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Old 15th January 2010, 09:51 AM   #1
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Default Simple SE checkout for dummies

So I finished up my Simple SE (finally!) and am just getting it loaded up into its new chassis. I "tested" it on a breadboard just to make sure it doesn't blow up and everything lit up, looked good, smelled normal, and made music.

My question is, how to I actually check the measurements to make sure everything is running right? I can find a pretty good checkout procedure on the Tubelab website for the Tubelab SE, but I can't find something similar for the Simple SE.

I would really appreciate if someone could walk me through with "you need to check X and you do that by checking "here" and looking for Y." I remember reading somewhere that there really isn't much to check on this amp and that its pretty much plug and play (and it did work) but I still want to check.

Sorry for the newbie questions, but I really want to make sure my new (and first) creation is running right so that I'll get plenty of life out of it.
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Old 16th January 2010, 04:34 PM   #2
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Anyone?
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Old 17th January 2010, 04:52 PM   #3
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Sorry. Simple SE is well Simple. There is no "Check Out" for it. Good Common sense rules here.

For mine:

Double/Triple Check all work

No Tubes in:
Check Filament Voltages
Check Transformer Voltage

With Rectifier
Check for B+ (briefly, depending on configuration could exceed cap voltage rating)

With Resistive load attached to speaker out (8ohm) and Tubes
Look For SMOKE
Check for AC Out
Check B+
Look For SMOKE

Try it on a cheap speaker
Look for SMOKE

ENJOY!

READ: Georges safety tips VERY IMPORTANT!!!!!!!!!
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Old 17th January 2010, 10:55 PM   #4
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Quote:
Originally Posted by SGregory View Post
Sorry. Simple SE is well Simple. There is no "Check Out" for it. Good Common sense rules here.

For mine:

Double/Triple Check all work

No Tubes in:
Check Filament Voltages
Check Transformer Voltage

With Rectifier
Check for B+ (briefly, depending on configuration could exceed cap voltage rating)

With Resistive load attached to speaker out (8ohm) and Tubes
Look For SMOKE
Check for AC Out
Check B+
Look For SMOKE

Try it on a cheap speaker
Look for SMOKE

ENJOY!

READ: Georges safety tips VERY IMPORTANT!!!!!!!!!
Thanks for posting this. I saw that you posted something similar in another thread but unfortunately I don't know where to check for filament voltage, transformer voltage, B+, or AC out?

I've read George's safety stuff and I've got the clips on my meter so that I don't have to touch anything while its live; know I just need to know where to stick the clips.

I appreciate your patience!
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Old 17th January 2010, 11:35 PM   #5
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I started to writeup a guide for doing some simple ohm and voltage checks for a new amp. You can see my photos here:
Checkout :: ohm00.jpg picture by Ty_Bower - Photobucket

You're probably already past this point. After the amp is up and running, you probably want to know the B+ voltage. It will vary depending on which power transformer you used, line voltage, and load (type of tubes installed). This is the dangerous stuff that will kill you, and it will probably be in the neighborhood of 450 volts DC. I use clip leads and attach them while the amp is off. Put the black lead to ground. The red lead can go to R4 - it is fairly convenient. You want the end of R4 that is closest to the edge of the board.

You probably also want to know the voltage at the cathodes of each power tube. Again, the clip leads might work well. Measure between ground and the end of R17/R27 that is closest to C12/C22. Knowing this voltage will allow you to do several things. First, you can verify that you are not exceeding the working voltage limit of the cathode bypass caps. Second, you can calculate the total current drawn by each power tube. To calculate the current draw, use Ohm's law (V=I*R). My cathode resistance is 810 ohms. With Sovtek 6550B, I measure 48.6 volts at the cathode. Solving for I gives 0.060 amps, or 60 mA per tube.

Once you know the voltage across the tube and the current, you can calculate the total power dissipated. You can either measure the plate voltage, or just assume it will be fairly close to B+ (probably within 10 volts). Take the plate voltage and subtract the cathode voltage. Multiply that result by the current (in amps) to give watts. For my case, 450 volts minus 48.6 volts gives about 400 volts across the tube. Multiplied by 0.060 amps gives 24 watts dissipated per output tube.

