Heartwork was the album that got me exploring more extreme music back in the 90s. This Mortal Coil is one of my warmup songs now too. Still love it after all these years
Desoldering all the output mosfets may have been the easiest way to get that board out, but it wont be easy to line up several dozen transistor leads with the holes/pads in the PCB for reassembly! Each row of mosfets should have had an aluminum strap bolted to them *before installing the board into the chassis* and then you could use machine screws from underneath the chassis gointo into threaded holes in the aluminum strap to pull the strap and attached mosfets down against the chassis, with some heatsink grease between them. A common assembly technique for hifi power amps.....
@@BradsGuitarGarage , Every now and then we do get lucky..... But regardless, I would happily strangle designers who come up with piss-poor mechanical assemblies like this.
Randall make some solid amps. I always wanted the original V2 version of this head, they sound brutal. Didn't Bruce Egnater design these ones? I know he did the Warhead 2 for Dime.
What are the little red-brown cylinders mounted to the board behind the big blue filter caps? Capacitors, or Wilkoman fuses? I've seen red-brown capacitors like that in a lot of older European hifi gear, and the bakelite shell develops microcracks and lets moisure in. If they're fuses, that's a bad way to utilize them because theyre typically soldered in place and so it would require massive disassembly to change them (although I see what looks like a white base underneath them and I suppose it could be a plug in socket if those are indeed fuses).
@@BradsGuitarGarage , yup, Wilkomman fuses or something similar. I've never seen them socketed, only soldered in place. BTW, there are also miniature fuses that look like a two-legged plastic transistor, sometimes seen in 70's/80's Japanese hifi gear.
Isopropanol is perfectly suitable naming; any alcohol can be named this way based on its carbon count: methanol, ethanol, propanol... Great job as usual Brad!
420w cure for constipation!! The cleans weren't as sterile as l was expecting... Good job mate... the silicon was orgasmic (there ya's go, splooge joke no1).👍🏼
Huh, I get free shipping from Mouser to Sweden, for orders over ~57 AUD, ships with fedex and takes 2-3 days. Weird that wouldn't apply to Australia, Sweden is hardly next to Texas 🙃
Gosh i couldve sworn those look like dry-joints @11:04 with the rings around the pads? Must be optical illusion on the vid. Nice work man, not for the faint-hearted.
Ive been using some really good 99.9% isopropyl on some boards recently, and I've noticed it sort of discolours the board, or maybe not so much discolours it, but it leaves almost like abit of a haze, have you ever noticed that with the strong alcohols at all?
Yes, that's some residue of flux left behind. Give it a few more rinses with clean alcohol and a cleaned brush. It gets less hazy each time. Then after 3 or so rinses, scrub off the remainder with a dry brush and it should look pristine.
@@BradsGuitarGarage, The hazy flux residue is much more noticeable if the board was manufactured with lead-free solder and you're cleaning it with alcohol. It's my understanding that leadfree fluxes were designed to be cleaned off with water, so perhaps distilled water would be the way to go, followed by alcohol at the end.
There is a repair cost/market price balance there, but if you're happy with the amp and the parts are generic / still available and the price is right, I think it's worthwhile. If there are tech who just refuse all S/S gear across the board, I'd suspect that perhaps they don't understand it.
you mentioned Egnater, my Tweaker 88 blew a few times before I gave up on it. I've heard it's usually a transformer issue, do you have any experience with them? Such a shame that an amp that nice should be so unreliable
Yes, they (not Bruce, the company who licensed his schematic and name) started cutting corners and cheaping out on the transformers. Replacements are available from Mercury Magnetics, however I suggest getting one sourced and installed by a tech whom is an authorised reseller, as they get great discounts and you'll likely get supply and installation for about the same price as the consumer retail cost of the transformer only.
A few classic hifi speakers such as the Quad electrostatic actually incorporate what is known as a "crowbar" protection circuit: if you exceed a certain input voltage a relay activates and short circuits the input of the speaker so that you won't blow the speakers, but unfortunately you might blow up your amplifier, especially if it's solid-state.
Kept waiting to hear some Heartwork during the demo. Honestly, like you said it’s not that bad at all construction-wise considering how many features it has going on and the ridiculous output. There’s definitely worse stuff out there that people would believe is infinitely better built than this amp.
How much actually makes it to the driver, though? You're talking 14-15 amps. You have 0.5 Ohms of combined cable and connector losses, you do the math.
Heartwork was the album that got me exploring more extreme music back in the 90s. This Mortal Coil is one of my warmup songs now too. Still love it after all these years
You’re damn right.
I am invested in that fender from last video
No matter how complex or simple A Randall is there's usually only one setting, You find it and leave it there forever.
Desoldering all the output mosfets may have been the easiest way to get that board out, but it wont be easy to line up several dozen transistor leads with the holes/pads in the PCB for reassembly! Each row of mosfets should have had an aluminum strap bolted to them *before installing the board into the chassis* and then you could use machine screws from underneath the chassis gointo into threaded holes in the aluminum strap to pull the strap and attached mosfets down against the chassis, with some heatsink grease between them. A common assembly technique for hifi power amps.....
I was dreading that, but they actually went straight back in.
I'm as surprised as you. Got a win for once!
@@BradsGuitarGarage , Every now and then we do get lucky..... But regardless, I would happily strangle designers who come up with piss-poor mechanical assemblies like this.
Great repair and playing too! Randall has some cool amps.
As a huge fan and friend of DUNN, I'll say Holy Crap...That thing is a beast 🤘 He will put it to good use 😁😁🔥🔥
I have that Maxon phase. I love it.
Sounds great. I love randall amps.
Randall make some solid amps. I always wanted the original V2 version of this head, they sound brutal.
