[tomb]

Quote:

Originally Posted by adamus /img/forum/go_quote.gif ahh yes..to many beers

Sounds like a good idea, though - the beers I mean.

 

[K5Doom]

Updates:

Ok, now I changed my zener, happy as I was, I turned on my amp only to realize that my tubes won't heat up, and my bias at "TA2L to GND, TA2R to GND" are to about 26V and they won't move. I previously set them up at 1/2 of the powersupply voltage. Proably because there is something defective with the tubes.

it's never going to work

Thank you.

 

[tomb]

Quote:

Originally Posted by K5Doom /img/forum/go_quote.gif Updates: Ok, now I changed my zener, happy as I was, I turned on my amp only to realize that my tubes won't heat up, and my bias at "TA2L to GND, TA2R to GND" are to about 26V and they won't move. I previously set them up at 1/2 of the powersupply voltage. Proably because there is something defective with the tubes. Thank you.

There are a couple of things you can try before you assume that the tubes are bad. It doesn't make sense that both of them would go out at the same time and frankly, in all the time of my building/listening to MAXes and Millett Hybrids before that - I've never had one go bad. Bad from the box - yes, but I've never worn a tube out to complete failure. So, I think it's unlikely that they just went bad.

So:
1. Check the pins and bend them all slightly outward. Sometimes people get glue on the contacts inside the sockets (like me) and the pins may make contact in a very specific position in the socket. Tilt the tube slightly one way or the other and it may lose contact. It only takes one pin - the right pin - to lose contact and fail to light the tube.

2. Check to see if you hit the trimmers - maybe adjusting the DB trimmers instead of the tube trimmers and vice-versa.

3. Check for continuity with the heater circuit resistor (assuming you used one). You should be able to measure voltage across that resistor, or confirm voltage in the circuit if you jumpered it. Lose that resistor or don't jumper those pads and the heaters/tubes will never light.

 

[K5Doom]

I placed a jumper instead of R1, and I checked the 3rd pin of the left tube as a V+ and the 4th pin of the right tube as a GND and I get a reading of 27VDC (and 27 at the R1 jumper) between the two. Tried to bend the pins, nothing changed. My BJTs are still at around 85 mV between TB2L/TA2L (right too)

 

[tomb]

Quote:

Originally Posted by K5Doom /img/forum/go_quote.gif I placed a jumper instead of R1, and I checked the 3rd pin of the left tube as a V+ and the 4th pin of the right tube as a GND and I get a reading of 27VDC (and 27 at the R1 jumper) between the two. Tried to bend the pins, nothing changed. My BJTs are still at around 85 mV between TB2L/TA2L (right too)

The measurement you describe doesn't check for anything, regardless of which way you're counting the pins.

If you want to check for proper voltage on the heaters, measure the following:
Left Tube - top pin (12 o'clock position) to pin #3 (1:30 o'clock position - the pin between 12 o'clock and 3 o'clock). This should read ~13.5VDC.

Right Tube - top pin (12 o'clock position) to pin #3 (1:30 o'clock position - the pin between 12 o'clock and 3 o'clock). This should read ~13.5VDC.

Go back and check #1 and #2 again.

 

[K5Doom]

kk lol sorry, I checked on the schematics on your website and checked on the V+ and GND there. Guess I got the wrong one. I'll go test it right now.

The left tube gets 27V (between the top one the one at it's right) and the right tube also gets 27V (actually 0V counting to pin #3 from the right, but 27V counting from the left, 10h30 position)

I'll recheck the potentiometers.

Just checked, and whatever direction I turn RA1L or RA1R, the voltage just stays at +/- 24V, it won't get higher or lower.

 

[tomb]

Quote:

Originally Posted by K5Doom /img/forum/go_quote.gif kk lol sorry, I checked on the schematics on your website and checked on the V+ and GND there. Guess I got the wrong one. I'll go test it right now. The left tube gets 27V (between the top one the one at it's right) and the right tube also gets 27V (actually 0V counting to pin #3 from the right, but 27V counting from the left, 10h30 position) I'll recheck the potentiometers. Just checked, and whatever direction I turn RA1L or RA1R, the voltage just stays at +/- 24V, it won't get higher or lower.

No offense, but you're going to have to be a bit more disciplined in what you're measuring and how - then in how you describe it. It does little good to stick the probes over any 'ol point and see what you get.

