Solid State Combo Amp Acting Up

polkaman81 · #1 01-08-2012, 07:56 PM

Hi gang,

My Crate BT1000 bass solid state combo amp started acting up recently. I've noticed the last couple times I've turned it on it produced a hum that was never there before and then it would go away after a few minutes. The last time I used this amp this weekend it hummed when I turned it on but then the hum did not go away. In fact, after practicing with the rest of the band for about an hour or so my signal cut out completely! It has a built in tuner on top and it was still giving a read out when I played but no sound out of the driver.

When I got home after practice I tore apart the cabinet and found nothing suspicious that would cause my sound to cut out. All of the connections to the driver and other parts of the amp were fine. The fuse had not blown. I put it back together and tried again. Same hum but then my bass would cut in for a bit and then go out. It is very strange. To me the driver seems fine. I'm guessing it has to be something in the electronics of the amp that would be causing this problem.

Any help is appreciated. This has been a great bass amp thus far and I would love to fix it and keep using it. Thanks!

impactwrench · #2 01-10-2012, 07:35 PM

it may be over heating, and it cuts out until it cools down. is that the 100 watt 1x15 combo? I had one (a crate bx100) about 15 years ago, my first big amp. I still have a bx25. Decent starter amps, but 100 watts could be a little on the small size for long band practices.

T-Bird · #3 01-10-2012, 08:03 PM

Hi.

Quote:

Originally Posted by polkaman81

Any help is appreciated. This has been a great bass amp thus far and I would love to fix it and keep using it. Thanks!

How much electronic appliance repair experience/skills do You posess?

The thing is, the problem may be just a simple one, like a cold solder or a bad PS cap, but diagnosing the problem and fixing it safely, may not be as simple if You have to start from zero.

What ever You decide to do, be safe.

Regards
Sam

polkaman81 · #4 01-11-2012, 07:28 AM

impactwrench, this is the Crate BT1000 100W 1x12 combo. I've used it for practices before and never had a problem. I've been using this amp regularly for almost a year now and have been very happy with it. I watch to make sure the limit light doesn't come on while playing. It doesn't appear that overheating is the problem.

T-bird, I don't have much experience in the electronic appliance repair area. I'm thinking I may have to take it in to get checked out and fixed properly. I am going to look at it some more and if it's only a solder problem, I know a few guys that can help me. It seems like bad PS caps are a common problem in smaller amps so I am going to looking into diagnosing where that is in the amp so I can check it out.

Thanks for your responses gentlemen!

elroyjetsn · #5 01-21-2012, 11:51 AM

If you haven't found anyone to repair the amp section. I could take a look at it if you like. I've repaired 2 of my bandmate's amp recently. Most of the time it's loose solder connects and,or corrosion. PM me if interested. You could just box-up the amp section to save postage.

Electronics' repairs has been a long-time hobby of mine.

Wayne

BassmanPaul · #6 01-21-2012, 12:06 PM

Is there no warranty on the amp or did you buy it used?

polkaman81 · #7 01-22-2012, 08:38 PM

BassmanPaul, I bought it used so no warranty.

elroyjetsn · #8 01-25-2012, 10:38 AM

Polkaman81,

If you try to pull the amp chassis out, be carefull to free the tuner snap-in module first. There should be a way to release it.

Oops, just noticed you already had it out....

Was that driver the 8 ohm Beta12a? Don't know how critical the Crate circuits are to impedence matching. My BT1000 seems OK with 8 ohms so far, but I am getting nervous.

Just came across a 4 ohm version, but it seems harder to find them in stock.

elroyjetsn · #9 01-25-2012, 12:36 PM

You may want to check the resistance on the driver to see if it's still anywhere near 6.8 ohms for 8 ohm driver or 3.4 ohms for 4 ohm driver.

NecroticImbecil · #10 01-25-2012, 12:53 PM

And here I thought only tube amps broke down.

T-Bird · #11 01-25-2012, 10:34 PM

Hi.

Quote:

Originally Posted by NecroticImbecil

And here I thought only tube amps broke down.

IME, it's actually the SS amps that break down more often.

SS amps are often considered to be lost causes if that happens, and quite frankly, it's true. Financial-wise anyway.

Regards
Sam

elroyjetsn · #12 02-26-2012, 02:35 PM

Don't know if it's the 8 ohm speaker or what, but my BT1000 dropped an output transistor at practice last week. By the end of practice it was sounding pretty thin and the volume had dropped off.

Pulled off the output transistors (MOSFETs) and tested them, one was open. Think it was the P. Ordered a new set (the original p was superseded by an improved version) got 2 sets just in case - 6 bucks US a pair.

She's working fine, now. Worried about balancing the loads between them, but after playing pretty loud for a while, they never got warm to the touch.

Sorry, that was 9 bucks plus shipping, Got mine from Mouser:

942-IRFP140NPBF
942-IRFP140NPBF
MOSFT 100V 27A 02/21/12 2 2.120 4.24

2 1

942-IRFP9140NPBF
942-IRFP9140NPBF
MOSFT PCh -21A 02/21/12 2 2.200 4.40

1RoHS: Compliant

Freight Merchandise Total
USD $8.64