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Post by thetragichero on Jan 20, 2020 23:53:26 GMT -5
might not look like much, but this is major progress in cleaning and organizing my workspace purchased 3 pedals off Craigslist, one of them was this boss flanger that wouldn't switch off momentary mode. instead of a rotary 4 pole switch it is apparently a 50k linear pot with 4 detents. popped the bottom off and sprayed a ton of contact cleaner. appears to work on the bench (based on the led). time to put it back together and try it in front of an amp from the schematic it doesn't have the normal boss flip flop switching, it's all on the main chip. so fingers crossed!
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Post by thetragichero on Jan 22, 2020 1:57:10 GMT -5
it's 40 degrees here in Florida, which is COLD for us hot blooded folk. one of the churches i play at is a cold night shelter so here i am manning the overnight shift, researching and sketching out a build to use some of these pentode tubes (6sj7 and 6sq7 in preamp and 6l6ga power amp) salvaged from the old hp test oscillator. will have to use a 12au7 for the phase inverter but i have a ton of those anyway
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Post by thetragichero on Jan 24, 2020 3:20:01 GMT -5
heaters wired up (besides the indicator led which i just ordered because i apparently didn't have 5mm blue on hand), rectifier wired up. most of the phase inverter besides where it connects to the power tubes. negative feedback resistor is in. have to wire up the output transformer secondary, finish the mains switch wiring and hook 'er up to the lightbulb limiter
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Post by thetragichero on Jan 25, 2020 2:19:03 GMT -5
awhile back i put a preamp in my first bass, an 85 ibanez rb850 my dad purchased off a coworker for basically nothing i never took the time to install the battery compartment, instead taping the battery to the body. wondered why it stopped working and i guess my janky install job caused a short somewhere... using a few forsner butts and my trusty 1/2 inch chisel i made a hole for the battery box and set out to wiring this up proper it works! sounds great. just need to tighten the truss rod a bit to get a little lower action and this will be back in my arsenal
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Post by thetragichero on Jan 26, 2020 20:58:17 GMT -5
after fixing a couple of bonehead blunders (I'm leaving one because it hasn't effected the sound, just an extra, unused filter cap node here we go, out of a Yamaha-branded organ speaker in an open back cabinet
played through the both jack, individual channel volumes and mids dimed, treble and bass backed off a bit. the jcm800 to soldano cold clipping trimmer all the way on the soldano side. this seems to be like a loose to tight control so I'm glad i put it in there. loose has more bass so not as nice for thrash riffing but for other styles i could see it be useful
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Post by newey on Jan 26, 2020 21:47:45 GMT -5
SOunds pretty crunchy! No pedal in there, just the amp? What guitar are you using?
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Post by thetragichero on Jan 26, 2020 22:17:47 GMT -5
just the amp. bridge humbucker on my blacktop jazzmaster gonna try it with 15s and 12s in the studio to get an idea what the cab wants so I'll see how it takes a tube screamer, rat, fuzz, etc it does clean up decently but i have marshallitis where i just want to turn all the knobs to 11
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Post by thetragichero on Jan 27, 2020 3:47:31 GMT -5
started on the intercom build. trainwreck express circuit with switches for all the mods
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Post by thetragichero on Jan 28, 2020 2:46:00 GMT -5
slow but sure work first two b+ nodes all hooked up, some more work on v1 and the front panel switches. gonna get creative with the tube/solid state rectifier switch. should be able to use the second pole to adjust the bias for the lower/higher b+ gotta knock off for bed
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Post by reTrEaD on Jan 28, 2020 13:32:16 GMT -5
gonna get creative with the tube/solid state rectifier switch. should be able to use the second pole to adjust the bias for the lower/higher b+ Switching between ss and tube for the rectifier radically changes the character of the amp. That's a wonderful choice to have at your disposal. Glad to hear you've also taken into consideration, the different bias requirement. You might also consider a switch to disconnect the NFB.