27V between the #3 pin and #4 pin on the Right tube pretty much means there's a dead short in the right tube, but honestly - I'm not sure what you're measuring. For the left tube, you should either get 13.5V or 27V, not 0V.

Are you measuring this with the tubes in or out?

Assuming the tubes are in - are you not getting any LED light? No orange glow from the center of the tubes?

What are you measuring when you get 24V and why the "+/-"?

I forget. Have we asked for pics, yet?


EDIT: OK - we definitely had pics. Let me study them some more, maybe I can spot something else.

 

[K5Doom]

By +/- I mean "more or less", didn't realize when I was writing it that it could be interpreted as -24V / +24V, sorry about that. I was measuring the GND - TA2L/TA2R

At first, I based my measurings on this diagram :

, 3rd and 4th pin.

The measuring I did was with the tubes in, powered on.

Sorry if I'm not very good at explaining my measurements, I'll make an effort to be more precise in how I describe it.

I'll get some pics a little bit later.

Let me rephrase my tubes reading: I get 27V for the left tube on pins 3-4 and 0V on the right tube, pins 3-4.

Just to avoid confusion, here are the points I tested:

 

[tomb]

Ah - that's the reverse of what I thought I had read. Much better! However, it looks like we have a short in the right tube - there should be voltage drop across the heater, which is what those two pins are connected to. Then it looks like the left tube's heaters are an open circuit (nothing there). At least we can confirm that you're geting voltage to the right places.

Here's some more questions -
1. After reviewing the thread again, I'm wondering - was the last time the tubes lit back in May? If so, I guess it could be quite possible that they've gone bad. It could've happened through accidental damage over a period of time - someone hits it while you were gone, knocks the amp on the floor, etc., etc. Are the getter flashes still silver on both tubes, or are they white?
2. Have you tried swapping the tubes from one socket to the other? Note that the right tube should be able to light even if the left tube is bad, but not the other way around.

2. What about the tube LEDs - did you install them and do they light?

 

[K5Doom]

Yes, the tubes were working the last time I tested it, which was maybe last week, I tried swapping the tubes, and neither of them would heat up, and I did not install the LEDs, I'll try and see if they work.

Just tested the leds, they both work, as well as the center one (if that is relevant).

For the getter flash, they seems ok (if I am looking at the right thing), but I can only see it partially since it's kind of blocked by the black tint on the glass of the tube.

 

[tomb]

Quote:

Originally Posted by K5Doom /img/forum/go_quote.gif Yes, the tubes were working the last time I tested it, which was maybe last week, I tried swapping the tubes, and neither of them would heat up, and I did not install the LEDs, I'll try and see if they work.

Just tell us what the voltage is between the LED holes at each position.

Although, I'm thinking that what you first suggested is true - I just have seen it before (both at the same time): the tubes are bad.

What about the getter flashes - are they still silver?

How about taking the tubes out and measure the #3 and #4 pin for resistance on the tubes themselves? Tell us what you get.

 

[K5Doom]

I get 13.6 ohm for the right tube and no continuity on the left one. I updated my last post while you were posting your reply with new information about leds (they work).

 

[tomb]

Quote:

Originally Posted by K5Doom /img/forum/go_quote.gif I get 13.6 ohm for the right tube and no continuity on the left one. I updated my last post while you were posting your reply with new information about leds (they work).

OK - we're getting somewhere. It does sound like the left tube is bad. 13.6 ohms is not really what I was expecting, but the heaters probably vary quite a bit when they're powered up. So, it definitely sounds like you have one bad tube.

Just to confirm, I fired up one of my MiniMAXes - I guess I've never actually tried this with a MiniMAX, but the old Millett Hybrid would light one tube if the other one was bad - if it was in the correct socket. It looks like a MiniMAX will not light the tubes unless both tubes are OK.

So, I guess it's time to get a new tube. Sorry this took so long and so much effort. It's just that I've never seen a tube just go bad in the middle of trouble shooting like that.

Needless to say, unless you can get the tubes to light, there will be no bias to adjust.

 

[K5Doom]

I'll get some new tubes (need to order some parts again, awh!!) and I'll update to let you know if it worked or not. I hope that fixes the issue. I think I'll just get a pair of each kind.

Anyways, thank you so much for your patience and your support!

 

[K5Doom]

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.