We had a 60s ac-30 piggy-back in our school band and the Guitarist/Vocalist would always manage to pull the amp off the cab and get the whole lit to fall face-flat in the stage. After a while it started making "strange" noises all on it's own so we opened her up and found that "Knucklehed" had managed to bend the chassis where the little valves sit so that the metal was touching them. We fixed it with a lump of wood and a hammer and some Russian valves from a Radio supplier. Best amp I had ever heard, the singer used to plug his mic into it when we played PA less pubs and parties. Then it when to VOX heaven after a huge fire destroyed the building we jammed and stored our gear in, even our "petty-cash" box for stix and strings and leads etc had been cracked open for it's contents( about £8)! Your video brought it all back...the best parts that is.
Dissimilar metals corrode differently. When joined it's called galvanic corrosion. I'm guessing as particular as you are about solder joints you all ready know that! 😊
I have the same model same year, I imagine. Work in progress. Got a new choke and a few other bits to replace. Mainly plate resistors which have gone high.
I tried to do some online research to discover the best fastener material to use when bolting/screwing aluminum to steel but conflicting information abounds. Apparently the aluminum invariably becomes the anode in the galvanic battery-pile in virtually any dissimilar metal combination, and so it's primarily the aluminum that oxidizes. Brass and copper are generally thought to be particularly bad choices for fastening aluminum to steel (although one website suggested using copper nails for fastening aluminum flashing, gutters and sidiing😳) but ordinary steel bolts are nearly as bad. Stainless steel would "seem" to be an ideal choice, but several websites noted that the type of stainless alloy is extremely important and some alloys will be much more galvanically active with aluminum than others. I did see one mention of stainless bolts that were specially plated with a mixture of zinc and aluminum flakes in order to prevent galvanic corrosion. There are of course prohibitions against using ordinary electrical outlets that have copper terminals in a home that was wired with aluminum romex cable, but the recommendations I found along those lines are hotly contested, with electricians and electrical engineers arguing about it. Anyway, what are the original bolts joining the two chassis panels made of, steel or brass? I don't think I clean them up and reuse them without doing a little research into more appropriate materials first. Some of the electrician types, including a few here in the comment field, are recommending using specific chemical formulations like "nialox" to treat the metal before you put it together but I don't know how well that will allow the two chassis to electrically bond.....
Lyle - make a cardboard template of the area you want to clamp and mark the holes - I’ll make you a clamp plate out of steel you can reuse for this task.
Hey Lyle, long time no comment! Have you ever thought about using Belleville washers for vibration and heat sensitive screws? I first became aware of them when I had to design a connection from current carrying conductors to a 250 deg C (482 deg F) heating element in a talc mill furnace. They handle thermal expansion and vibration significantly better than anything else I have come across.
Good eye Lyle. I know aluminum was cheap and light back then and the designers should have known about galvianic corrosion. I wonder if grounding wires from the steel chassis to the aluminum would help or cause more noise because of the "loops" it would create. Just asking.
Lyle, what about the possibility of painting the mating edges of the aluminum and steel with a conductive carbon- containing paint like they use to shield the body cavity of guitars?
I'm curious Lyle, much like looking at photographs of oneself from 10+ years ago, do you find yourself wondering 'What was I thinking?' much when you get to work on something again after that long? I imagine your knowledge and skills have increased in the intervening time, but do you find much fault in what younger you did then?
What is the purpose of 100 ohm screen grid resistors? That's too small of a value to drop voltage or be of any use with controlling current or oscillations.
Generally, dissimilar metals should ideally be buffered or isolated from contacting each other. For example, with Ampeg SVTs (non-rack-mount types) the preamp section with the aluminum housing/tray and face plate is physically separate--other than a wire connection with Molex type plug--from the power/output section of the amp which has a painted steel chassis enclosure. The two sections are mounted separately to the Tolex'd plywood outer shell. Preamp section up top. Power section on the bottom.
Lol, but..... galvanic action would actually prevent moss and lichens from growing on the chassis. Just as antifouling paint containing copper is used to paint the bottom of boats to prevent algae and barnacles from growing on it, and inboard or outboard motors will have a sacrificial zinc tab on the submerged parts so that the steel, aluminum, and brass parts of the propeller drive mechanism don't degrade.
We had a 60s ac-30 piggy-back in our school band and the Guitarist/Vocalist would always manage to pull the amp off the cab and get the whole lit to fall face-flat in the stage. After a while it started making "strange" noises all on it's own so we opened her up and found that "Knucklehed" had managed to bend the chassis where the little valves sit so that the metal was touching them. We fixed it with a lump of wood and a hammer and some Russian valves from a Radio supplier. Best amp I had ever heard, the singer used to plug his mic into it when we played PA less pubs and parties. Then it when to VOX heaven after a huge fire destroyed the building we jammed and stored our gear in, even our "petty-cash" box for stix and strings and leads etc had been cracked open for it's contents( about £8)! Your video brought it all back...the best parts that is.
I learn something new every video. Keep them coming please.
Stash-o-shit…. i’d buy that for a dollar!
😅😂😅
It’s cool you used this amp for a video. You didn’t HAVE to show evidence of a typical amp tech learning curve. Kudos.
Good to hear that a pro like you are also still learning and making new observations!
I love my AC-30, truly a magical amp
11 years between drinks? Not too shabby 🍻
Reinforcement of chassis is a great idea😉👍👍
Can't wait to see the results and hear this one😃👍
😎✌👍❤🖖
Hey Lyle, if you call it die scheissenstache, you can charge substantially more to clean it. Some guy named Reinhold told me that..
