Zombie1965 Posted March 28, 2016 Share Posted March 28, 2016 (edited) [color=#141414][font=Arial, Helvetica, sans-serif][size=3]Ok so this issue started a few months ago around last september and is getting worse. My head is a HA3500 and is about 10-12 years old. Its been a great amp and is well used. When the issue started it presented itself as an intermittent low volume crackle that wold ride on the back of certain notes down the lower end of the fret board. At first It only seemed to happen with my passive bass plugged into the passive input jack and I put the problem down to the bass. I spent an evening replacing the Pots, jack and Capacitor (I thought this was the issue)and re wiring in my bass. and at next practice all seemed solved.... for an hour or so.....then the issue returned. I switch to another bass, an active one and plug it into the active socket and all seemed OK. Bamboozled by my issue, I continued playing that active bass for a few weeks while trying to solve the problem with the passive jack. I took the lid of the head and checked the connections on the jack, they all seem good. Just for good measure I cleaned out the inside of the chassis with an airline and changed the tube for a brand new 12AX7 Groovetube. [/size][/font][/color] [color=#141414][font=Arial, Helvetica, sans-serif][size=3]Still the problem persisted with the passive channel. We had a few gigs over the Christmas period and I continued with the active channel and active bass with no issues then we had a long break with January and February off. First rehearsal this year first week of march, I plug in the active bass and noticed that crackle is present, much like when i first noticed it on the passive channel. I had another cab available, so just to confirm this is the head I plugged in the other cab. The problem persists. I also retried the passive bass, its that bad the amp sounds very sick indeed. I am 100% sure the issue is with the head. I have also noticed that when a loud guitar strum is played on a different guitar this can cause a low level crackle on my amp from across the room. The crackle seems unaffected by changes to ether the pre amp settings, compressor or EQ but is louder with louder volume settings. So i'm asking for help to identify where my problem lies. [/size][/font][/color] [media] [url="https://www.youtube.com/watch?v=v4wL7u8B5tA"]https://www.youtube....h?v=v4wL7u8B5tA[/url] [media/] [color=#141414][font=Arial, Helvetica, sans-serif][size=3] The issue is present on the above video at 4:05 -4:20 ish and again 5:03 Ish I'm guessing a bad solder joint somewhere, are there any known week areas? are theses prone to failing with age? A bad cap maybe? Dodgy transistor? Anyone Able to take a stab? [/size][/font][/color] [color=#141414][font=Arial, Helvetica, sans-serif][size=3]I have gigs approaching and really need this Damn think back up and running. I have a good working knowledge of Electronics, although troubleshooting them is not my forte, I have access to a decent multimeter that can do both resistance and diode checks and I don't mind getting stuck in. Are there any known test points and values I can use to test? [/indent] [indent]Last of all, can anyone recommend an Amp tech in the Herefordshire/South Shropshire area, that could likely get this amp back up and running fairly quickly? Thanks in advance. [/size][/font][/color] Edited March 28, 2016 by Zombie1965 Quote Link to comment Share on other sites More sharing options...
barkin Posted March 28, 2016 Share Posted March 28, 2016 Try an instrument lead between the effects loop in/out (send/ return). The contacts on the switched jack sockets can act up. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted March 29, 2016 Share Posted March 29, 2016 Really hard to diagnose with this distance, intermittent faults are always tricky anyway. One problem with the 3500's is the power supply, there's a separate set of caps and associated components for the pre-amps and the caps are just soldered into the boards with no support. Over time the weight of the cap pushes the track off the board and will also find out any poor solder joints. That's what caused the crackle in mine and when I went online I found a number of people with similar problems. The best way to find an intermittent fault I find is with a freezer spray. The nozzle will allow you to rapidly cool one component at a time. Cooling the dodgy component or joint will usually create the fault at will or even cause the amp to cut out momentarily. The other thing with an old Hartke is that there may be a series of faults. having said that once i cured my power supply faults mine has gone on strong. Good luck though Quote Link to comment Share on other sites More sharing options...
Norris Posted March 29, 2016 Share Posted March 29, 2016 I just remembered the freezer spray trick and then Phil beat me to it Quote Link to comment Share on other sites More sharing options...
mikeydee Posted March 29, 2016 Share Posted March 29, 2016 Sounds like it is a dry join opening up with temperature and responding to vibration (coupled from the speaker), Agree, freezer spray might help identify be careful with lid off tho. Quote Link to comment Share on other sites More sharing options...
ahpook Posted March 29, 2016 Share Posted March 29, 2016 (edited) Have you been at all the controls and sockets with some switch cleaner ? Effects loops need a good clean, even if you never used as they're wired to interrupt the signal path. I'd get the top off again and give it a good slow look over, check all connections, ribbon wires and the the like. Then get in with the freeze ray Edited March 29, 2016 by ahpook Quote Link to comment Share on other sites More sharing options...
