Two different preamps (one octal and one regular) in a Tweed Delux "clone"

[andrewRneumann]

Damn!!!!!!!
I just realized that the two 2 W resistors between B+1-B2 to B3 were wrong. They were 18 Ohm and 5,1 Ohm. Not 18k Ohm and 5,1K Ohm. There have been a lot of resoldering at those three points. Can I cut them and twist the new ones around the caps "legs" or or is it better to cut them out close to the resistor and make a small hook to attach the new one or do I need to resolder the whole eylet?
I'm a bit uncertain that i have the proper 2W values resistors at home. What's the closet value that is OK? Must it be 2W?
Measurments of the resistance is done. Plates and screens measured against closest power cap connection and all other values are measured against chassis ground. Too bad I realized the wrong value on the resistors after...
Need to measure again? And the main question is should I prioritize sleep, family, work, dog or amp?
Specs for the tubes:

https://www.evatco.com.au/assets/images/12ax7%20pin%20out%20configuration%20ecc83.jpg

6SJ7 @ The Valve Museum

6SC7 @ The Valve Museum

6V6GT @ The Valve Museum

V1 V2 V3 V4 V5
Pin 1 0,5 0 17,5M O.L O.L
Pin 2 32K 49 0,6 50 50
Pin 3 814 0 4,68K 155 149
Pin 4 49 4,7M 416K 464 464
Pin 5 49 0 0,2 227K 223K
Pin 6 0,5 0,4 0,983K 227K 223K
Pin 7 0,973M/32,3K 49,5 49 49 49
Pin 8 814 0,5 49 270 270
Pin 9 49

Regarding Pin 7 on V1 the resistance changed with the S2 switch.
All values are in Ohm unless it states anything else.

Well hey that’s exactly why we do this. Glad you found that error. Do you have a solder-sucker? De-soldering device? I would want a good solid connection in there. The first resistor (B+1 to +2) really should be 2W and the second one (B+2 to +3) can be 1W.

I will do my best with the chart you provided. It’ll take me a while before I have time to decipher those preamp tubes. I should have a response by tomorrow.

 

[andrewRneumann]

Damn!!!!!!!
I just realized that the two 2 W resistors between B+1-B2 to B3 were wrong. They were 18 Ohm and 5,1 Ohm. Not 18k Ohm and 5,1K Ohm. There have been a lot of resoldering at those three points. Can I cut them and twist the new ones around the caps "legs" or or is it better to cut them out close to the resistor and make a small hook to attach the new one or do I need to resolder the whole eylet?
I'm a bit uncertain that i have the proper 2W values resistors at home. What's the closet value that is OK? Must it be 2W?
Measurments of the resistance is done. Plates and screens measured against closest power cap connection and all other values are measured against chassis ground. Too bad I realized the wrong value on the resistors after...
Need to measure again? And the main question is should I prioritize sleep, family, work, dog or amp?
Specs for the tubes:

https://www.evatco.com.au/assets/images/12ax7%20pin%20out%20configuration%20ecc83.jpg

6SJ7 @ The Valve Museum

6SC7 @ The Valve Museum

6V6GT @ The Valve Museum

V1 V2 V3 V4 V5
Pin 1 0,5 0 17,5M O.L O.L
Pin 2 32K 49 0,6 50 50
Pin 3 814 0 4,68K 155 149
Pin 4 49 4,7M 416K 464 464
Pin 5 49 0 0,2 227K 223K
Pin 6 0,5 0,4 0,983K 227K 223K
Pin 7 0,973M/32,3K 49,5 49 49 49
Pin 8 814 0,5 49 270 270
Pin 9 49

Regarding Pin 7 on V1 the resistance changed with the S2 switch.
All values are in Ohm unless it states anything else.

I think I wasn't specific enough about where to measure the plates and screen for the preamp tubes. You need to measure from the correct pin to the B+3 supply capacitor (the last big one in the power supply.)
V1 pins 1 & 6 should be 100K
V2 pin 6 should be 1M, pin 8 should be 100K
V3 pins 2 & 5 should be 220K (or did you leave them 100K?)

V3 pin 1--if you grounded it, it should read 0. I thought you said you were going to ground that pin.

