Yamaha E1010 rack delay

[m1989jmp]

Hello,

I've recently picked up a busted Yamaha E1010. It had blown both 500mA T fuses and after replacing those, input level meter is maxed out at all times and no sound is coming through.

In addition to that, when twiddling mixer pot around, DC-on-the-wiper kind of scratching is heard.

I'll start by going through instructions in the service manual and reporting reference voltages here, but wanted to check beforehand if anyone recognizes these symptoms.

Any help is much appreciated.

[J M Fahey]

**do you have the 220V model?**

To begin with, schematic shows 4 fuses.

* an unlabelled 250mA T (delay type) on 220V mains, might be inside an IEC socket

* F1 & F2 on the Red secondary wires.
I find it weird that they specify 0.75A there for North American models and 315mA for the European ones, because secondary does not know or care about primary voltage which is a separate wiring, matching locally available mains, please check what you actually have there .

* F3 on one of the Blue secondary wires.
Again weird because they specify 0.5 A for North American mains and 250mA for Europe ... weird because of what I wrote above.

In principle I am suspecting you might one of the low voltage rails, probably +15 or -15 which would give symptoms similar to what you see, but thereīs also 1000 other possibilities, start by checking those fuses and reporting back.

Just turn device on briefly and turn off again, we donīt want damage spreading further.

You mkight build a lamp bulb limiter and use it until we know more, but use a small lamp, maybe 15W or so.
You may use one of those small socket lamps designed for sewing machines or similar, maybe a fridge lamp.
Always an old style filament lamp of course, not a modern LED or CFL thingie, we want a red hot wire inside a glass bulb here.

[m1989jmp]

**do you have the 220V model?**

To begin with, schematic shows 4 fuses.

* an unlabelled 250mA T (delay type) on 220V mains, might be inside an IEC socket

* F1 & F2 on the Red secondary wires.
I find it weird that they specify 0.75A there for North American models and 315mA for the European ones, because secondary does not know or care about primary voltage which is a separate wiring, matching locally available mains, please check what you actually have there .

* F3 on one of the Blue secondary wires.
Again weird because they specify 0.5 A for North American mains and 250mA for Europe ... weird because of what I wrote above.

In principle I am suspecting you might one of the low voltage rails, probably +15 or -15 which would give symptoms similar to what you see, but thereīs also 1000 other possibilities, start by checking those fuses and reporting back.

Just turn device on briefly and turn off again, we donīt want damage spreading further.

You mkight build a lamp bulb limiter and use it until we know more, but use a small lamp, maybe 15W or so.
You may use one of those small socket lamps designed for sewing machines or similar, maybe a fridge lamp.
Always an old style filament lamp of course, not a modern LED or CFL thingie, we want a red hot wire inside a glass bulb here.

Yes, it's 220V version, fuses are of correct values.

I'm using a limiter, there's no excessive current draw. 15VDC rail is shot, -15VDC is fine and 8VDC one is reading 10.5VDC unloaded. The problem seems to be on the main board (luckily) as I've tried disconnecting the top PCB, so I'll get it out and go from there, thanks a lot.

[J M Fahey]

Yes, it's 220V version, fuses are of correct values.

Which are??????????
2 sets of "correct values" are mentioned plus you mention 2 fuses whikle schematic shows 4.
Can you answer my simple question on post #2?
With numbers, please.

I'm using a limiter, there's no excessive current draw. 15VDC rail is shot, -15VDC is fine and 8VDC one is reading 10.5VDC unloaded. The problem seems to be on the main board (luckily) as I've tried disconnecting the top PCB, so I'll get it out and go from there, thanks a lot.

So you are missing a 15V rail, what I expected, and as said before, explains your symptoms.

Please disconnect +/- 15V supply from load, we want to know whether supply itself has failed or the load is pulling it down.

What voltage do you measure on unloaded supply +15 and -15 V output pins?

[m1989jmp]

Which are??????????
2 sets of "correct values" are mentioned plus you mention 2 fuses whikle schematic shows 4.
Can you answer my simple question on post #2?
With numbers, please.


