dmccombe7

A lot depends on where you are on the supply feed. I live in a village and i'm one of the first houses after the transformer and at one time all my home light bulbs were going one after the other. I have an electrical background so tested myself and the voltage was 250V Contacted Scottish Power and they put a monitor on the house and found it spiking very regularly to 262V They dropped the tap on the transformer which is located in the field behindme on a pole. Been ok since but the engineer said the voltage at the far end of the street was approx 10V lower than mine so its a bit of a balance act to get it right. The problem happened at a rehearsal in Wanlockhead but the Mesa has a rather large transformer and pretty sure it could cope with voltage changes. Nothing else was affected just my amp. On the gig last night the amp worked fine altho i turned the amp off when not in use plus i decided to drop the Gain a bit and reduce the drive on the tubes. No idea if these things stopped the volume drop but the amp wasn't on any more than approx 1hr 30 mins at a time. Dave

I have seen a few on line reports of it while researching the problem i experienced. Perhaps its just a valve quality or spec issue. The guy i use said ecc83 valves are rated up to circa 400V and from what i've read the Mpulse 600 runs at 390V. For me that's quite close to spec limit and maybe the poor quality valves are failing after a while. ? I have no idea as i'm not an expert in this area by any means so i can only take advice from others with similar amp problems. One of the posts i read was from an electronics engineer who repaired his own amps and he came across this same issue and changed an item on the board to drop the HT voltage to the valve in line with other valve amps. Dave

Looking from the front of the amp what valve is V2 as i cant see any markings on the board. I found your thread from 2017 i think it was and i've let the repair guy read it so he knows what's been happening with some valves. Thanks for getting back to me. Dave

misunderstood the message and deleted my original comment so this post now means absolutely nothing. I dont know how to delete a post

Post some pics if you can as i'm not familiar with the models and will need to google them. Dave

Kinda thought that. Thanks for confirming tho.

Is the bias not just for power tubes. Didn't think it was required for preamp tubes. ? No expert on it. Dave

Both nice looking basses. That Ibanez would look cool in my 70's Glam covers band Dave

I came across the issue on an earlier BC thread about Mesa Mpulse valves Steve. Seems that you need to use either Mesa or JJ 12ax7 valves if they need replacing. Dave

I looked at valves just in case it was a dodgy connection of the valves or they had loosened off in transit. Both were good tight fits but i did note that one was a Mesa and the other a Phillips. Someone else mentioned this to me and i asked GSE guy if he was aware of it but he said 12ax7 valves are rated up to 400V or there abouts and he cant see any reason why any good quality 12ax7 wont work in that slot. I believe it was the V2 position. I'm taking it in on Tues for the guy to check it out. I have spare 12ax7 valves from my Ampeg days before the Mesa that came from Watford Valves. I think they are Harma valves. Was going to change the valves anyway but a lot of places dont have any in stock at moment and might be one of those 3 mth pre-order things again. The current valves have been in since i bought the amp and its been fine up until few days ago. It worked fine yesterday at home at same GAIN setting but lower master volume in the house but the valves would be doing the same work at same Gain setting. Will wait and see what the GSE guy finds. Would be good to hear what happened with @rumblefish and outcome before i take in for repairs.

Bit out of the way for me but always handy to know for future. Thanks for this Dave

I've looked at them in past and all good reports but i went with GSE and haven't been disappointed. Its good to have back-ups tho LOL thanks again for replying. Dave

Cheers @agedhorse i've just replied to your other comment on volume drop out. Thanks again for replying and appreciate the recommendation. I'll keep everyone posted on outcome. Its an older amp so a few minor probs is to be expected. I had it running at home at higher volumes for about 2hrs today and it was fine. Getting checked out next week. Dave

Thanks for getting back to me @agedhorse always appreciated. They got back to me and said they dont do Mesa gear now for past year. I've contacted a guy i've used many times when i owned Ampeg gear and he has worked on several Mesa amps over the years. Taking to him on Tues. Glasgow Studio Electronics might be worth adding him to your repairers list altho i'm not sure how that all works for Mesa. The other option was Fretronics who are on your list but got no response from them at all. I've used GSE many times and happy with his work over past 10 years. Dave

Called Glasgow Studio Electronics as he's the guy i've been going to since 2012. He said he's done a lot of Mesa repairs over the years and suggested it probably isnt a tube but he'll run a distortion test thru the full amp and confirm what the fault is. I'm probably happier using GSE especially as he knows Mesa gear too. Plus he's always been reasonably priced for anything i've had done. Dave

Sent a message to Fretronics and will speak to the guy who repairs most of my gear over past few years at Glasgow Studio Electronics. His website shows Mesa as one of the companies he has worked on. I've also heard of Flynn amps so if all else fails i might try them. Dave

Anyone have suggestions for Mesa repairs in Scotland preferably Central belt area. Tried Westside Distribution but they dont do Mesa gear now and couldn't offer an alternative in UK. Not sure if @agedhorse can offer any help ? Dave

I'm contacting you from the treatment centre with my pineapple and ham pizza but i do agree on the front and back pick up positions. Dave

Yes i'd def buy more especially thru my 2nd home. 😂 Dave

I struggled to find a supplier for them that had them in stock and just gave up. Amazing strings with a really nice clear tone and great feel to them. They didnt feel as tense as the Elixirs i've tried over the years. Dave

Brilliant Rob. More Camel please. Dave

Brilliant guys and thanks for help and advice. I will unplug and replace the valves as the amp just in case its that simple. I wont tackle anything else in my amps even tho i have a background in Industrial Intsrumentation. I'm not good enough to fault find on amps. I've contacted Westside Distribution in Glasgow which isnt too far from me if they can take a look at it. I think that's who Andy @agedhorse from Mesa recommended on another Mesa post somewhere. That's good news about the passive bass either working or not. I've been very lucky over the years not to experience any major bass guitar faults when playing. Amps are always a problem especially if 2nd hand but i've got the Mesa TT800 on order and hopefully i wont experience any probs with that when it arrives. Dave

Having done the usual google search i found that this volume drop out can be caused by tube failures altho most lost volume completely but some reported volume drop outs. No idea how old the valves are so might be worth replacing them and see how it goes from there. The general concensus from most techy backed guys on line reported that Mesa amps generally dont have quality issues with circuitry and soldering etc. Having said that i guess after time any amp can still get soldering problems thru time and just wear and tear. Dave

If its internal amp issue i'll take to a pro as i'm not confident enough to tackle that type of work. I think you might be right tho as i had similar issues with my Ampeg SVT3 with soldering issues and cracked tracking on the circuit board. The thing that's throwing me a bit is that the P bass sounded fine but the amp had only been switched on for approx 1 hr with it whereas the amp had been on for several hours when using the Jazz. Dave

Didn't have enough time to try the Jazz again but will fire it all up today at home and see what happens but wont be able to try at same volumes. Will check all tubes are seated properly or might just swap them over with some spares i had for my Ampeg SVT3. Not sure how to check a bass pick up for a breakdown. I'll replace the speaker cables too just in case one of them was starting to go. Luckily enough i bought a back up amp just in case i had any issues with the Mesa as its getting a bit old now. I have a Blue Angels biker gig on Sat night and would rather use the Mesa as it has more depth. I've contacted Ghostbusters just in case of poltergiest issues @ambient😂 Dave