It's unsettling yet somehow reassuring to know that I'm going to make mistakes as a new hobby builder. I have an AX84 build under my belt and do the servicing on a couple of smaller tweed clones I own (Victoria 5112 & Blankenship Fatboy). I'm about armpit deep into building a BFDR head and am feeling the stress. I think the ease of putting the AX84 together gave me the wrong impression of the actual complexity in amp construction once you go past a single power tube. Love what you're doing on this channel.
New and exciting mistakes! Love it! I tell my students the same thing. As long as you don't lose life or limb, there is no learning substitute for an honest mistake.
The problems with old tweed amps are well documented. A kit amp opens the opportunity for the introduction of all new problems. Having said that, I still think they are worth the challenge of learning something new...
Sparkler tip: Resistors can conduct/short through their body to other parts. The resistor coatings are not to be considered non-conductive. In short don't touch or let yer resisters touch.
Hi Psionic audio! Love this video love your channel I am subscribed! Thank you for sharing your years of expertise, and for being honest/accurate when explaining all things about amps! Quick question: what is your opinion on class D amps (eg: Seymour Duncan, power stage, quilter, etc). I am currently using the 50 W “the amp” buy milkman sound, and it works and sounds good for the music that I do. Hope to hear from you take care !
I have built a few weber and mojotone kits and the board mounting is always iffy. So many mistakes I've made... On a weber princeton, I had a coated black screws mounting the board to the chassis so close to the high wattage bias resistors, it arched to the nearest eyelet and was detectable with my stereo-scopic toast-o-meters. On my last Mojotone Vibrochamp build, I drilled my own holes (almost had to and probably should have pulled the OT) and went with some plastic push through standoff snappy thingies that you see on car accessory replacement plastic bit assortments. Shady I know, but since I have made mounting mistakes in the past that led to arching, and I made the amp for a close friend who might want to do more mods and pull thr board down the road, I went with the plasic fasteners and I was really proud of that. Now with the release of this video, my braggadocio recurs. Wish I could post some pics of these here...
You’re correct. Mojotone does not drill the fiberboard or chassis for mounting screws. It’s one of my gripes with their kits/boards, but simple enough to rectify. Well, if you know how to rectify it anyway. I build my “vintage replica” amps like they came from the factory. Sheet metal screws and all. The research took a lot longer to do than one would think. Thankfully, I found very helpful people with original amps on forums and CZcams that helped out considerably.
Gidday Lyle! Geez, she's a flappin in the breeze! Yeps, I reckon you've nailed it mate! Even you yourself said that - "the board had moved from where it was yesterday". So yeah, I'm givin you the cigar for this one! So, do reckon that incorrect, short blast of ac to a grid, or wherever it went, could've caused that valve to go slightly microphonic? - or had you noticed that earlier? It just seems a little coincidental that the same valve is involved. Is the board actually bolted to the chassis anywhere, or is it only supported by the external wiring? I wonder do the instructions specify this? Do the instructions warn the builder of possibility of this short happening? In the overhead view of the board & chassis it looks to me like the board could easily be made say, a half inch narrower, & still have heaps of width to accommodate all the components - even the filter caps? I think it might be an idea to write to Mojotone (?) to inform them of this deficiency in their design, & suggest they change it accordingly. It doesn't seem like a major, expensive change, but one that would eliminate the possibility of this ever happening. You found the problem in a matter of minutes, but imagine the sheer panic of an inexperienced builder with his brand new amp humming it's tits off? I think if you sent the letter rather than the customer, this suggestion might be taken more seriously by the supplier. The other thing is, if one of the valves is slightly microphonic already, with the amp being brand new, is it likely to get even worse down the track? I'm just wondering if the customer should push for a replacement valve? Great video mate, thanks! 👏
I blew a capacitor yesterday working on my most complex amp build yet, I had 100v on the cathode, that sucker went off like a 22 magnum, I didn't have the ground wire connected on the grid leak resistors for the power tubes. All that voltage went right to the cathode and a big pop. I was testing something else, I should have looked alittle closer. I'm building a super reverb with the channels coupled together, to make it 1 channel and my master volume controls V2, so it's gets double the gain when u turn both volumes up. It gets loud, really loud, tons of headroom.
Great Channel, have you heard of, and would you consider doing a review of the Monoprice stage right 15 watt all tube amplifier? They are less than $250, come in a nice cabinet with a nice handle, celestion 12-in speaker, 3 12ax7's and two el-34s I think that's right spring reverb, it's great......... for the price.
