First Fire Up...

[v00d00blues79]

I just fired up my Bangkok chassis for the first time and i'm getting no output whatsoever from this thing... I've gone through and checked the grounds and whatnot, but i'm kinda stumped at this point. These are my voltages under load: The CL1 and OD1 voltages are stumping me as to why they are so low...

CL1:
Pin 1 - 176vdc
Pin 3 - 1.5vdc
CL2:
Pin 6 - 200vdc
Pin 8 - 1.6vdc
OD1:
Pin 1 - 162vdc
Pin 3 - 1.34vdc
OD2:
Pin 6 - 235vdc
Pin 8 - 1.8vdc
PI:
Pin 1 - 321vdc
Pin 2 - 40vdc
Pin 3 - 62vdc
Pin 6 - 328vdc
Pin 7 - 40vdc

B+1 - 473vdc
B+2 - 472vdc
B+3 - 458vdc
B+4 - 365vdc
B+5 - 362vdc


Any help would be greatly appreciated!

Thanks,

Andy

[Normster]

Andy, post some pics if you can. I might be able to see something. If you've got no sound at all, are your tube filaments all lighting up?

[v00d00blues79]

Filaments light up. Getting roughly 3-4 a side. I will have to see if i can get some current pictures. The ones i have are from before the last round of changes. I replaced the crap caps that i had in there with some Xicon MPP's and an OD or two. From the voltages posted, do you see anything out of place? The trannies were from a BF Bandmaster donor and were good when they were pulled... I also think i may have a problem with the bias circuit as well... no matter what i do, the voltage on pin 5 of the power tubes doesn't change very much.

Thanks,

Andy

[groovtubin]

I just fired up my Bangkok chassis for the first time and i'm getting no output whatsoever from this thing... I've gone through and checked the grounds and whatnot, but i'm kinda stumped at this point. These are my voltages under load: The CL1 and OD1 voltages are stumping me as to why they are so low...

CL1:
Pin 1 - 176vdc
Pin 3 - 1.5vdc
CL2:
Pin 6 - 200vdc
Pin 8 - 1.6vdc
OD1:
Pin 1 - 162vdc
Pin 3 - 1.34vdc
OD2:
Pin 6 - 235vdc
Pin 8 - 1.8vdc
PI:
Pin 1 - 321vdc
Pin 2 - 40vdc
Pin 3 - 62vdc
Pin 4 - 40vdc
Pin 6 - 328vdc

B+1 - 473vdc
B+2 - 472vdc
B+3 - 458vdc
B+4 - 365vdc
B+5 - 362vdc


Any help would be greatly appreciated!

Thanks,

Andy

[dogears]

Your cathode voltages are very low on the preamp tubes. It looks like you have the pin 3 and pin 8 resistors reversed on V1 and V2. Which plate/cathode values did you use? Looks fishy.....

[groovtubin]

Your cathode voltages are very low on the preamp tubes. It looks like you have the pin 3 and pin 8 resistors reversed on V1 and V2. Which plate/cathode values did you use? Looks fishy.....

[mlp-mx6]

PI Pin 4 should be a heater connection! What is DC doing on there, and what are you doing measuring it?

4 & 5 are strapped together for one heater connection, 9 is the other. 1, 2, 3 are one triode, 6, 7, 8 are the other.

[dogears]

JIm I know my stuff. Looks like he has the pin 3 and pin 8 cathodes reversed. I meant on the a and b triodes of each tube. On both tubes. THat would not be his issue, BUT that explains the big voltage differences and the cathode voltages.

Your cathode voltages are very low on the preamp tubes. It looks like you have the pin 3 and pin 8 resistors reversed on V1 and V2. Which plate/cathode values did you use? Looks fishy.....

the tube IS conducting, NO cathode voltage would indicate an open plate, learn some theory Scott!! He has more problems than that, it`s DEF not that FISHY!!!!!!!!! Man you know how ta callem don`t ya??

[dogears]

Unless Andy is using the wierd values Norm has in his clone

Andy which is it?? Wierd values of Norm's amp?? Or, mismatched cathode resistors to plate resistors?

