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Problem with my SPX90
Old 8th May 2019
  #121
Quote:
Originally Posted by grantb3 View Post
That's R18? The 1.5k? I think that's the one I had to replace and I had to replace a ceramic disc cap too, probably C29.

I don't see a big issue with subbing that cap, but if you need to order parts I would recommend ordering the rest of the electrolytics on that board.

My board was quite dark from the heat too. Whether or not other components are bad remains to be seen. If you are replacing (all) the caps then might as well measure the resistors and check the diodes with a meter. If your meter doesn't do coils you can get cheap LCR testers on eBay that are usable.
Yea same one. I'll get some 330uf just to be sure. I should have all of them at that point (for the electros) except the 2200uf.

I've been using a multimeter to check the old caps while on the board using DC. So far they showed sub 1v even testing just after powering up (and then unplugging). Not sure if they are supposed to read higher in that scenario or if I'm testing it properly (most things online talk about removing them and then charging with a 9v battery). Should have checked the new ones I installed to see if they read ok (have put the unit away for now so will do when I get back on it).
Old 8th May 2019
  #122
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12ax7's Avatar
 

Just go ahead and replace all the electrolytics in the damn thing.

Believe it or not, doing this is apt to solve (or prevent) most issues (about 90% of the time).

(Just make sure the polarity is always correct when soldering them in, and you'll be fine.)

...Or I guess you could just keep on piddling around:

Remember that (as old as they are) EVERY electrolytic cap in that box has now reached the time for consideration of "end of life" issues.

If you just go ahead and replace 'em all; you'll probably save a whole lotta time over the next couple of years. (You really don't have anything to lose anyway, right?)
.
Old 8th May 2019
  #123
Quote:
Originally Posted by 12ax7 View Post
Just go ahead and replace all the electrolytics in the damn thing.

Believe it or not, doing this is apt to solve most issues (about 90% of the time).

(Just make sure the polarity is always correct when soldering them in, and you'll be fine.)

...Or I guess you could just keep on piddling around:

Remember that (as old as they are) EVERY electrolytic cap in that box has now reached the time for consideration of "end of life" issues.

If you just go ahead and replace 'em all; you'll probably save a whole lotta time over the next couple of years. (You really don't have anything to lose anyway, right?)
.
I will do, for now I'm just curious as to which one is the culprit. This is the first time I've tried this but it was dead easy so not hesitant to replace the rest now. Just need to order the ones I was missing.
Old 8th May 2019
  #124
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Quote:
Originally Posted by Jesse Skeens View Post
I will do, for now I'm just curious as to which one is the culprit. This is the first time I've tried this but it was dead easy so not hesitant to replace the rest now. Just need to order the ones I was missing.
...Well, if you replaced 'em ALL (and it fixed it), ya really wouldn't give a tinker's patoot which one was the culprit, now would ya?
.
Old 8th May 2019
  #125
Quote:
Originally Posted by 12ax7 View Post
...Well, if you replaced 'em ALL (and it fixed it), ya really wouldn't give a tinker's patoot which one was the culprit, now would ya?
.
My curiosity would
Old 8th May 2019
  #126
Gear Nut
In these switching power supplies, at that age, in that heat you have electrolytic caps that are bad and those that are about to go bad. And then you have the collateral parts eaten by the caps that went bad and/or the glue. HOPEFULLY the transistors and transformers are OK.