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Post by thetragichero on Jan 28, 2020 15:59:15 GMT -5
that's what i have labeled as the "loose" switch, disconnects negative feedback and shorts around the presence pot (so the be 22k tail resistor just goes to ground)
tested the most recent hammond build through 2x12 heppner alnico, 2x12 Eminence alnoco, and 1x15 rola. sounded best/most balanced through the 15 so looks like I'll be making a 30x19.5x12 cabinet. found a forum post giving instructions on how to do it with a single sheet of plywood so that's what I'm gonna do. have them rip it in store for me
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Post by thetragichero on Jan 29, 2020 3:38:09 GMT -5
added tone and volume controls, tone stack bypass, bright switch, smooth switch (basically a feedback loop from plate to grid. 40M resistance when it's not in smooth mode, 20M resistance when smooth switch engaged) instead of a metal plate with a logo, i may try to use some nixie tubes to light up something on the. i have an old frequency counter that uses them that will be on my list to disassemble. TON of npn germanium transistors in there begging to be made into fuzz boxes
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Post by reTrEaD on Jan 29, 2020 9:11:42 GMT -5
that's what i have labeled as the "loose" switch, disconnects negative feedback and shorts around the presence pot (so the be 22k tail resistor just goes to ground) Cool, you already had that sussed. I just had a slightly different thought. If your loose switch simply shunts the capacitor for the presence control, that pot now becomes the loose control. You might prefer your original idea because it's simpler to engage the full-on loose mode. But having the amount of NFB adjustable does have its own benefit.
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Post by thetragichero on Jan 29, 2020 16:37:36 GMT -5
getting faster! sealed 1x15 cabinet. no screws/nails until it's time to attach the baffles and 2x2 supports
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Post by thetragichero on Jan 29, 2020 23:23:32 GMT -5
cutting out early tonight (been staying up until 4am lol) but here's how i ended it picked this up relatively cheap with the intentions to use it as a preamp for my bass (i have a niiice bass preamp/di but I'd rather sell it and keep playing cheap weird stuff). hooked it up to my power amp and sounded great, but i wanted the option of an xlr di out so i drilled a big old hole and installed an xlr jack i purchased for some reason or another. paralleled the trs output and Bob's my uncle (it's true. when we were young my cousin Bobby and i were practically raised as brothers). can't find an output impedance listed but a mention of being low enough to drive 600 ohm load so should work for the long cable run to the mixer at church have yet to try it with an fuzz box in front but one of the reasons i went with an ancient dbx is these old designs are said to distort pleasantly while i was in there i increased the power supply filter capacitance a bit. tomorrow i have to fashion some rack ears so's i can put this in my 3u bag
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Post by thetragichero on Jan 30, 2020 13:09:04 GMT -5
scrap of steel i had wasn't a full 1u in height but i think it would be fine even with just two screws
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Post by thetragichero on Jan 31, 2020 23:19:42 GMT -5
2x12 (pine) and 1x15 (hardwood ply) cabinets run through the router table so that my corners will fit. i probably encounter the most fear when it comes to that damned router table. the 2x12 needs a groove cut into it for the piping to hide the seam as i purchased two 2 yard sections of tolex (over two orders) instead of one 3 yard section predrilled the holes to attach the front baffle as it will be difficult enough to screw
played with some 20 year olds at a young adults service tonight and i am absolutely gassed. no more work for today
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Post by thetragichero on Feb 6, 2020 3:15:16 GMT -5
crazy week (couple of weeks, really) where i didn't get nearly as much work done as I'd like tonight i got both rectifiers wired up and going to the switch and started the bias circuit (first fixed bias build but this will be good practice for the big marshall build). remembering the orientation of the electro caps was certainly a challenge (since the bias is a negative voltage, the + end goes to ground instead of the negative end... positive end always goes to the end with the highest potential... still seems 'off' lol) the other day chatted with a guy from a facebook group who expressed interest in a low wattage tube power amp for his solid state stomp box preamp. after digging around the smaller potential donor chassis from organs and measuring out where everything would go i started drilling holes. cleaned everything off, primed, painted, and today applied waterslide labels and hit with a ton a clear poly. the joys of waterbased poly: it'll be dry enough tomorrow to sand all my runs (better to ask for forgiveness than permission, tight?) and buff out and start building using the transformers i took out of my fender excelsior along with a deluxe/vibrolux choke that'll be here Wednesday. input jack goes to a long tailed pair phase inverter. since the preamp will have its own volume I'm putting the master volume after the phase inverter. should give the most tonal control. 2x6V6 although i think the 6L6G i removed from the test oscillator will work as well (slightly mismatched ot at 8k instead of 6k6 but that's close enough). adjustable fixed bias with negative feedback and a presence control. will also have a line out so that there is an option to feed it into a bigger power amp. fun project. the guy liked my price but hasn't committed to buying it, which is okay. I'll send him progress photos and eventually sound samples. worst case it goes up on reverb
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Post by thetragichero on Feb 7, 2020 0:27:43 GMT -5
got the front and rear baffles of the 1x15 cabinet shaved to fit, speaker hole cut, reinforced, painted black, etc. only have a picture of the template i used for the hole... piece of the drum set i still haven't sprayed black dry fit for this 2x6V6 (6L6G, possibly?) power and bring made almost entirely from stuff i had on hand (besides the $10 filter choke that'll be here next week). unsure on the knobs
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Post by thetragichero on Feb 13, 2020 0:50:54 GMT -5
picked up a couple of old Baldwin organ chassis along with a 15" rola speaker for 30 bucks today ended up with more than i thought i would: 2 BEEFY power transformers (360-0-360 and 350-0-350 with a TON of filament current from the pile of tubes this thing required), 2x6L6 output transformer (supposed to be for an 8 ohm load, will need to do some measurement and math to figure out the actual primary impedance), 7h choke, and some sort of weird piece of iron with 3 leads (one of which was grounded) spent the evening stripping components from terminal strips and touching up black paint on the power transformers. figure I'll get a fender-type build and with an added output transformer something 2xkt88
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Post by reTrEaD on Feb 13, 2020 11:59:48 GMT -5
and some sort of weird piece of iron with 3 leads (one of which was grounded) Got any pics of that?
