Quote:
Originally Posted by fender3x
You're actually correct, one of the original speakers from my 410TX cab has a little white sticker stuck to the frame that reads Peavey Model 121 Imp. 8 Ohms.
Printable View
Quote:
Originally Posted by fender3x
You're actually correct, one of the original speakers from my 410TX cab has a little white sticker stuck to the frame that reads Peavey Model 121 Imp. 8 Ohms.
Update:
The glue I used to glue the dust caps back on the speakers seems to have dried, so all the speakers are ready to go back in the cab, on Tuesday this coming week, I'll pay a visit to my local Jaycar Electronics store and see if they have any acoustic dampening material in stock, and I'll buy as many rolls of it I can, next stop will be to my local Bunnings store for a set of new castors, and some nuts, bolts, and washers for attaching them to the cab, will also buy a new cordless drill while I'm at it.
Update:
Just spent what seemed like two hours trying to remove the four mounting screws for the tweeter speaker so I could test it to see if it still works, only to find that it doesn't, so I'm going to have to buy a replacement one, Jaycar stock a 100W 8 Ohm piezoelectric tweeter that I think may work fine as a replacement, it only costs about Au$12.00 or so, the speaker has a rotary attenuator knob for the tweeter mounted on the back panel, so I can adjust the tweeter level if need be, hopefully the attenuator rheostat isn't burnt-out.
Update:
I managed to make quite a bit of progress on the repair/restoration work on my Peavey 410TX bass cab, you should have seen the ton of dirt and detritus I had to clean-out of the cab along with the foul-smelling acoustic dampening material, just as well that I was wearing a pair of rubber dishwashing gloves at the time, amongst the dirt and detritus I "evicted" from the cab was a rodent skeleton of some kind, I kid you not, the cab still needs a good vacuuming-out to remove the last vestiges of dirt and detritus from it, the post office on Cavenagh St happens to have cordless vacuum cleaners in stock, so next fortnight I'm buying myself one.
I have managed to get all the new castors installed on the cab this afternoon, so that's one less thing for me to do.
Update:
I decided to give the interior of my Peavey 410TX bass cab a good clean-out with a scouring sponge soaked in some water and pine-o-clean, it was still pretty grotty after giving it a good sweep-out, but it looks clean enough inside now, this bass cab actually had a crossover circuit built onto a pcb, which had the original input socket soldered onto it, since the new NL4 Speakon socket I'm going to be using as the new input socket, is going to create some clearance issues, I have elected to re-build the crossover circuit using an old-school breadboard point-to-point style method of construction which involves using a suitably-sized piece of 12mm thick pine wood to mount some 8-way tagstrips which will be used for mounting all the components used in building the crossover circuit.
I have made some drawings of the crossover circuit and also a drawing of the new breadboard layout which I think should work perfect, for those interested, I will post pics of my hand-drawn crossover circuit as well as the breadboard layout if you're interested in building one for yourself, I will also include component values too.
And as promised, here are my hand-drawn versions of the crossover schematic in my bass cab, as well as a breadboard layout:
Attachment 44090
Attachment 44091
As you can see, the schematic for the crossover is really simple, it consists of what looks to me to be a High-Pass LC T-Filter formed by a 3u3/250V Polypropylene Cap, a 15uF/100V Polypropylene cap, and a 200uH air-cored inductor, the output of the High-Pass LC T-Filter goes to a constant impedance rheostat, there's also that 1.0mH iron-cored inductor going to four bass speakers wired in series-parallel, that's there to stop high frequencies going to the bass speakers.
Here's my theory of how the crossover works.......
For frequencies from say 1Hz up to the cutoff frequency of the LC High-Pass Filter, the 3u3/250V Polypropylene capacitor will appear to be an open-circuit, remember a non-polarized capacitor is nothing more than two conductors separated by an insulator, now for a capacitor the resistance at pure DC should ideally be infinite, as you increase the frequency the resistance to AC decreases and more of the signal flows through the capacitor, in electronics AC resistance is also known as impedance.