Didn't Bruce Egnater design these ones? I know he did the Warhead 2 for Dime.
Something tells me you didn't watch the whole video. LOL!
@@BradsGuitarGarage I was just super excited to give you more engagement!
Also, hit the front end of that thing with a Maxon OD9 to make it tight as hell chuggz!!!
What are the little red-brown cylinders mounted to the board behind the big blue filter caps? Capacitors, or Wilkoman fuses? I've seen red-brown capacitors like that in a lot of older European hifi gear, and the bakelite shell develops microcracks and lets moisure in. If they're fuses, that's a bad way to utilize them because theyre typically soldered in place and so it would require massive disassembly to change them (although I see what looks like a white base underneath them and I suppose it could be a plug in socket if those are indeed fuses).
They're small radial fuses. I think they are on sockets, yes.
Marshall and others use them often, just soldered in place.
@@BradsGuitarGarage , yup, Wilkomman fuses or something similar. I've never seen them socketed, only soldered in place. BTW, there are also miniature fuses that look like a two-legged plastic transistor, sometimes seen in 70's/80's Japanese hifi gear.
Isopropanol is perfectly suitable naming; any alcohol can be named this way based on its carbon count: methanol, ethanol, propanol... Great job as usual Brad!
Strictly speaking, the preferred name is propan-2-ol...
Mahalo Brad! Interesting amp.
420w cure for constipation!!
The cleans weren't as sterile as l was expecting...
Good job mate... the silicon was orgasmic (there ya's go, splooge joke no1).👍🏼
Huh, I get free shipping from Mouser to Sweden, for orders over ~57 AUD, ships with fedex and takes 2-3 days. Weird that wouldn't apply to Australia, Sweden is hardly next to Texas 🙃
Gosh i couldve sworn those look like dry-joints @11:04 with the rings around the pads? Must be optical illusion on the vid. Nice work man, not for the faint-hearted.
They are riveted stakes for the source resistor standoffs.
Similar to that seen in some Peavey amps.
@@BradsGuitarGarage ah that makes sense
ATMega microprocessor... basically an Arduino controlled amp that's pretty neat
Yes, it's quite common.
Blackstar and many others use a similar arrangement.
Ive been using some really good 99.9% isopropyl on some boards recently, and I've noticed it sort of discolours the board, or maybe not so much discolours it, but it leaves almost like abit of a haze, have you ever noticed that with the strong alcohols at all?
Yes, that's some residue of flux left behind.
Give it a few more rinses with clean alcohol and a cleaned brush.
It gets less hazy each time.
Then after 3 or so rinses, scrub off the remainder with a dry brush and it should look pristine.
Yeah, similar to that!
You never get rid of the residue 100% until you buff it, essentially.
@@BradsGuitarGarage, The hazy flux residue is much more noticeable if the board was manufactured with lead-free solder and you're cleaning it with alcohol. It's my understanding that leadfree fluxes were designed to be cleaned off with water, so perhaps distilled water would be the way to go, followed by alcohol at the end.
Interisting. I'll give that a try next time. Thanks mate.
I'd been lead to believe that most techs won't work on SS amps and would generally suggest you tossed them out and get a new one. This gives me hope.
There is a repair cost/market price balance there, but if you're happy with the amp and the parts are generic / still available and the price is right, I think it's worthwhile.
If there are tech who just refuse all S/S gear across the board, I'd suspect that perhaps they don't understand it.
you mentioned Egnater, my Tweaker 88 blew a few times before I gave up on it. I've heard it's usually a transformer issue, do you have any experience with them? Such a shame that an amp that nice should be so unreliable
Yes, they (not Bruce, the company who licensed his schematic and name) started cutting corners and cheaping out on the transformers. Replacements are available from Mercury Magnetics, however I suggest getting one sourced and installed by a tech whom is an authorised reseller, as they get great discounts and you'll likely get supply and installation for about the same price as the consumer retail cost of the transformer only.
@@BradsGuitarGarage thanks mate
Can't wait to get this home and riff it, but howcome it never sounds as good as those clips you did when I play it? 😂
CARCASS!!!!!!!!!!!!!!!
Alaska shipping is awful 😖 I feel your pain 🤪
The connectors you forgot the name of are called JST.😉
I was into it real [too] serious until the " 2-ohm Crowbar " remark. Thanks for snapping me out of it.
You no like exaggerations?
A few classic hifi speakers such as the Quad electrostatic actually incorporate what is known as a "crowbar" protection circuit: if you exceed a certain input voltage a relay activates and short circuits the input of the speaker so that you won't blow the speakers, but unfortunately you might blow up your amplifier, especially if it's solid-state.
Kept waiting to hear some Heartwork during the demo. Honestly, like you said it’s not that bad at all construction-wise considering how many features it has going on and the ridiculous output. There’s definitely worse stuff out there that people would believe is infinitely better built than this amp.
Absolutely! It makes repair a bit of a pain, but it's pretty well thought out, overall.
2 ohm? Any Peavey from the1980's can run that all day, and smirk at you.💪
How much actually makes it to the driver, though? You're talking 14-15 amps.
You have 0.5 Ohms of combined cable and connector losses, you do the math.
@@BradsGuitarGarage Good God man! I don't do math! I was told there would be no math!😂
*Dad and mum, what planet are you from and what convinced you to pack up and leave. Yeah na?
Just different enough to not cop a copyright strike. LOL!
That amp is complicated to the point of silliness.
I like your videos, but you talk so fast, and my southern US ears have a hard time understanding you sometimes.
Sorry mate, there was a section where I spoke fast as a comedic thing to explain something that was kind of a tangent.
I normally don't do that.
I had the prototype for this amp. Was not impressed.