Component lay out on ESU micro select

[woodone]

Seems to be problem solving day.
Got an Kato F3 locomotive with an ESU LokSound decoder installed (73800).
Loco quit running for client ,sent back to me, showed short. Pressing down on the decoder the sound would try to start but I noted the finger pressing down was feeling heat. So I removed the decoder and found a burned spot right over a small component .
This is the second decoder to fail in this loco. No signs of wiring problems, shorts(other than the decoder it self) or anything strange seen?
Trying to I.D. The burned component to see if it was the audio amp that failed.

[peteski]

Seems to be problem solving day.
Got an Kato F3 locomotive with an ESU LokSound decoder installed (73800).
Loco quit running for client ,sent back to me, showed short. Pressing down on the decoder the sound would try to start but I noted the finger pressing down was feeling heat. So I removed the decoder and found a burned spot right over a small component .
This is the second decoder to fail in this loco. No signs of wiring problems, shorts(other than the decoder it self) or anything strange seen?
Trying to I.D. The burned component to see if it was the audio amp that failed.

Take a closeup photo and point out the component.  Also, some components normally run a bit warm on decoders, but in your case it seems to be more than the standard amount of heat (plus you say there is a short).

[woodone]

Thanks, Peteski.
Will do- take me a bit to do. Photos are not my strong suit, has U well know.  LOL

[peteski]

I never owned  one of those decoders. But I suspect the audio amplifier is a similar chip that they use on other boards. It will be almost square black chip with 8 metal nubs (4 on each opposite sides).  If you see a visible burn mark on it (as if the magic smoke was released), then as you said, it is probably blown.  Shorting one of the speaker leads to the chassis would likely cause that.

[woodone]

I would have thought you had used the LokSound Micro Select. (73800).
I was real careful when removing the decoder so I could inspect the install. The speaker is mounted in a blind hole at the rear part of the frame. Wires are run through a small hole with caulking holding the wires . The wires to the speaker are soldered and covered with caulk too. No parts of the shell even come close to touching the wires.
But with this being the second decoder to fail I would really like to find a cause.
Just to keep on throwing parts at it without finding the reason for the failure does not set well with me.

[tehachapifan]

I experienced a couple failures with this decoder that I believe was possibly attributed to the default master volume being set too high for the speaker. The default master volume was I think 180 out of 192 and, at the time, I believe I was using .5W (7W max) speakers. With my (still-admittedly-limited) understanding of how this stuff works and with those particular speakers, I believe the volume would actually need to be set closer to around 90 or 100 to stay safer and not blow the amp (although I've heard the decoders may deliver 1W to as much as 3W to the speakers but, again, my knowledge is admittedly limited on this). In my case, both failures were preceded by increasing sound distortion and crackling. Now, whenever I do an install, I turn the master volume way down prior to first firing up the sound and then I'll slowly increase the volume some until it sounds about right and doesn't show signs of distortion. I also usually turn all independent volumes way down on top of that, except for the horn.

[peteski]

While I bought the long-board Selects (the ones I did the writeups on), I have  never bought the wire-in version. On those I only own the full-featured V4 micros (56899), and I think the components are laid out differently on those (going by the photos I found online).

[peteski]

I experienced a couple failures with this decoder that I believe was possibly attributed to the default master volume being set too high for the speaker. The default master volume was I think 180 out of 192 and, at the time, I believe I was using .5W (7W max) speakers. With my (still-admittedly-limited) understanding of how this stuff works and with those particular speakers, I believe the volume would actually need to be set closer to around 90 or 100 to stay safer and not blow the amp (although I've heard the decoders may deliver 1W to as much as 3W to the speakers but, again, my knowledge is admittedly limited on this). In my case, both failures were preceded by increasing sound distortion and crackling. Now, whenever I do an install, I turn the master volume way down prior to first firing up the sound and then I'll slowly increase the volume some until it sounds about right and doesn't show signs of distortion. I also usually turn all independent volumes way down on top of that, except for the horn.

