Category electronics

100 2N5087 transistors, sorted by hFE.

In order to ensure that the left and right channels of the Millett Hybrid MAX headphone amp sound the same I’m trying to ensure that all parts used in each are balanced. So, I ordered 100 pieces of each of the 2N5087 and 2N5088 transistors. I was able to get four parts which consistently metered identically, so those are used in order to ensure that the current to the tubes is kept consistent. For the other twelve transistors I was able to get matched pairs (at least) and ensure that the values are the same for each ear. That should work out well.

This evening I also figured out the template for the rear panel, drilled it, ensured that the parts fit, then put it together. I’m pretty happy with how all the parts fit, although I did have to shorten the heatshrink on the phono connectors so that the wire could bend better. When I test fit the PCB and the rear panel everything fits nicely, although the wires will be a little cramped.

Since I placed all the matched transistors, new 1/4″ jack, and replacement tube sockets I’m now ready to wash the board and finish it up. If things go as planned I’ll have it working either tomorrow or friday. Hopefully it’ll sound good, although I imagine that won’t happen until the tubes are burned in and biased, I’ve selected the tubes I wish to use, and it’s all done.

I also have to make the front panel (should be easy), potentially cut the shaft of the potentiometer shorter to fit the knob (risky, not really easy), possibly drill some arrays of vent holes on the top, front, and rear panels (easy, if I drill them right), cut the tube holes, and finish assembly. There’s also deciding on the set of tubes to use, so I’ll probably run it without a top at work for a while, but I’m not sure yet… That’s all up in the air.

Oh! I should also really make a photo to iPod dock connector cable… Or maybe I’ll just buy a new dock and use a phono to 3.5mm cable… Hmm….

Getting there…

Well, the Millett Hybrid MAX that I’ve been working on is coming along. I ended up doing a few things to it tonight. First, I removed the tube sockets because I was going to fit new, hollowed out sockets and LEDs beneath the tubes. However, after some calculations I found that the LEDs connect right to the main 27V rail, and thusly the current limiting resistors have to sink a whole bunch of power. For the sake of not putting such a load on the power supply, simplicity, and a few other things I’ve opted not to illuminate the LEDs. (I would have needed something like 2W resistors.) So, new sockets will go back in place.

I also removed a bunch of the transistors. Because I want both sides to be balanced as closely as possible I ordered a lot of 100 of each of two types of transistors which can affect this. I’ll then match them and ensure that they are installed symmetrically.

Finally, I removed the 1/4″ headphone jack, because I decided I wanted a different type. I think I’m also going to put in a 3.5mm jack, just as soon as I have to place another order with Mouser.

I fitted a few of the new parts that came in, specifically some 1/8W resistors I had to purchase, because the exact required value of 1/4 watt weren’t available. 1/8W should be plenty for here, I think. I also fitted three more heatsinks.

Basically, as soon as my Mouser order comes in tomorrow I’ll have everything I need to almost completely finish the amp. Hopefully I can do so over the next couple of days. Sure, I won’t have the 3.5mm jack, but I can use an adapter for the time being.

I realized tonight that I’ll have to cut down the shaft on the really expensive, really nice Alps pot, but I think I can handle that.

Metering Power Consumption by two v2.0 RS232 to Eaton Leonard Interfaces
(Click for more photos (photo gallery retired)…)

Well, they are done. I worked for quite a while last night and for a good part of the day today, and all of the first production run of v2.0 RS232 to Eaton Leonard Interfaces is complete. They have all been bagged up and are sealed in a box waiting for me to deliver them in about a week and a half.

If you go to this page (photo gallery retired) you can also see a bunch of images I took of all the boards tiled together. These would be good for the background of product literature or something.

Missing LEDs and Power Connectors Only

Well, these are coming along nicely. All I have left to do tomorrow is install the LEDs and screw terminal power connectors, then I can wash and dry them and begin testing. Hopefully every single one will pass. They should, unless there are bad parts.

If they don’t, I’ve got a few spares of each part, just in case…

I also need to get some exercise tomorrow. I’m not yet sure what I’ll do, though… Maybe roller blading, maybe just a walk in a park. At least tomorrow is forecasted to be fairly nice weather-wise.

20 PCBs with Resistors.

Nothing special here, I just fitted all the resistors to the first production run of the v2.0 boards I’ve been working on. I’ve got about 1.5 weeks to get them finished, so I’m probably going to do one step per night. Tonight was resistors, tomorrow ICs, then… well… maybe I’ll do more over the weekend. After ICs will be the caps, then the transistors, then the pin headers and RJ45 jacks, then the LEDs and screw terminals. Then washing, drying, testing, packaging…

…or, something. :) It’ll all get figured out / built / tested in time.

RS232 to Eaton Leonard Interface v2.0
(Bottom View)

Well, there it is. That’s one of the first pieces of the RS232 to Eaton Leonard Interface v2.0, part of the lot of five I assembled tonight. They are bagged up and ready for delivery so that the customer can test them out before the inital install (at one of their customer sites) at the end of the week. The PCBs were ordered last week as a prototype run and they arrived today, so I got to work as soon as the UPS driver showed up with the box.

Everything went great with the boards, and the v2.0 design meets all its goals. It is simpler than v1.0, easier for me to assemble, uses fewer parts (both count and type), and can be configured to talk to itself. Yep, this one can act as either end of the cable. Thanks to this the jumpers can also be configured so that a simple loopback can be plugged into its EL connector and all the electronics on the board can be tested outside of a production environment. (This makes testing loads easier for me as well.)

So, that’s about it. I’ll be assembling the rest of the first run this week and weekend and hopefully delivering them early next week. Yay!