| Author | Message | ||
| jazzyvee
Senior Member Username: jazzyvee Post Number: 3323 Registered: 6-2002 |
I have just encountered a problem with my mesa boogie head. I did a gig with it on Friday and it was fine no problems. Today i was just starting my practice session and initially the playing volume was fine, then all of a sudden it dropped to about 50% volume, started crackling and giving a distorted sound then a few seconds later it was back up to normal sound. At first I thought there was a problem with my DS-5 again, so I took out the plug and used a standard jack and the sound was just the same. Just to be sure I tried a different bass which I know has fresh batteries and the same thing happened after a few seconds of playing. So I'm pretty sure it's something to do with the amp. I've never had a problem with it before and it's the amp i use on most gigs. Any ideas? Jazzyvee | ||
| edwin
Senior Member Username: edwin Post Number: 1418 Registered: 5-2002 |
Are there tubes? If so, check those. Also, if there are send/return loop jacks, exercise those. They can have switches which get dirty and cause the symptoms you describe. | ||
| tncaveman
Intermediate Member Username: tncaveman Post Number: 156 Registered: 2-2011 |
I've had that happen on numerous amps/guitars/basses and it always seems to be a plug/jack issue or a pot that needs to be exercised. The contact cleaners help too. Stephen | ||
| pace
Senior Member Username: pace Post Number: 923 Registered: 4-2004 |
Cables?!? Are any of your patches of the solderless George L / Lava variety? If you've deduced that it is occurring within the Mesa, then check the board for any cracked solder joints, especially if the jacks are surface mount. Also check the filter caps' connection to the board, sometimes the solder joints crack, if so, after resoldering, you can use a glue gun to reinforce the caps on the board. | ||
| alembic76407
Senior Member Username: alembic76407 Post Number: 711 Registered: 5-2002 |
Preamp tubes would be my guess same thing is going on with my Boogie 400+ David T | ||
| xlrogue6
Advanced Member Username: xlrogue6 Post Number: 248 Registered: 8-2002 |
If you've got one of the earlier Walkabouts (2 inputs instead of one with a switch) it may be your FX loop, which lacked a bypass switch in that era. If yours is of that era, try jumpering the loop jacks with a short cable. If that's not it, there have been a couple of circuit updates to the Walkabout that apply to serial numbers under 2001. | ||
| jacko
Senior Member Username: jacko Post Number: 3326 Registered: 10-2002 |
I had an identical problem years ago on a trace elliot. Turned out to be dry joints on the PCB. Thumping the top of the amp hard would usually 'fix' it for a short while. Graeme | ||
| jazzyvee
Senior Member Username: jazzyvee Post Number: 3334 Registered: 6-2002 |
Strangely enough as I've been playing it this week it hasn't repeated the effect it had on Sunday so it's probably gonna be one of those dreaded intermittent problems. I'm gonna try the Jumper cable and if that doesn't solve it I will take the back off and check the joints etc. Jazzyvee | ||
| keith_h
Senior Member Username: keith_h Post Number: 1844 Registered: 2-2005 |
J-V, Most of the heads and preamps that have any type of effects or insert loops use switches on the 1/4" jacks. These will oxidize over time when not exercised and cause distortion. I suggest you get some Caig's DeOxit and spray the connectors and then exercise them by inserting a plug in and out a few times. If you wish to be more thorough open the unit up and use the DeOxit and a business card to burnish the contacts, if they are not enclosed in a housing. A relay contact burnisher would be better but this is not something most folks would have lying around. Keith | ||
| jazzyvee
Senior Member Username: jazzyvee Post Number: 3336 Registered: 6-2002 |
I tried the jumper cable between send and return jacks and the volume and quality of the sound jumped up incredibly so it must have been deteriorating for a while. In actual fact I had wondered a while ago if I had blown one of the the speakers or tweeter because of the intermittent scratchy sound but now I doubt that is the case. This weekend I'm gonna spend some time checking my gear out as I have a couple of important showcase gigs for festival promoters comming up next month. Maybe i will get time to take the back off and have a clean up inside. Jazzyvee | ||
| rustyg61
Senior Member Username: rustyg61 Post Number: 778 Registered: 2-2011 |
That must be an inherrant problem with Mesa, our guitar player has a small Mesa Boogie amp that has cut out on him on several gigs & after that last time he said he jupered the effects loop & it went away too. | ||
