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Post by markfromhawaii on Mar 2, 2023 12:22:11 GMT -5
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Post by Peegoo 🏁 on Mar 2, 2023 14:49:10 GMT -5
I've gone back and forth on it; we kicked it around earlier in the thread. Diodes do not provide the 'soft start' a tube does, but many builders think it's really not a problem. I did add the Merlin DCCF Mod to V2 per Pete's recommendation in post #18. I installed diode rectification in my Princeton Reverb back in 2010; it has no standby switch and it has not caused any weirdness with any of the tubes.
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pdf64
Wholenote
Posts: 557
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Post by pdf64 on Mar 3, 2023 4:48:30 GMT -5
He builds nice amps but that article is a complete waste of time and data, it contains a factual error and contradicts itself. “ By the time the 5Y3 conducts high voltage, the tubes are heated and ready to conduct” is plain wrong, a 5Y3 conducts with 5 seconds of power up, the other valves take around 20-45 seconds. He vacillates from standby has no technical benefit, eg “ a standby switch is a convenience supplied to guitar amps … So why do amps have standby switches? They are installed as a convenience for the operator … high quality tube stereo amps, like those made by McIntosh also don’t have standby switches. Remember that many stereo tube amp connoisseurs and audiophiles use these kinds of amps sans standby switches. I have never read an issue about the lack of standby switches on stereo tube amps” to “ Always use a standby switch when dealing with a solid state rectified amp. The immediate surge of high voltage on a tube isn’t the best for its long-term life. Power on your amp, then wait a minute or so and engage standby switch to the run position.“ DrZ models with valve rectification and a standby switch use a hot switching arrangement. Which is pointless and puts significant stress on the rectifier every time the switch is flipped from standby to operate mode. I suggest to avoid using standby with such amps.
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Post by Peegoo 🏁 on Mar 9, 2023 8:32:46 GMT -5
Itching to get this thing started.
I'm awaiting some resistors that were backordered...most all parts suppliers are having their own supply issues.
The good thing about this delay is it's forcing me to take my time and think about each step in the build, so when I dive into the Black Lagoon with the hot stick in my teeth I'll know exactly how I'm going to do it. I have done a little pre-assembly like adding caps/resistors to pots and tube sockets, making up buss bars, etc. Doing these small parts out of the chassis makes it a lot easier to see and work cleanly.
I think I'm going to build this one to Mil-std. You know, adding the little bends to the component leads, etc. It's more work, but it has been proven to prevent thermal stress from damaging the parts.
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Post by Pinetree on Mar 9, 2023 9:04:50 GMT -5
Artist depiction of the actual process.
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Post by Peegoo 🏁 on Mar 9, 2023 11:11:53 GMT -5
I found this image years ago on an electronics supplier's Website. The thing is, it was only the pic on the left, in an ad for a soldering station.
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Post by Ricketi on Mar 9, 2023 11:51:08 GMT -5
yowza ! cold soldering?
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Post by Peegoo 🏁 on Mar 13, 2023 16:38:04 GMT -5
Okay...parts are in, time to get going. I've been going back and forth on how I'm going to assemble this thing. I have a turret board and an aluminum chassis. I could easily punch it for tubes, etc. It would be an easy build, but it would look like many other home-builds. But I also have a derelict Eico HF-12 mono integrated amp from 1959 that has room in the ventilated metal case for everything. It's not in bad shape, and I'll be able to fit all the controls on the front panel. The cool thing is this amp originally used three 12AX7s and a pair of EL84s, which precludes having to butcher the chassis to make the conversion. I am leaning this direction. It will outwardly look like a tired old piece of electronica, but will have some personality and contain a brand new fire-breathing amp inside. I think that's what I'm-a gonna do. The Selector on the left would be the volume (gain), and the 2nd knob from the left marked Volume would become the master volume. I'll stick the input jack, power switch and fuses on the rear panel with the line out and speaker jacks.
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Post by Pinetree on Mar 13, 2023 17:04:17 GMT -5
I approve.
