• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Amp shut down, need advice

Freez

Freez

Nov 8, 2008
832
933
Detroitish
#1
Hoping one of our resident amp gurus can help me out; I was playing with some buddies a couple years ago, and was using a friends Kustom Groove 210 combo (600 watts). Amp sounded great, then out of the blue it just shut down. IIRC, you could still hear it, but very quietly. Now fast forward; it's 2 years later and the friend just offered to give me the amp. I went and picked it up last night, but haven't yet had a chance to plug it in and check it out. But I was hoping someone here might have an idea as to what the trouble could be. Once I check it out I will report back here exactly what is (or isn't) doing, but if you have any preliminary suggestions as to what the issue COULD be, I'd love to hear them. Unfortunately, I don't remember what the amp was set at as far as master volumes and such; I just showed up and played thru it, sounded good so I didn't even look at the settings. Sorry guys, I know it's not much info.
 
#3
B-string said:
1st see if it works. 2nd try a speaker cab instead of the built-in speakers. 3rd try an instrument cable to "loop" the effects send and effects return.
Click to expand...

Thanks B-string, #1 and #2 very clear, but to clarify #3, you mean just run a cable between effects send and effects return? What am I hoping to see/hear when I do this, will it somehow indicate a problem? (Sorry for ignorance; I don't use effects so am clueless about the send and return).
 
#4
Looking for a possible problem in the internal pass-though from pre to power amp section. Looping effects is providing an external path from pre out (effects send) to power amp in (effects return.)

This also provides tests 4 and 5

4.run a different (known working) preamp (effects send) into the "broken" amp's effects return.

5.Run the broken amp's effects send to a known working amp's effects return.

That will isolate the problem to preamp side or power amp side on the broken amp.
 
  • Like
Reactions: Freez and B-string
#5
Freez said:
Thanks B-string, #1 and #2 very clear, but to clarify #3, you mean just run a cable between effects send and effects return? What am I hoping to see/hear when I do this, will it somehow indicate a problem? (Sorry for ignorance; I don't use effects so am clueless about the send and return).
Click to expand...

The effects return jack has internal contacts that connect the preamp to the power amp. Unused the contacts can (and do) get a micro-corrosion. Many amps have these serial effects loops and symptoms of the corrosion are many. Not limited to: no sound, low output, crackling, poor sound, squeals.
 
  • Like
Reactions: Freez and T_Bone_TL
#11
Ok, so after watching my Lions do what they do, I hooked up the amp, using my G&L SB-1. Thanks for the link to the manual B-string; I used their recommendations per setting the gain, etc. Manual says to bump the gain until the green light is flashing regularly, which I did. It goes on to say that if the red clip light comes on, you should switch the input from passive bass to active bass. Low and behold it was working great; green light flashing regularly, no red clipping light at all.... as it was later on a Sunday night, I kept it at a medium low volume, and played it for about an hour. Then this morning, after everyone had gone to work, I bumped it up to fairly loud rehearsal volume, using the master, not the gain. Plugged in the G&L SB-1 and hit a couple notes. I noticed that the red clip light flashed very quickly, like a blink, so I changed the input from passive to active, which causes a -12db cut in the signal going into the pre amp. I played for about 3-4 minutes, and the volume dropped quickly and sounded farty while doing so. Now it makes no sound at all. but the green flashing light is still working when I play, just no sound comes out. So, any thought guys? Thanks again for all the help!
 
#12
Hmmm, well I'd still recommend the battery of tests that B-String and T_Bone suggested earlier in the thread. But, based on my limited knowledge, if you're still getting the green light, I would think that means the pre-amp at least is working. Problem is more likely in the power amp section, or possibly the speakers have gone. In addition to the effects send/return tests you can (and should!) do, is there way you can try hooking up the amp head to a different speaker cab? That way you can know quickly and for sure whether or not the speakers in your combo are the culprit
 
  • Like
Reactions: T_Bone_TL and B-string
#14
So, you have an intermittent issue - not uncommon, just harder to troubleshoot - something that fails when it's warmed up. Test 1 has been done, with a variable result - run tests 2, 3, 4,& 5 and report back - as needed, run test 1 again until it fails, and then run 2-5, and report back with results. The idea is to narrow down where the problem actually is before ripping it open (or sending it to someone else to rip open.)
 
#16
Ok, the amp is still not working, but I did as many of the tests as I could; I can't try another speaker cab because the only speaker output on the head is a speakon, and I don't have any cabs that take those (or speakon cables either). I really think the speakers are ok; it worked the other day when I first plugged it in, so if the speakers were fried when the amp first broke down 2 years ago, they shouldn't have worked at all this time, should they?

I have a Tubeworks combo that works great. I ran the effects send from this amp to effects return on my Tubeworks and it worked fine. When I ran the Tubeworks effects send into effects return on the broken amp, it did not work. So my problem appears to be in the power amp section, not the preamp section, right? Makes sense; preamp lights react as if they are getting the signal. Tried plugging bass directly into effects return on broken amp, no sound. Looping send/return on broken amp, no sound. So guys, what do you think? And what should my next step be?
 
#20
No Speakons? Egad, we'll have to send the TB Correct Connector Team over to sort you out!

More realistically, you're now entering the point of taking things apart, if you are comfortable doing that and careful not to get you or anyone else zapped when doing so. Or haul it in for repair.

Your gut feeling is probably right, but probably right does not have the clarity that checking does - when you get the head out, you should have speaker wires, and you can rig up something to connect those to your speaker connectors to try the speaker on its own, and the power amp section on its own. Then you KNOW. It could be as simple as a loose connection in the speaker (or to the speaker.)
 

Latest posts

Top Bottom
Back