CEBergheim

Hello,

I've just experienced what happens when you try to do something you're not sure about how to do right.

15 minutes ago I tried to measure bias voltage on my 1959 SLP. I connected a bias probe with multimeter to the first tube socket. Then I connected the black cable to "COM" and the red cable to "V&mA". When I turned the amp on (after letting it heat up for a few minutes), nothing happened on the multimeter. I figured out that the "10A" input on the multimeter probably was the right one to use, and connected the red cable to this.

When I turned the amp on, there was a noise (like when you unplug your guitar), and the amp didn't respond when I played my guitar. There's still no sound coming from the amp, although the amp turns on and the tubes start to glow.

Have I blown a fuse or a transistor? And, will this be easy to fix?

I feel really stupid right now.

Best wishes,

Chris

RachelMorgan

Don't know. Take it to an amp tech. Be prepared for the lecture. I'll give you the lecture free here: [smart-a$$ed post]



[/smart-a$$ed post]

__________________
Guitars: ESP LTD Alexi-600 V; Gibson SG Standard; Schecter C-1 Hellraiser (JB/'59 w/ JB coil tap)
Amps: Randall Lynch Box; Peavey 6505+; Fender HR Deville.
Board: Typically a tuner and TS808
Speakers: Two Avatar Contemporary 212s

luekemeyer

If you connected the red lead to the A or mA on the meter, you shorted the circuit on your amplifier through the 10A fuse (A) or 400mA fuse in the meter. My meter is a Fluke 85III and those are the values of the fuses in my meter.
The red lead should be inserted into the V / ohm input of the meter for measuring voltage. The A and mA input of the meter is for measuring amperage and must be connected in "series" of a circuit so that current flows through the meter. Without looking at the circuit of your amp, hopefully you just blew a fuse on the amp PCB.

CEBergheim

Thanks, I hope that's the case. I checked the fuses after the accident. The mains fuse looks good, but the HT fuse has a small, dark area on the inside of the glass. Do guitar repair shops have fuses lying around for sale?

luekemeyer

You can measure the resistance of the main and HT fuse to see if they are good. 0 ohms = good. The HT fuse could be blown.
I assume there are fuses on the boards within the amp that could have been blown. Not sure if the tubes can be damaged by shorting the bias. I was just looking at the schematics for my amp and the current would be pulled resistors if shorted. Could damage resistors or other components. Most fuses can be purchased at Radio Shack or electronic warehouses.

CEBergheim

I've checked the fuses with a multimeter. The mains fuse is ok, but the HT fuse is damaged. I'll replace it tomorrow, and hopefully this solves the problem.

Thanks for your response!

CEBergheim

Problem solved! I put in a new 1A 250V fuse, and now it works again.

poeman33

Don't you just love happy endings. Imagine what that would have cost to take it to a dealer to have him figure it out. THIS is what the forum is all about.

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