You can compare the dissipated against rated limits to verify your tubes are running in a safe region. Of course, the numbers don't tell the whole story. You really need to inspect the plates in a dark room, looking for signs of red glow. You also want to peer in through the plate holes (if any) and look for bright spots on the screen or control grids.

You might also want to checkout the front end for reasonable operation. You can measure the cathode voltage of each section on the 12AT7. You'll be checking at R10/R20. The math works the same as the power tubes. The cathode resistors are 220 ohms. Each section should be drawing roughly 8~10 mA, regulated by the CCS. Expect to see about 1.7~2.2 volts at the cathode.
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Old 18th January 2010, 12:06 AM   #6
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Quote:
Originally Posted by Ty_Bower View Post
I started to writeup a guide for doing some simple ohm and voltage checks for a new amp. You can see my photos here:
Checkout :: ohm00.jpg picture by Ty_Bower - Photobucket

You're probably already past this point. After the amp is up and running, you probably want to know the B+ voltage. It will vary depending on which power transformer you used, line voltage, and load (type of tubes installed). This is the dangerous stuff that will kill you, and it will probably be in the neighborhood of 450 volts DC. I use clip leads and attach them while the amp is off. Put the black lead to ground. The red lead can go to R4 - it is fairly convenient. You want the end of R4 that is closest to the edge of the board.

You probably also want to know the voltage at the cathodes of each power tube. Again, the clip leads might work well. Measure between ground and the end of R17/R27 that is closest to C12/C22. Knowing this voltage will allow you to do several things. First, you can verify that you are not exceeding the working voltage limit of the cathode bypass caps. Second, you can calculate the total current drawn by each power tube. To calculate the current draw, use Ohm's law (V=I*R). My cathode resistance is 810 ohms. With Sovtek 6550B, I measure 48.6 volts at the cathode. Solving for I gives 0.060 amps, or 60 mA per tube.

Once you know the voltage across the tube and the current, you can calculate the total power dissipated. You can either measure the plate voltage, or just assume it will be fairly close to B+ (probably within 10 volts). Take the plate voltage and subtract the cathode voltage. Multiply that result by the current (in amps) to give watts. For my case, 450 volts minus 48.6 volts gives about 400 volts across the tube. Multiplied by 0.060 amps gives 24 watts dissipated per output tube.

You can compare the dissipated against rated limits to verify your tubes are running in a safe region. Of course, the numbers don't tell the whole story. You really need to inspect the plates in a dark room, looking for signs of red glow. You also want to peer in through the plate holes (if any) and look for bright spots on the screen or control grids.

You might also want to checkout the front end for reasonable operation. You can measure the cathode voltage of each section on the 12AT7. You'll be checking at R10/R20. The math works the same as the power tubes. The cathode resistors are 220 ohms. Each section should be drawing roughly 8~10 mA, regulated by the CCS. Expect to see about 1.7~2.2 volts at the cathode.
Ty:

That was SUPER SUPER helpful (especially the photo walk through) and exactly what I needed. This should end up being a sticky for all the newbies out there like me to help us figure out what we are doing. It's really nice to know things like "such and such pin is such and such and should read at such and such."

Thanks for taking the time to do that and walk me through. MUCH APPRECIATED!
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Old 18th January 2010, 01:19 AM   #7
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Ty: that is a nice write up.
bigjppop: If you are planning to use this amp as a learning tool. Which it is great at. Take the time and write the tube pin numbers on the board where you can see them when mounted in the chassis. (power off of coarse). I also wrote the identification for each of the screw terminals. In my case I mounted the components to the back of the board so the silkscreen was not visable when mounted. This helped a bunch as I was documenting a few set points. It also helps when looking at the schematic and knowing where things are.

Each amp will be a little different due the the various possible combinations as Ty mentioned. Tube variation will also cause differences.

Outside of a bad component, mistake in assembly, or a bad calculation for the transformer/cathode resistor/output tube, this amp will work. The operating points are soldered into circuit and no adjustment should be necessary. A few basic checks as shown above is all it takes to get it running.

