Blueman2

@ang728, at first I thought your picture of the blown SiC was one of my photos! Pretty much exactly the same pattern. See below. Hoping the Cree I am now using will fare better.

The Blue Hawaii lives! Got my shipment of Cree C2M1000's and replaced the 4 parts that appeared bad. Turns out the BC557B was not bad. I had just tested it incorrectly. So just the c2m1000, the 24V diode, and the 2N3904. My guess is that the alternate part I used for the C2m1000 was not quite up to the task and the inrush current of the startup finally killed it. I will probably replace the positive PSU's chip as well since I got 5 of the C2M1000's for future repairs as needed. I had not adjusted the balance of the amp since I first built it, and decided to check the voltages. After 30 minutes warm up, balance and offset are still +/- 1V. Impressive given the number of hours I have put on that amp over the past 3 years.

mwl168, great to hear from you! It blew just as the HV power delay relay clicked on (I have a 45 second delay after LV and filaments turn on before HV turns on). So probably an inrush current issue if there was no short.

Good thought, Kerry. I checked but the resistance levels on the negative side are about the same as positive side for the amp boards. PSU itself does not show a short. I plan to rebuild the PSU, test it on the bench at low input voltage, then ramp it up. Could just be one of the silicon devices was weak and took the others along with it.

Hello all! Long time since I have posted here but I continue to lurk. I just had the negative power board go out on my Blue Hawaii. The c2m1000 literally blew its top off. 3 other components also bit the dust in the process. Parts are ordered and will replace in next couple days. All other parts appear to test OK. Looking at the parts that failed, any ideas on the cause or which part failed first that led to the others failing? And more importantly, are there any parts you recommend I replace regardless of how they test, given the mode of failure? The Amp had been working great over the past few years, though with the Carbon and my trusty old SRX Plus, it sometimes went several months between uses. EDIT: I just recalled that I did the build when the C2M1000 was out of stock, so used the SCT2H12NZGC11 from Mouser listed in my Feb 2021 post in this thread (right hand column below). Maybe that was the issue?

I think so. However, I am not sure that the shunt PSU was ever finalized. I recommend going with one of the GRHV variants for the power supply. But the SRX itself remains a great, simple to build amp.

Ah. Very ingenious!

Whaaat? Did you hack apart a TO-247 casing to put that SMD into it? Insane. 😄

What is your setup for creating boards? Do you use a small CNC router?

Nice.

@JoaMat, what is it for?

I have successfully used the ROHM version (3rd column in the list above) for over a year in the Carbon amp with no issues, but I think that part is also out of stock? Used the one if the first column (which has good availability now) in a GRHV with no issues, but not on a Carbon. But from the specs, it should work as well as the other two.

I applaud this thread!!! On point 1 that James made, I am very guilty of helping cause this issue. I have mixed comments on the GRHV across threads for Blue Hawaii BJT, Carbon, and a few others as well. Just to make sure that it is almost impossible for anyone to learn from what I did. 😁 On point 2, I have tested 2 alternatives to the C2M1000170D, and both appear to work fine. One of them is pretty new and usually in stock: https://www.mouser.com/ProductDetail/?qs=vHuUswq2%2Bsy%2BS7yfkaWaCA%3D%3D Item on left is the one that is in stock. Item to the right is the alternative that I successfully used as well, but often not in stock. Middle is the standard part which appears to be quite elusive.

Yes, this baby will keep you warm in the winter. I ended up doing the same, starting with 17mA and then increasing to 20mA after it was running for a couple days. Not sure it really made much difference in either sound or heat production, but just wanted to push the envelope.

[embarrassed] Yes, yoke. [/embarrassed] Sigh.