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Discussion in 'Shock Brother's DIY Amps' started by Henry, May 18, 2017.
Wally, I can't read the values on the schematic but it looks like a cathodyne phase inverter to me.
Rob, it has to be. With the ipad air, I just wasn't seeing the junction connecting the cathode to the grid of the power tube....but on a bigger screen I now see it. Maybe a cup of caffeine helps, too?!?
Thanksfor the comments and evaluation Rob and Wally. I had a good look at the 5f6a circuit diagram this morning to see if I could discern some similarity without a great deal of success.
As for a cathodyne phase inverter, you're referring to the part of the circuit that inverts the incoming AC into DC, correct? And I assume that the cathodyne part means the process occurs in one of the tubes.
I appreciate the suggestion for the mod Rob and what I'll do is get the amp running as it is designed and then I'll make the modifications.
Last night I installed the transformers, tube sockets, pots, input and output jacks and the switch.
The construction notes are a step by step process that can be difficult to interpret;
"Run the mains cable through the chassis grommet and cable tie the mains cable" I assume that means cable tie it to itself so it can't be pulled back through the grommet?
Anyway, I can smell the hot soldering iron and the Lamington calls.
Go Henry!.... that's a fine start...
"what I'll do is get the amp running as it is designed and then I'll make the modifications."
I think you're right on the cable tie.
I am right on the brink of pulling the trigger on one of these - may just scratch my itch. The classic tweed [5f1 - 5e3 etc] kits are way to expensive for me by the time I add currency conversion and shipping out here to Straya
Just finished a five hour session. I completed the power supply and started the output section. I think I've learned a bit more about the amp's design and it has mostly to do with the cost of power transformers that cannot be sourced locally.
One of the initial reasons I was inclined to buy a kit was by-passing possible errors in part selection (incorrect ratings and the like). One of the factors that deterred me was the kits I wanted needed to be shipped from overseas but the initial cost of some of the PTs plus the shipping made the exercise cost-prohibitive. Another Australian member (Fiat_cc, thanks mate) put me onto a guy in Melbourne who could supply most of the parts for a Haworth 5e3 kit but the numbers didn't stack up.
So Grant Wills, the developer of the Lamington, came up with a power supply that uses two smaller, cheaper locally available PTs that, wired together, deliver the 300 volts+ required to run these types of circuits. I enjoy these sorts of challenges and the discipline of continually reviewing what you've done, testing for continuity. What I guess isn't available with this particular exercise is the opportunity to throw a couple of photos out into the forum and have collective experience applied to them. Never mind, here's where I'm up to as of this afternoon...
And if you decide to pull the trigger old picker, I'm your man
thanks henry that's great to have someone who knows a bit more than me to bounce off - know nix about how these things work - but have done a deal of soldering, can build cabs blah blah and done a little chopsticking in live amps.
I am thinking though of maybe using 6v6's, incorporating a low power switch and using a hammond chassis - the early lams called 5/15 had that. no idea what mods would be needed but daresay circuits and diagrams will be around. Another Idea is to buy a fender frontman or similar and use the chassis / cab / speaker and do an Uncle Doug style build using the Lam circuit. You can buy em on evil bay at AU$60 -$80
From the looks of the tranny array and reading some of Darry'ls [valvetone] build threads on AGGH a few of the valvetones use a similar array of locally sourced units from jaycar / altronics
Some basic understanding of tube audio amps is necessary, imho....but the modern age of kit building does not stress this. At this site....http://www.valvewizard.co.uk/...you will see on the left hand a listing of the preamp, the phase inverter, the output section and the power supply. Have fun reading. Ime, this will make your experience with your amp much more fulfilling and rewarding.
...thanks henry that's great to have someone who knows a bit more than me to bounce off - know nix about how these things work - but have done a deal of soldering.
O dear, I hope I haven't mislead you Olepicker. I confess to a murky understanding of electronic theory and, like you, have done lots of soldering. I sorta meant that if I got this amp to work (not a surety by any measure) maybe I could help you stumble through the same process. Your comments have also intrigued me, can we be talking about different kits? The kit I sourced is from a Brisbane (Queensland, Australia) outfit, Valveheaven. It sounds to me like you're referring to an English operation. Anyway, like Wally observes, a basic understanding of tube amps is required but...not necessary. Seems to me to be a pity that the true understanding of these "redundant" technologies is a bit like coopering or smithing or writing longhand; skills and knowledge that need preserving but lack the glamour that attracts the young . I'll do my bit though I wouldn't describe myself as young, except if it was young and stupid, and then only the latter.
