struts

Many thanks @spritzer. 1M/5M in the divider would take it down to 483V. Is that the right ballpark or would you take it down even further (this is for a T2)?

Quick questions regarding a voltage divider to take a 580V Stax bias line down to 520V for HE90 (I believe the spec is 500V but I remember reading a post once that @spritzer had measured a number of HEV90s and found the average to be closer to 520V). - I assume that the difference in bias is somehow related to differences in the membrane construction between the two, maybe the coating? - Is there a real risk of damaging HE90s running straight off Stax bias? I.e. can the additional potential actually lead to the membrane making contact with the grid? Does anybody have any practical experience of this or is this just speculation? - By my math a 576k coupled with a 5M to ground should do it (along with a 10M in series). Are these the values others have used? Grateful for any clues for the clueless.

These kind of problems are fascinating. IME there are two ways to approach troubleshooting them: cause-and-effect (work the list from most likely theoretical cause on down) and logical elimination (what's changed? Voltage, PS itself (grounding etc), umbilical(s), etc.) Out of interest was it electrical or mechanical* hum? Assume the former since it was channel specific? * of course we all know the reason transformers hum - because they don't know the words.. ?

Yup, unfortunately mine look like the suspect ones . I'll see if I can get them desoldered over the weekend and send them off to you, Craig. I hope Dalbani have stocks, I noticed you cleaned out Vintage Parts!

Inu, How did you determine they were counterfeit? Just by the measurements or are there any other telltale signs? I noted Craigs comments about the lead frames above, I wonder if this is a common characteristic of counterfeit parts? If so, I wonder why? Seems silly to go to all the trouble of producing such exact copies and then making such an easily identifiable mistake..

That's an extremely kind offer Craig. Everything is soldered in place but I haven't started testing as I haven't got the umbilicals made up yet. Sounds like for the sake of a couple more weeks it would be wise to pull the 3675s and send them over to you. Rather that than risk silicon genocide and a protracted and complex troubleshoot. Please could you PM me your address?

Craig, Were any of your 'suspect' C3675s from Dalbani? Where have you reordered from? If Dalbani has been supplying duff silicon I'm in trouble, sourced nearly all silicon from them...

Good point Craig, I was thinking about the receptacle-to-chassis interface but not the interfaces between the chassis plates themselves. Of course the WHOLE chassis must be tied to safety ground. Doh!

Sorry people. I seem to be suffering massive late-night brain-fade. I have figured out the answers to most of my questions. Now bed.

Hi guys and seasons greetings, After a very long hiatus caused by work and waiting for my RK50 which has FINALLY arrived I am 99% ready with the build and almost ready to start testing. Few questions regarding final assembly: 1. Wiring the umbilicals. What are people doing here (in terms of assigning wires to pins)? I guess it's not too important that power supplies are interchangeable between units (at least not for me up here in Sweden!) but there must be some arrangement that works better/best with this mixture of high and low voltages, AC and DC. 2. Related to the above I was thinking of doubling or quadrupling up on the heater wires (looks like I have plenty of pins) as it will be carrying a couple of amps and I am worried about heat build-up around the pin if I only use one. Anyone done this? 3. Finally, max length? I was thinking of about 1m. 3. Is the 'collar' of the mains receptacle meant to be in the inside or the outside of the case? Seems to be enough room to mount inside and the switch is still reachable. Outside would work too but it would require a bit of forcing and I am worried about scraping off some of the anodizing and creating an additional earth path. 4. Similarly with the Amphenol chassis plugs/sockets. Seem to work fine with the chassis plate inside the chassis but is this what was intended? Any pros/cons I'm missing? 5. Finally, I have in mind that there was a late modification involving piggy-backing DIP sockets with a passive component in between but I cant for the life of me find it in the thread. Could someone post a short description, a link or the magical search terms? Many thanks in advance.

Sorry, just back from a week/long business trip to India. Must sleep now but I'll get on it as soon as I wake up.

Thanks spritzer. Is A, B or C best for this application?

I assume you mean you're avoiding the LSK389 which seems to be real hard to get ahold of. Are you going with K170s? If so, which ones? Also, please specify BL or GR etc. for 2SC parts where it's critical.

Yup, that one too. Thanks!

Good news and bad news. The good news is that onlinecomponents can supply the RK50 for $655 , the bad news is that the lead time is 12 weeks not 8 Meanwhile my build is s l o w l y progressing...amp, ps...amd yes, I realized the diode needs flipping and the resistors crossing...

I cleaned up the V1 BoM correcting a couple of errors and adding Mouser part nos. Now with Kevin.

I have a pile. More than happy to send you some, PM me your address if so. If you want a buffer stock you could also check out this fleabay seller.

I'm in for 16 Justin.

Those were the 2SK246s. Don't know if the 3381s are equally critical. Anyone?

Jeez what a PITA. Having spent virtually all day on the phone to my insurance company (my wife backed into a rock, thanks honey!) I can certainly empathize regarding companies that needlessly raise your blood pressure. I'll hang on too. I am anyways still waiting for my RK50, 3381s backordered at Dalbani and the relay backordered at Mouser.

Looking great KG. One of each for me please!

Thanks Craig. We are not worthy!

Craig, Thank you for correcting me, I guess I skipped that class.. You provide an uncomfortable reminder that if I had paid more attention back at university I might have made it as an engineer and not have moved into sales! So if the molded body only dissipates one third of the heat, where does the rest go?

Heat dissipation on the FQPF part (TO-220F) is specified at 59W vs 178W for the FQP (TO-220) package. I'll stick with the latter.

Even better, although Scott just beat you to the punch on this one via PM. Apart from instant availability the really great thing is that these ebay sellers usually have incredibly low shipping fees. For instance this seller charges $3.90 worldwide, about 1/10th of Future Electronics' min delivery charge to Sweden Just don't know how Spritzer does it, he must be paying the same or more than me. I'm guessing shipping fees are going up end up being about 25% of the cost of his amp! Thanks for all the help guys.