HELP! How do you use an oscilloscope???

[dragonbat13]

I have a soltec scope that my dad left me when he passed away. He used it to build HI-Fi amps. I don't know how to use it.'

I have a 74 twin reverb. I installed a pre cbs kit from torres. I also installed new tubes. I run two kt66, biased correctly of course, into an 8 ohm load. I also installed new sprague filter caps and replaced the coupling caps with orange drops. here is my problem: Before I started the cbs conversion I had the reverb channel and the normal channel didn't work. I think that was due to a bad preamp tube or filter cap. Now I have the normal channel but the reverb channel doesn't work. If I pull V1 I have no sound from the reverb side. If I install V1 the reverb side works about half power. I have checked every thing in the circuit on V1. I think that something in the reverbe or tremelo side is grounding out and dumping some gain.

Back to the scope. I want to use the scope to trace the signal through the reverb circuit to see if I can find where it falls off. Does anybody know of a website to learn how to use it for this job. The tech at the music store said that the scope can make life tons easier for this awesome hobby. I just need to know how to use it without burning it up. Thanks to all who can help a newbie who is lucky enough to own a scope with no idea what to do with it!

[dragonbat13]

I wrote above that I checked the circuit in V1. I meant V2.

[Funkalicousgroove]

Check the values of your plate and cathode resistors, they may have drifted quite a bit.

There is a tutorial on how to use a scope on the Tektronics site.

for your problem I usually use a signal generator and a "tracer" amp

[drz400]

I have a soltec scope that my dad left me when he passed away. He used it to build HI-Fi amps. I don't know how to use it.'

I Back to the scope. I want to use the scope to trace the signal through the reverb circuit to see if I can find where it falls off. Does anybody know of a website to learn how to use it for this job. with no idea what to do with it!

http://www.doctronics.co.uk/scope.htm

[Funkalicousgroove]

Also Make sure you have a 12AX7 in V1 and not a 12AT7, an AT7 in V1 may cause that problem, since it draws alot more current.

[Luthierwnc]

+1 on the signal generator. You will also need a dummy load. This is a really big resistor. My two came from an electronic surplus store. One is a dedicated 8 ohm and the other has a slide band to adjust the resistance. I think they are each 200 watts. hook either end to a 1/4 jack and put it where the speaker goes. Your dog will never forgive you if you leave a speaker connected when you run a high sine wave through the amp. Thoses resistors get pretty hot so put them where they don't have to be grabbed in a hurry.

I don't always use my rig according to the regs. Sometimes what I am looking for are how the wave distorts at various points in the circuit. Does the image get fuzzy. What are the magnification factors (you turn down the volts).

One thing I am sure is not in the book is checking ground loops. Turn the amp on with no signal. Attach the probe ground at the chassis ground and touch probe at the same point. Dial in a very clear line on the screen. Then touch the other ground points in the amp. If the line starts blurring, you might have electric potential between the two points. Holding the probe over the amp when you have a signal going in looks like a theremin wand. It will show AC cross-talk when it passes over unshielded emf. It ain't rocket science but then, I'm not a rocket scientist.

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