But sure OP, if you get a kit and have a crack then I'll help if I can
Finished the output stage and was well into the pre amp when this photo was taken.
I would have started the cabinet(s) as well but there was a big Sunday lunch next door and I didn't want to spoil the celebration with saws and drills.
Saved a huge F§€k up at the death of today's session. Written instructions are a real art, as is the reading of them. Mind you, if pressed to explain I may need to plead the fifth.
Whatever those are, trev333 - they look like they'd taste really good with a nice hot cup of coffee.
Those, good sir..are Lamingtons....
The lamington is a classic Australian culinary icon - easier to maker than an amp:
as you'll discover here
A brief history
They are not traditionally consumed with coffee. To get the full impact lamingtons should be accompanied with unsweetened tea - coffee is ok but overpowering-
Being able to follow this build through with you Henry will be of great help to me. Indeed it is valve heaven kits and designs I am looking at.
I found out today on the AGGH that Grant has a new design under development called the SOLO. It is a single ended design using an EL34. I believe it may use 6v6 and 6L6 as well for different power outputs and tones.
Thanks for that Old Picker, knowing my luck it'll be just the amp that I WAS after Never mind, such is the way of the world. I finished wiring the Lamington this evening so by my reckoning it took be between 12 and 14 hours. I estimate troubleshooting will take 12 to 14 weeks. But it was fun OP and from what you've written I don't know why you're holding off, maybe you've already got a good amp, don't have the time or space? Whatever, I can recommend the process as a great way to focus the mind.
These are some of the things that occurred to me while I was tinning and tipping;
SS amps and the evolution of digital technology shunted aside a group of highly trained specialists. All my acquaintance with electronic theory is post 60s. As I have come to superficially appreciate vacuum tube technology it seems almost like something you needed to have an intuitive feel for, although I'm sure there were tried and tested courses for the understanding of radio amplification and radar 101 etc back in the day. I think I could understand how someone who went through such training and the subsequent development of SS technologies (whilst being a part of that development) could resent the idea that 50 or so years later a bunch of dilettantes could go onto the internet (do they remember ENIAC, the tube 'puter?) and buy a step-by-step kit that might, just might (with a lot of help from folks who really know about this stuff), build a Tweed Deluxe. Without understanding much more than a diagram and how to turn a soldering iron on.
I re-evaluated how I thought of Leo Fender. Sure, I understood he was a radio-repairman/entrepreneur but I assumed his major contribution was two iconic guitar designs. Now that I understand a little more about his overall contribution I think his musical instrument amplification designs may be more important than the froth and bubble of the guitars, not wishing to take anything away from Leo, it's just a lopsided view I had from being a player rather than a technician.
I wondered what sort of a guy LF was to work for? When I was young and stupid I did some "process" work not exactly production line but the same manufacturing philosophy was applied. The idea that you could apply that to something like a musical instrument would be a hard compromise to reach as the "boss". The output over quality conundrum. I'm sure there are testaments to what Fender was like to work for but I've never encountered them so, as I was soldering, I wondered. I also have an interest in management styles and was interested to read about icons like Henry Ford, John Spedan Lewis, Lee Iacoca, Branson, Jobs, Sinclair, Dyson and Zuckerberg. I wondered how Leo approached his employees and coaxed or coerced them.
Also, how long did it take for one of the workers (weren't they mostly ladies?) to wire say a 5e3? As I said above, the Lammy took me 12 to 14 hours without making the damn thing work, that is, just to wire it. Assuming you had a trained operator were they wiring an amp a day, two? I'm sure there are output figures that can tell us Fender's production volumes throughout the 50s and up till the CBS sale but as I was sitting there soldering I thought of the (mainly women?) who did this job day in day out and wondered what they thought? I wondered if any of them had any interest in amplified music...
Anyway, pics or it didn't happen.
I'm worried about that last image. Something tells me that those cables shouldn't go across the transformer but I couldn't avoid it. One other thing Old Picker, the Lammington kit was complete. Nothing was missing, kudos to Grant Wills.
Now to get the bastard working...
Seems to be a lot of longish wires inside. Is there anything in the manual regarding how the wires should layout?
Improperly wired input and speaker jacks are common reasons new builds are silent.
Is there any hum or hiss at the speaker or is it truly silent?
Have you done a voltage chart? If so, did you hear any pops as the voktages were checked? Starting at the power tubes plates and working back through the circuit toward the input preamp, one should hear increasingly louder pops at each stage with the input preamp pop being the loudest. If you don!t hear a pop at any point along the way,.you have found a problem area. This test is as old as tube amplication is.