Hartke HA3500/VX3500 combo troubleshoot.

[Sly13]

Issue - When playing @ high volume the sound will be reduced to almost nothing and it takes about an hour to a day for it to go back to normal. Then the next time its played it goes back to being at a reduced volume level.


IE - Playing at half volume, plays fine, then maybe if I hit a powerful note at some point the amp starts playing at a very low volume.



Steps I've taken so far (for my learning process feel free to call me an idiot)

I've checked all my speakers they seem to work fine. My horn appears to have been blown, I can't get any sound out of it.

So I'm narrowing it down to either the circuit board inside the cab maybe one of them resistors or the HA3500 itself.


Any thoughts? Am I on the right track or way off? Anyone with experience with this problem? Any recommendations on troubleshooting steps?


Thx
~Sly13



(Edit) After tracing the Cab board I can rule that out as the cause of the issue being none of those resistors could act as a -limit switch- to hold sound at a lower level, they're only in line with the horn.

[52 Bill]

Issue - When playing @ high volume the sound will be reduced to almost nothing and it takes about an hour to a day for it to go back to normal. Then the next time its played it goes back to being at a reduced volume level.

IE - Playing at half volume, plays fine, then maybe if I hit a powerful note at some point the amp starts playing at a very low volume.

What you describe sounds like a mechanical break in the signal path. If you have an FX loop try plugging in a spare cord from the send into the return jack. If this brings back the volume, the jacks need to be cleaned.

Try giving the amp a whack with your fist (turn down the reverb first). Does this cause the problem to appear or disappear?

My horn appears to have been blown, I can't get any sound out of it.

(Edit) After tracing the Cab board I can rule that out as the cause of the issue being none of those resistors could act as a -limit switch- to hold sound at a lower level, they're only in line with the horn.

Did you test the resistors with a meter? If one of them has open circuited, the signal will not get to the horn.

Unhook one wire to the horn. Test the horn by touching a 9 volt battery across its terminals. Do you hear a clicking sound from the horn? If you do then the horn is ok and the problem lies elsewhere. If there is no sound from the horn, then the horn is bad and will need to be repaired or replaced.

[Sly13]

What you describe sounds like a mechanical break in the signal path. If you have an FX loop try plugging in a spare cord from the send into the return jack. If this brings back the volume, the jacks need to be cleaned.

Try giving the amp a whack with your fist (turn down the reverb first). Does this cause the problem to appear or disappear?

I'll give that a try in a sec, need to find a spare cord first.

Did you test the resistors with a meter? If one of them has open circuited, the signal will not get to the horn.

Unhook one wire to the horn. Test the horn by touching a 9 volt battery across its terminals. Do you hear a clicking sound from the horn? If you do then the horn is ok and the problem lies elsewhere. If there is no sound from the horn, then the horn is bad and will need to be repaired or replaced.

I did your 9volt test and didn't hear anything at all so I guess the horn is bad.

[Sly13]

well I popped the top off of the HA3500 and checked my passive/active inputs...


Then when i tried to play again the thing was dead silent... I gave the amp a wack like you said and it started to go. I noticed that it was playing fine but the longer i played the more likely it would start to get that raspy, crunching sounding going on. crackle pop etc.


Any more thoughts?

[52 Bill]

... I gave the amp a wack like you said and it started to go. I noticed that it was playing fine but the longer i played the more likely it would start to get that raspy, crunching sounding going on. crackle pop etc.

Like I said, it sounds like there is either a loose part or bad connection somewhere in the amp. When the connection is made the amp plays, when the connection breaks, the amp stops working.

Did you ever try the FX loop patch cord test?

If that didn't do it, next try the chopstick test. If you feel comfortable with working on the amp while it's plugged in and running, take an insulated tool or a wooden chopstick and tap, or push on the components on the pc board, while listening to the signal. If you find something that causes the signal to start and stop, check the component to see if it has broken off or has come unsoldered from the board.

If you don't feel comfortable working on the amp while it's plugged in, just visually inspect all the parts on the pc board to see if you find anything that has broken loose.

