Airline GIM-9131A knowledge/repair question

[g1]

The reverb in the video sounds proper.
To ground the input, plug a cord in and touch the tip of the open end to the chassis.
Alternately, plug a guitar in and turn the guitar volume off. If the hum/buzz quits, it is normal noise being picked up by the guitar pickup.
Also note that the reverb tank will pick up noise at higher reverb settings.

[btah]

Heading out of town so I will pick this up next week. However, I thought of another question. If the buzz had something to do with the input jacks, wouldn't it then go through the volume controls and the buzz would get louder as I turn up the volume? Does it not mean that if the volume of the buzz doesn't change, the issue would be past the volume control, hence, after the jack?

[g1]

You are correct if the volume (or reverb) on the amp does not affect the level of buzz.
However, at the beginning of the video, it seems there is no buzz until you turn up the volume on the amp. It also seems that the buzz changes as you move the guitar around. This would imply hum being picked up by the guitar.
In any case, grounding the input or turning off the guitar volume should tell you whether the problem is in the amp or not.

[btah]

I haven't dropped this. Just haven't gotten back to it yet.

[btah]

Winter showed back up so I thought I would pick this up again. The good news is, most of the buzz/hum went away since I last was working on it. The last thing I did was clean the pots again so maybe there was something lurking there.

So, what I have left is instead of buzz/hum I get a little hiss. Somewhat along the lines of between tracks on a cassette. Volume doesn't affect it. It is really quiet, but it is there. So, a question would be, should this thing be dead-ass silent with no input hooked up? Since I am not a musician and have no experience with these, I don't know if some level of noise is normal.

The only other issue that I can find is that with no input hooked up when I turn up the reverb I get buzz/hum and it gets louder as I continue to turn up the reverb. However, it isn't really loud, just something that I notice. Again, not sure if I should be able to turn reverb all the way up and it should still be dead-ass silent.

[Richard]

Some hiss is common in guitar amps and sometimes noise creeps in through the reverb. This is probably normal but it's hard to say.

[52 Bill]

So, a question would be, should this thing be dead-ass silent with no input hooked up?

The only dead-ass silent amp is one that is dead.

More modern amps will be quieter, but even they will have a certain amount hiss and noise. Well at least the analog ones.

Old amps like this one will have some hum and hiss, but the music will always drown it out.

And be sure that the reverb tank is mounted so that the side with the output jack is as far away from the power transformer as possible.

[btah]

Thanks Bill and Richard.

Well, unfortunately, now I have a "dead" amp. I hooked a CD player up as an input and had it on last night for about an hour or so. I noticed one of the panel lights was not lit. I toggled the panel switch light and the amp went dead. Power is still coming into the amp so it isn't a supply issue. Also, if I put the amp in standby mode, the standby light lights up but it is very, very dim. Odd to me but the panel lights are getting 120-something volts but they don't light up. It is almost as if the reset button is pushed.

By the way, how does the reset button work? Is the circuit closed normally and opens when you push the button or the other way around? How do you check the functionality of the reset button, or better yet, bypass it temporarily?

[btah]

And, as you are thinking "look at the schematic, it should tell you", I have looked for the reset switch on the schematic several times and I just can't find the darn thing...

[g1]

On the schematic it is CB1, near the AC plug. It should close when working, and open while being pressed, or under fault conditions.
If you want to bypass it, you should disconnect it and put a fuse there instead, otherwise bypassing it leaves the amp unprotected.
You can test it by measuring AC volts across in when running. Should be close to zero volts.

[btah]

Thanks. I see it on the schematic. I was looking for a switch with a "SW" mark on it. When I look at the switch, one of the wires is the white wire coming from the plug and has zero volts with the black DVM black lead to the chassis and the red lead to the lug. The other wire has has 124 volts. That doesn't change at all when I press the button. Is that what you mean by testing it? Not sure what you mean by putting a fuse in place of the switch. You simply mean putting a fuse between the two wires? My lack of electronics experience tells me that touching a wire with voltage to a white neutral wire is a bad things and usually results in swearing.

[btah]

Looking at the wires that go in/out of T1. The two wires that feed pins 2 and 7 of the 6L6 tubes have no voltage (it should be DC at that point, right?). The two wires that I think are input to the transformer (one connects to the black wire coming from the plug and the other is coming from the power switch) both have 124 volts AC. There is a ground wire which appears to be good. The other two wires, not sure what they do but one seems to be the source of voltage going to the standby switch, anyway, those two wires have 11 volts (both AC and DC). It would seem that I have "goes into transformer" but nothing coming from the transformer. Is that a fair interpretation?

[52 Bill]

Looking at the wires that go in/out of T1. The two wires that feed pins 2 and 7 of the 6L6 tubes have no voltage (it should be DC at that point, right?).

Transformers only work with ac voltages. The voltage that goes to pins 2 and 7 of the 6L6 tubes should be 6.3 Vac. This winding may have a center tap so if you read the voltage to ground it will read 3.2 Vac to ground on each pin.

All of the voltages coming directly from the transformer will be ac.

[btah]

Thanks. Given that I have 124 volts on two wires going to the transformer, 124 volts on two wires that come from the transformer and hook up to the standby switch (one of them ends up going to the switch), but zero volts on the two wires feeding the 6L6 tubes (pins 2 and 7), does that totally, without question, condemn the T1 transformer?

Among other things, I am not sure why the panel lights would be out. There is voltage going to them and the whole transformer path seems like a it is total separate from the path going to the transformer.

[g1]

Measuring AC volts, do not measure to ground. Put one probe on each of the 2 wires going in to the transformer (primary side). Do you measure 124VAC ?