| Posted by Markus | January 20, 2021 - 11:25 am |
| Hi Steve, thanks for your advice! I will try to find a heatsink in case I have the impression that it might become critical! Regards, Markus |
| Posted by Steve L. | January 19, 2021 - 04:34 pm |
| Hi Markus, Without the heatsink you would certainly be okay with 12AX7 and other low-level tubes. I guess 6L6 and EL34 would be okay. Perhaps the main concern would be rectifier tubes like 5U4 and GZ34. By the way, if the issue is mainly sourcing the heatsink, a similar-sized chunk of aluminum could suffice. In fact, I considered doing that because it would allow me to use a bigger piece with more thermal mass. However, since the heater may be left on for an extended period, I realized that the extra thermal mass wouldn't necessarily be a key factor. Since the heatsink was endorsed by the module vendor, I decided that was the safest course. |
| Posted by Markus | January 19, 2021 - 02:53 pm |
| Hi Steve, do you think I will also need a heatsink if I mainly test 12AX7 tubes and only up and then a EL34 (1.5A) or 6L6 (0.9A)? Regards, Markus |
| Posted by Steve L. | January 19, 2021 - 10:32 am |
| Hi Markus, You're very observant! The heatsink was a late addition and didn't make it into most of the pictures. Of course, it is shown in the HRB construction section of Part III. It's also slightly visible in slide 28 of the gallery in Part III. Thank you for bringing this to light. I do recommend using the heatsink as the XL4005 chip can get quite hot when maximal heater power is being delivered. That heating is what limits the HRB to a continuous 2 or 3 amps, versus the 5 amps or so which it can deliver for short periods at 6.3V. |
| Posted by Markus | January 19, 2021 - 02:19 am |
| Hi Steve, one more question: in your instructions on how to build the heater supply you indicate that a heat sink has to be mounted to the XL4005 while there is no heat sink in the images of your completed µTracer. Does the XL4005 require heatsinking? Regards, Markus |
| Posted by Markus | January 12, 2021 - 01:14 am |
| Thanks for your explanation, Steve! I totally forgot about your sense lines. |
| Posted by Steve L. | January 11, 2021 - 02:39 pm |
| Thanks, Markus. The 2-pole DC-type jacks were needed to support a second channel, required by the remote sensing feature of the heater regulator board. That eliminates the voltage drops in the heater and ground connections. Quoting from Appendix B: "A highly accurate heater voltage source would be of little value if nothing were done about voltage drops in the heater and ground connections. With the connectors and wires, it’s pretty easy to find 0.1Ω; or more. At 3A, that drops 0.3V or about 5% of 6.3V, which is way too much error from that one contributor. Hence, I decided that remote sensing for the heater supply is necessary. With remote sensing, the regulator sets the voltage at the socket, rather than at the regulator’s own output. It does that by using separate wires to bring back the voltages at the two heater pins. Very little current flows in these sense lines, insuring that the regulator is seeing what is actually at the socket pins. Notice, however, that this implies that two separate lines must be connected to each pin: drive and sense. That requires two-pole connectors." By the way, for convenience in connecting lab equipment to the tube, the red banana jacks are also provided for each pin. Those also use the sense lines, making it easy to measure the tube's pin voltages without error from voltage drops. |
| Posted by Markus | January 11, 2021 - 02:01 pm |
| Cool report! Why did you use DC-type jacks for the tube pins and the voltage sources and not banana jacks? Regards, Markus |
| Posted by Steve L. | September 16, 2020 - 06:57 am |
| Hi Hoby, Thank you for your kind message. I'm not sure what you mean by, "I need bin hex files" but I will be happy to help if you have further questions. If you are looking for files such as schematics and panel art for this project, the download links are at the end of Part II of this article. Best wishes for your project. |
| Posted by hoby | September 16, 2020 - 06:17 am |
| Congratulations on successful article work. I will do it as a hobby. I need bin hex files. thank you. elektordu@gmail.com |