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Post by Peegoo 🏁 on Mar 13, 2023 19:14:58 GMT -5
We have a quorum!
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Post by Leftee on Mar 13, 2023 20:30:14 GMT -5
If you paint it weird I’m in.
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Post by Peegoo 🏁 on Mar 14, 2023 8:44:46 GMT -5
If you paint it weird I’m in. I considered that, but I think I'm going to leave it looking the way it is (wolf in sheep's clothing). I might knock the dust off.
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Post by Leftee on Mar 14, 2023 18:19:25 GMT -5
I’m still in. I just tested the weirdness waters.
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Post by Peegoo 🏁 on Mar 15, 2023 10:06:46 GMT -5
I've discovered why this old Eico amp appeared unused, save for the mild surface corrosion and dust. These things were sold in two forms: complete amps, and as a kit of parts the buyer assembled themselves. This one appears to have been put together by someone that was inexperienced in soldering because more than half the component leads were loose in their terminals. The builder stuck the leads through the hole and dripped a blob of solder on it to make the connection. It's like they put it together, it failed to work, and they tossed it into a box. I got this thing at a hamfest in Manassas in the late 80s. I think I paid $6 for it. But it's got a beefy PT and OT and they both work. So my goal is to strip it out, clean it up, and then P2P it using terminal strips. I may put all the large power caps and resistors on a small turret board because I think I may not use a multi-cap. I did get a laff out of one thing here. In the top pic lower right is the PT. Immediately to the left you can see one of the heater runs (black and tan wires, twisted very tightly). You can see more of these above and in the center. But look at the heaters running to the V1 socket on the left by the solder sucker. It appears the builder reached that point and thought, "this twisting of wires thing is a pain in the arse. Screw that noise!" The bottom pic is after scrubbing the bare chassis in hot soapy water in the sink. I particularly like how it is stamped with the EL84 mounts at a 45-degree angle. This allows the taller tubes to fit in the low-profile enclosure.
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Post by Leftee on Mar 15, 2023 10:31:55 GMT -5
Thinking about this…
I have an ancient Dukane chassis with good iron. 2x6L6 and 3x12AX7.
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Post by Pinetree on Mar 15, 2023 11:12:14 GMT -5
And twisting heater wires is SO easy...
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Post by Tinkerer on Mar 15, 2023 11:28:39 GMT -5
I'm very much looking forward to seeing what you create here! I've never come close to attempting anything like this, and am curious about how you decide what to keep and what to replace? For these kinds of projects, in addition to the transformers, are there other components that are worth salvaging and reusing? How do you decide what's worth keeping and what's being penny wise and pound foolish to not replace?
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pdf64
Wholenote
Posts: 557
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Post by pdf64 on Mar 15, 2023 12:15:13 GMT -5
And a rectifier socket?
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Post by Peegoo 🏁 on Mar 15, 2023 12:50:41 GMT -5
I'm very much looking forward to seeing what you create here! I've never come close to attempting anything like this, and am curious about how you decide what to keep and what to replace? For these kinds of projects, in addition to the transformers, are there other components that are worth salvaging and reusing? How do you decide what's worth keeping and what's being penny wise and pound foolish to not replace? Hey brother. I've converted a bunch of amps like this. I recycle as much as is practical, but it comes down to keeping what's really robust and reliable and tossing the stuff that simply goes bad over time, because I don't want to have to replace it in a year or two when it finally smokes. There are things that are okay to keep, but generally there are always things that go straight into the bin. Off the top of my head, keeper items include -Power transformer -Output transformer -Chassis -Chokes and inductors (if in spec) -Tubes -Tube sockets if they're in good shape -Fuse holder -Lamp fixture and bulb -Power switch -Cement wire-wound resistors (if in spec) -Metal film resistors (if in spec) -Pots (if in spec and not too mauled) -Jacks (if in good shape) -Knobs -Wire (clip off the burned/twisted ends) -Terminal strips -Solder lugs -Screws and nuts Items that automatically go into the