Starting a Deluxe Lite in a Stout Chassis (COMPLETE)

[Willabe]

That's a very good idea. Relating the layout to the schematic may seem overwhelming at first but the more you do it, the better your understanding of "how it works". Eventually, you'll use the schematic whenever trying to understand a circuit operation and for troubleshooting. The layout is great for building a circuit or identifying components while troubleshooting, but contributes very little toward understanding the circuit. All of my projects start with a schematic. The layout is developed from that schematic.

+1

Many of the new members that are just starting to build amps will post a layout drawing instead of a circuit schematic saying it's easier for them to read or that they can't read or follow a schematic.

You have to be able to read a schematic, it's really not hard at all. It just takes a little time and you'll get it.         

[Ambugaton]

Ok, I am trying to grasp how the cap can will be placed in this circuit. After looking through the schematic this is what I picture it looking like. Am I way off? I did notice that there is a 220K/1W resistor that goes to ground right before the first cap but it is tied in through the 5 VAC PT wire that I am not using. Not sure if it is still needed.

[Ambugaton]

Forgot to add that "B" goes to pin 6 of each power tube.

[Willabe]

The cap can drawing looks correct to me.

On the 220K R, I think that's just a B+ rail bleeder, but I'm not sure without seeing a schematic.


 

[Ambugaton]

Here is the schematic. If it is a bleeder resistor, from a short amount of reading... this is used to bleed the charge from the caps when the amp is turned off?

[sluckey]

Forgot to add that "B" goes to pin 4 of each power tube.

No. B goes to pin 6 of each power tube.

[Ambugaton]

Yes! My mistake.

[Willabe]

If it is a bleeder resistor, from a short amount of reading... this is used to bleed the charge from the caps when the amp is turned off?

Yes. Most of us would keep it.

I did notice that there is a 220K/1W resistor that goes to ground right before the first cap but it is tied in through the 5 VAC PT wire that I am not using.

No, it's tied to the rectifiers B+ side not the 5dcv heater side. (Sorry, not thinking, the 5dcv has the full B+ floating on it.)

[sluckey]

You need some insulation on that long diagonal jumper (middle of board) that passes between two closely spaced turrets. You are also missing several jumpers. Better fix all this before you move on.

[Ambugaton]

You need some insulation on that long diagonal jumper (middle of board) that passes between two closely spaced turrets. You are also missing several jumpers. Better fix all this before you move on.

Will do. Just finished getting the paper removed. Won't make the mistake again... what a pain.

[sluckey]

Lookin' like a Hoffman board now.   

[Willabe]

Yeah that looks good now! 

I'm glad Sluckey spotted that paper, I thought it was a white/un-dyed verson of vulcanized fiber board. 

[Ambugaton]

Made the rest of the jumpers. Can't believe I missed that many. Was getting late I guess.

[Ambugaton]

Seems like I am short 01 diode, and 01 25uF cap. How much would it piss Doug off to send such a small package? I don't believe these are available locally but I will check. There is a small radioshack but it looks like all they will have are 22uF/35V caps... don't know what effect that will have. Who knows, maybe I can find em.

I also had another layout vs schematic question. The two 100K/Rs from V1-1 and V1-6 appear to be 1W resistors on the layout but the schematic did not specify. I used 1/2W resistors here, any issue with that?

[John]

How much would it piss Doug off to send such a small package?

As long as you pay the shipping, he doesn't care.

[Ambugaton]

I was able to find a 22uF/50V radial capacitor at radioshack...

I have a question about the SS rectifier though. This whole time I thought I needed 3 1N4007s on each side of the 330VAC secondaries... but given that I wouldn't ever expect anything close to 2000V, I could just use 2 of these on each side?

[John]

That should be fine.

[Ambugaton]

Morning Everyone. I pushed through and finished the amp last night. Plugged it in a limiter and hit the switch... and got nothing. Turned out to be a burnt bulb! Powered the amp up and everything seemed ok. Had -56VDC for bias voltage. Plugged in the tubes... and instantly knew I had to switch the OT leads. Popped off the NFB just to get readings and had the following:

2.7 VAC on all filaments (seems normal)

V1-1: 170
V1-3: 2.82
V1-6: 176
V1-8: 2.75

V2-1: 265 VDC
V2-2: 20.2 mv
V2-3: 63
V2-6: 253
V2-7: 21
V2-8: 63

V3-1: -36
V3-3: 468
V3-4: 468
V3-5: -36
V3-6: 468

V4-1: -34
V4-3: 464
V4-4: 466
V4-5: -35
V4-6: 469

I did somehow screw up wiring in the pots... might be from transposing from the layout to the chassis. Once again... should have confirmed with the schematic. Lesson learned. I don't know how to tell if my readings are within range unless I can compare to one of Doug's AB763 builds?

[sluckey]

V2-2 should not be 20mV. It should be equal to the voltage on V2-7.

What is the voltage on V3-8 and V4-8?

B+ is very high. Which PT did you use?

Does it make any sound?

[Ambugaton]

V2-2 is 20VDC not mv. Don't know how i made that mistake.

PT is 041316 330-0-330

Yes it makes sound and sounded pretty good without the NFB, having the pots wired incorrectly, and cold biased. Very quiet as well.

[Ambugaton]

I did not place the 220k bleeder resistor. Would that cause higher plate voltage? The thing sounds fantastic. I biased for slightly below 18 watt dissipation. I could use a little less clean headroom... But I play with pedals so that's not such a big deal.

[Ambugaton]

Looks like I need to read up on the 6V6. 18 might be a little hot

[sluckey]

I did not place the 220k bleeder resistor. Would that cause higher plate voltage?

Putting that resistor in circuit 'might' drop the B+ a volt or two. Very insignificant drop.

[sluckey]

Looks like I need to read up on the 6V6. 18 might be a little hot

18 watts is fine for two 6V6s. But if each 6V6 is idling at 18W, yes, you need to drop that considerably. A 6V6 is good for about 14 watts plate dissipation. I like to run at 70% wich is about 9.8 watts per tube.

[Ambugaton]

Let me know if this sounds right.

My plate voltage is 466. The mv reading on the 1 ohm resistor/ground is 22. I then multiply 466 x .022 and that is plate dissipation? Says it is about 10w per tube.

[sluckey]

 

[Ambugaton]

Sweet. Well thank you Sluckey. For the amp, the advice, and the fun. Thanks.