[holland]

ok, thanks. I've got some 0.1uf/160v MK1839 on order, which according to some sites help the M-Cap. I'll try it with the VitQ and will order a couple of different Obbligatos and possibly mundorf silver/oil and silver/gold. It's for the output coupling caps. 0.1uf helps me save money. I was wondering if it needed to be 10% of the value, but I guess not.

 

[bhjazz]

Quote:

Originally Posted by holland /img/forum/go_quote.gif ok, thanks. I've got some 0.1uf/160v MK1839 on order, which according to some sites help the M-Cap. I'll try it with the VitQ and will order a couple of different Obbligatos and possibly mundorf silver/oil and silver/gold. It's for the output coupling caps. 0.1uf helps me save money. I was wondering if it needed to be 10% of the value, but I guess not.

Whoa, wait! 160V will not work. The Bijou runs at 250V! Caps rated at 250V would be the minimum. I thought you were going to use the 600V VitQs....which would be fine.

 

[holland]

Yeah, I'm going to try a number of different bypass caps. 160V should be fine, I think. 250V is the B+, but the output DC isn't at B+ level. It should be about 125V. 160V should cover it. I can measure the DC to be sure.

The MKP1839 is only available in 160VDC. I have Vit Q 0.18uf/600V which I will try and I think the Mundorf S/O and S/G are at 1200V.

 

[bhjazz]

Good point! OK. As long as you are in the know about the voltage. I'd hate to be responsible for blowing some big-dollar caps in your house! Have fun, and do post your findings. I'd love to know how it all turns out.

 

[holland]

ugh, took my case apart to allow for bypass cap tweaking and took the opportunity to measure some voltages. My B+ has sagged *alot* to 229V. I now have it set to 225V for regulation. I did some quick measurements and my tranny is putting out 280V-0-280V (Rcore type), might have to do some debugging here, grrrr.

Not happy. /me starts to pull up the schematics.

Will start some bypassing later, I guess.

 

[holland]

Alex, what is the output of the EZ81 supposed to be? I'm measuring 308VDC out of pin3. Pin 1 and Pin 7 differential measures 570VAC. Relative to CT, I measure ~285VAC.

308VDC seems low to me. Drop across R7 and R8 are about 34.5VDC. I'm using Regal Mod with 6N1P input and 6N6P-i driver.

Edit: 34.5VDC over R7 and 34.5VDC over R8, so about 70V drop total.
Edit: Heater is 6.8VAC.

 

[Ferrari]

I’m not Alex and also too busy with this thing

, but just opened my Bijou, checked the voltage of my PS at pin 3 of the EZ81 and got ~315V. 308V at that point seems to be a bit low but acceptable I think (~2.5% off).
Is your measured heater voltage loaded or unloaded ?

 

[holland]

Thanks Ferrari, much appreciated.

My heater voltage is loaded. Looking at the current across R7 and R8, it seems high at 105mA. Do you get similar? I'm going to warm up the amp and take pin measurements to see if I can find where the current is going.

 

[zkool448]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif I’m not Alex and also too busy with this thing

Ferrari, whatever it is you're working on it looks brilliant already -- btw, what is it?

holland, not sure if this helps but I also have an R-Core and done regal's mod. EZ81 pin 3 mine measures at about 325VDC. I get 580VAC with meter leads on pin 1 & 7 (both at ~291VAC relative to CT). Heater voltage loaded but a bit high than I'd like which is at ~7.18VAC.

Voltage drop readings for R7 & R8 total is 53.3vdc (R7 = 26.7vdc, R8 = 26.6vdc)

 

[holland]

What tubes are you using zkool448? I think one of my drivers went bad.

 

[holland]

Hmm, weird. Measuring Pin2 of the 6N6P-i on the right side pulls in about 79V. On the left, it's 113V. The left is steady, the right, as soon as I probe it, it drops down in voltage and settles around 79V. Something's amiss. I can't quite reach the 330n caps to measure the voltages on either side, and it's hard to probe the tubes as I have a bracket over the board to hold the tubes up.

 

[holland]

Thanks Ferrari and zkool. I replaced the 6N6P-i with 6N6P and it's steady now. I can hold 250v. It was a bad tube, guessing it's on the left side.

 

[zkool448]

Glad you found the problem holland. I fired up my Bijou once and also had wrong readings. Thought I fried one of my FETs then accidentally discovered the culprit after swapping the input tubes.

One of the socket pin hole had become loose/opened it wasn't making contact with the tube's cathode leg. Squeezed it back to shape and problem was solved. You might want to double check your sockets just in case your tube might still be ok.

 

[Ferrari]

Quote:

Originally Posted by holland /img/forum/go_quote.gif Thanks Ferrari and zkool. I replaced the 6N6P-i with 6N6P and it's steady now. I can hold 250v. It was a bad tube, guessing it's on the left side.

Good to know the problem is solved, holland.


Quote:

Originally Posted by zkool448 /img/forum/go_quote.gif Ferrari, whatever it is you're working on it looks brilliant already -- btw, what is it?

It’s a tube amp… hehe.

Well, it’s a kind of tinkerman project, intend to be a transformer coupled one-stage tube amp to drive 32Ω/300Ω headphone.
I have been playing around for a while with some high gain tubes 6S45p-E triode, D3a pentode (in triode mode) and 6N30P-DR dual triode + Sowter output transformer as one-stage amp with very good result (there are probably more tubes that's technically up for this task).
So, I decided to put it in a neat enclosure instead of P-P wiring on my desk.

On the left of the picture is the amp chassis. Due to the different pin layout of the tubes, I created some tube bases to make them exchange-able. The chassis on the right houses the DC power supplies: 6.3V heater and 150V/180V B+.

 

[amphead]

That is a beautiful looking project Ferrari!

Balderon NICE WORK! Keep us posted for the sound.

Well I'm working on an underground laser light show for my nephews band. He will be playing at an underground club. This gives me my first chance to do a public light show. My green laser at 80mw is quite bright. The red laser at 325mw is pinkish/orange because of the power. And my 384mw ultraviolet/violet laser is a bright pink beam with bluish streaks because it causes dust particles in the air to become flourescent as well as the psychedelic posters in the club. Luckily they have invested in a fog machine.