[Sly13]

Like I said, it sounds like there is either a loose part or bad connection somewhere in the amp. When the connection is made the amp plays, when the connection breaks, the amp stops working.

Did you ever try the FX loop patch cord test?

If that didn't do it, next try the chopstick test. If you feel comfortable with working on the amp while it's plugged in and running, take an insulated tool or a wooden chopstick and tap, or push on the components on the pc board, while listening to the signal. If you find something that causes the signal to start and stop, check the component to see if it has broken off or has come unsoldered from the board.

If you don't feel comfortable working on the amp while it's plugged in, just visually inspect all the parts on the pc board to see if you find anything that has broken loose.

For the FX loop check you want me to take an extra cord and run from the normal send output .. to the FX loop input then through the FX output back to my cab?

[Enzo]

No. Simpler than that.

Your effects loop has two jacks - send and return. Plug a cord from send to return.

it is a sort of hard wired external bypass arrangement.


That amp has one lonesome tube in the preamp, doesn;t it? I find that sometimes the little film caps around the socket, sitting up off the board on their leads a little bit, can break off. Poke them with a chopstick and see.

Also, along the rear edge of the preamp board are some multiwire connectors from the power transformer. Wiggle those and see if it has an effect. I find the solder cracked under those from time to time.

[techineer]

I've seen a number of the Hartke amps with broken solder connections on the foil side of the circuit board, especially on the jack connections.

The boards are wave soldered, and often don't get a secure solder connection on the larger pads. The stress from plugging/unplugging cables often breaks the solder around the pins of the jacks. However, it's not limited to the jacks. To find it, you will have to disassemble and remove the circuit board, turn it over and do a close inspection of all the solder connections. Be sure and label the connectors so you can put it back together correctly.

Equipment built after the implementation of ROHS in Europe often has solder problems. It often doesn't properly wet (bond with) the component leads and pads, is more brittle and generally a pain in the ***.

[Sly13]

k awesome I did the FX loop test, not only does it fix the issue but it for sure sounds cleaner and louder when i have the cable on the FX loop. I pushed in all the nomex plugs, gonna keep an eye on it and try to use the chop stick method to find the source of the problem.

However at the point of actually finding the problem I think I lack the tools or skill to actually fix it.

Is leaving the cable on the FX loop a good option for a perm. fix?

[Enzo]

Won't hurt it in the slightest.

What it usually means is dirty contacts on the return jack, which means clean or replace the jack most times. On this unit ther eis also a balance control for the loop and a small circuit. Possible problem on that little board.

[techineer]

The FX loop jacks have switches in them that pass the signal on through the jack when there is no plug in it. The contacts on these switches tarnish and start to interrupt the signal.

Before you try to replace the jacks, you can try this: Get a can of Caig De-Oxit D5 spray. (Do not substitute!) Shoot a small amount in each jack and run a plug in and out a few times. This stuff has something in it that breaks down the tarnish and improves conductivity in the jack switch. Do NOT use a cleaner.... that won't solve the problem. We've found the DeOxit to solve a lot of problems of this type.

For a more detailed description of the problem and solution, see: Preston Electronics

[Stoffie1974]

HA3500

Hi,
I've had a lot of HA3500's on the bench with ALL having the same problem ... bad soldering !! Especially the 7815 & 7915 stabilizers
It's a known problem especially since they are not made in the USA anymore.
I still have one (HA7000, one of the last produced), and it failed on me to. So i disassembled it completely (you have to do that to access the copper side of the preamp board), even the amp pcb's (disconnect the power T's) an resolder EVERYTHING ... yes it took me several hours and yes there were A LOT of bad solders in it (dark mat grey instead of shiny), but it never failed me again !!
In fact, it's quite a good amp now, but i prefer my ampeg SVT3pro.
I would not recommend "fixing" this with the loop though, one day, and most likely when you're on stage, it WILL fail !!

Grtz

[gambitron]

http://revver.com/video/2009465/windows-error-music/