electronic recycle bin are -All capacitors (multi cap, electrolytic, ceramic discs, tone caps, bypass caps, coupling caps) -Carbon comp resistors (they generate noise in the signal, even when new) -Carbon film resistors (they're noisy too, even when brand new) -Selenium rectifiers -Rubber grommets in the wire pass-throughs (they dry out and crumble) -Power cord (they're usually only two conductor and brittle/cracked) When removing components you may save, be very gentle so you don't stress the point where the lead enters the component. This is especially important on older transformers because the wire insulation can be brittle. And don't cook the components when removing them. If you're like Leftee and have an old non-guitar tube amp you'd like to convert, dive right in. The best thing to do is consider the tube compliment your 'donor' amp has, and build a guitar amp that already uses those same tubes. For instance, Leftee's DuKane amp could be converted into a tweed Deluxe-type amp, and it will easily sound as good as a $3K booteek amp. The real bonus is that fantastic tone will be coming from something you built yourself. There are schematics and layouts for many amp types all over the Web. My example here (this Eico) is a little complicated because it was an integrated amp designed for use with a phonograph, tape deck, radio, etc. There's a lot that needs to be chopped out to turn it into a guitar amp. Same goes for tube-powered tape players...lots of non-guitar-amp stuff in there that needs to be gone. The absolute ideal amps for conversion are mono PA amplifiers that use preamp and power tubes common in guitar amps. The tubes are important because common "guitar" tubes are widely available and a lot cheaper than non-standard tubes. For preamp tubes, the nine-pin 12AU7, 12AX7, 12AY7 are ideal. Octal preamp tubes (6SN7, 6SL7, 6SJ7 etc.), are cool too but getting harder to find. The EF86 pre tube is a good one but can be difficult to keep nice and quiet and prevent oscillation because of its gain structure. For power tubes, anything with EL84/6BQ5, 6V6, 6L6, EL34, 5881, KT66, etc., are good starting points. If this sounds like the sort of thing you might enjoy (I bet you will!), read this linked doc front to back about three times before you fire up your soldering stick. Matter of fact, copy the text, print it and stick it into your binder where you keep schematics. If you don't have one, start one; you're going to need it www.geofex.com/article_folders/old2new.htm
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Post by Peegoo 🏁 on Mar 15, 2023 12:52:13 GMT -5
Yes, it originally had an EZ81 in there. But I'm doing silicon diodes in this one.
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Post by Tinkerer on Mar 15, 2023 14:48:01 GMT -5
Thanks so much Peegoo! I am continually awed by the breadth of your knowledge, the generosity with which you share it, the encouragement and support you so graciously offer, and your wonderful self-deprecating sense of humor that makes reading your posts just flat out fun!!
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Post by Peegoo 🏁 on Mar 15, 2023 14:53:34 GMT -5
Thanks so much Peegoo! I am continually awed by the breadth of your knowledge, the generosity with which you share it, the encouragement and support you so graciously offer, and your wonderful self-deprecating sense of humor that makes reading your posts just flat out fun!! I am not an expert in any of this stuff. Pete really helped me on this design. I just have some tools and I'm not afraid to use 'em!
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Post by Peegoo 🏁 on Mar 17, 2023 23:08:06 GMT -5
Okay, I had a little time to burn my finge...I MEAN work on wiring up this circuit. I started with the stripped chassis and installed the transformers and tube sockets. The transformers were in pretty good shape but with just a tiny amount of surface rust, so I gave them a coat of gold paint to match the gold perforated top panel. I installed the choke and yeah, I decided to go with a cap can because it's pretty tight under the chassis in the power section. I need two 20uf and one 40uf caps, and this multi-cap will cover it because it has four 20s (dumb luck I had this in stock). I can parallel two of them for the 40uf cap. Next task was the rectifier, which I mounted on two opposing terminal strips in the same spot as the original tube rectifier socket. I used 1N5408 (1kV) silicon diodes, two in series per leg, to help keep them cool in operation. I needed to scrunch them together so I clipped the leads short and did a wire wrap, soldered over. Here's the heater circuit hooked up, along with the lamp and hum balance pot (that round brown rheostat at the bottom). That's the HT fuse up top. This is fun!
