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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 5th December 2019, 02:57 AM   #11
ejr12 is offline ejr12  United States
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I can get pictures up loaded.

I do not have test equipment other than the multimeter.

How would I go about putting an ac signal into the input?

This is all new to me.
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Old 5th December 2019, 05:53 PM   #12
w5jag is offline w5jag  United States
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Well, after posting pictures of your board, then the next step would be to locate the thread in this forum about taking simple resistance and dc voltage checks on completed SSE boards.

Finding that thread and doing the resistance / voltage checks on your board would be a reasonable starting point and good experience learning about the board. I suspect your board is fine since there's not much to go wrong - the CCS chips are about it.

Your problem likely is / was incorrect input wiring, it almost always is.
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Old 8th December 2019, 03:11 AM   #13
ejr12 is offline ejr12  United States
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I did some looking on the forum today for the checkout protocol that ty prepared. Unfortunately, photobucket is showing private and I cannot see it. If anyone can direct me to a link, Id appreciate the continued help
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Old 8th December 2019, 06:32 AM   #14
lykkedk is offline lykkedk  Denmark
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Quote:
Originally Posted by ejr12 View Post
I did some looking on the forum today for the checkout protocol that ty prepared. Unfortunately, photobucket is showing private and I cannot see it. If anyone can direct me to a link, Id appreciate the continued help
Hello there

You can upload pictures here on site.

Look here :: How do I upload images or files? | diyAudio Helpdesk

Jesper.
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Old 30th December 2019, 05:14 PM   #15
ejr12 is offline ejr12  United States
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Sorry for the delay and lack of pictures. Work has been busy. And, although the board was probably okay, I decided to start from scratch with a new board. This gave me a chance to clean up the solder joints, etc. (Once I get one amp working, I will probably work on chasing the problem down and setup a second amp).



I have the new board working, but I have encountered two problems:


(1) The rectifier tube does not appear to work (no glow and no sound when tube rectifier is selected). I am not sure if my tube went bad or if something else. Advice on how to check would be greatly appreciated.


(2) When I select UL (CFB not installed yet), everything works fine for 5 to 10 minutes. Then, I get a terrible squeal/feedback noise. Any idea what may be causing this. My setup is Edcor Transformers (GSXE).


Thanks
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Old 1st January 2020, 08:04 AM   #16
lykkedk is offline lykkedk  Denmark
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Ejr12.

Eventhrough i find it hard to understand the two quistions, i can tell you that the squeek you hear are MOST properly dc going through somewhere. If you for example have some volumecontrol/potentiometer, and DC is passing there, you for sure gets squeksss among other unpleasant noises, but again i cannot understand the two quistions you have?

Howto meassure the rectifier tube i did see a post here about it.

Good luck.

Jesper.
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Old 1st January 2020, 04:03 PM   #17
ejr12 is offline ejr12  United States
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Quote:
Originally Posted by lykkedk View Post
Ejr12.



Eventhrough i find it hard to understand the two quistions, i can tell you that the squeek you hear are MOST properly dc going through somewhere. If you for example have some volumecontrol/potentiometer, and DC is passing there, you for sure gets squeksss among other unpleasant noises, but again i cannot understand the two quistions you have?



Howto meassure the rectifier tube i did see a post here about it.



Good luck.



Jesper.


Thanks for the effort to help. Ill try to explain a bit more.

I set the amp up in standard triode mode as suggested on the tube lab site. All worked well.

I then decided to add the UL switch. I followed the wiring diagram from the we site. When I turn the amp on, I hear music and all sounds right. But after about five to ten minutes of playing, I suddenly get very loud feedback/squealing.

The speaker terminals are directly wired to the output transformers at this time, as I have not tried CFB yet.

I have a choke and run time cap installed.

I do not have a volume pot yet. So source rca (using an iPhone right now) are directly connected to the board.
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Old 1st January 2020, 04:18 PM   #18
lykkedk is offline lykkedk  Denmark
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Hey...

Quote:
I do not have a volume pot yet. So source rca (using an iPhone right now) are directly connected to the board.
When i build my AlephJ i also used an Ipad to connect directly via 3.5" jack, like you do with youre phone right now. I had with one (defective? i donno for sure) cable, the sourceresistors got hot and the amp was bahaving very very strange in one channel, until i tried another 3.5" jack-cable... Just saying! - Can you perhaps try another source just to be sure?

Good luck.

Jesper.
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Old 2nd January 2020, 06:10 PM   #19
Captn Dave is offline Captn Dave  United States
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This squealing problem never happens unless you are in UL mode, is that correct? You listened for hours in triode with no issues? Then I’d have another look at the wiring diagrams supplied with your output transformer to see that you have correctly identified the the UL tap and that you have wired it per the drawing. I’d also get the feedback loop working to see if that stops the oscillation. That’s what feedback is for.

The rectifier may not have the 5 volt winding connected properly. Check to see that the yellow leads are connected to the board at the correct block. Next test it at the tube base. This can be exceeding dangerous to test because while that winding is only 5 volts at AC, it’s at lethal voltages at DC. The full B+. So switch off the power, let it set for a few minutes, Check for no B+, set up your meter across pins 2 and 8 with clip-on test leads. Test for AC by powering up the amp while you are standing back. Do this with the solid state rectification switch open.

EDIT: A safer and simpler way would be first to test the 5 volt AC at the tube would be to first pull the tube. Do this with the solid state rectification switch open. Be safe. Use clip leads.

Last edited by Captn Dave; 2nd January 2020 at 06:13 PM.
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Old 2nd January 2020, 06:28 PM   #20
ejr12 is offline ejr12  United States
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Thank you both for the ideas. I will give these a try this weekend.

As for the tube rectifier, I am pretty sure I have the yellow taps in the correct location, but I will check again. The tube was working (ie glowing), when I first tried the amp, but in subsequent tests it stopped. I do not recall what, if any changes, occurred between the working/not working state. I noticed the problem the next day when I was trying some additional tests.

As for the UL taps, I believe I got them right. But, again I am new to this. I have included the transformer wiring diagram with this post. I have the blue/white wire connected to the UL tap.

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