Vote for Ike in 2008

[Shannon Parks]

Can I ditch the cathode biasing circuit: the two big electrolytics & big 5W WW resistors? I could then put the extra PPP bias circuit and hookups there.

[EWBrown]

The cathode biasing circuitry isn't too important, if that option is desired, it could always be added off-board along with the (extra) power tubes.
That allows for bigger cathode resistors or those Dale "heatsink" power resistors.

Might as well save the valuable PCB "real estate" and put something else better on it, or just physically "downsize" it as things develop.

Since you mentioned fuelling up on some coffee / aka "brain juice":
( I don't drink coffee too often, as a little bit of caffeine goes a LONG way with me, but when I need a serious jump start, it works miracles for me)

Just stay away from that strange coffee from Madagascar, of which the coffee beans have been "processed" by passing through the digestive tract of a certain species of Lemur. :o Yellow_Light_Colorz_PDT_09 Yellow_Light_Colorz_PDT_06 (yes, there is actually such a thing, and it is VERY expensive).

update, this stuff is actually from the Phillipines, where they also consider "balut" as a delicacy...

http://technically.us/eat/x/philippine-civet-coffee/


just my "dos pesos" worth for the day Yellow_Light_Colorz_PDT_03

/ed B in NH

[dhuebert]

I know I've said this elsewhere, but...I say: keep the sockets on board, put four output tube sockets for optional PPP, all octal, 535 volts B+, no cathode bias option.

Don

[WA4SWJ]

Shannon,

I'd vote for fixed bias only. Makes it easier to use a broad range of output tubes. Leave the 10 ohm resistor in of course for cathode current measurement.

[hifi725]

You wrote. "Hmmm. Must. Have. 100W. Watt. Tube. Amp. " The Allen Organ type 90 mono blocks are 90 watts, not 100, but close. These do pack a punch with only two KT88's.

[Shannon Parks]

You wrote. "Hmmm. Must. Have. 100W. Watt. Tube. Amp. " The Allen Organ type 90 mono blocks are 90 watts, not 100, but close. These do pack a punch with only two KT88's.

I think I've hit >80W with a pair of KT88s before. Aggressively biased, of course. :)

Thanks for the comments, guys. It has helped a great deal.

[audiog]

What about a stereo pcb? Or a symmetric placement of the components on the single pcb to easy put two of them like a stereo pcb?

Great Idea to renove eiclone project.

Ciao, Giuseppe

[Shannon Parks]

Two could be mounted side by side, Giuseppe, but I think the weight becomes an issue. For example, the Eico HF89 about breaks my back carrying it around, and the steel chassis still flexes.

[Shannon Parks]

OK - what about the bias pots? Do people hate/love them? Do I make sure that WW subs are a little easier?

[EWBrown]

I loke the multi-turn bias pots, they are much easier to tweek-in than are than single turn trimmers or pots.

On one of my ST70 rebuilds, I uset two linear 10K 10 turns Bournes "helipots" that I salvaged from a dead SS regulated power supply. Makes for tweeking the bias really nice and simple - and I used the locking shaft collars to hold the settings. THe old standard issue Dynaco pots were just too "touchy" for my liking.

For the WW resistor locations, perhaps some "multi-pads" like you have for the caps on the Poseidons, would make "resistor rolling" easier, or at least more universal.

/ed B in NH

[dhuebert]

what about the bias pots?

Keep the multi turn pots but turn them around so clock-wise rotation makes the cathode current go up.

Don

[WA4SWJ]

I agree with the multi-turn pot comments. I like them too.

[EWBrown]

If you do like I do and mount the pots on top, the rotation is reversed so CW rotation becomes increased bias current. Or the leads could be bent and, the pot mounted "backwards" which accomplishes the same thing...

I still have yet to finish the 6S4A CCS modified ST35 unit, the board is all "converted", just this darn martian bug, and general winter-caused SAD lassitude has taken over...


/ed B in NH

[erichayes]

Shannon, the 1773's controls were selected for ergonomics and noise. It's much easier to ballpark the bias with one control, balance with another, and finalize with the first, rather than "climbing the ladder" with two bias controls. The AC balance controls were mounted below chassis to prevent audiot users from tweaking them and increasing distortion.

The type K pot, along with the J, has been around since WWII, is mil spec, and (goes without saying) is one of the most reliable pots available. It's rated at 2 watts, but isn't wirewound (wirewound pots tend to introduce distortion). And, with their locking collets, a row of four type Ks has a real authoritative look.

I concur on the weight factor. I built two prototypes of stereo versions of the Eiclone on 10X17X3 aluminum chassis. They weigh in at 45 lbs and have a definite "swayback" appearance. Without the bottom plates attached, the chassis feel more like jello than metal.

[Shannon Parks]

Shannon, the 1773's controls were selected for ergonomics and noise. It's much easier to ballpark the bias with one control, balance with another, and finalize with the first, rather than "climbing the ladder" with two bias controls. The AC balance controls were mounted below chassis to prevent audiot users from tweaking them and increasing distortion.

Thanks for bringing this up, Eric. It is funny that I hadn't thought of this yet, as my ST70 & Poseidon driver use this method and I always hated trying to set the bias on the Ikes - very sensible and much, much more PPP friendly. Should be a simple change. I'll add extra connections for type K pots.

Good ideas, Don & Ed. I'll switch to an inline Bourns-type pot, instead of the 'V' pin pot. That would allow you to mount the pot either way depending on how it is mounted.