As a person whose second language is German, I absolutely cracked up when I read your comment!! 😂
Dissimilar metals corrode differently. When joined it's called galvanic corrosion. I'm guessing as particular as you are about solder joints you all ready know that! 😊
Smear a little noalox between layers, might help.
@@digthisbigcrux Dow Corning (DC 4) now Molykote, works amazingly in applications like this. I put that $hit on everything.
@59panelvan just like Frank's hot sauce 🤣🤣
@digthisbigcrux noalux is an electricians best friend. I was thinking the same thing.
I like the hardware upgrades you are proposing. It will be fun to see it get all the upgrades and repairs.
Hearing stash-o-shit made me cough/laugh the coffee outta my mouth 😂 thanks for another enlightening video Lyle
I have the same model same year, I imagine. Work in progress. Got a new choke and a few other bits to replace. Mainly plate resistors which have gone high.
I tried to do some online research to discover the best fastener material to use when bolting/screwing aluminum to steel but conflicting information abounds. Apparently the aluminum invariably becomes the anode in the galvanic battery-pile in virtually any dissimilar metal combination, and so it's primarily the aluminum that oxidizes. Brass and copper are generally thought to be particularly bad choices for fastening aluminum to steel (although one website suggested using copper nails for fastening aluminum flashing, gutters and sidiing😳) but ordinary steel bolts are nearly as bad. Stainless steel would "seem" to be an ideal choice, but several websites noted that the type of stainless alloy is extremely important and some alloys will be much more galvanically active with aluminum than others. I did see one mention of stainless bolts that were specially plated with a mixture of zinc and aluminum flakes in order to prevent galvanic corrosion.
There are of course prohibitions against using ordinary electrical outlets that have copper terminals in a home that was wired with aluminum romex cable, but the recommendations I found along those lines are hotly contested, with electricians and electrical engineers arguing about it. Anyway, what are the original bolts joining the two chassis panels made of, steel or brass? I don't think I clean them up and reuse them without doing a little research into more appropriate materials first. Some of the electrician types, including a few here in the comment field, are recommending using specific chemical formulations like "nialox" to treat the metal before you put it together but I don't know how well that will allow the two chassis to electrically bond.....
Lyle - make a cardboard template of the area you want to clamp and mark the holes - I’ll make you a clamp plate out of steel you can reuse for this task.
Fender washers in a Vox. Dogs and cats living together. A sign of the times?
🤣🤣🤣
Is that Ampism!?
Love the “Stash-o-shit” comment!😂
Hey Lyle, long time no comment! Have you ever thought about using Belleville washers for vibration and heat sensitive screws? I first became aware of them when I had to design a connection from current carrying conductors to a 250 deg C (482 deg F) heating element in a talc mill furnace. They handle thermal expansion and vibration significantly better than anything else I have come across.
Now that's pretty dirty! Thanks for sharing.
T-shirts should be made of your latest trademark.😂
Good eye Lyle. I know aluminum was cheap and light back then and the designers should have known about galvianic corrosion. I wonder if grounding wires from the steel chassis to the aluminum would help or cause more noise because of the "loops" it would create. Just asking.
Lyle, what about the possibility of painting the mating edges of the aluminum and steel with a conductive carbon- containing paint like they use to shield the body cavity of guitars?
I hear Stash-o-Sh*t is playing Coachella this year. I think Bend the Flange Back is opening for them...
Stash-o-shit is already owned by mesa
Hahahaha!!
Lyle and Brad shd print up Mesa Doodie shirts or similar..
Triple Rectalfied?
I'm curious Lyle, much like looking at photographs of oneself from 10+ years ago, do you find yourself wondering 'What was I thinking?' much when you get to work on something again after that long? I imagine your knowledge and skills have increased in the intervening time, but do you find much fault in what younger you did then?
Can you please do a video on how to check resistors for drift?
Does that anti corrosion goo they use on household load centers help?
Such a strange layout for an amp. Always cool to see these things though.
Nice video. Galvanic corriosion was predictable i guess though.
What is the purpose of 100 ohm screen grid resistors? That's too small of a value to drop voltage or be of any use with controlling current or oscillations.
Maybe all the fluff, debris (Stash-o-shit) was there to dampen vibration??
Hope the old Mullards are still kicking...same Bat time, same Bat channel!!
Wouldn’t it be best to build the amp from just one type of metal with different thickness to avoid the corrosion?
Generally, dissimilar metals should ideally be buffered or isolated from contacting each other.
For example, with Ampeg SVTs (non-rack-mount types) the preamp section with the aluminum housing/tray and face plate is physically separate--other than a wire connection with Molex type plug--from the power/output section of the amp which has a painted steel chassis enclosure. The two sections are mounted separately to the Tolex'd plywood outer shell. Preamp section up top. Power section on the bottom.
SOS = Stash-O-S...
Tried Zener on screengrids? Like 20V
To the owner, where the heck are you storing this amp!? Sheesh.
Looks Ike it was stored (and used) in a barn.
If you don't clean the amp, it will used as proof for evolution in a couple of years. Not too far away from having lichens and moss growing there,
Lol, but..... galvanic action would actually prevent moss and lichens from growing on the chassis. Just as antifouling paint containing copper is used to paint the bottom of boats to prevent algae and barnacles from growing on it, and inboard or outboard motors will have a sacrificial zinc tab on the submerged parts so that the steel, aluminum, and brass parts of the propeller drive mechanism don't degrade.
Whats wrong with sm mica cap ?
From experience, Lyle says that the mica caps marked SM sometimes fail.
The connections need de-ox.
Under the sea, under the sea, where amps are wetter, darling its better, cause they are so rustee.