[Ampersand]

Well, I jumpered a pin from RA4L to the jack and got sound!!! So I guess the delay circuit is the culprit. Now I must figure out which part. Any ideas??

Earlier in the build, I mistakenly soldered the CM1 47uF elec cap in a spot in the power supply and had to desolder it and move it. Its possible I burned up the cap. Would a burned up cap in CM1 cause this problem???

Thanks,
Mike

 

[Ampersand]

Well, I swapped out CM1 for another 47uF cap I had laying around. That didn't work, so I swapped out the BD139 for another and BINGO, I have sound. Thank goodness, because that Relay looked like a #@&%* to desolder.

So finally i can enjoy my BG version of the MAX. BTW, I know the Can't Miss Max Build #1 bypasses the BGs with K42's or VitQ's, but what was the consensus of using BG's to bypass BG's?? I'm currently not bypassing at all

Thanks,
Mike

 

[pinkfloyd4ever]

Quote:

Originally Posted by Ampersand /img/forum/go_quote.gif Well, I swapped out CM1 for another 47uF cap I had laying around. That didn't work, so I swapped out the BD139 for another and BINGO, I have sound. Thank goodness, because that Relay looked like a #@&%* to desolder. So finally i can enjoy my BG version of the MAX. BTW, I know the Can't Miss Max Build #1 bypasses the BGs with K42's or VitQ's, but what was the consensus of using BG's to bypass BG's?? I'm currently not bypassing at all Thanks, Mike

good to hear. I wish I could comment on the bypassing issue, but I just replaced my K42s with vitamin Qs last night and still haven't gotten around to trying my .47uf BG NXs...plus I haven't been able to hear with my left ear for like a week and a half cause of this damn ear infection...def need to call the doctor back tomorrow

btw, anyone know if theres much of a break-in period for VitQs?

 

[amphead]

Quote:

Thanks man, I measured continuity between pin 2 and pin 3 on both tubes. One reads up to 110 ohms and then falls at a constant rate ohms and the other reads 0 ohms. Looks like thats the issue.

Cronic, that would actually show working heaters on both of those tubes. Colin was telling you that if you measured infinite resistance on the heater that it was bad(open circuit). However, the tube that measured 110 ohms, might be having problems anyway.

Ampersand, kudos on your fix. Another Max Lives!!!

 

[John Wilson]

Sad news...I can't get the DB's on one side below .940 mv and the other side below .835 mv!!! The tubes bias fine at 13.5 v, And ps at 27v. For what it's worth the MJE 243 and 253's are about 9 years old...never used..stored in there bags. May I;ll get new ones. JW

 

[tomb]

Quote:

Originally Posted by amphead /img/forum/go_quote.gif Cronic, that would actually show working heaters on both of those tubes. Colin was telling you that if you measured infinite resistance on the heater that it was bad(open circuit). However, the tube that measured 110 ohms, might be having problems anyway. Ampersand, kudos on your fix. Another Max Lives!!!

It may be that he measured those pins with the tubes in the board.

Cronic, try measuring the pins on your tubes when they're pulled from the sockets. Colin made a great guess based on your description of the problem. It can also be caused by bad contact with the tube pins in the socket. After you've checked the pins when the tubes are out, try canting them in the socket until the LEDs light.

 

[tomb]

Quote:

Originally Posted by John Wilson /img/forum/go_quote.gif Sad news...I can't get the DB's on one side below .940 mv and the other side below .835 mv!!! The tubes bias fine at 13.5 v, And ps at 27v. For what it's worth the MJE 243 and 253's are about 9 years old...never used..stored in there bags. May I;ll get new ones. JW

I've looked at your pic on page 366 of this thread. You've got a real good pic there of the DB section. A visual inspection doesn't indicate anything wrong. So, let's start the standard drill, John:

1. Verify the test points that you are trying to measure. The test points do nothing but measure the voltage at the leads of the RB10 or RB11 resistors.

Left Channel: One probe is in TA2L. The other probe is in TB1L or TB2L.
Right Channel: One probe is in TA2R. The other probe is in TB1R or TB2R.

2. If that's correct, you need to verify your parts.

Trimmers:
RB12L and RB12R are 2K trimmers

Transistors:
Even to Odd on the small transistors to the pads on the board. 2N5088's go on QB3, QB5, and QB7. 2N5087's go on QB2, QB4, and QB6.

QB1 is the PN4392 JFET.

MJE253's go on the middle sinks on the Right side of the sinks.
MJE243's go on the outboard sinks on the Right side of the sinks.

Resistors:
RB1R: 1K ohm
RB2R, RB3R: 10 ohm
RB4R, RB5R: 100 ohm
RB6R, RB7R: 220 ohm
RB8R, RB9R: JUMPERED
RB10R, RB11R: 2.2 ohm Power Resistor

Please, DON'T CHEAT - make an honest attempt at this and let us know. If this doesn't indicate something, there are other things that we can try.

 

[cronic]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif It may be that he measured those pins with the tubes in the board. Cronic, try measuring the pins on your tubes when they're pulled from the sockets. Colin made a great guess based on your description of the problem. It can also be caused by bad contact with the tube pins in the socket. After you've checked the pins when the tubes are out, try canting them in the socket until the LEDs light.

They were measured out of the board. I wiggled them to and fro while in the socket and nothing changed.