A nice little nod to "Airplane". lolI am going to build a 1987 style ampusing. Hoffman board and his "hot mod". I would be grateful if you could post the YT links to the videos you did on proper grounding for Marshall amps.
@@goldenboy8167 Thanks for that tip, JoJo! It seems like Burbank is the capital of amp repairs. I used to take my amps to a place called Kruse Kontrol Amplification which was also in Burbank. Sadly, for me, the owner of that business closed shop and returned to Germany. I will look up Bob the next time I need repairs.
Many of Mojotone's chasses come with warnings such as "Modifying or drilling this chassis will compromise the chrome finish. Flaking or peeling of the chrome may occur." This leaves some kit builders with damage if they drill new holes to secure boards. The 5E8-A chassis is one of these. Amplified Parts stocks chasses with the same finish and lack of sufficient mounting holes, but on the 5E3, it's the round hole for the power cord that particularly irks me. Either do all the work for me, or give me a chassis i can modify without ruining the finish.
I fail to see how drilling a hole in the chassis underneath the eyelet board would compromise the chrome plating, at least not anywhere that it'd be visible from outside the amp. Unless the chrome was so poorly bonded to the chassis that drilling a hole in it would allow moisture to get under the chrome and cause it to peel somewhere else,, a number of inches away from the non-original, hand-drilled hole. This seems unlikely.
@@goodun2974 The chrome is extremely poorly bonded. There are forum posts about it - the plating separates and seems to "fracture" in a spider web pattern.
@@goodun2974 It makes no sense to burden the buyers with that question. Why do reputable companies like Mojotone and CE Distribution/Amplified Parts sell such poorly made chasses? They're the ones who ought to be doing better.
@@stevencraig , well, the manufacturers definitely need to be called out on this, but ultimately the end users who buy these things are enabling shoddy manufacturing and *dangerous electrical practices* to continue. Buyers should complain to the companies until the product is improved; and since the problem is purported to be "well-known" in the kit-building community, builders should boycott the Mojo and CDE chassis in favor of a different supplier, if possible; alhough granted this might be difficult considering the current supply-chain issues. Does Hoffman get their chassis from MOJO or CDE, or from somewhere else? Other recommended suppliers? Anyway, chrome that flakes off is one thing, but AN UNMOUNTED AND UNSECURED BOARD WITH HIGH VOlTAGE ON IT IS DANGEROUS! No factory-assembled electrical or electronic device would pass UL testing with an unsecured board; and although a product sold as a kit likely doesn't fall under the usual UL or other electrical testing procedures, the potential for electrical shock or fire is high. This should not be allowed to continue. Perhaps Mojo can come up with some type of retrofittable insulating standoffs/mounting hardware that are glued to the chassis under the eyelet board with high temperature epoxy? The only other recourse is to drill your own holes. If it was me I would probably drill holes as needed, but I guess this raises the specter of chrome flaking off and causing short circuits.
I have a rolling chair and I was inside a chassis, checking voltages in an initial power up of a new build. I inadvertently rolled my chair a couple of inches and rolled over a stray piece of bubble wrap. The rapid popping of the air cells came as close to a heart attack as I think I've ever been. Even though I've done it tons of times and I always am very aware of where my hands/fingers/probes are, I still get butterflies a little. Out of curiosity Lyle, do you ever get butterflies when working on amps anymore?
Thank you so much for these videos! I am considering building a kit amp... do you have any recommendations on kits or things to watch for? It would be a great video to hear your opinions!
@brenthorrocks Gidday Brent! I was lookin around at stuff & there was a 'british jtm45' kit that looked pretty cool with quite good documentation, & quite a few mod options available. I probly would have bought myself one had I not already spent about $600AUD on a pos epiphone amp that I'm having to rebuild & modify.
I know that the design of the amp has that inherent issue with the board standing too far out and unsupported, but couldn't the owner just tilt/angle one side of the resistor away so the leg is farther from the other component? Perhaps that might be an easier fix than taking it apart?
Just curious, in this day in age of litigation and people not taking personal responsibility. What levels of indemnity do amplifier technicians need to take on to protect themselves from lawsuits?
I'd guess no. glue in a hidden spot, like underneath a board makes service work hard or nearly impossible , plus hot glue is going to melt at some point.