At some frequency the AC impedance of the 3u3/250uF capacitor is going to be low enough to allow the maximum signal level through to the 200uH air cored inductor, but, inductors behave in the opposite way to capacitors, as frequency goes up so does the AC resistance or impedance of an inductor, the 200uH inductor is there to stop ac signals going to circuit-ground so the signals are left with only one other path to take, and that's through the 15uF/100V polypropylene capacitor.
Now, if the high frequencies try to go through the bass speakers to ground, they will be stopped by the 1.0mH iron-cored inductor since the AC resistance of an inductor increases with frequency.
As a side-note the letter H is used in electronics for the unit of Inductance known as the Henry, a 1 Henry inductor is a very large unit of inductance and you're more likely to see inductors in the mH (milli-Henry) or uH (micro-Henry) range, but 1H and larger values of inductors do exist.
Sidenote two, I deliberately kept maths to a bare-minimum in my theory of how the crossover works, because the maths gets quite complex, and I wanted to keep the explanation as simple as possible, of course, I could go ahead and calculate the cutoff frequency of the LC High-Pass T-Filter if I wanted to.
I think you probably know way more than I do about this, but I am not sure that it would be a good trade to use a piezo tweeter. I found a manual for this cab:
https://assets.peavey.com/literature...s/80301559.pdf
Attenuater knobs don't work too well with piezos. Also, particularly in a bass cab, they would not need a crossover. At least that is my understanding. Unfortunately the manual doesn't tell you much about what sort of tweeter it came with, just that the crossover frequency is 3.5 kHz.
...so I did a little more digging, and I think the OEM tweeter is a Fostex 024H27 ... These seem to have been rather widely used in bass cabs. I found them listed as used in your 410TX cab, as well as in SWR cabs. Usually these seem to be in the neighborhood of $15 USD. I mean...as long as you are rebuilding the crossover...in for a pound... ;-)
Quote:
Originally Posted by fender3x
You may well be right too, well, if I can find one of those Fostex 024H27 tweeters going for something like Us$15.00 or the equivalent in Au$ then yeah, I will seriously consider buying one, cheers for that mate, I'll see if there are any on eBay, to be honest, I really didn't know what make/model number the original tweeter was so I ended up buying the Piezo tweeter from my local Jaycar Electronics store as a last resort, I didn't even know if the original tweeters were still available.
I don't know if Fostex makes them anymore, but they seem relatively common. I found a bunch on ebay...but I am in the US so YMMV ;-)
Yeah, it can't hurt to have a look, you never know, I might score myself a good bargain.Quote:
Originally Posted by fender3x
I just posted pics of my hand-drawn crossover schematic and breadboard layout, tomorrow I might see if I can get my printer/scanner/copier up and running and make scans of them that are clearer.
Update:
Popped-by my local Jaycar Electronics store yesterday to buy some bits and pieces I needed to build the new crossover for my Peavey 410TX bass cab, I found that Jaycar did not have any 15uF/100V polypropylene caps in stock, so I had a bit of a think to myself about how I could solve the problem, and then remembered I could put two lower value caps in parallel to make up the needed capacitance value, I did a quick calculation and found that if I put an 8u2/250V cap in parallel with a 6u8/250V I would effectively get a 15uF/250V cap which would be perfect, Jaycar did have some 3u3/250V polypropylene caps in stock though, so I bought two 8u2/250V caps, two 6u8/250V caps, and two 3u3/250V caps, I also bought eight 8-way tagstrips, and some self tapping screws and washers while I was at it, next week I will be paying a visit to my local Bunnings store for some suitably sized 12mm thick pine wood for the breadboard, as well as some other things I'll need and hopefully the bass cab should be working by the end of next week.
Update:
Managed to make some more progress on the restoration work on my Peavey 410TX Bass Cab, a few minutes ago I finished wiring-up the new crossover for the cab on it's breadboard, here's a pic of it ready to be installed in the cab.
Attachment 44230
Very tidy looking work. Did you ever find a Fostex tweet?
Quote:
Originally Posted by fender3x
Not yet I haven't, I'll have to keep looking.