| jacko
Senior Member Username: jacko Post Number: 3328 Registered: 10-2002 |
What if you want to use the effects loop? graeme | ||
| rustyg61
Senior Member Username: rustyg61 Post Number: 779 Registered: 2-2011 |
I don't know, our guitar player just bought a new amp while he's trying to figure out the Boogie problem. | ||
| keith_h
Senior Member Username: keith_h Post Number: 1845 Registered: 2-2005 |
When you jumper the effects loop you bypass the bypass switches built into the connector. These switches allow the signal to pass through when you aren't using the jacks. The fact that the jumper resolves it indicates to me that oxidation on the contacts is what is causing the problem. I run into the same thing on my Navigator. Since the connectors never get used they don't open and close to keep the contacts clean. A little DeOxit on the contacts and exercising to allow the contacts to wipe and I'm good to go for another couple of years. Note: I am not an endorser for DeOxit but it is easy to find at your local Radio Shack and works well. Keith | ||
| cozmik_cowboy
Senior Member Username: cozmik_cowboy Post Number: 1405 Registered: 10-2006 |
I'm jealous, Keith; went looking a couple days ago, and my local Cell-Phone-Plan Shack had never heard of it (got a can of CRC QD Eletronic Cleaner at the hardware - anyone know anything I should know before I spray in any pots?) Sorry for the highjack; glad the problem's figured) Peter | ||
| xlrogue6
Advanced Member Username: xlrogue6 Post Number: 249 Registered: 8-2002 |
DeOxit is vastly superior to the stuff from the hardware store, but tends to be at best a temporary fix for the oxidized switching contact problem. Best fix is a add the loop bypass switch that's now a standard feature on the Walkabout--an easy job for any tech who knows what they're doing. | ||
| tncaveman
Intermediate Member Username: tncaveman Post Number: 157 Registered: 2-2011 |
I have been using the CRC cleaner for a long time with good results. I now use the Deoxit. I think it works a little better on pots. But the CRC is great on jacks. They have a follow up spray too that's a lubricant that helps keep the plugs and jacks operating well. Stephen | ||
| keith_h
Senior Member Username: keith_h Post Number: 1846 Registered: 2-2005 |
Peter, I'm surprised you couldn't find it at your Radio Shack. It should be in the section that none of your clerks would go into. You now the one with the electronics parts. :-) Looking at the spec's the CRC should be fine for the connectors. I would not try to use it on pots though. As Stephen mentioned there is a DeOxit version that comes with a separate contact lubricant. I've used it on some automotive connectors and it seemed to help. Keith | ||
| cozmik_cowboy
Senior Member Username: cozmik_cowboy Post Number: 1408 Registered: 10-2006 |
"...the one with the electronics parts. :-)" :-( Consists of 5 small drawers of caps. Sounds like you're fortunate enough to still have an old-school RS, where you used to be able buy everything you need to build a radio (my brother did it when we were kids) - and employees geek enough to give you instruction! Peter | ||
| keith_h
Senior Member Username: keith_h Post Number: 1847 Registered: 2-2005 |
Not sure about everything to build a radio. I mean they don't even have a tube tester. Thankfully I do. Keith | ||
| xlrogue6
Advanced Member Username: xlrogue6 Post Number: 250 Registered: 8-2002 |
So the problem with my Walkabout(or one of them at least) turns out to be the switching contacts on the input jacks. I'm going to change them out to the current arrangement of one jack and an active/passive switch later today (unless it turns out to be easier to sub in Switchcraft 12A jacks, which take at least a couple of decades to develop these kind of problems!). Obviously, this only applies to older units like mine with 2 inputs. | ||
| xlrogue6
Advanced Member Username: xlrogue6 Post Number: 251 Registered: 8-2002 |
So it is indeed easier (in my estimation, anyway) to replace the Cliff jacks with Switchcrafts rather than installing a switch (I like the aesthetic better as well). If you go this route, you'll need the 12L long bushing shorting jacks and the S1029 insulating shoulder washers that make the Switchcrafts fit the Cliff holes perfectly. Additional benefit is that the jack nuts can now be tightened with a regular nut driver instead of finagling them with needle nose pliers. Be sure to use a lockwasher behind the shoulder washer in the rear and the chrome dress washer over the one in the front so the jack doesn't loosen. |