So, yeah, in this instance replace them all.
Old 8th May 2019
  #127
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grantb3 you're wrong. Again. Wrong about the glue, wrong about replacing all caps (that's using an elephant gun to kill a mouse). And you're quite inaccurate about the rest as well. Read Leeyoo's post on the VERY FIRST PAGE OF THIS THREAD.
Quote:
Originally Posted by Jesse Skeens View Post
Can I put a 470 into the spot of a 330
Definitely not. You can use a higher voltage rating, yes, but if you change the capacitor you'll change the frequency in the SMPSU. Recipe for disaster.
Old 8th May 2019
  #128
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Quote:
Originally Posted by Jesse Skeens View Post
My curiosity would
You're young yet.
.
Old 8th May 2019
  #129
Gear Nut
I'm not recommending he change that cap value, and in fact I recommend changing all the electrolytics on that board for same, but I don't follow that logic at all. It's the last filter cap. Are you saying if you remove the main board (load) from the power supply that will also alter the frequency? I would say the biggest fear in subbing that cap is the added in-rush stress in charging it from off.
Old 8th May 2019
  #130
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Read Leeyoo's post.
Old 20th May 2019
  #131
Ok an update. Put in R18 and C20 today. When powering on I got a quick flash on the display and then nothing. If I turn off and on again there's nothing, but if I wait a few minutes I get a very dim flash before going dark.

Have checked over a few times to make sure the cap was right (25V 330uf and correct polarity). R18 was 1.5k and 1/2 watt. Anything I can try at this point?

Prior to this the unit would power on with the top block of LEDs full and the bottom have dim but on.
Old 20th May 2019
  #132
Also just tested and it still receives audio, the input meter works (nothing on the main LCD still) but no output of audio.
Old 20th May 2019
  #133
Gear Nut
At least it's not blowing a fuse. What do the supplies measure? My advice is to change all those electrolytics and clean that junk off the component side of the board. But if it's stable enough to leave on for a moment then you should measure the rails.
Old 20th May 2019
  #134
Quote:
Originally Posted by grantb3 View Post
At least it's not blowing a fuse. What do the supplies measure? My advice is to change all those electrolytics and clean that junk off the component side of the board. But if it's stable enough to leave on for a moment then you should measure the rails.
I've never tested power rails before. Looking at the schematic I see what looks like 3 pairs of +5 (1-3 ground and 4-6 hot). I assume I measure in pairs then, 1/4, 2/5, 3/6?

Cheers
Old 20th May 2019
  #135
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Are you saying you haven't replaced every capacitor in the PSU?
Old 20th May 2019
  #136
Quote:
Originally Posted by madtheory View Post
Are you saying you haven't replaced every capacitor in the PSU?
Not yet. I initially took off R18 and C20 as they looked bad. Prior to changing them the LED at least light up. After changing them it doesn't. I just wanted to rule out I did something wrong at this stage before replacing more caps as I expected worse case it would do what it had done prior, not get worse.

Is it possible fixing these two components would make it act worse initially?

At the moment about half of them are replaced.
Old 20th May 2019
  #137
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Quote:
Originally Posted by Jesse Skeens View Post
Not yet. I initially took off R18 and C20 as they looked bad. Prior to changing them the LED at least light up. After changing them it doesn't. I just wanted to rule out I did something wrong at this stage before replacing more caps as I expected worse case it would do what it had done prior, not get worse.

Is it possible fixing these two components would make it act worse initially?

At the moment about half of them are replaced.
No you'll have to replace all of them, because they work in tandem, basically. What you've done is a bit like having 4 flat tires and only fixing two. The car still won't go
Old 20th May 2019
  #138
Gear Nut
You're in no man's land, you need to take a bunch of stuff off and clean that board. That one coil is probably OK, but it's sitting in gunk. Not good. And of course all the caps.
Old 20th May 2019
  #139
Quote:
Originally Posted by madtheory View Post
No you'll have to replace all of them, because they work in tandem, basically. What you've done is a bit like having 4 flat tires and only fixing two. The car still won't go
Ok will do
Old 20th May 2019
  #140
Quote:
Originally Posted by grantb3 View Post
You're in no man's land, you need to take a bunch of stuff off and clean that board. That one coil is probably OK, but it's sitting in gunk. Not good. And of course all the caps.
Which coil is that exactly?
Old 20th May 2019
  #141
Gear Nut
There are a couple of green cylinders there, that are sitting in gunk. Remove them, clean the legs (carefully) and the board. There's even a jumper that looks gross. The whole thing should look mint-ish. Take lots of before pics so you can remember how things go.
Old 21st May 2019
  #142
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Here we go again.