So you are missing a 15V rail, what I expected, and as said before, explains your symptoms.

Please disconnect +/- 15V supply from load, we want to know whether supply itself has failed or the load is pulling it down.

What voltage do you measure on unloaded supply +15 and -15 V output pins?

I meant to say that fuse values are as labeled on the chassis/PCB; mains is 250mA, F1&F2 are 500mA and F3 is 250mA. F1&F2 were fried, so I replaced them.

My mistake, -15V rail is shot and +15V is fine. When I unload the supply, I get -7.5V instead of -15V, rotating trimpot doesn't change anything. +15V rail is fine, value changes when rotating trimpot.

When loaded, -15V drops to 0V.

With disconnected power supply, I measure continuity between -15V rail and ground points on the main board, so something is shorting the -15V rail to ground.

[The Dude]

Something ought to be getting hot. "Finger test" it and see if you can detect a hot IC, bypass cap, etc.

[J M Fahey]

Rather than preamp eating too much and loading supply down I expect a damaged supply which canīt supply more than 7.5V **unloaded** (hint hint) .

[m1989jmp]

Rather than preamp eating too much and loading supply down I expect a damaged supply which canīt supply more than 7.5V **unloaded** (hint hint) .

Power supply -15V side is damaged for sure, but I also detect a short between -15 and ground points where voltage is supplied to the preamp nodes with the supply disconnected completely.

I'll try and see if I can spot something getting hot. If that doesn't work, there are numerous jumper wires for distributing supply voltage around. I suppose I could snip one by one going from the last one until there is no more continuity between -15 and ground?

Thanks for the suggestions, I appreciate it.

[m1989jmp]

Ran into this blog:

http://soundular-electronics.blogspo...ay-part-2.html

I figured I might as well start from the tantalum caps he mentions.

After locating and pulling the offender out and there's no more continuity from -15V rail to ground. I now measure around 1-2kOhm resistance from both 15V rails to ground.

Why were these used anyway and not just plain electrolytic ones?

Back to the power supply; the schematic calls for 2SD526, but I'll use BD243C since I have it. I, however, can't find 2SC1815 anywhere locally. Can I just use something like 2N5551 instead if it turns out I have to swap those too?

Edit: I actually listed components in the +15V supply, it should've been their complementary transistors, since it's -15V supply that failed.

[m1989jmp]

So, I've pulled TR3 because it was shorted and I get -15VDC back, adjustable with VR1. Everything is disconnected from the power supply, just to make clear.

Replaced with new working 2N5401, voltage drops back to -7.5VDC, not adjustable with VR1.

Edit: forgot to upload the picture.

[J M Fahey]

I think you connected 2N5401 the wrong way, check pinout.

It is just a 15mA current limit to protect supply, it has NO effect at all if you are not loading supply ... unless you forgot to disconnect *all* loads that is.

Get supply working first, then worry about the rest of the circuit.

In fact you should be able to drive, say, a 2k2 resistor to ground, about 7mA load, with no trouble and full adjustment range.

[Enzo]

You can replace 2SCxxxx types with 2Nxxxx types with similar specs, but remember the pinouts are NOT the same.

[m1989jmp]

That did the trick, thank you both. I checked only where the Emitter goes and just assumed that they have identical pinout given it's the same package.

I've plugged it in and apart for some pot scratching, I think it's good to go!

Needless to say, I've checked if the supply is fine when loaded with 2k resistor per JM's advice and checked all rails again for shorts on all boards.

[m1989jmp]

Can anyone explain why was tantalum cap used instead of electrolytic in this particular spot? Should I replace them with tantalum again or go with electrolytic cap (maybe with higher capacitance as I've seen some people online suggest)?

I suppose these failed because of 16V voltage rating on a 15V rail.

[g1]

They are very prone to failure if exposed to over-voltage.
Not sure why they chose it in this application. The main advantage is reduced size, but I don't think that would be a factor for this unit. They also last longer (don't dry out) and can usually withstand more temperature variation.