Authentic JTM 45/100 build diary. Clips added.

[Roe]

I must admit I'm quite sceptical. sometimes CCs are chosen for looks only

[VintageCharlie]

Yes, but it's not like the 2w's would be much more expensive than 1w's - i think they wouldn't risk it because of few cents savings.

[Roe]

I don't know but I've seen enough CCs failing to use metal oxide in this position

[VintageCharlie]

Had some of the amps you've seen with failed cc's voltages under 500v? or were they all above?

[Roe]

last amp I saw had 470v. what's the point anyway? these resistors will not affect tone, just reliability

[shakti]

Actually, Larry thinks they will affect tone as well...read his German thread about the JTM45 build. I can't remember the technical explanation (let alone fully understand it, reading it in German and all).

And how is it theoretically different from the plate load resistors, which are also seeing the B+ voltage? It's well established that in that position, the resistor type makes an appreciable difference.

[Roe]

Actually, Larry thinks they will affect tone as well...read his German thread about the JTM45 build. I can't remember the technical explanation (let alone fully understand it, reading it in German and all).

And how is it theoretically different from the plate load resistors, which are also seeing the B+ voltage? It's well established that in that position, the resistor type makes an appreciable difference.

damn, you got me thinking now.

[VintageCharlie]

Two of the best builders around and one of the most experienced guys on the forum (Larry) probably wouldn't do it, unless there was a reason. BUT, the reliability issues don't sound good though.

[VintageCharlie]

I'd be very thankful for any advice how to test the CC's properly to make sure there are no moisture issues or other stuff going. Demonufo suggested baking them slightly. This sounds adventurous Has anyone done this - is this recommended? What temperatures, etc.?

Thanks!

VintageCharlie

[neikeel]

I'd be very thankful for any advice how to test the CC's properly to make sure there are no moisture issues or other stuff going. Demonufo suggested baking them slightly. This sounds adventurous Has anyone done this - is this recommended? What temperatures, etc.?
Thanks!
VintageCharlie

I know that I have been helping you with some of these bits but, Karlis I think that you may now officially have sniffed a cork too many

[demonufo]

Of course baking would only be recommended if the storage history of the CC's is dubious. To be quite honest there aren't really any effective tests for resistors like there are for caps, certainly not for moisture ingress.
The only time I've ever bothered to do this was for a restoration job on an old fender, and the British Made RS packaged CC's I was using had been salvaged from a metal cabinet in an aircraft hangar, where they had been residing for god knows how many years, no longer required by the avionics team (which was good for me, 'cause I "rescued" hundreds ).
When building clones I would tend to stay away from traditional CC's (but have used Riken's, which technically speaking are somewhere between CC and CF in there makeup, although I think bright blue might look a little stupid in a JTM45/100 clone )
CC's have their place and can sound very sweet though in the right amp. And a 45/100 is one that most definitely I would consider the right amp, it's just I'm not very comfortable with the idea of using CC's in such positions myself. To be fair though, the only 2W CC's I have are pretty average ones I got from Weber, not premium such as Stackpole or AB.

[VintageCharlie]

Yes, i'm actually really getting more and more into cork sniffing (and, yes, i am a bit high and obsessed). There are details i'm concerned with right now that i didn't bother at all a couple of months ago. It's just that after all the effort and time invested in this, i don't want to let it down at any point.

I think i'll take the risk and go with the 2w AB cc's for the corresponding spots and leave you the chance to say "i told you so" if something goes into flames. I have also AB mil spec 2w's in 10k and 8.2k - so maybe these will go into the build instead of the standard 2w's.

And i suppose i will go for the Dickinson spec and maybe even after an exact replica of it - with exactly the same parts, etc. And in the end age the cabinet and spray EXP on it

[shakti]

Well, I had AB CCs in those positions on my previous JTM45/100, running GECs at 560V, with no issues at all. I think you'll be fine...

[neikeel]

Well, I had AB CCs in those positions on my previous JTM45/100, running GECs at 560V, with no issues at all. I think you'll be fine...

Sounds very past tense Do you still have it?

[shakti]

Still have the GECs...amp sold, parts being collected for an even more authentic one. Not quite Karlis-level of attention to detail, but it should be nice.