Help me understand this fan circuit please

[Randall]

Eden WTB800 cuts out when it's been played for a while. Owner says he doesn't think the fan is coming on. It happened in outdoor Florida heat, and again during rehearsal under inside A/C. Setting on the bench at idle, there is no fan. I measure 17vdc on pin 6 to ground, but not to pin 5. I disconnected J5 and applied 12v to pins 5&6 where the fan wires are, and I see the fan works.

So, what mechanism turns this fan on? T1 -T5 are transformer connections. T1 and T4 are tied together and to the AC inlet as well as transformer primary, I think. T3 and T5 are tied together, and to a transformer wire.T2 comes off the transformer as well. I can't really see what any of this is connected to on the board.

eden_wt800c_sch.pdf

[Enzo]

Your link comes up "blocked" for me.

[Randall]

Ah, yes it is, my bad. I have fixed it. Page 4 is where the fan connector is, but I just am not seeing the thermistats or anything else really.

[nosaj]

Ah, yes it is, my bad. I have fixed it. Page 4 is where the fan connector is, but I just am not seeing the thermistats or anything else really.

MOV
A varistor is essentially an open circuit until its breakdown voltage is exceeded which point it begins its resistance drops steeply. A thermistor is more of a temperature sensitive resistor; it's not "normally closed", it's a resistor.

nosaj

[Randall]

By thermistat, I meant the thermal device that turns on the fan. It's what it is referred to at the Eden forum, where all I could glean is this amp has two. I do find three of them in this amp, but I don't find them on the schematic.

I don't think the MOVs on that print have anything to do with this.

[nosaj]

By thermistat, I meant the thermal device that turns on the fan. It's what it is referred to at the Eden forum, where all I could glean is this amp has two. I do find three of them in this amp, but I don't find them on the schematic.

I don't think the MOVs on that print have anything to do with this.

You can use them to control fan speeds.

nosaj

[nosaj]

By thermistat, I meant the thermal device that turns on the fan. It's what it is referred to at the Eden forum, where all I could glean is this amp has two. I do find three of them in this amp, but I don't find them on the schematic.

I don't think the MOVs on that print have anything to do with this.

So if you found them in the amp , what info is on them?

nosaj

[Randall]

The MOVs are free standing in the AC transformer connection part of the power supply. I can't see any info, they are buried.

[nosaj]

The MOVs are free standing in the AC transformer connection part of the power supply. I can't see any info, they are buried.

What about the thermisitors you said you found in the amp not on the schematic?
nosaj

[nosaj]

What about the thermisitors you said you found in the amp not on the schematic?
nosaj

i see one of the mov's connected to T1 an T3 which go directly to the Fan, Granted this is just a WAG. But if enough voltage was drawn from T3 the MOV opens causing the fan to run. So if my supposition is correct jumpering the MOV would turn on the fan.
Just a WAG but take it as you will.

nosaj

[Randall]

Same deal, everything is buried under something. I would have to disassemble to get a look, and I am hoping for some more insight before I have to do that.

Here are voltage readings on J5:

1 - 0.08 vac
2 - 17 vdc
3 - 0.08 vac
4 - 17 vdc
5 - 17 vdc fan black
6 - 17.3 vdc fan red

So somehow, pin 5 must go towards ground to turn on the fan?

[nosaj]

Same deal, everything is buried under something. I would have to disassemble to get a look, and I am hoping for some more insight before I have to do that.

Here are voltage readings on J5:

1 - 0.08 vac
2 - 17 vdc
3 - 0.08 vac
4 - 17 vdc
5 - 17 vdc fan black
6 - 17.3 vdc fan red

So somehow, pin 5 must go towards ground to turn on the fan?

Anyway you can check voltage at T3?

nosaj

[nosaj]

Eden WTB800 cuts out when it's been played for a while. Owner says he doesn't think the fan is coming on. It happened in outdoor Florida heat, and again during rehearsal under inside A/C. Setting on the bench at idle, there is no fan. I measure 17vdc on pin 6 to ground, but not to pin 5. I disconnected J5 and applied 12v to pins 5&6 where the fan wires are, and I see the fan works.

So, what mechanism turns this fan on? T1 -T5 are transformer connections. T1 and T4 are tied together and to the AC inlet as well as transformer primary, I think. T3 and T5 are tied together, and to a transformer wire.T2 comes off the transformer as well. I can't really see what any of this is connected to on the board.

[ATTACH]54538[/ATTACH]

Have you seen this? Fan installed incorrectly? Somewhere else I read fan should cut on at 130 degreeshttps://www.talkbass.com/threads/dav...ution.1318128/
nosaj

[Randall]

"i see one of the mov's connected to T1 an T3 which go directly to the Fan"

I don't think so. The fan is connected to pins 5 and 6 on J5. No direct connection there that I see.

"Have you seen this? Fan installed incorrectly? Somewhere else I read fan should cut on at 130 degreeshttps://www.talkbass.com/threads/dav...ution.1318128/"

I have seen this. I can't tell which way the fan is going if it doesn't turn on. Anyway, it has worked for years just fine until now.

"Anyway you can check voltage at T3?"

123 vac to ground.

What do we call these devices, thermal breakers, thermistats? according to Eden rep on the forum there are two of them. I wonder how they are wired up, depending on whether they are normally open or normally closed. Are they in series or parallel, AND, what would be the harm in making them on all the time? Seems like then the amp wouldn't have to cool down when it got hot, because maybe it wouldn't get hot.

[nickb]

i see one of the mov's connected to T1 an T3 which go directly to the Fan, Granted this is just a WAG. But if enough voltage was drawn from T3 the MOV opens causing the fan to run. So if my supposition is correct jumpering the MOV would turn on the fan.
Just a WAG but take it as you will.

nosaj

I think you might short out the AC power input if you did that. I expect that T1/T2/T3/t4 are there to allow you to connect two 115V primary windings in series or parallel for 115/230V operation.

It looks like the thermostats are connected in parallel, one going to pins 3 and 4 and the other to pins 1 ans 2 of J5. Thus shorting out pins 1 1nd 2 ( or 3 and 4) would turn on the fan. Also it seems that the T2 terminal is a tap on the primary winding so please exercise care.