Oscope ?

[g1]

it looks like the light bulb is not just in series with hot end of the plug. Does anyone think that the bulb should be wired up differently here?

It's wired up right. Try drawing it out without the voltmeter and it's 1A fuse. 3rd prong ground is not shown. Think of 2 prongs of wall outlet where variac is shown.

[gtrplayr1976]

Here is the very simple layout to build the Lamp Limiter with the variac and meters. I like how it has the switch to take the bulb in and out of circuit for different test purposes. Also I am posting the source page to where I discovered this build, so we can read/credit the original post for his contribution. Look towards the bottom of this web page and his schematic is on the next page. I uploaded that image here so you can download it from MEF.

Beomaster 4000 (type 2408) Circuit Differences -

Edit: My one thought here is that it looks like the light bulb is not just in series with hot end of the plug. Does anyone think that the bulb should be wired up differently here?

Thanks DrGonz78 !

[gtrplayr1976]

Signal Generator

So I opened the signal generator last night. Looks pretty clean inside ,but I'm not sure if it works. The little indicator on the front comes on, but I don't see any signs of life from the tubes. I can't find a free manual download anywhere ,just a schematic. A couple of the resistors (?) look like they have white substance on them.

[Leo_Gnardo]

So I opened the signal generator last night. Looks pretty clean inside ,but I'm not sure if it works. The little indicator on the front comes on, but I don't see any signs of life from the tubes. I can't find a free manual download anywhere ,just a schematic. A couple of the resistors (?) look like they have white substance on them.

Some of the old tube test gear use tubes with low-voltage filaments that don't light up very brightly. Also a pull & push just like with guitar amps can sometimes break a corrosion layer that's preventing conduction. And ye olde tube pin scrub too. You could check the output with your AC voltmeter and if you read some voltage it's likely to be OK. Wouldn't worry about old resistors growing a little "hair" or other discoloration. Rust never sleeps, that includes corrosion of allsorts.

[gtrplayr1976]

Some of the old tube test gear use tubes with low-voltage filaments that don't light up very brightly. Also a pull & push just like with guitar amps can sometimes break a corrosion layer that's preventing conduction. And ye olde tube pin scrub too. You could check the output with your AC voltmeter and if you read some voltage it's likely to be OK. Wouldn't worry about old resistors growing a little "hair" or other discoloration. Rust never sleeps, that includes corrosion of allsorts.

Thanks Leo. I plan to check it this evening. I have a true RMS meter also,and didn't realize it

[gtrplayr1976]

Some of the old tube test gear use tubes with low-voltage filaments that don't light up very brightly. Also a pull & push just like with guitar amps can sometimes break a corrosion layer that's preventing conduction. And ye olde tube pin scrub too. You could check the output with your AC voltmeter and if you read some voltage it's likely to be OK. Wouldn't worry about old resistors growing a little "hair" or other discoloration. Rust never sleeps, that includes corrosion of allsorts.

OK..it seem to have an output. Tubes light up ,and meter moves. Replacement oscope should be here today ,so I'll have the wrecked one for some spare parts.

[catstrat]

o-scope

I have a Tenma scope i got from MCM for 375 bucks or so. It's dual channel and has a LCD readout. It does anything i need it for. I really don't use it that much except when i'm modding an amp or tracing down a circuit that has lost it's signal. I've bought several scopes off Ebay but i don't have very good luck with them.They're are good deals to be had from Ebay. i just haven't been that lucky So i just bought the Tenma. Almost any scope will do for audio work. Good luck

[gtrplayr1976]

I have a Tenma scope i got from MCM for 375 bucks or so. It's dual channel and has a LCD readout. It does anything i need it for. I really don't use it that much except when i'm modding an amp or tracing down a circuit that has lost it's signal. I've bought several scopes off Ebay but i don't have very good luck with them.They're are good deals to be had from Ebay. i just haven't been that lucky So i just bought the Tenma. Almost any scope will do for audio work. Good luck

The replacement I got seems to work ,but now I need to learn what to set ,and where to connect it ,and the signal generator.

[catstrat]

Hello. Here is the way i set up my generator and scope when tracing down a circuit. I usually set the generator to about 300 to 400 millivolts and that may be too much. I modded my generator so i can just use a guitar cable and go directly into the input jack of the amp. I set the scope so i get a good screen trace meaning you can see both the top and the bottom of the wave when you've turned the amps volume all the way up. For this type of work i don't know if there is a set way to adjust everything. A good place to start is to measure the signal directly from the generator with your scope and get a feel for the controls of both the scope and generator. As far as troubleshooting i usually start from the output section and work my way to the preamp section, but again i don't think there is any certain way to do it. I'm certainly not the expert on the subject but this method works for me. Everyone here probably has their own way and i suggest you listen the others on here as well. Good luck.

[gtrplayr1976]

Hello. Here is the way i set up my generator and scope when tracing down a circuit. I usually set the generator to about 300 to 400 millivolts and that may be too much. I modded my generator so i can just use a guitar cable and go directly into the input jack of the amp. I set the scope so i get a good screen trace meaning you can see both the top and the bottom of the wave when you've turned the amps volume all the way up. For this type of work i don't know if there is a set way to adjust everything. A good place to start is to measure the signal directly from the generator with your scope and get a feel for the controls of both the scope and generator. As far as troubleshooting i usually start from the output section and work my way to the preamp section, but again i don't think there is any certain way to do it. I'm certainly not the expert on the subject but this method works for me. Everyone here probably has their own way and i suggest you listen the others on here as well. Good luck.

Thanks catstrat. It was suggested to me to use 50mv, so I will give that a try. I need to make up a cable to connect to my generator also. I think I have some 1/4 in plugs somewhere. Trial ,and error time