Glad it happened while you had it because otherwise it would’ve happened as SOON as he got the amp home. Never while testing it when he picks it up. Dang gremlins have a sense of humor.
Why not re-position that horizontally mounted resistor a bit further from the vertically mounted one that is suspect? Give it maybe 1/2" gap from the one mounted on that flexing board.....
This was a rare case where I was hired more to diagnose than to do the work. The owner wants to do it. The only charge I made was 22k instead of 56k to get the bias out of the freezer.
The one on the preamp tube socket is the cathode follower plate load resistor. The pairs of 100ks are for both plate loads of the first two preamp tubes as well as I think “mixer” resistors for the channels.
Are used to advertise that I would rescue botched Amp Build’s, but I no longer do that. I usually have to end up completely tearing down and rebuilding the amp and that’s a huge time suck
Yeah mate I've had to do the same thing with a dodgy car transistor amp (on a pcb) for an old school mate. No way could I charge him correctly for all the time involved. It would be a much bigger nightmare in a valve amp! I guess you could charge them say, 200 bucks for a quick, minimum spec 'just get it going' rebuild, or 400 bucks for proper job? But yeah, I'd hate to have to do the quick fix repair though. Not always a comfortable choice when you're trying to make a living.
While a single 5U4 can supply enough current for a pair of 6L6s, there's a significant voltage drop across the tube. Fender chose to parallel two 5U4s to reduce the voltage drop. A fortunate byproduct: roughly half as much current in each plate in this configuration. So they run cooler and last longer. In later versions of the Twin, a quad of 6L6s was fed by a single GZ34. Even later, the quad was fed by a solid state diodes.
This is Exhibit A as to why you generally prefer to not work on kits. Although you can take comfort in the knowledge that you may have saved somebody from a smoke-show.
Mojo has some pretty horrible documentation and seem to keep bad design features out of "authenticity." Their 6g16 Vibroverb instructions still wires the standby switch before first filtering node.
Sounds like Mojotone doesn't have their shit together. Watching this series, it's like they a) defaulted to the original circuit design, not accounting for discoveries made that would make the amp safer and better; and b) have shitty directions/resources. Lyle, any intel on who makes quality kits?
Why am I looking at every Electrolytic Capacitor on the fiber board oriented with the positive down EXCEPT the farthest one? This is a KIT? Big mistake to prank builders that way.
@@robotsongs , At first glance I thought it meant potentially fatal to the owner/player and not merely fatal to the amplifier itself. So maybe not an accurate descriptor of the fault that was found......
This is why the eyelet cardboard boards sucks. I'm so sorry, I love vintage and vintage-looking stuff but this kind of boards are the worst, they are a pain in the ass. Probably the worst and unsecure way to build a board for an guitar amp.
Double bonus points for the Airplane! reference!
Roger, Roger. What's our vector, Victor?
I picked the wrong day to stop sniffing glue...
1:48-2:18 we are all holding our breath, listening hard. Better suspense than Alfred Hitchcock ever devised, I say.
Never has it become more clear than here...that the small details matter the most.
Glad you're on it Lyle.😎👍
It's unsettling yet somehow reassuring to know that I'm going to make mistakes as a new hobby builder. I have an AX84 build under my belt and do the servicing on a couple of smaller tweed clones I own (Victoria 5112 & Blankenship Fatboy). I'm about armpit deep into building a BFDR head and am feeling the stress. I think the ease of putting the AX84 together gave me the wrong impression of the actual complexity in amp construction once you go past a single power tube. Love what you're doing on this channel.
I thought I was the only one still saying clearance Clarence. ❤
New and exciting mistakes! Love it! I tell my students the same thing. As long as you don't lose life or limb, there is no learning substitute for an honest mistake.
I just love watching a master at his work. And the narration... Priceless.
Outstanding diagnosis.
The problems with old tweed amps are well documented. A kit amp opens the opportunity for the introduction of all new problems. Having said that, I still think they are worth the challenge of learning something new...
I learn from you. Could never thank you enough. ☮️❤️😊
Its all about clearance..... Clarence. Brilliant Airplane reference!
Great work as usual. And yep His work looks nice in this MJT Kit.
500th thumbs up. Clean and neat... Cheers!
Sparkler tip: Resistors can conduct/short through their body to other parts. The resistor coatings are not to be considered non-conductive. In short don't touch or let yer resisters touch.
