Hartke 3500 died!

keiththebassist · #1 01-29-2013, 10:28 AM

My beloved Hartke has finally coughed out. It's been a great amp for many years so I am now a sad boy.

It started to cut out intermittently and it seemed like a loose output cable/jack connection at my bass. When I wiggled the output cable at the jack it came back to life for a short while. I did this back and forth thinking it was my output jack or a bad 1/4 inch cable. Eventually it quit and wouldn't come back.

After a bit of struggling the amp began to just fart out and distort the speakers really badly, producing almost no volume. It's definitely the amp, when I plopped my Hartke 2000 onto my stack it sounded like it always has, fantastic. I had it serviced maybe six months prior by a tech with decades of experience. He cleaned up various electrical connections, replaced the input jack and threw a new tube in. basic maintenance stuff.

Any light bulb ideas as to where to start? I'm not super savvy with amp electronics so I'm in need of some tb wisdom here... Thanks in advance!

T-Bird · #2 01-29-2013, 10:43 AM

Hi.

Have You tried the "usuals":

#1 a patch cord onto the FX loop.
#2 a new (or old) known-to-work tube.

Regards
Sam

Bass_Pounder · #3 01-29-2013, 10:45 AM

A second approval for completing the "loop" in your FX loop.

bassgod0dmw · #4 01-29-2013, 10:46 AM

It very well could have been the cable or the jack that was bad, and it finally blew the amp because of it.

Did you try a new cable back when you thought it might have been the cable?

keiththebassist · #5 01-29-2013, 10:50 AM

Quote:

Originally Posted by T-Bird

Hi.

Have You tried the "usuals":

#1 a patch cord onto the FX loop.
#2 a new (or old) known-to-work tube.

Regards
Sam

Not familiar with the patch chord trick...

keiththebassist · #6 01-29-2013, 10:51 AM

Quote:

Originally Posted by bassgod0dmw

It very well could have been the cable or the jack that was bad, and it finally blew the amp because of it.

Did you try a new cable back when you thought it might have been the cable?

Yeah I tried multiple basses and cables, all leading to the same result

T-Bird · #7 01-29-2013, 11:04 AM

Hi.

Quote:

Originally Posted by keiththebassist

Not familiar with the patch chord trick...

A regular 1/4 plug cord from the FX send to FX return. The shorter, the neatier.

Most FX loops, including the HA3500 IIRC, are connected between the pre-amp and the power amp, ie. in series, so either or both jacks have a switch that disconnects (or shorts) the signal chain between the pre- and the power amp.
That switch becomes oxidised or dirty if not used regularily, and produces the symptoms You described.

If You look at the back of the older amps with FX loops, you'll often notice a short patch cord in there

.

Regards
Sam

B-string · #8 01-29-2013, 11:08 AM

Quote:

Originally Posted by keiththebassist

Not familiar with the patch chord trick...

Use an instrument cable, one end into the effects send, other end plug into the effects return. Try the amp with the cable in place.

keiththebassist · #9 01-29-2013, 12:17 PM

Thanks all, I'll give that a try in the next day

BAce · #10 01-29-2013, 09:40 PM

There's a small driver transistor on the amp board that can burn out. It's not attached to the heat sink, just on the main amp board. One blew on my Hartke 3500 MOSFET and sounded exactly as you described, OP. Was easy to spot--little black mark on the circuit board. Tore it apart, replaced the transistor, good as new. Took an hour.

keiththebassist · #11 03-06-2013, 05:41 PM

Quote:

Originally Posted by BAce

There's a small driver transistor on the amp board that can burn out. It's not attached to the heat sink, just on the main amp board. One blew on my Hartke 3500 MOSFET and sounded exactly as you described, OP. Was easy to spot--little black mark on the circuit board. Tore it apart, replaced the transistor, good as new. Took an hour.

Thanks! Sadly, I see nothing that looks burnt. And to the other posters, the patch cable connecting the jacks of the effects loop did not fix it

Still need help!!!

Ezmar · #12 03-06-2013, 06:22 PM

If you have a local electronics guy, I'd bring it in for diagnosis.

Snakeman1066 · #13 03-06-2013, 06:24 PM

silly question, but have you checked the fuse?

Floyd Eye · #14 03-06-2013, 06:24 PM

Send it to Larry Hartke.

figuredbass · #15 03-06-2013, 07:41 PM

Quote:

Originally Posted by bassgod0dmw

It very well could have been the cable or the jack that was bad, and it finally blew the amp because of it.

I would tend to doubt that the amp blew for this reason since the 3500 does have output short circuit protection that trips an internal relay (switch) that disconnects the amp from the speaker jack if it senses a short, and remains off until the short is eliminated.

figuredbass · #16 03-06-2013, 08:02 PM

Quote:

Originally Posted by keiththebassist

It started to cut out intermittently and it seemed like a loose output cable/jack connection at my bass. When I wiggled the output cable at the jack it came back to life for a short while. I did this back and forth thinking it was my output jack or a bad 1/4 inch cable. Eventually it quit and wouldn't come back.

This may be your best clue. The fact that you could bring it back by wiggling the speaker cable points to a probable loose connection and not a component failure, since components don't tend to repair themselves once they've gone. The two speaker output jacks on the 3500, while mounted to the rear panel, are also soldered directly into a mini PC board specifically dedicated for those two jacks. After years of plugging in and out (especially if the outer jack nuts become loose where the jack can move) the stress can weaken the jacks' solder joints to the point where the connection is broken altogether.

Of course this is only one possible cause, but very often when an amp "blows" it isn't the whole amp that blows, but a fairly cheap component. The other cause can be a connection problem: bad solder joint, internal connector plug/socket. The 3500 is a highly repairable amp so it's just a matter of diagnosing the exact cause.

Snakeman1066 · #17 03-06-2013, 08:15 PM

Quote:

Originally Posted by figuredbass

This may be your best clue. The fact that you could bring it back by wiggling the speaker cable points to a probable loose connection and not a component failure, since components don't tend to repair themselves once they've gone. The two speaker output jacks on the 3500, while mounted to the rear panel, are also soldered directly into a mini PC board specifically dedicated for those two jacks. After years of plugging in and out (especially if the outer jack nuts become loose where the jack can move) the stress can weaken the jacks' solder joints to the point where the connection is broken altogether.

Of course this is only one possible cause, but very often when an amp "blows" it isn't the whole amp that blows, but a fairly cheap component. The other cause can be a connection problem: bad solder joint, internal connector plug/socket. The 3500 is a highly repairable amp so it's just a matter of diagnosing the exact cause.

After many years of faithful service mine also quit last year....local tech diagnosed a bad solder joint.....was an inexpensive fix.

keiththebassist · #18 03-06-2013, 10:37 PM

Quote:

Originally Posted by Floyd Eye

Send it to Larry Hartke.

As much as I'm sure he would take care of me, I would feel a little guilty taking up his time (and therefore money) fixing an amp that I didn't even buy new.

Not being savvy on amp diagnostics, I think sadly I may just have to take it to my tech. Which is frustrating since I had the amp totally looked over and cleaned up less than a year ago. I play through it a lot but I'm not a gig warrior so it hasn't seen a TON of miles since its last check up. Oh well, cost of being a musician I guess.