If you use 4 ohm or greater impedance speaker, theoretically you cannot damage the amplifier.  When the volume is too high, the audio signal will get clipped (sound distorted), but that should not fry the amplifier.  Or, if the speaker (even if it has the correct impedance) is rated for lower power than the amp can supply, then if it is driven by the amp with power above its rating, the speaker might be damaged (the voice coil will burn up).  Or the speaker cone suspension might get damaged from being deflected beyond its working limit.

[RBrodzinsky]

While I bought the long-board Selects (the ones I did the writeups on), I have  never bought the wire-in version. On those I only own the full-featured V4 micros (56899), and I think the components are laid out differently on those (going by the photos I found online).

The Select Micro and the V4 Micro use the exact same board and layout. Microcode is the only difference (well, and normally, the Selects have a yellow “S” while the V4 have a blue “4” written on the shrink wrap). I can snap some hi-res macro photos of them, if it will help with Jerry’s issue. (I have one V4 and 8 Select decoders not installed, yet; I’ve been procrastinating).

[peteski]

The Select Micro and the V4 Micro use the exact same board and layout. Microcode is the only difference (well, and normally, the Selects have a yellow “S” while the V4 have a blue “4” written on the shrink wrap). I can snap some hi-res macro photos of them, if it will help with Jerry’s issue. (I have one V4 and 8 Select decoders not installed, yet; I’ve been procrastinating).

Ok, then I can take a photo myself tomorrow.  I guess that the "stock" photos of I found online were not really of the 73800.  Actually, this makes more sense now.

[woodone]

The speaker is an 8 OHM speaker, I will have to see the watt rating has I don’t recall. The speaker is one that SoundTraxx used to supply. 1/2 diameter with a Mylar cone.
Sorry about no photos of the board yet.
I have family from out of state, so that has taken me away from DCC work.

[Point353]

Two photos of a 73800 decoder from a German eBay listing:

[peteski]

While I haven't reverse  engineered this decoder, here is the likely location of the audio amp.

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[tehachapifan]

….Or, if the speaker (even if it has the correct impedance) is rated for lower power than the amp can supply, then if it is driven by the amp with power above its rating, the speaker might be damaged (the voice coil will burn up).  Or the speaker cone suspension might get damaged from being deflected beyond its working limit.

I kind of suspect this is what happened and then that speaker failure then caused something to fail on the decoder...which I guess I assumed was the amp but maybe not. also, I've only ever used 8 Ohm speakers.

It seems to me that wattage ratings of speakers is not covered very well in various literature and it always seems to be somewhat unclear what wattage a sound decoder is putting out. You can find plenty of references as to what the Ohm rating the speaker needs to be but not the wattage. I've since found some 9X16mm speakers rated at .8W (1W max) that I typically use, which seem to hold up well.

[peteski]

I kind of suspect this is what happened and then that speaker failure then caused something to fail on the decoder...which I guess I assumed was the amp but maybe not. also, I've only ever used 8 Ohm speakers.

It seems to me that wattage ratings of speakers is not covered very well in various literature and it always seems to be somewhat unclear what wattage a sound decoder is putting out. You can find plenty of references as to what the Ohm rating the speaker needs to be but not the wattage. I've since found some 9X16mm speakers rated at .8W (1W max) that I typically use, which seem to hold up well.

The decoder's audio amp rating is clearly stated in the manual (and on the packaging of the long-board decoders).  I don't have them handy, but I believe it is 2W max. (that would be with a 4 ohm speaker). With an 8 ohm speaker the amp will only be able to supply 1W of power.  Or maybe it is 4W@4ohm and 2W@8ohm?

As for speakers, the same is true: if you find the manufacturer's data sheet, the power rating is clearly stated. So are lots of other parameters, like frequency response and sensitivity. But if you pick your speakers up from a 3rd party supplier (like a model RR vendor who resells the speakers), then it is up to them whether they provide the power rating or not. Unfortunately.