Hoppe's Brain

Has this happened to you? You’re installing or testing a Hoppe’s Brain PCB and the magic smoke gets out somehow? It happens to every tech, including me, see below. (Backwards transistor, oops.)

This is a bummer, and a lot of work to fix, and even if this PCB was repaired, it wouldn’t look very nice. I want my customer’s projects to look and work nice! I don’t make the boards so pretty just for people to have scorch marks on them.

If your board is smoked, and you want a do-over, here is my “Do-Over” policy. I’ve been doing this for people for years, but haven’t defined it officially until now.

It’s no secret that quality PCB’s have become cheap to manufacture. The PCB itself is not where the value lies in buying a Hoppe’s Brain board. The value is in their design, and the support I provide. The actual board is a tiny percentage of my own costs. (Parts, however are increasingly expensive and I don’t mark them up much.)

So, if you have well and truly smoked your board and want a new one, I can offer you that at close to free.

My boards come in three flavors; Board-Only, Board with Parts, and Fully Assembled.

If you bought:

• Board-Only: A new board for free, plus shipping, about $10 continental US.
• Board with parts: A new board for free, plus shipping, but I cannot sell individual repair parts. All parts are available at reputable vendors like Mouser and Digikey. Part numbers are in my ADCOM BOMs document linked here.
• Fully Assembled:
  • A new bare board for free, plus shipping, and you perform your own repair, with your own parts. ~or~
  • Send it to me for repair at a rate of $75/hr, capped at $200 maximum. No parts charge. If I cannot re-work the board to work perfectly, and look decent, I will just replace it entirely. If I wouldn’t use it, I won’t send it to you.

Proof of destruction:

I don’t need your board back, but before I can send you a new board, I need proof you have destroyed the original.

Just drill a big hole through it and send me the picture! (Harvest the parts you want to keep first.)

Replace those weird NEC 2SD746/B706 transistors with your choice of TO-3P or TO-247 transistor without compromising thermal performance! These are used in Pioneer SX 80-series receivers, some Phase Linear, MCS and Luxman amplifiers.

2SD746 / 2SB706 to TO-3P / TO-247 Transistor Adapters / Heat-Spreaders

Replace a TO-3 transistor with your choice of TO-3P or TO-247 transistor without compromising thermal performance! Looks cool too.

TO-3 to TO-3P / TO-247 Transistor Adapters / Heat-Spreaders

I’m trying out my new TO-3 to TO-3P adapters on this Marantz 1060 that’s been sitting around my shop, 90% complete for the last few years. They look so cool!

I think these Sanken 2SC4468’s —that I found in my junk bin— are going to be a better fit for the 1060 than the usually recommended ON Semi MJ21194. The MJ21194 is a super high-power device, 250W, with a big 5.5mm die, and big Cob and Cib to go along with it. And only 4MHz. (Minimum spec, it’s probably more like 10MHz) The original Hitachi 2SC897’s are only 60W, with a much smaller die, and low Cob. This is only a 30WPC amp, so why use a 250W transistor? The Sanken 2SC4468 is 100W, 250pF Cob, and its 20MHz Ft is a closer match to the 15Mhz of the 2SC897.

The 1060 is a well-compensated amplifier, I’m not too worried that it will oscillate with these slightly faster transistors. But I have yet to actually test it, this amp still needs work!

This is so cool, the selection of transistors that could be fitted is vast! Not just MJ2119X. Pick the best transistor for the job. And soldered to an adapter, even better thermal performance! (I’ll be doing experiments to test this assertion soon.)

Update 2024.04.20

Changed my mind! ST 2SD1047 instead. Even lower Cob, 150pF… If I’m going to test the concept of using lower capacitance devices in the 1060, well these are even lower.

Got another one! TO-66’s are even harder to get replacements for than TO-3. Again the usual solution is to bodge a TO-220 in place, but the TO-220 tab is much smaller than the TO-66 case, the thermal performance is not as good. This copper heat-spreader + TO-220 transistor should actually offer better thermal performance than the original TO-66; there’s more copper mass overall.

They’re on the way from the fabricator, they should be available in late April.

On the heels of the launch of my MT-200 Adapters, these solid copper adapter plates adapt new transistors to old formats. Available soon! I just need to test them, but there’s zero reason they won’t meet expectations. Actually these adapters should offer better thermal performance than the original devices. There’s more copper mass overall, so the heat-spreading action should be superior.

Introductory offer: FREE! (If you can help)

I need some help from my customers! I have not yet tested these adapters in any actual amplifiers or receivers. But I have every reason to believe they’ll work perfectly. If you succeed in installing these adapters in your amp or receiver, and can provide me with clear pictures of your install that I can use on this product page, and some user-experience feedback, you will receive a refund for your purchase, up to $45 (8 adapters). Also, if you find you cannot make them work, you’ll receive a refund. I can provide support though the process; you can call or email me about it. We’ll figure it out. If it doesn’t work, it doesn’t work, and that’s the deal. (But it’s probably gonna work.)

MT-200 to TO-3P / TO-247 Transistor Adapters / Heat-Spreaders