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Post by thetragichero on Feb 13, 2020 14:04:27 GMT -5
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Post by reTrEaD on Feb 13, 2020 14:15:58 GMT -5
why would one want two inductors to ground? Maybe for some sort of tone circuit, but if so, why such a high inductance value? Puzzling, indeed.
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Post by sumgai on Feb 15, 2020 0:31:39 GMT -5
[ and some sort of weird piece of iron with 3 leads (one of which was grounded) It's an 'autotransformer'. In the great majority of cases, there is only one winding, with a tap. Depending on the current vs. voltage requirements, the thing can be used to either a step-up or step-down a voltage. Wikipedia might be your friend. HTH sumgai
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Post by thetragichero on Feb 15, 2020 12:03:23 GMT -5
ooooh so with the auto transformer used to step up the 50v-0-50v tap on one of these solid state transformers ought to give me just enough voltage (after bridge rectification) for the plates of a couple 12ax7 tubes for a preamp...
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Post by frets on Feb 15, 2020 13:20:46 GMT -5
I asked my Uncle who knows everything “organs” says the autotransformers were also called “interstage filters” and used for phase inversion and phase splitting. Given I didn’t follow anything else he told me - that’s all I got. I wrote it down and have no idea what it means.
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Post by thetragichero on Feb 15, 2020 13:48:33 GMT -5
if it were a 50% tap then yes i could use the transformer instead of a phase inverter tube (musicmaster bass amp probably the most notorious for this). imagine a world where big chokes and transformers were cheaper than capacitors or an extra tube! I'll be determining the output transformer turns ratio/impedance/etc anyway so I'll hook up this autotransformer to my VerySafe™ testing rig and figure out what it does
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Post by thetragichero on Feb 16, 2020 19:37:36 GMT -5
out of solder so until my order gets here i have to figure out other stuff to do here is my VerySafe™ transformer tester setup (notice the power strip) two different solid state transformers into the autotransformer gave me 255vac and 332vac. once rectified should be perfect for a tube preamp! have the two Baldwin power transformers and the output transformer on my list to test tonight
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Post by thetragichero on Feb 16, 2020 22:55:25 GMT -5
finished measuring the Baldwin power and output transformer specs so i am posting these here for the next fella (or gal) who tries to search Google like i did mains voltage generally runs 120-122v
512-19211d red 369v-0-369v (eBay listing i found said 360v so that computes) green nominal 12.6v filament (measured something like 14.4v unloaded since there were about 80000 12au7 run off this. with all that heater current capacity no reason not to rectify it and drop it down a bit with rc filters, in my opinion) orange 5v rectifier filament (5u4 i believe so 3a) yellow 6.3v nominal (the 6l6 heaters were run off if this)
f-c 512-19205-b red 360v-0-360v (eBay listing said 350v ct) green 12.6v nominal (not as many 12au7 as the other transformer so this measured close to 14v unloaded) blue 17.4v (listing said 15v)
512-19234b output transformer 3k:8 ohm
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Post by thetragichero on Feb 17, 2020 12:30:59 GMT -5
had intermittent power problems with this preamp when it was in a rack case going back to 2013. i even sent it to a tech who couldn't make it fail. so of course it started working again and i installed it in something that I'm about to ship off to a guy but i want to test it just one more time. dead so i start looking and what do i find? only is a problem when i have it coiled up neatly guess i shall be replacing the power cord
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