerant of an overload, which is BAAAAD.

The detraction would seem that the 22 ohm would be contributing to the heat load, but it's only shifting it slightly away from the pass transistor...

DOES IT LOOK LIKE A FACTORY PART INSTALLATION???

I would guess that it's not a factory part. It's wider than the pad holes. The board looks hacked on so much, it's really hard to tell.

At this point we are just doing the board layout. We would like to try and confirm the original part type if possible so we can have the pad spacing correct.


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I will look to see what mine has in it, it is opened up now so it is no big deal to check. I will report back shortly.
 
THAT board is a hell of a mess. I would take away the soldering iron of anybody involved, and hand them a broom and tell them to stick with floors.

R212 looks smaller than 2w while r210 might be 2 watts. NEITHER is original. Not those green hot dogs.
 
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Regardless of the exact values, that should not distract you from making the pcb. That is if you are to make an exact duplicate. You have all the lead spacings, outlines, holes etc. I realize that it is a lot of work.
I have done lots of layouts, a lot of the time, it is making the libraries.
You are fortunate, you have the placement, routing done, that is the skill and are able to do it in two layers.
Good luck. Suggest you make a test jig to test it out.
 
In my 1980 both R210 and R212 both have color codes gold, black, black and brown. They are a light gray in color and are both the same size. They had the white cloth covering so I believe they are original. I hope this helps answer your question, if not if you would pm me your email I will gladly send you pictures.
Trevor
 
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