Zombie1965 Posted March 29, 2016 Author Share Posted March 29, 2016 (edited) [quote name='Phil Starr' timestamp='1459242821' post='3014625'] Really hard to diagnose with this distance, intermittent faults are always tricky anyway. One problem with the 3500's is the power supply, there's a separate set of caps and associated components for the pre-amps and the caps are just soldered into the boards with no support. Over time the weight of the cap pushes the track off the board and will also find out any poor solder joints. That's what caused the crackle in mine and when I went online I found a number of people with similar problems. The best way to find an intermittent fault I find is with a freezer spray. The nozzle will allow you to rapidly cool one component at a time. Cooling the dodgy component or joint will usually create the fault at will or even cause the amp to cut out momentarily. The other thing with an old Hartke is that there may be a series of faults. having said that once i cured my power supply faults mine has gone on strong. Good luck though [/quote] did your issue sound like the one on my video? [url="https://www.youtube.com/watch?v=v4wL7u8B5tA"]https://www.youtube....h?v=v4wL7u8B5tA[/url] 4:05 - 4:20 intermittent on B notes and again at 5:03 - 5:15 ish again on the C and B Any idea what these caps were labeled as on the board? Are you talking ot the 2 big caps that are upright nect to 2 big transistors mounted to a heatsink? cheers Edited March 29, 2016 by Zombie1965 Quote Link to comment Share on other sites More sharing options...
Zombie1965 Posted March 29, 2016 Author Share Posted March 29, 2016 [quote name='ahpook' timestamp='1459262208' post='3014894'] Have you been at all the controls and sockets with some switch cleaner ? Effects loops need a good clean, even if you never used as they're wired to interrupt the signal path. I'd get the top off again and give it a good slow look over, check all connections, ribbon wires and the the like. Then get in with the freeze ray [/quote] Yep I spent all day yesterday, carefully cleaning all the jacks and pots with an airline and switch cleaner, I checked all the internal leads and connections then started poking around with a multi meter, trouble is I have no idea (apart from resistors) of what the values are meant to be Inside looks good, Not much dust and grime, no bulging caps, no signs of overheating etc. I'm sure I have an issue like a dry or loose cap etc.... its just trying to locate the thing. I think amp tech's in my area are like ninjas , I cant seem to find any that look at e guitar/ bass stuff. DJ stuff there seem plenty. Quote Link to comment Share on other sites More sharing options...
ahpook Posted March 29, 2016 Share Posted March 29, 2016 [quote name='Zombie1965' timestamp='1459270238' post='3014982'] Yep I spent all day yesterday, carefully cleaning all the jacks and pots with an airline and switch cleaner, I checked all the internal leads and connections then started poking around with a multi meter, trouble is I have no idea (apart from resistors) of what the values are meant to be Inside looks good, Not much dust and grime, no bulging caps, no signs of overheating etc. I'm sure I have an issue like a dry or loose cap etc.... its just trying to locate the thing. [/quote] My apologies for the egg-sucking tutorial ! Intermittent faults are the very devil to tie down, especially if there no clues like obviously dead components. Be nice to be able to check the boards from below, look for any dodgy traces...that might be the next step... See what our very own Phil Starr recommends as he knows the unit. Quote Link to comment Share on other sites More sharing options...
steve-bbb Posted April 17, 2016 Share Posted April 17, 2016 had similar ish problem with HA2500 head - sent it off to local amp tech who complete overhauled the speaker out jacks and send/return jacks which cured the problem Quote Link to comment Share on other sites More sharing options...
Zombie1965 Posted April 17, 2016 Author Share Posted April 17, 2016 [size=6]******SOLVED******[/size] It was the power connector (IEC socket) inside the amp was making a poor connection with the power leads. obviously the intermittent was due to the vibrations shaking the worn connector loose. Simple fix.... Quote Link to comment Share on other sites More sharing options...
mikeydee Posted April 17, 2016 Share Posted April 17, 2016 Excellent stuff such a relief when you get it nailed Quote Link to comment Share on other sites More sharing options...
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