JIm I know my stuff. Looks like he has the pin 3 and pin 8 cathodes reversed. I meant on the a and b triodes of each tube. On both tubes. THat would not be his issue, BUT that explains the big voltage differences and the cathode voltages.

Your cathode voltages are very low on the preamp tubes. It looks like you have the pin 3 and pin 8 resistors reversed on V1 and V2. Which plate/cathode values did you use? Looks fishy.....

the tube IS conducting, NO cathode voltage would indicate an open plate, learn some theory Scott!! He has more problems than that, it`s DEF not that FISHY!!!!!!!!! Man you know how ta callem don`t ya??

[Normster]

Andy, a few thoughts after looking at your old pics...
1. As Groove said, make sure your NFB isn't grounded.
2. Recheck your FET jack wiring to make sure you're not grounding the signal.
3. Pull V1 & V2 tubes and inject a signal to the PI. (You can probably use a headphone out jack from a cheap CD player or something.) If you have sound, install V2 and repeat, then V1. As Groove said, work your way from back to front.

Also, I assume you meant pins 6 and 8 on the PI voltages since 4&5 are filament.

[Normster]

Your cathode voltages are very low on the preamp tubes. It looks like you have the pin 3 and pin 8 resistors reversed on V1 and V2. Which plate/cathode values did you use? Looks fishy.....

That's an easy mistake to make if you use Dumble's early layout. The Ck/Rk closest to the tube goes to pin 8 while the one farthest away wraps around the back side of the tube to pin 3. I guess it depends on whether Andy was as anal as I was about the layout.

However, once you get the amp up and running, I do think you'll have some tweaking to do on the plate voltages. I have over 50V difference in plate voltage between CL1 & CL2, but only about 20V difference between OD1 & OD2.

[dogears]

Yes, but like I pointed out, you have the 50v difference because of your intentially mismatched plate/cathodes.

Your cathode voltages are very low on the preamp tubes. It looks like you have the pin 3 and pin 8 resistors reversed on V1 and V2. Which plate/cathode values did you use? Looks fishy.....

That's an easy mistake to make if you use Dumble's early layout. The Ck/Rk closest to the tube goes to pin 8 while the one farthest away wraps around the back side of the tube to pin 3. I guess it depends on whether Andy was as anal as I was about the layout.

However, once you get the amp up and running, I do think you'll have some tweaking to do on the plate voltages. I have over 50V difference in plate voltage between CL1 & CL2, but only about 20V difference between OD1 & OD2.

[Normster]

Yes, but like I pointed out, you have the 50v difference because of your intentially mismatched plate/cathodes.

What concerned me was his OD plate readings. There's only 24V difference between CL1 & CL2 which is probably in the ballpark. However, there's 73V difference between OD1 & OD2. I don't think I've ever seen that much on any schematic. I generally see about 190-210 on CL and 210-230 on OD with no more than 10V difference on either. (Except in the case of my amp, of course.) Andy's B+ voltages look about right so I wonder if there's some connection between the plate voltages and an open/short somewhere else in the circuit? I think I'd be suspicious of the relay ground maybe going to common rather than no/nc. That would kill the signal for both channels and maybe cause the voltage drop.

[dogears]

Norm,

Andy's voltage difference is exactly what I woudl expect if he put the 2.2k on the 220k and the 3.3k on the 150k.....

"The Amazing Kreskin"

[v00d00blues79]

WOW... i just woke up and everyones been busy! As far as the values for the plates and cathodes, those are the "Weird Normster values" as you put it dogears. I did make the mistake of running the CL1&2 and OD1&2 to the wrong sides of the preamp tubes. Essentially everything is run in sequence. First plate to first half of pre, second plate to second have of pre.

Normster - with the values currently in your amp, what are your voltages if you get a second?

Also, I am getting some interesting readings when i turn my DMM to check for continuity between runs. it appears that no matter what, once i flip the stand-by on, i get ground continuity all over the place and in places where i really wouldn't expect it to be... I'm going to have to go through this today with a clear mind and see what i can find.

Thanks everyone for your help!


Andy