Plate voltages in C4S'ed Foreplay 2?

[zacster]

I have a FPII that I built, 15 years ago according to the receipt that I have, with the C4S mod in it.  I haven't actually used it for a while now, and had pulled some caps out for use elsewhere.  I'm looking to do a project that uses 2 nine pin tubes and thought I could reuse the chassis and transformer/PS from it, as well as some other parts of it. 

My question is what were the plate voltages to the 12AU7, and the expected current from the CCS?  I can't just measure as the PS caps were pulled, otherwise I'd just plug it in and check.  I can't find the original documentation for either the FP or the Anticipation and there doesn't seem to be anything either here at BH or elsewhere.  I remember the VoltSecond page on the C4S, but that is gone too. 

In looking at the undersides you can tell the builder didn't know what he was doing (that would be me).  Also, that magnet wire was a PITA to work with.  I actually used the leftover magnet wire in another project, but this time I had gotten the hang of it and it is much neater.  Teflon OFC wire for me now.  It's hard to believe it has been 15 years since I built this.  It was my first tube anything.

[Paul Joppa]

The original Foreplay (my manual is dated 1998) ran 157v from the power supply, and 45v on the voltage amp plate, current was 1mA. The cathode follower had 50v at the cathode, running 1.7mA.

I think the v2.0 was about the same, but I don't have a manual or circuit at hand. I don't recall the specs on the FP-2.0 power transformer, which was somewhat different. If your transformer has markings, let me know what they say (a picture maybe?) and I can advise on appropriate maximum current.

The FP-III (manual dated 2005) regulated the B+ to 150v, and ran about 3.6mA through each triode. This raised the first stage plate to around 70-75v. I am not sure but I think the FP-III current increase was made possible by the much larger PT-3 power transformer.

[zacster]

Well my wife found the original manual, so I'm good now.  All specs agree with what you have, and all of my readings were about 10-15% higher.  It's funny looking at the schematic now, I didn't understand a thing about it when I put it together.  I'm far from an expert but at least I can follow it now.  My manual is from 2000.

I'm looking to build a transformer coupled driver to my 6B4G modified ST-70 using a mix of ideas from Lynn Olsen and KandK audio and others I've seen.  I've done a side by side of my amp with Paramours and they were completely different, not surprisingly.  My amp could pound it out while the Paramours were very sweet and detailed.  I'm trying to get the best of both.

Thanks for helping.

[zacster]

Well, my wife did find the FP II manual, but I've spend the last 2 months cleaning 25 years worth of crap from my basement and the C4S manual didn't turn up.  Every other DIY project manual did. 

What was this capable of?  Can I get 60ma from it?  The comments I see doing a search show much lower current capacities.  I'm just trying to use what I have.  It took 2 months to clean that basement and we threw out 20+ contractor bags of stuff plus a lot of large furniture so far and our agreement is that anything new going in has to have something come out!:)  Something 1" square won't take up space, but I have a whole pile of parts.

[Paul Joppa]

I assume you are asking about 60mA from the C4S. The output transistor can dissipate a bit over 0.4 watts, which means it can drop a maximum of 6.7 volts at 60mA.