My Son's first Tube Amp Kit

[topround]

Call me a proud father..I am  /
My brother gave my son, whose forte is building things, a 8 watt tube amp kit for Xmas,
We practiced soldering, and he is pretty decent at it. I think building models with glue gave him a clue as to what is supposed to happen. He respected the heat, after 3 burns , and now I feel pretty confident he can do almost anything...Scary for a newly minted 10 year old boy. Next will have to be schematics!!

All went well, except no sound , since I am electrically illiterate I had no answer, it seemed to go together perfectly but who knows? He is totally bummed, I am totally proud!! I told him not to give up, we will figure out what went wrong, Daddy has lots of audio friends who can help
Here are some foto's

[topround]

Sorry fotos did not load

[richidoo]

Mike, you can use the "additional options" button to upload the pics from your PC to the forum. Then press choose file, and point to a picture on your computer, then hit more attachments to add more pics.  Maybe this is what you already tried?   When you press "Post" it will upload them and it should work.

The URLs of the pics in your post are on your local computer.

[tmazz]

....... He respected the heat, after 3 burns .......

Mike,

Have your son but Vitamin E on those burns. Just break open a capsule and soak the burn on the Vitamin E oil inside. The pain and the visible signs of the solder burn will be gone in no-time. Learned this trick from a lab professor in engineering school and it has never failed me.

BTW, although it is frustrating now to not have it work first try, he will be much more proud of something he had to really work at to get functional. Sweat equity is a wonderful teacher.

Tom

[AcidJazz]

Good for Andrew...Mike, have him reflow all the solder joints, even if they look good they can be iffy. Another first-time-solder-error is too much heat which can sometimes ruin a small part.
My very first project didn't work either, so that's normal. 
He shouldn't feel discouraged.

[topround]

Thanks guys,
I am going to try to measure the resistors when I get home today and see if we fried one or more.
He is so bummed he says all he wants to use now is solid state!
Can you imagine? He expected so much, so the fall was great, but we will pick up the pieces and start again, Soldering ain't the same as Legos and model planes, he has to learn that.
I will tell him your stories to make him feel better.
Thanks

Mike

[JLM]

If interested, Decware has some top notch sounding and simple kits at reasonable prices.  Plus they are a small American company and I'm sure willing to help over the phone.

[shep]

I built my first Heathkit SS amp at around that age and it promptly went up in smoke  Had to wait 40 years to dare pick up a soldering iron again...Don't let him give up! He'll be all the prouder when he gets it right and it makes music.

[rollo]

Cool. Just think in a few years an inhouse modder at your fingertips.


charles

[richidoo]

I was about 12 when I started switching from RC airplanes, rockets and boat models to electronic kits. I just missed the Heathkit and Lafeyette era, but I still had their catalogs. I tried building circuits from experimenters book from RS. I used a hobby iron, thick solder and toasted the ICs I was soldering to. It was disappointing when it didn't work.

Could be burnt parts, but probably only caps would be sensitive to that since no ICs. He can desolder them and check the values with a multimeter to be sure. Resistors should be fine.  He should just double check that he didn't make a circuit mistake, bad connection, or blew a fuse because of a mistake. Mistakes are a good way to learn.

It's too dangerous for him to probe the circuit for correct voltages to find the fault quick and easy, but it would be cool if he could look over the tech's shoulder when he debugs the amp. Then he can understand what he did wrong, maybe the guy can explain the mistake in terms Andrew can understand, then he will be encouraged to try again.

Every tube newbie has these feelings. "Tubes rule" after you come up to speed, but usually not at first. Worse yet when it's DIY and you have no mfg to complain to.

[BobM]

Hey Mike, I told Vinny on Saturday that he would be de-bugging that little amp in about a week's time. 

Here's a couple of things to think about:
- If you're going to measure resistors they have to be out of the circuit. You can't just measure them in place.
- Did the kit provide you with measurement points to test your AC and DC voltages? That would be the first place to look. It will help you determine which stage the error is likely to be found in.
- As was mentioned before, check all your solder connections. it is all too likely that you just have a cold solder join somewhere.
- Be very careful of tube amp's when plugged in. They carry lethal voltages.
- Check your trannie wiring. There's usually a lot of wires and they can be confused easily, even when color coded.
- Check the orientation of polarized parts. If one is in backwards it can stop everything from working, especially diodes.

Hey, this is your first project also, right? There's always a glitch somewhere that has to be ferretted out. Tell your son that this will always happen on any electrical project. I would be suspicious even if it DID work correctly out of the box, because there's always something that I missed or did wrong, and that is real experience talking.

Good luck.

[mgalusha]

Mike,

What kit is it? This one perhaps: http://www.s5electronics.com/l8stereo.html

They have high res photo of the amp board, so we might be able to figure out where things went amiss. On the right side of the board are some pads marked B+, gnd, fil and fil. You should be able to measure from gnd (ground) to B+ to find out if you have high voltage. Set your meter on the highest DC volts scale and be really careful as it's likely over 300 volts. Assuming of course that is the one. I don't see any diodes on the board tho but they have to be somewhere.

mike

[mgalusha]

If it is the K-8LS then here is a thread on diyaudioprojects on it, including the schematic

http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=585

[JLM]

I waited until just after college to do DIY Hafler pre and power amp kits, circa 1980.  I had my old roommate, who was an electrical engineering major and had worked at Electro Voice help (do most) of the pre, but he only over saw the work on the power amp a few weeks later.

Having a mentor to help guide as much as needed was essential.

[topround]

I encourage and provide. Unfortunately I am not electrically literate, but I do have several friends who are good at this sort of thing, but they cannot really mentor and oversee but can help.
Just like everyone here offering help and advice.
I really appreciate it!


Thanks
Mike