Clearance Clarence . Roger Roger. 🖖
Hi Psionic audio! Love this video love your channel I am subscribed! Thank you for sharing your years of expertise, and for being honest/accurate when explaining all things about amps! Quick question: what is your opinion on class D amps (eg: Seymour Duncan, power stage, quilter, etc). I am currently using the 50 W “the amp” buy milkman sound, and it works and sounds good for the music that I do. Hope to hear from you take care !
Well said about identifying screw ups because you've done it yourself.
I have built a few weber and mojotone kits and the board mounting is always iffy. So many mistakes I've made... On a weber princeton, I had a coated black screws mounting the board to the chassis so close to the high wattage bias resistors, it arched to the nearest eyelet and was detectable with my stereo-scopic toast-o-meters. On my last Mojotone Vibrochamp build, I drilled my own holes (almost had to and probably should have pulled the OT) and went with some plastic push through standoff snappy thingies that you see on car accessory replacement plastic bit assortments. Shady I know, but since I have made mounting mistakes in the past that led to arching, and I made the amp for a close friend who might want to do more mods and pull thr board down the road, I went with the plasic fasteners and I was really proud of that. Now with the release of this video, my braggadocio recurs. Wish I could post some pics of these here...
You’re correct. Mojotone does not drill the fiberboard or chassis for mounting screws.
It’s one of my gripes with their kits/boards, but simple enough to rectify. Well, if you know how to rectify it anyway.
I build my “vintage replica” amps like they came from the factory. Sheet metal screws and all. The research took a lot longer to do than one would think. Thankfully, I found very helpful people with original amps on forums and CZcams that helped out considerably.
I recently refurbished a 30 year old PCB amp. The traces would frequently come off the board with only a little heat from the soldering iron.
Gidday Lyle! Geez, she's a flappin in the breeze! Yeps, I reckon you've nailed it mate! Even you yourself said that - "the board had moved from where it was yesterday". So yeah, I'm givin you the cigar for this one!
So, do reckon that incorrect, short blast of ac to a grid, or wherever it went, could've caused that valve to go slightly microphonic? - or had you noticed that earlier? It just seems a little coincidental that the same valve is involved.
Is the board actually bolted to the chassis anywhere, or is it only supported by the external wiring? I wonder do the instructions specify this? Do the instructions warn the builder of possibility of this short happening?
In the overhead view of the board & chassis it looks to me like the board could easily be made say, a half inch narrower, & still have heaps of width to accommodate all the components - even the filter caps?
I think it might be an idea to write to Mojotone (?) to inform them of this deficiency in their design, & suggest they change it accordingly. It doesn't seem like a major, expensive change, but one that would eliminate the possibility of this ever happening.
You found the problem in a matter of minutes, but imagine the sheer panic of an inexperienced builder with his brand new amp humming it's tits off? I think if you sent the letter rather than the customer, this suggestion might be taken more seriously by the supplier.
The other thing is, if one of the valves is slightly microphonic already, with the amp being brand new, is it likely to get even worse down the track? I'm just wondering if the customer should push for a replacement valve?
Great video mate, thanks! 👏
Super Sleuth!
Maybe MJTone was confused. "Floating tremolo" refers to the pitch bending device on the guitar, not the circuit board in the amp.
I blew a capacitor yesterday working on my most complex amp build yet, I had 100v on the cathode, that sucker went off like a 22 magnum, I didn't have the ground wire connected on the grid leak resistors for the power tubes. All that voltage went right to the cathode and a big pop. I was testing something else, I should have looked alittle closer. I'm building a super reverb with the channels coupled together, to make it 1 channel and my master volume controls V2, so it's gets double the gain when u turn both volumes up. It gets loud, really loud, tons of headroom.
Clearance ... Clarance! 🤘- how's the thumb/hand lately?
Great Channel, have you heard of, and would you consider doing a review of the Monoprice stage right 15 watt all tube amplifier? They are less than $250, come in a nice cabinet with a nice handle, celestion 12-in speaker, 3 12ax7's and two el-34s I think that's right spring reverb, it's great......... for the price.
Wow! That board was simply floating? Suspended by the wires? Good catch!
A nice little nod to "Airplane". lolI am going to build a 1987 style ampusing. Hoffman board and his "hot mod". I would be grateful if you could post the YT links to the videos you did on proper grounding for Marshall amps.