 

[tomb]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif It may be that he measured those pins with the tubes in the board. Cronic, try measuring the pins on your tubes when they're pulled from the sockets. Colin made a great guess based on your description of the problem. It can also be caused by bad contact with the tube pins in the socket. After you've checked the pins when the tubes are out, try canting them in the socket until the LEDs light.

Try putting the 12AE6 that measured good in one socket and one of your good 12FK6's in the other. See if you can bias the 12AE6 under that scenario. At least it will prove that one 12AE6 tube is good (needless to say, the amp won't sound very good doing that, but it won't hurt it).

 

[cronic]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Try putting the 12AE6 that measured good in one socket and one of your good 12FK6's in the other. See if you can bias the 12AE6 under that scenario. At least it will prove that one 12AE6 tube is good (needless to say, the amp won't sound very good doing that, but it won't hurt it).

Good deal, I will try that when I get home tonight. Thanks everyone for your awesome help.

 

[chilly]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Thanks for the compliment! I hate to say this, but using IEM's is probably not the best choice with a tube amp, even if it is a hybrid. You may need 100ohm output resistors or more to tame the gain and also the noise. Most likely, the noise in the pot you're hearing is tube noise. Scratchiness occurs if the tubes aren't completely stable and/or have some less-than-optimum connections on the pins. Try switching the tubes and see if that alters the pot noise slightly. If it's an ALPS, it's probably the tubes plus your IEMs.

Hey Tomb,

I agree, IEM's are probably not the best for tubes... with harmonics and hashyness( is that a word? ) My problem is, over the ear and on the ear phones tend to hurt over a very short time. where as my IEM's I can wear all day with no discomfort.

I do have the Soha working very nicely now, with 22ohm resistors in the output, that still gives me pretty good bass, although I might change a couple of the caps for a more accurate bass.

The Max, obviously needs more time to burn in, and I just ordered other tubes to give them a shot...

The pot noise is not too big of a problem, as I usualy don't turn the amp up and down a lot, it pretty much stays in one place.

Plus I only use my headphone amps at work, and the IEMS totally isolate me from my loud game playing co-workers. They are really into team fortress 2.

Again, thanks to you tomb, and everyone else for all your hard work.

-chilly


I also had purchased a second Max board... maybe I'll build a very fancy one... like Ferrari's.... ideas anyone???


hmmmmmm

 

[John Wilson]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif I've looked at your pic on page 366 of this thread. You've got a real good pic there of the DB section. A visual inspection doesn't indicate anything wrong. So, let's start the standard drill, John: 1. Verify the test points that you are trying to measure. The test points do nothing but measure the voltage at the leads of the RB10 or RB11 resistors. Left Channel: One probe is in TA2L. The other probe is in TB1L or TB2L. Right Channel: One probe is in TA2R. The other probe is in TB1R or TB2R. 2. If that's correct, you need to verify your parts. Trimmers: RB12L and RB12R are 2K trimmers Transistors: Even to Odd on the small transistors to the pads on the board. 2N5088's go on QB3, QB5, and QB7. 2N5087's go on QB2, QB4, and QB6. QB1 is the PN4392 JFET. MJE253's go on the middle sinks on the Right side of the sinks. MJE243's go on the outboard sinks on the Right side of the sinks. Resistors: RB1R: 1K ohm RB2R, RB3R: 10 ohm RB4R, RB5R: 100 ohm RB6R, RB7R: 220 ohm RB8R, RB9R: JUMPERED RB10R, RB11R: 2.2 ohm Power Resistor Please, DON'T CHEAT - make an honest attempt at this and let us know. If this doesn't indicate something, there are other things that we can try.

Thanks Tom. Followed your instructions vehemently. All is correct per build instuction. No cheat. JW

 

[tomb]

Well, dadgum, John!

Maybe we're looking at this the wrong way.

You say that for one DB that you "can't get the DB's on one side below .940 mv" and also, "the other side below .835 mv!!!"

Well, let's review something I didn't catch before:

Desired bias on DB's: 66.000 mV to 110.000 mV.
You're measuring 00.940 mV and 000.835 mV, but you're trying to go lower?

I think we're a couple of decimal points behind. Actually, I'm surprised that you can get them to go that low. 25.000 mV to 40.000 mV is typical with the trimmers turned about 20 turns down.

I hope this is the issue. Sorry I didn't catch it before making you go through all that trouble.

 

[John Wilson]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Well, dadgum, John! Maybe we're looking at this the wrong way. You say that for one DB that you "can't get the DB's on one side below .940 mv" and also, "the other side below .835 mv!!!" Well, let's review something I didn't catch before: Desired bias on DB's: 66.000 mV to 110.000 mV. You're measuring 00.940 mV and 000.835 mV, but you're trying to go lower? I think we're a couple of decimal points behind. Actually, I'm surprised that you can get them to go that low. 25.000 mV to 40.000 mV is typical with the trimmers turned about 20 turns down. I hope this is the issue. Sorry I didn't catch it before making you go through all that trouble.

I was hoping I was miss reading the meter. I V is 1000MV,Right? I was thinking I was almost at 1V at .940. Let me go back and try it again. JW

 

[John Wilson]

tb2l to ta2l=0.84VDC~tb1l to ta2l=0.87VDC~TB1R to TA2R= 0.98VDC~TB2R to TA2R=0.99VDC. JW