If the gunk is hard, leave it, and the components sitting in it, well alone.

Just do the caps. All of them.

And read leeyoo's post. Guy knows what he's talking about. Explains how and when these components will fail.
Old 21st May 2019
  #143
Quote:
Originally Posted by madtheory View Post
Here we go again.

If the gunk is hard, leave it, and the components sitting in it, well alone.

Just do the caps. All of them.

And read leeyoo's post. Guy knows what he's talking about. Explains how and when these components will fail.
His first post says to read the other thread, is he talking about this post?

Yamaha SPX 90 Power Supply
Old 21st May 2019
  #144
Have replaced all the caps except C24 as I hadn't ordered that yet. So far same result since adding the last cap and resistor.

Will try adding C24 and go from there.

Also how does it work that the input works but not the rest. Is that connected to a different part of the power supply?
Old 4 weeks ago
  #145
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I can't find the specific one now- read all his posts

I can't really answer your second question without looking over the schematic. But ya, most things work as interconnecting blocks, analogue sections, digital sections, display, LEDS and sometimes logic sections are separate, often but not always separate supplies required, but all working together.

Service manual is good, the usual Yamaha world class engineering. IIRC there's a block diagram as well as the schematic. Add in the data sheets for each IC and you're ready to diagnose.
Old 4 weeks ago
  #146
Quote:
Originally Posted by madtheory View Post
I can't find the specific one now- read all his posts

I can't really answer your second question without looking over the schematic. But ya, most things work as interconnecting blocks, analogue sections, digital sections, display, LEDS and sometimes logic sections are separate, often but not always separate supplies required, but all working together.

Service manual is good, the usual Yamaha world class engineering. IIRC there's a block diagram as well as the schematic. Add in the data sheets for each IC and you're ready to diagnose.

On the +5 pinout only one of them is red, is that the only hot one? According to the schematic it seemed like there were 3.

R18 was corroded in there pretty good so wondering if taking that out (even though I tried to do carefully) is what caused the screen to start to go black instead of lit.

I noticed most of the coils around there (L4 for one) have a lot of green corrosion on the pegs so might be something to replace as well.
Old 4 weeks ago
  #147
Gear Nut
I've never had a coil actually die (the green ones) but there is sufficient trouble at the board level that I've removed them, cleaned and tested and then put back on to a cleaned board. I had a jumper wire on one Yamaha SMPS that got eaten but I can't remember which Yamaha unit.
Old 4 weeks ago
  #148
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Just go ahead replace all the electrolytic caps; then at least you'll know they're all good (and how old they are).

In my opinion, electrolytic caps should be in sockets.

(They go bad more often than tubes.)
.
Old 4 weeks ago
  #149
I need to order the 2200uf but in the meantime I decided to check the voltages on the rails.

I got a nice 4.97 on the +5 rails, the +18 was a little high around 19.5V but I assume that's not too bad.

The issue seems to be that I got nothing on the -18 rails. I traced the components before then and it looks like L5 is a possible suspect there (the cap around there I replaced already).

There's some green corrosion on the legs, the L4 looks worse (more corroded on the leads) and it's fairly wobbly now as if it's about to break off.

The 2200uf is on the +5 side which looks fine, I'll still replace it but it doesn't seem to be what's causing the issue.
Old 4 weeks ago
  #150
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Measuring the voltage with a DMM won't show you the ripple, which is caused by a failed cap and is the most likely (but not the only possible) cause of the fault in your unit. So even though your 5V seems "nice" on the DMM, it ain't necessarily so. Check the schematic, get a 'scope (they're fun and you only need 15MHZ for vintage audio gear, those are cheap).
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