I wish you lived in the Los Angeles area. I would bring all of my amps to you for repairs. In my opinion, a man as knowledgeable as you is priceless!
Bob Dixon in Burbank. Amphole is the company name
@@goldenboy8167 Thanks for that tip, JoJo! It seems like Burbank is the capital of amp repairs. I used to take my amps to a place called Kruse Kontrol Amplification which was also in Burbank. Sadly, for me, the owner of that business closed shop and returned to Germany. I will look up Bob the next time I need repairs.
Also I had Roy Blankenship work on my JMP 2203. He's really good too. Just very busy!
Roy is excellent.
Many of Mojotone's chasses come with warnings such as "Modifying or drilling this chassis will compromise the chrome finish. Flaking or peeling of the chrome may occur." This leaves some kit builders with damage if they drill new holes to secure boards. The 5E8-A chassis is one of these.
Amplified Parts stocks chasses with the same finish and lack of sufficient mounting holes, but on the 5E3, it's the round hole for the power cord that particularly irks me.
Either do all the work for me, or give me a chassis i can modify without ruining the finish.
I fail to see how drilling a hole in the chassis underneath the eyelet board would compromise the chrome plating, at least not anywhere that it'd be visible from outside the amp. Unless the chrome was so poorly bonded to the chassis that drilling a hole in it would allow moisture to get under the chrome and cause it to peel somewhere else,, a number of inches away from the non-original, hand-drilled hole. This seems unlikely.
@@goodun2974 The chrome is extremely poorly bonded. There are forum posts about it - the plating separates and seems to "fracture" in a spider web pattern.
@@stevencraig , well, that sucks! And people buy such poorly made chassis why?
@@goodun2974 It makes no sense to burden the buyers with that question. Why do reputable companies like Mojotone and CE Distribution/Amplified Parts sell such poorly made chasses? They're the ones who ought to be doing better.
@@stevencraig , well, the manufacturers definitely need to be called out on this, but ultimately the end users who buy these things are enabling shoddy manufacturing and *dangerous electrical practices* to continue. Buyers should complain to the companies until the product is improved; and since the problem is purported to be "well-known" in the kit-building community, builders should boycott the Mojo and CDE chassis in favor of a different supplier, if possible; alhough granted this might be difficult considering the current supply-chain issues. Does Hoffman get their chassis from MOJO or CDE, or from somewhere else? Other recommended suppliers? Anyway, chrome that flakes off is one thing, but AN UNMOUNTED AND UNSECURED BOARD WITH HIGH VOlTAGE ON IT IS DANGEROUS! No factory-assembled electrical or electronic device would pass UL testing with an unsecured board; and although a product sold as a kit likely doesn't fall under the usual UL or other electrical testing procedures, the potential for electrical shock or fire is high. This should not be allowed to continue.
Perhaps Mojo can come up with some type of retrofittable insulating standoffs/mounting hardware that are glued to the chassis under the eyelet board with high temperature epoxy? The only other recourse is to drill your own holes. If it was me I would probably drill holes as needed, but I guess this raises the specter of chrome flaking off and causing short circuits.
I'm going to be building a 5E8-A in the next few weeks. We'll see how badly I do....
I have a rolling chair and I was inside a chassis, checking voltages in an initial power up of a new build. I inadvertently rolled my chair a couple of inches and rolled over a stray piece of bubble wrap. The rapid popping of the air cells came as close to a heart attack as I think I've ever been. Even though I've done it tons of times and I always am very aware of where my hands/fingers/probes are, I still get butterflies a little. Out of curiosity Lyle, do you ever get butterflies when working on amps anymore?
"Only new and exciting mistakes" quotable
I’d love to hear how Leo grounded these. Brass plate?
Thank you so much for these videos! I am considering building a kit amp... do you have any recommendations on kits or things to watch for? It would be a great video to hear your opinions!
@brenthorrocks Gidday Brent! I was lookin around at stuff & there was a 'british jtm45' kit that looked pretty cool with quite good documentation, & quite a few mod options available. I probly would have bought myself one had I not already spent about $600AUD on a pos epiphone amp that I'm having to rebuild & modify.
