Did Something Bad to my Amp

Count Bassie · #1 05-08-2010, 12:44 PM

Just happened, and I'm a little wigged.

My daughter has a violin recital coming up and I'm accompanying her on upright for a tune. I got a Barcus Berry screw-on pickup for my old Czech doghouse and jigged a cable for it. I'd planned to run it into my 250SMX and a single Bag End cab.

I plugged the cable into the input and got a very low-level signal. Then I plugged into the Return on back of the amp. Seems to me I've done this before woth other amps... anyway the jack was a little stubborn, so I thought a minute... then went and jammed the plug in there, thinking it was just a jack clips inside being stubborn. Dunno- did the amp not like what I was trying to do?

Then I got a low-but-dangerous-sounding 'hum' from the head- which isn't going away. No signal from the upright's bridge-mounted pickup.

No signal from my electric bass going to the input now either. %*@&... what did I do? By the way- the Level control for the FX Loop was at +4.

Am I screwed until it can come back from a tech shop now? Very bad timing, I have a major gig in a week. Going to have to use the AMP BH-420, which is definitely not the 250SMX.

Edit: I got the Barcus-Berry pickup- a 3150M- without the preamp. I have a mixer, and this Trace head... it was the cheap way to go and I thought I could make it work

Jason P Bass · #2 05-08-2010, 12:48 PM

I would get an amp from Guitar Center to meet your gig requirements in the next 29 days. On day 30, take it back.

In the meantime, it sounds like you need someone with some technical skills to look inside the amp. It sounds like something mechanical might have broken regarding the FX return jack, but it could be anything.

Good luck

**B-string** · #3 05-08-2010, 12:55 PM

Effects return jacks usually interrupt the signal from preamp to poweramp. If you have an effects level control you may have a series/paralell switch that can be switched to paralell to restore audio. The effects return jack needs some minor repair or replacement.
Sounds like that pickup is not stong enough on it's own without a preamp or is defective?

BassmanPaul · #4 05-08-2010, 01:22 PM

Usually effects loops are running at a line level. As Mr. B states the signal level from a pickup will be insufficient to drive the loop fully. You have broken the return jack on your amp and, just as Mr. B opines, you will have to replace the jack.

If something doesn't fit where it's supposed to you have something wrong. The "Birmingham screwdriver" approach is never a good idea.

Paul

Count Bassie · #5 05-08-2010, 01:48 PM

Quote:

Originally Posted by BassmanPaul

Usually effects loops are running at a line level. As Mr. B states the signal level from a pickup will be insufficient to drive the loop fully. You have broken the return jack on your amp and, just as Mr. B opines, you will have to replace the jack.

If something doesn't fit where it's supposed to you have something wrong. The "Birmingham screwdriver" approach is never a good idea.

Paul

I inserted a 1/4" phone plug into the Return jack. Inside I found the jack itself had a distorted metal clip, which is why it was hard to insert the plug.

As far as the damage, I can see that I may have inserted the wrong kind of signal into that location. A couple items though:

1) The relay that buffers when you use the Standby switch has always gone 'pop' when I use it to turn the amp off (Standby>Power off). That doesn't seem right.

2) The Effects Level knob on front of the amp doesn't really function properly either.

I bought the amp used, and it had obviously taken a whack by a previous owner. I brought it to a guy to fix a couple issues, but obviously we're not done yet- aside from my possible oaf-ish move here.

Thanks for the replies.

Funny. It seems to me I've used that effects loop before, without incident. This (this is an after-edit) has just occured to me... weird.

**B-string** · #6 05-08-2010, 01:52 PM

The return jack should be a simple fast repair, the signal you plugged in had no affect on the amp. The bent "clip" on the jack is the problem.

Count Bassie · #7 05-08-2010, 01:55 PM

Quote:

Originally Posted by B-string

The return jack should be a simple fast repair, the signal you plugged in had no affect on the amp. The bent "clip" on the jack is the problem.

This is why there's almost no output?

Count Bassie · #8 05-08-2010, 01:58 PM

Quote:

Originally Posted by B-string

Sounds like that pickup is not stong enough on it's own without a preamp or is defective?

The pickup is a tiny Barcus-Berry screw-on device, that usually wants to come with a preamp thing. I, broke bastard that I am, opted to deal with getting to line level some other way. I have a small mixer, for instance.

I understand about the FX loop and interrupting the signal from pre-to-power. There's no parallel switch though.

It's all clearing up for me now a bit, thanks for the help you guys.

**B-string** · #9 05-08-2010, 02:04 PM

No problem, you will need to use the mixer to boost the signal level into the amp. While waiting to repair you could try a short guitar cable from the effects send to effects return jacks. If you can still get a good connection in the return jack it will restore the missing signal through the amp head.

Count Bassie · #10 05-08-2010, 02:16 PM

Quote:

Originally Posted by B-string

No problem, you will need to use the mixer to boost the signal level into the amp. While waiting to repair you could try a short guitar cable from the effects send to effects return jacks. If you can still get a good connection in the return jack it will restore the missing signal through the amp head.

I tried it, to no avail. If that had worked, truth be told, I'd just keep using the thing! Now I have to have it fixed properly. Fine...

Thanks again B.

**B-string** · #11 05-08-2010, 02:19 PM

Quote:

Originally Posted by Count Bassie

I tried it, to no avail. If that had worked, truth be told, I'd just keep using the thing! Now I have to have it fixed properly. Fine...

Thanks again B.

Sorry it didn't work. Sometimes can get you by in a pinch.

Count Bassie · #12 05-08-2010, 02:31 PM

Quote:

Originally Posted by B-string

Sorry it didn't work. Sometimes can get you by in a pinch.

That's alright. It'll have to wait a couple weeks while my tech is on vacation. (Urgh...)

I'll just have to give the AMP BH-420 (recently got) an honest run now. It's only been to one gig so far, since I've owned it. I know the AMP stuff is a pond-rippler around here, so I'll take the oportunity to A/B it with the Trace.

I love my Trace though. That little amp is the schniz, I tell ye. Through 2 Bag End S15-Ds it's a potent, punchy little box. Gonna miss it for a bit.