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PostPosted: Sun Aug 27, 2006 1:00 am 
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I'm working on my sIII kit this weekend. A few questions:

- First, my turret board was wrong. On the right side, the middle lug where the two .0047u caps come together was too far to the left. So I just joined the pieces and soldered them together. Will that cause problems later on?
- Next, tube socket locations. I count 8 socket holes on the back of my chassis, and one large one in the front for the big 32/32. (Whatever that is... haven't gotten that far yet.) Looking at the chassis from the bottom, let's call them tube cutouts 1-8 looking left (under transformer) to right. I was planning to put the rectifier in 1, skip 2, put the EL84s in 3,4, 12AX7s in 5,6,7 and skip 8. Make sense?
- Finally, I assumed that the big "684K/630V" cap was the .68uF on the far right of the board (C2).

More fun tomorrow.


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PostPosted: Sun Aug 27, 2006 9:22 am 
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I think the turret board you received, had an extra row of turrets in it so you ended up with the parts one hole to the right. You can move them or leave them. There should be no problem either way.
This has been changed on the latest set of boards as I also found it confusing. An extra set of turrets is good for mods, but can be confusing.

On the tube cutouts. Yes, there are extra holes now. Your plan makes perfect sense. Put rectifier close to the trasnformer.

The large yellow cap is marked 684 which is the code for 0.68uF - you figured that out to.

I also explain this decoding in the manual:

The first two are the 1st and 2nd significant digits and the third is a multiplier code. Most of the time the last digit tells you how many zeros to write after the first two digits. A capacitor marked 104 is 10 with 4 more zeros or 100,000 pF which is otherwise referred to as a 0.1 µF capacitor.

So, take the first two digits add number of zeroes muliptlier specified in third digit to get pf and convert to uf.

Code pf uF
510 51 0.0000510
181 180 0.00018
501 500 0.0005
472 4700 0.0047
103 10000 0.01
123 12000 0.012
203 20000 0.02
223 22000 0.022
104 100000 0.1
684 680000 0.68

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PostPosted: Tue Aug 29, 2006 1:43 pm 
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I didn't have enough of the twisted pair to wire up the tube heaters, so I made some of my own. Once I got it all together, I saw that it was supposed to be 22 gauge solid code, not stranded core. Should I swap this out, or will it be OK? I have some 18 gauge solid core that I can use if I need to change it out.


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PostPosted: Tue Aug 29, 2006 8:35 pm 
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Nope, use what you have. That's fine. 22 ga minimum Stranded can take more current than solid anyway.

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PostPosted: Fri Sep 01, 2006 2:57 pm 
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The red/black 230V lead on the power transformer, does this go anywhere? Or do I clip it off along with the white (or was it yellow) 0V wire? The wiring chart I has shows the S2 transformer instead of the Heyboer.


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PostPosted: Sat Sep 02, 2006 7:09 am 
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synthetic,

Tie them both off (Red/Black and Yellow/White). Please see updated drawings at:

viewtopic.php?t=689

Also tie off the 5K primaries on the OT.

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PostPosted: Sun Sep 03, 2006 7:03 pm 
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Wow, a bunch of changes in the new drawings. The main change I saw was the TMB volume resistor.

I'm about to switch it on. The instructions said to check the voltages coming off the power transformer before plugging in the tube rectifier, and I want to make sure these are close enough before going forward. I'm using your Heyboer power transformer. The 240V (Red/Black) and 5V (Yel/White) are tied off. Red/Yellow and Green/Yellow go to ground. Here's what I'm seeing (all AC volts):

Red (x2) should be 290V, reads 309V
Green (x2) should be 6.3V, reads 3.4V
White should be 6.3V, reads 8.9V
Yellow should be 0V, reads 4V

Am I reading this wrong, or have I done something wrong? The White and Yellow leads are the main concern. Thanks again for your help.


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PostPosted: Sun Sep 03, 2006 7:59 pm 
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Quote:
Wow, a bunch of changes in the new drawings. The main change I saw was the TMB volume resistor.


The resistor across the two pins on the volume has been there from the beginning. It's not on the TMB, jsut the sIII.

The 240V (Red/Black) and 5V (Yel/White) are tied off. Red/Yellow and Green/Yellow go to ground. Here's what I'm seeing (all AC volts):

Red (x2) should be 290V, reads 309V

Green (x2) should be 6.3V, reads 3.4V
:?: Check to make sure one of those leads is not going to the ground lug on the tag strip.

White should be 6.3V, reads 8.9V
Yellow should be 0V, reads 4V
:?: What do you read across White - Yellow?

synthetic,

Some AC voltages seem a bit high. :?: What is your house Line voltage 125 or so?

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PostPosted: Sun Sep 03, 2006 8:26 pm 
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OK, I figured out that those voltages are expected to be high with no tubes in the unit. However, I'm getting high volts across the rest of the tube sockets with the recifier in:

V1
1: 414v
3: 0v
6: 414v
8: 0v

V2
1: 414v
3: 0v
6: 418v
8: 0v

Any clues?


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PostPosted: Sun Sep 03, 2006 9:05 pm 
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B+ is 420VDC


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PostPosted: Sun Sep 03, 2006 10:31 pm 
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B+ seems OK without tubes.

