Aikido all in one heater issue

[cjkpkg]

I am having a wierd issue with my octal all in one heaters.

6sl7 / 6sn7 regulated supply voltage doubler.
Tubes out I get 12.5v with tubes in I get 4.0V. I even experimented and put the jumpers in parallel instead of series as if I had 12v tubes - I have a crappy set of these tubes to experiment with. I still get 4V with this arrangement.

Xformer is an edcor XPWR106 Power transformer for a 120V, 60Hz. line to 550V (275-0-275) at 125mA center tapped and 6.3V at 4A.

I think my next course of action is to wire up as full wave bridge for 6.3V...

Would a faulty regulator cause this discrepancy between being accurate with no load and cause a huge drop under load? That is about the only other thing I can think of...

[cjkpkg]

OK...
6sl7 draws .3A
6sn7 draws .6A

Total is 1.8A, I half the amperage by doing a voltage doubler - down to 2A. Plus whatever the regulator draws....I think I may have just answered my own question...I think the full wave arrangement wired in parallel will get me closer to my 6.3V target...

[Original Burnedfingers]

Why not do this?

I believe there was a percentage of the B+ supply somewhere around 70volts to apply to the heater bias tap. It made my Aikidos quiet without going to DC heaters.

[cjkpkg]

WOW...chalk this one up to assuming the labeled bags that the parts come in are correct...those that have ordered kits from Broskie know what I am talking about.

So, one of the caps for the heater PSU section looked exactly like the specified 10,000uF cap but it was actually a 350V 47uF cap...

I replaced with the correct one - had a spare kicking around - and voila...getting 6.2VDC on the heaters.

[BZed]

You didn't read the value on the part when you installed it? OK.

[cjkpkg]

Originally Posted by BZed

You didn't read the value on the part when you installed it? OK.

Neither did Broskie when he put it in a ziploc baggie labeled 10,000uF 16V...just sayin...

[mashaffer]

That's OK, on my last amp build I left of the VAS grid leaks entirely. Wonder why the goofy voltage readings here... Doh!

[BZed]

First rule of kit building is "Inventory the parts". It is possible for anyone to make an error. The first instruction in a Heathkit manual is to inventory the parts to make sure you have all the right parts. Then check them as you install them. Last is to double check before you power the circuit.

[ryuji]

Originally Posted by BZed

First rule of kit building is "Inventory the parts". It is possible for anyone to make an error. The first instruction in a Heathkit manual is to inventory the parts to make sure you have all the right parts. Then check them as you install them. Last is to double check before you power the circuit.

+1

Dont trust the labeled value, test EACH component as you lay it out, no '9 are good/exactly matched so far, this 10th one should be fine' I've personally seen resistors/capacitors that have been way off. If i need five resistors i buy 8 and throw away the three worst ones straight to the trash

LCR meters are a near-must. cheap too. Most multimeters have the ability to check diodes and many do transistors

[Tony]

Originally Posted by 6BG6GA

Why not do this?

I believe there was a percentage of the B+ supply somewhere around 70volts to apply to the heater bias tap. It made my Aikidos quiet without going to DC heaters.

this is a well known technique to combat hum and noise....with direct coupled circuits, it is mandatory to bias the filaments with dc so as not to exceed the cathode filament insulation voltage ratings....a look at the data sheets will confirm this...

for B+ of 200v
R1: 220K
R2: 82K (54V), 120k (70V)
C1: 22u@100V, 22uF is a minimum
R3, R4: 100 to 470 ohms