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Post by Pinetree on Mar 17, 2023 23:38:13 GMT -5
Very nice.
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Post by Peegoo 🏁 on Mar 20, 2023 14:07:57 GMT -5
Chipping away at it. I'm reusing wire, resistors, etc., from previously-gutted electronica, so some of the parts & wire are brand new and some look like they're 70 years old...because they are. This old wire is a hassle to work with because the insulation gets really soft with just a little heat. But I'm making it work. You can see how I make notes right on the parts to help keep me straight; I have hooked things up wrong in the past. I'm working from the schematic, and as I add a component or a wire I scribble it out on the schematic. I'd get totally discombobulated if I didn't do this. I've improvised a few things here. I needed a 15-watt 120 Ohm resistor for the power stage. I didn't have one so I put a 20 Ohm and two 50 Ohm resistors in series with the bypass cap in parallel. It's double the wattage called for by the circuit but that will just help it run cooler. There's about a 3mm gap between the middle resistor and the cap to keep the cap running cool. The multi-cap wired up. I put two of the 20s in parallel for the 40uf I needed. Here's a shot of the chicklets on V2. I have some power stuff close to it, and it may make noise. If it does, I'll change it. But space is really tight on the power side of the chassis. A few more connections to make here. The two sockets for the EL84s wired up...a lot jammed into a small space. I have a few more connections to make on the terminal strip. This old-school method of circuit construction is a royal pain in the donkey, but I love the challenge. I hope I don't have to take it apart
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Post by Pinetree on Mar 20, 2023 14:19:56 GMT -5
Looks very good so far.
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Post by Peegoo 🏁 on Mar 20, 2023 14:29:43 GMT -5
As long as the smoke stays inside all the parts I'll be happy. Like Leftee said earlier, "Okay, untry it!"
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Post by Tinkerer on Mar 21, 2023 0:33:45 GMT -5
Very, very nice - beautiful work!
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Post by Peegoo 🏁 on Mar 23, 2023 8:56:24 GMT -5
I've got this thing about wrapped up. The front panel is done; it's a separate piece of stamped steel with a brass faceplate that covers a large cutout in the steel, so I had to install some brass screws top and bottom to support the pots mounted directly to the plate. The original Eico amp used long-shaft pots mounted to the chassis, so the brass plate didn't need this extra support. SELECTOR is actually the pre-volume, and VOLUME is master volume. These knobs are Dakaware phenolics and came from a derelict Hickok scope from the mid 1960s. The original Eico knobs were cheap plastic and they were disintegrating. The rear panel presented some challenges because it was punched for old-school screw terminals mounted on phenolic insulator boards--not 1/4" jacks. Here's the two fuses and power switch. I decided to install an IEC socket rather than have a permanently-attached power cable. I think it's a wash as far as which power cable connection is best, but I had these sockets in stock so I used one. I stacked up a few star washers on the power switch to bring it inside the chassis a bit farther. Here's an outside shot. I am going to use a 250V 2A fuse for the mains instead of a 1A. Like I mentioned above, the rear panel was not going to cooperate... So I made an adapter plate from aluminum, 1" wide and 1/8" thick. It looks like a GUHOR stick (you radio geeks will know what that is) or some kind of drafting tool. I installed it in the rear panel to support the jacks. I decided to omit the line-out jack from this build...I can always add it later. The Ohms are out of order because the brown wire (4 Ohms) above was too short to reach the far left jack. Why didn't I simply extend the wire? I!!! Don't!!! KNOW!!! [Pee Wee Herman reference there] I'll probably change that. Outside shot. The guitar's input jack is on the far right, out of shot. I'm gonna review each component and all the connections per the schematic. Then I'll power it up on the dim bulb doodad and take voltage measurements. If everything checks good, I'll plug tubes in and check voltages again. Wish me luck. If you live near Annapolis and your lights flicker or completely go out, you'll know I have failed.
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Post by Pinetree on Mar 23, 2023 9:09:48 GMT -5
It needs are some DYMO Labelmaker labels.
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