Check the wring of the 1.5K dropping resistor across the can cap, the 8.2K and 2.2K dropping resistors. The you will have to put some tubes in to see how the voltage settles down.
Do that, take a quick B+ and see if it's in the 350VDC range, and make some measurements on the pins of the tubes.

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PostPosted: Mon Sep 04, 2006 11:28 pm 
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The voltage seemed so far off that I didn't want to risk blowing up tubes, and your voltage chart is for tubes out. But I'll try this if you don't think they're far off enough to damage anything. The resistors you're talking about are R21, R22 and R23?

On an unrelated note, I noticed that C10 has changed from 470uF/50V to 47uF on the new drawing (ver 11). What's the reason for the change, and should I order a replacement part? Or is this a typo?

Thanks for your help. I only cross-posted on 18W because I was being impatient and thought someone might answer sooner. :)


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PostPosted: Tue Sep 05, 2006 5:57 am 
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Jeff, you're building a TMB but posted this as an sIII. That just confused me; no problem though.

Yes those are the resistors.

TMB Docs at :
viewtopic.php?t=688

C10 can be anything from 25 uf up to 500 uf or even more. the smaller the value, the less bass gets through.

Here are the calculations in an 18 watt amp with 120 ohm resistor:

470 uF bypass Cap on power tubes:
f = 1/(2*PI*R*C)
= 1/(2*PI*120*470uF)
= 0.2.8e-6= 3 Hz

220 uF bypass Cap on power tubes:
f = 1/(2*PI*R*C)
= 1/(2*PI*120*220uF)
= 0.2.8e-6= 3.8 Hz

47 uF bypass Cap on power tubes:
f = 1/(2*PI*R*C)
= 1/(2*PI*120*47uF)
= 0.2.8e-5= 28 Hz

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PostPosted: Tue Sep 05, 2006 10:39 am 
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I'm building an sIII. I'll try to take a picture tonight.


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PostPosted: Tue Sep 05, 2006 1:20 pm 
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Ok, well, we must have our wires crossed. I'll look over the pics tonight.

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PostPosted: Tue Sep 05, 2006 9:59 pm 
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Oh yeah, I did something sorta stupid during construction, but didn't think it would matter. (Here it comes, I imagine Coco spitting coffee all over the monitor...)

Remember when I ran out of twisted pair in post 3 of this thread? It's because I wired the tube heaters in parallel, not series. You can see that in the "power transformer" shot below. If anyone wants full-res versions of these (4372x2906), let me know. My cold solder joint will probably be as big as a blueberry at that resolution.


Wide shot:
http://www.jefflaity.com/misc_pix/amp1.jpg

Turret board:
http://www.jefflaity.com/misc_pix/amp2.jpg

Power Transformer
http://www.jefflaity.com/misc_pix/amp3.jpg

Power tubes:
http://www.jefflaity.com/misc_pix/amp4.jpg


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PostPosted: Tue Sep 05, 2006 10:40 pm 
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From a high level, it looks pretty good. Did you try the tubes yet?

As far as the heaters, it's just a lot more wiring & potential for hum. I hope it works out for you. It will work fine.

Make sure all your grounds are solid.

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PostPosted: Wed Sep 06, 2006 12:52 am 
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OK, with tubes in:

*V1*
1= 138
3= .76
6= 150
8= .78

*V2*
1= 152
3= 123
6= 238
8= 150

*V3*
1= 196
2= 42
3= 60
6= 194
8= 60

*V4*
3= 8
7= 311
9= 300

*V5*
3= 8
7= 308
9= 300

Heater voltage is still 3.2 VAC on each side. B+ voltage with tubes in is 325V. The voltage coming out of the wall is 120.0 VAC.

The amp got hotter than I expected it to. Then again, my only tube amp experience is with the Blues Junior, and I didn't get too close to that when it was opened up. So maybe it's fine. There's a slightly... I won't say burning smell because it never got intense. I think it's just the natural tubes heating up smell. But everything else I've built has been solid state, so I don't know what's normal. :)

Am I close? Let me know if there's anywhere else I should check the voltage.


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PostPosted: Wed Sep 06, 2006 7:59 am 
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*V2* 3= 123 ? should be closer to 1.2VDC? Confirm & check.

B+ voltage with tubes in is 325V? B+ is lon the low side, should be closer to 340 DC?

Heaters should have 6.3 VAC across OK if 3.2 VAC on each side to ground.

Are any components getting hot? Or the trannies? If you smell something odd, stop & carefully check things out.

Beware of the High Voltages.

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PostPosted: Wed Sep 06, 2006 10:36 am 
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Quote:
*V2* 3= 123 ? should be closer to 1.2VDC? Confirm & check.


Whoops, missed the decimal point. Make that 1.23V.

Quote:
B+ voltage with tubes in is 325V? B+ is lon the low side, should be closer to 340 DC?


I'll test this again tonight. Maybe I tested the wrong side of the cap.

Quote:
Heaters should have 6.3 VAC across OK if 3.2 VAC on each side to ground.


Aha, that's what I have.

Quote:
Are any components getting hot? Or the trannies? If you smell something odd, stop & carefully check things out.

Beware of the High Voltages.


Should I have a load on the output during testing? It occurred to me last night that I probably should. I have something I can rig together. That could explain the smell.


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