Maybe insulation on the wire of the resistor would help
What sound is it when the over drive sounds funky.....fizzy and as you turn up the lar mar ppimv a 1/3 of the way its piercing high notes
"only new and exciting mistakes" - I'm going to have to quote you on that one. Are there license fees to pay?
one thing is for sure, those speakers are definitely worn-in (in a good way) ... heck I should bring you my amps just to have THAT done
Ars axial filter caps in the 32u range....are they any good...they seem smaller than f and t
I know that the design of the amp has that inherent issue with the board standing too far out and unsupported, but couldn't the owner just tilt/angle one side of the resistor away so the leg is farther from the other component? Perhaps that might be an easier fix than taking it apart?
Just curious, in this day in age of litigation and people not taking personal responsibility. What levels of indemnity do amplifier technicians need to take on to protect themselves from lawsuits?
That's a Roger on t he vector Victor over over
What's the vector, Victor?
Could this be fixed by using hot glue and just tack it to the chassis? great video, thank you!!
I'd guess no. glue in a hidden spot, like underneath a board makes service work hard or nearly impossible , plus hot glue is going to melt at some point.
@@gregdude92 thanks for the reply!
Glad it happened while you had it because otherwise it would’ve happened as SOON as he got the amp home. Never while testing it when he picks it up. Dang gremlins have a sense of humor.
Why not re-position that horizontally mounted resistor a bit further from the vertically mounted one that is suspect? Give it maybe 1/2" gap from the one mounted on that flexing board.....
This was a rare case where I was hired more to diagnose than to do the work. The owner wants to do it. The only charge I made was 22k instead of 56k to get the bias out of the freezer.
What are those tan resistors with the white stripes? ...and it looks like there are 4 series pairs of preamp plate resistors?
The one on the preamp tube socket is the cathode follower plate load resistor. The pairs of 100ks are for both plate loads of the first two preamp tubes as well as I think “mixer” resistors for the channels.
Are used to advertise that I would rescue botched Amp Build’s, but I no longer do that. I usually have to end up completely tearing down and rebuilding the amp and that’s a huge time suck
Yeah mate I've had to do the same thing with a dodgy car transistor amp (on a pcb) for an old school mate. No way could I charge him correctly for all the time involved. It would be a much bigger nightmare in a valve amp!
I guess you could charge them say, 200 bucks for a quick, minimum spec 'just get it going' rebuild, or 400 bucks for proper job? But yeah, I'd hate to have to do the quick fix repair though.
Not always a comfortable choice when you're trying to make a living.
@@nevillegoddard4966 preach!
What's the deal with the two rectumfrier tubes? I missed a video, right--this was already explained?
While a single 5U4 can supply enough current for a pair of 6L6s, there's a significant voltage drop across the tube. Fender chose to parallel two 5U4s to reduce the voltage drop. A fortunate byproduct: roughly half as much current in each plate in this configuration. So they run cooler and last longer. In later versions of the Twin, a quad of 6L6s was fed by a single GZ34. Even later, the quad was fed by a solid state diodes.
Here's to new and exciting mistakes....
This is Exhibit A as to why you generally prefer to not work on kits. Although you can take comfort in the knowledge that you may have saved somebody from a smoke-show.
Mojo has some pretty horrible documentation and seem to keep bad design features out of "authenticity." Their 6g16 Vibroverb instructions still wires the standby switch before first filtering node.
So did this model. I gave the owner the heads up on that fix.
Sounds like Mojotone doesn't have their shit together. Watching this series, it's like they a) defaulted to the original circuit design, not accounting for discoveries made that would make the amp safer and better; and b) have shitty directions/resources.
Lyle, any intel on who makes quality kits?
Why am I looking at every Electrolytic Capacitor on the fiber board oriented with the positive down EXCEPT the farthest one? This is a KIT? Big mistake to prank builders that way.
Love your videos, but please be careful with clickbait
It sounds like clickbait but it’s actually accurate. But yeah, right up on the line.
Is “poor kit instructions almost killed a tube” any better?
@@PsionicAudio thanks for replying; I'd say yes!
@@PsionicAudio I don't think "near fatal flaw" is clickbaity.
Hey, the algorithm must be fed!
@@robotsongs , At first glance I thought it meant potentially fatal to the owner/player and not merely fatal to the amplifier itself. So maybe not an accurate descriptor of the fault that was found......
This is why the eyelet cardboard boards sucks. I'm so sorry, I love vintage and vintage-looking stuff but this kind of boards are the worst, they are a pain in the ass. Probably the worst and unsecure way to build a board for an guitar amp.