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How to troubleshoot the MiniMax ? - Page 4

post #46 of 54
11/3/09 at 8:23pm
Quote:
Originally Posted by K5Doom View Post
Grrr now I'm back to where I started. My relay is still not working...

Now, the measurements I get since I replaced the zener:

2 points at DM1: 2.21V
GND-RM1: 26.9V
DM2-GND: 1.75V

Looks like I'm still not getting 12V at the relay...

I almost have any of the parts in stock at my place by now (I even have a spare relay), help me change the right thing! I really want to seal this up, and listen to my music through it soon!

For the tubes part, they are now firing up fine since I replaced the bad one.
Replace both the BD139 and the Darlington transistors. Those are the only active parts in the entire circuit. As long as you have the correct resistors and diodes in their correct places, and the diodes are oriented correctly - the only things that can be messed up are the transistors.
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post #47 of 54
11/3/09 at 8:29pm
Thread Starter 
Ok, I'll do that, will report back when it's done.
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post #48 of 54
11/9/09 at 8:13pm
Thread Starter 
Geez, Removing those transistor correctly was a real PITA but I still managed to do it without damaging the board too much, but still no luck. Exact same thing as before...

What the hell is wrong!!!!?
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post #49 of 54
11/10/09 at 3:04am
Quote:
Originally Posted by K5Doom View Post
Geez, Removing those transistor correctly was a real PITA but I still managed to do it without damaging the board too much, but still no luck. Exact same thing as before...

What the hell is wrong!!!!?
Either you still have a part in the wrong place, or the wrong part in the right place. Double check everything again and again. We've done this before already, but you need to check everything again. The only other possibility is a bad relay, but I haven't seen or heard of one yet. Your latest measurements prove that you're not getting 12V to the relay, anyway.
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post #50 of 54
11/12/09 at 3:13am
Thread Starter 
I ended up shorting the relay-delay for now, so I can at least enjoy it, 6 months later. I might reopen it but not now. If I do, I'll try to do a better job. I'll just always leave it on. For now.
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post #51 of 54
11/12/09 at 4:14am
Quote:
Originally Posted by K5Doom View Post
I ended up shorting the relay-delay for now, so I can at least enjoy it, 6 months later. I might reopen it but not now. If I do, I'll try to do a better job. I'll just always leave it on. For now.
I'm sorry it came to that, but we were stumped on this one. I still think there's something wrong with the parts - there's never been an instance where someone was not able to make this circuit work in the MAX/MiniMAX. Unlike some isolated reports of unstable relay-delay circuits in other amp designs, cetoole's implementation in the MAX family has never had an issue - it works every time if the correct parts are used in the correct orientation.

Anyway, I'm sorry I couldn't help you solve it.
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post #52 of 54
11/12/09 at 4:28pm
Thread Starter 
Yeah it's strange, but it's fine, at least the main part is working perfectly now. It looks good on my desk and sounds great. I guess I should be careful with it though? What kind of precautions I should take?

Right now, I just leave it always open, it has been for the last 2-3 days, is that bad for the tubes? And how could I damage my headphones, I tried to quickly turn it off/on with cheap headphones (not my SR325is) to test it and could not get any crackling/boom sound (don't know what it's called). So, basically, what should I avoid doing?
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post #53 of 54
11/12/09 at 6:21pm
Quote:
Originally Posted by K5Doom View Post
Yeah it's strange, but it's fine, at least the main part is working perfectly now. It looks good on my desk and sounds great. I guess I should be careful with it though? What kind of precautions I should take?

Right now, I just leave it always open, it has been for the last 2-3 days, is that bad for the tubes? And how could I damage my headphones, I tried to quickly turn it off/on with cheap headphones (not my SR325is) to test it and could not get any crackling/boom sound (don't know what it's called). So, basically, what should I avoid doing?
I'm not sure what you mean by "open." If that's just open to air - I don't see an issue except that it will collect dust. If you actually mean ON for 2-3 days, then no - I don't think that's a good idea at all. Some of the vacuum tube commercial amp users think you should leave a tube amp on all the time. I disagree strongly with that philosophy.

As for precautions if your relay-delay is not working, it's the turn-on that's bad. There's 27V across the headphone jack output until the output caps start to charge. That drops in milliseconds, but you still might see 10 or 12 volts for 10 seconds or thereabouts - that's definitely bad for your headphones. Wait until you see the orange glow in the tubes - then it should be OK to plug the headphones in.

EDIT: If you quickly turned it off and on, chances are the output caps didn't discharge all the way and provided some protection. From a cold start would be the worst.
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post #54 of 54
11/14/09 at 5:35pm
Thread Starter 
Ok thank you. Sorry about the word "open", it's a literal translation from a french expression we use. I meant "Turned On", I didn't read-proof my text enough. I'll take your advice and turn it off when I don't use it and just be careful not to plug my headphones in before +/- 30 seconds.
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