I'm going to be running some tests on the crossover using my function generator, and scope, I will be using two 8.2 Ohm/1W metal film resistors to simulate the speaker loads, this is just to check that the crossover works as it's supposed to, 1W metal film resistors will do fine since the signal level coming out of the function generator is only line level, not speaker level and I will using the function generator to input a signal into the crossover, the power level I'm dealing with is not high enough to do any real damage.
Sounds like a good plan...unless that iron core coil rusts off it's mount. Ha! I have not gotten to the point of building the crossover in the cab build I am slowly working on, but every time I look at component prices I like the idea of repurposing more! It's one of the nice things about your restoration here. Waste not, want not, rock out ;-)
Not including the 1.0mH iron cored Choke and the 200uH air cored choke, the rest of the parts, tagstrips and caps, didn't really cost much at all, I bought the 8-way tagstrips and caps from my local Jaycar Electronics store, the wood I used was an off-cut from a piece of 12mm X 140mm X 1.2m pine I bought from Bunnings yesterday, the red and black wire is some 7.5A Auto/Marine power wire, again bought from Jaycar.Quote:
Originally Posted by fender3x
But yeah, I do like the whole idea of re-using electronic parts, and stuff you have lying around.
I guess it's an ethic I "inherited" from my parents, see, in my family as I was growing-up as a kid, we always had a strong diy tradition, my mum used to make her own dresses, my dad built our HiFi system, he also did his own carpentry, plumbing, mechanical, and electrical work too, he was a machinist/mechanic by trade, he even designed/built a big reflection telescope because he was into astronomy as well, he also owned a movie camera he used to shoot home movies, one time he built a meat smoker from scratch.
Me and my two brothers were the same too, we used to make our own toys out of bits of wood, my older brother, George, used to build his own Hotrods and compete in races at the local speedway track.
Update:
I'm just in the process of installing all the new white dampening material in my Peavey 410TX cab, turns out I had ordered more than enough of the material to treat the entire insides of the cab with some material to spare, looks like Murphy is on holidays for me, that is, if you're familiar with Murphy's Law.
Update:
Just finished installing the Crossover and all the original speakers in the 410TX cab and......She Works!!!!!
The cab is now making sound again, just need to get the tweeter installed.
Great news. Murphy must be holidaying in Perth!!:rolleyes:
Just been trying it out with the Fender Super Twin and my 6-string bass, it has a really fat and warm sound to it if you turn up the volume.
Going to do a demo recording of it later on so you can hear what it sounds like.
Here's what it currently looks like:
Attachment 44253
That is the perfect mad scientist rig. You just need to install a flux capacitor on your pedalboard ;-)
Sent from my LE2125 using Tapatalk
Quote:
Originally Posted by fender3x
Those are a bit obsolete now, although they do the job, I found that replacing Flux Capacitors with just a single Quantum Field-Vector Non-Linear Singularity Stasis Ion-Injector Subspace E-Zone Generator gets better results by boosting the parallel-axis by polynomial equations, in layman's terms that's very similar to 5th Dimension inversion of non-reality to reality without the inevitable annihilation of antimatter and matter.
Well no one wants that. Makes perfect sense when ou put it that way.Quote:
Originally Posted by DrNomis_44
Update:
Just uploaded a quick demo recording of my bass rig to my Soundcloud account, Fender Super Twin amp plugged into a Peavey 410TX cab:
https://soundcloud.com/drnomis_44/bass-rig-demo
Update:
This afternoon I made a mounting bracket for the new piezo tweeter from a couple of pieces of 3mm MDF sheeting glued together with some PVAS glue, also had to pay a visit to Bunnings this afternoon too, to buy a few needed things including some sheets of sandpaper, gave the mounting bracket a spray with some matt black paint and I've been waiting for it to dry, will install the piezo tweeter tomorrow and do another test-out to see how it sounds.
Update:
Earlier this morning I installed the new piezo tweeter in the 410TX cab and tried it out with the Super Twin and my 6-string bass, seems to be working great so far, here's a pic of my finished Bass Rig:
Attachment 44294