I assume you are building this as a Triode SE, correct? If not, do so as George suggests. Add CFB and try UL later.


The transformer/cathode resistor/output tube combination should be known and you should be comfortable with it well before you are ready to plug it in. You can post your selection for comment if you wish to get a second opinion. George did alot of homework with this and his writeup is good, but being new not all of it may make sense on the first go around. It didn't for me.
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Old 18th January 2010, 07:54 AM   #8
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Quote:
Originally Posted by SGregory View Post
Ty: that is a nice write up.
bigjppop: If you are planning to use this amp as a learning tool. Which it is great at. Take the time and write the tube pin numbers on the board where you can see them when mounted in the chassis. (power off of coarse). I also wrote the identification for each of the screw terminals. In my case I mounted the components to the back of the board so the silkscreen was not visable when mounted. This helped a bunch as I was documenting a few set points. It also helps when looking at the schematic and knowing where things are.

Each amp will be a little different due the the various possible combinations as Ty mentioned. Tube variation will also cause differences.

Outside of a bad component, mistake in assembly, or a bad calculation for the transformer/cathode resistor/output tube, this amp will work. The operating points are soldered into circuit and no adjustment should be necessary. A few basic checks as shown above is all it takes to get it running.

I assume you are building this as a Triode SE, correct? If not, do so as George suggests. Add CFB and try UL later.


The transformer/cathode resistor/output tube combination should be known and you should be comfortable with it well before you are ready to plug it in. You can post your selection for comment if you wish to get a second opinion. George did alot of homework with this and his writeup is good, but being new not all of it may make sense on the first go around. It didn't for me.
Thanks for the suggestions. This is my first build and as such, learning as I guy. Good thoughts on writing down the pin numbers and terminal numbers before installing in the chassis.

So far its just been wired and tested in Triode SE but I plan to add the wiring/switches for UL and CFB.

The Simple SE is a great learning tool, especially when coupled to the people in this forum!
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Old 18th January 2010, 08:30 AM   #9
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What did you use for OPT's? I use CFB, but did not like UL.
I should correct that last statement. I liked UL for the first 10 minutes but found it quickly got hard to listen too.

If you have tested it in Triode mode now is the time to get out the clips and measure voltages, calculate bias current, and also important is to look at the tube data sheet and see the operating point. Like Ty suggested.

I would also suggest that you listen to it for a while in triode and learn what it can and can't do. Then go the next step. I was a big fan of having ZERO feedback initially, but found that with my budget OPT's I ultimatley comprimized and used CFB.

Glad to see someone else is up at these hours.
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Old 18th January 2010, 08:36 AM   #10
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Quote:
Originally Posted by SGregory View Post
What did you use for OPT's? I use CFB, but did not like UL.
I should correct that last statement. I liked UL for the first 10 minutes but found it quickly got hard to listen too.

If you have tested it in Triode mode now is the time to get out the clips and measure voltages, calculate bias current, and also important is to look at the tube data sheet and see the operating point. Like Ty suggested.

I would also suggest that you listen to it for a while in triode and learn what it can and can't do. Then go the next step. I was a big fan of having ZERO feedback initially, but found that with my budget OPT's I ultimatley comprimized and used CFB.

Glad to see someone else is up at these hours.
I actually live in Tokyo so its not to late for me

I used the big Edcor OPT's for my build and so far I'm pretty pleased/impressed. I wired everything up on a breadboard to test in Triode just to make sure I had put the board together correctly. Unfortunately, since my workshop is my kitchen table, I had to take it apart and but it away until its ready to go into its chassis (which I'm sanding a getting ready for its oil finish right now). Once I get it all put into the chassis, then I'll do final checkout and test the UL and CFB to see how I like them. I figure I might as well put in the switch so I at least have the option to try them as I make adjustments to my system.

With everyone's guidance here on this thread I should be able to check everything and make sure I've got a setup that will last a while. One last question, you mentioned checking for AC at the output; how would I do that?
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