I have a problem with a multi watt dual rectifier head.
It keeps blowing fuses and a rectifier tube.
Using the light bulb mains lead method, even with both rectifier tubes out of the unit and on standby it seems to be drawing quite a bit of current. No change with power tubes also removed.
Is this likely to be the large filter caps going or any other suggestions?
Thanks in advance
If the rectifier's are not in circuit then there would be no B+ vdc. So I can't immediately imagine the caps are the issue from that standpoint. Of course posting a schematic would be a good thing. It seems the transformer may have other windings -/+15v rails and your heater's winding. Try disconnecting all secondary connections when in doubt. Light bulb shining with secondary taps disconnected from circuit is not good. Right now from what you have written we need to clarify what you are describing and a schematic. We need voltage readings if the light bulb is not shining bright.
Hey, Psabin8951,
I'm no expert, but a couple of things popped in my mind.
Which fuses does it blow - primary or secondary?
As I understand Mesa Dual Rectifiers, it should have a rectifier selector switch. Does the amp do that with solid-state rectifier selected?
Could it be a short on the primary side of the power transformer? 🤔
Like DrGonz78 said, a schematic and voltage readings would help.
You need to be super careful and you must know what you're doing if you ever decide to tinker with it yourself. As you probably know, there are lethal voltages inside that thing. If uncertain, take it to a tech.
Not necroposting for fun, but for op's go as I'm sure he already took care of this. This is for anyone else who might run into a similar issue with the mesa Rectifier solo amp.
First off, the Mesa Dual, and Triple Rectifier Solo heads are to say it nicely, a major pain in the dick to work on. It doesn't matter if you have an old two channel, three channel, or multi watt. You're dealing with a thin dual sided pcb with very delicate and small traces because these amps came with all the bells and whistles and literally no rhyme or reason it seems to how or rather why it was laid out from schematic to physical board. You'll have a ferrite bead next to your diode bridge rectifier on the board and the ferrite bead is placed right by the input in the scheme. Optocouplers that are part of the channel switching matrix and a button load for nothing but to keep the amp stable.
Catch my drift? If you deal with normal tube amps or even a rediculous solid state amp with a pcb layout that flows from essentially input to output. The rectifier solo? I honestly believe Randall Smith nicked Mike Solano's SLO and decided to Germanize that amps schematic just to show how clever an engineer he was. Really.
Ok popping fuses and killing the rectifier tube? Check everything between the IEC receptacle and Rectifier switch. White neutral, black hot. Reflow the solder joints even if they appear good. Test the PT for a short each red leg should read 340VAC (I'm assuming you don't need hand holding here otherwise this is not the amp to learn on unless you're insane and poor like I am. 25 years Marshall 3210, 1959, 2203, Randall rh200 for a couple months the 3channel dual rec. I'm my own tech. Too easy to brick this amp if only a neophyte) red wire with black stripe 40vac, red/yellow earthed, browns shouldn't be connected. Yellow is 5VAC Green 3VAC, gen/yel earthed. Again reflow every solder joints even my amp worked flawlessly til I took it off standby at a gig and one of the bands before I played used my cabinet apparently and I didn't check it before I was about to play and took it off standby. Heard the zzzt and saw a powertube pop. Shut down before I smelt the ozone. Blew out two of the 4007 diodes that are part of the switching matrix and populate the board via shotgun taking out 6 adjoining resistors, two filter caps and carbonized the pcb of about a silver dollar sized spot on both sides of this lovely piece of "Art Through Technology". Did I mention there are parts on the pcb that have no serious reason the be smack dab center pcb when they obviously be best suited on the power side region of the board? Try spending a few months on forums and calling techs regionally to see if anyone had a ver G 3ch dual using a similar pcb cause heck when amp bugs are found they are sorted and new boards are created even in same version. Just so I could see what connected to what where and how it was routed so I could hard wire the bits and bobs back to make her breath fire and beat you with a baseball bat again. Which brings me back to the rectifier circuit again. Check all the diodes in the rectifier circuit en total. Reflow all joints as you go. After I put mine back together I wound up finding over 65 cold joints that were from the factory and I had to pokemon everything just for my own sake and ocd. Ok diodes. Apparently the diodes that were used for the 3 channel versions circa 2002-4 didn't like being near heat for extended times. So, if you see a diode close to a tube socket anywhere up to an inch away replace it and leave the legs a little long to the diodes(as there will be a few more than you're like) have some space 1/2"-3/4" should do. Seriously. My screw up took out a powertube socket, a tube, the 1k resistor to it and fuse. Normal stuff right? First power up post repair is when two diodes from said switching matrix about killed the amp amp had been gradually brought up on my cardiac too and as done as I was about 115Vac on the amp I heard the diode blow didn't see a spark or nothing but the pcb suddenly had a silver dollar sized black mark. And oh that lovely smell of burnt ozone and plastic. Honestly I didn't even see it happen I was looking at something else. My dvm or the variance maybe. The tube sockets are pcb mounted 🖕🏻🤬 and not even the heavy duty good kind of janky pcb mounted tube sockets but the el cheapo plastic ones. I guess they made up for that by making the control pots connected with badass perfectly pro level flown connections. So yeah. Diodes are way way too many and they're small guys. Really there's a lot on this amp that could stand to be beefed up via better board components. I'm not slagging Mesa at all as I get it. Sometimes manufactures have to use what they have on hand. How many fender or Marshall amps all use the exact same value components every time? I've been in enough 1959s and 2203s to know positively certain parts make it in and some amps have close but not spec parts. We're talking caps or resistors mostly. This amp I look at as most likely one that was assembled some Thursday morning in Petaluma, Ca in 2002 and the tech wiring it up was that weeks beer run guy before they all left at lunch to hit the surf starting their weekend and some *s!!t* got overlooked. It worked when it left the factory went right into the rig for Pitbull Daycares guitarist and he sold it to me in 2008. Worked perfectly until I made a rookie error before I flipped the amp to play mode and that's when all the stuff appeared. No worries. I got it fixed as well as some mods that got rid of some of the notes swell that amp has by design which allowed it to be able to get some percussive attack with palm damped chugging. Not anywhere like I would like (Engl), but it works til I can pick up something else.
Otherwise the amp is pretty straight forward. I have a schematic with part list I would like to upload if anyone wants/needs it. It's not multi watt but you can't get those until the company moves past that model. But I've been told the multi watts utilize something akin to the simulclass Mark amps with something like a step down transformer that allows the amps to drop in output power. (Look into Power Scaling as I bet it's closer to what the TUT books describe than anything else.)
Can someone explain how to up this file? (11pg pdf)
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