Did you by chance swap the readings on pins 5 & 6 of the V5 & V6? It would make more sense for each pin 6 to read 223K and each pin 5 to read 227K. Or maybe you have them right and you accidentally read pin 5 or pin 6 twice? I would check those again--they are in the ball park, but for some reason the screen grid resistor doesn't seem to show up in your readings.

So... assuming you get the right plate and screen resistances for the pre-amp tubes, all of this makes good sense to me. Nice job.

 

[Jerry garrcia]

Well hey that’s exactly why we do this. Glad you found that error. Do you have a solder-sucker? De-soldering device? I would want a good solid connection in there. The first resistor (B+1 to +2) really should be 2W and the second one (B+2 to +3) can be 1W.

I will do my best with the chart you provided. It’ll take me a while before I have time to decipher those preamp tubes. I should have a response by tomorrow.

It was just late here in Sweden and I have been averaging 5-6 h of sleep for the last couple of nights. Was looking for the easiest way out. Have a solder-sucker and will fix those connections. While I’m at it I will also fix some possible cold joints on the board.

 

[Jerry garrcia]

I think I wasn't specific enough about where to measure the plates and screen for the preamp tubes. You need to measure from the correct pin to the B+3 supply capacitor (the last big one in the power supply.)
V1 pins 1 & 6 should be 100K
V2 pin 6 should be 1M, pin 8 should be 100K
V3 pins 2 & 5 should be 220K (or did you leave them 100K?)

V3 pin 1--if you grounded it, it should read 0. I thought you said you were going to ground that pin.

Did you by chance swap the readings on pins 5 & 6 of the V5 & V6? It would make more sense for each pin 6 to read 223K and each pin 5 to read 227K. Or maybe you have them right and you accidentally read pin 5 or pin 6 twice? I would check those again--they are in the ball park, but for some reason the screen grid resistor doesn't seem to show up in your readings.

So... assuming you get the right plate and screen resistances for the pre-amp tubes, all of this makes good sense to me. Nice job.

I’ll recheck them. I misunderstood and measured plate and grid from the wrong spot to the preamp tubes. I’ll do this right this time. I’ll present a new reading today regarding V1-V3 and after new R 2W new readings B+1 - 3. Tnx.
Regarding ground on V3 pin 1 I grounded it from OT ground to output jacks ground to V2 pin 1. Then the values should de the same…

 

[Jerry garrcia]

I think I wasn't specific enough about where to measure the plates and screen for the preamp tubes. You need to measure from the correct pin to the B+3 supply capacitor (the last big one in the power supply.)
V1 pins 1 & 6 should be 100K
V2 pin 6 should be 1M, pin 8 should be 100K
V3 pins 2 & 5 should be 220K (or did you leave them 100K?)

V3 pin 1--if you grounded it, it should read 0. I thought you said you were going to ground that pin.

Did you by chance swap the readings on pins 5 & 6 of the V5 & V6? It would make more sense for each pin 6 to read 223K and each pin 5 to read 227K. Or maybe you have them right and you accidentally read pin 5 or pin 6 twice? I would check those again--they are in the ball park, but for some reason the screen grid resistor doesn't seem to show up in your readings.

So... assuming you get the right plate and screen resistances for the pre-amp tubes, all of this makes good sense to me. Nice job.

One other thing. I can’t get the 2 w resistors before Friday I think. I will do the readings with 5,1 and 18 kOhm 0,25w resistors to se if everything is ok with the readings. To save time. Then I will resolder in the 2w resistors once they arrive and hopefully start up this baby.

 

[andrewRneumann]

One other thing. I can’t get the 2 w resistors before Friday I think. I will do the readings with 5,1 and 18 kOhm 0,25w resistors to se if everything is ok with the readings. To save time. Then I will resolder in the 2w resistors once they arrive and hopefully start up this baby.

I wouldn't bother installing the wrong ones just to take a reading. Your patience is commendable.

 

[andrewRneumann]

Here’s another area that has got me concerned. I can’t quite make the colors out on the PI plate resistors. I think you installed 220K. Regardless, they look like low wattage. I would replace them with at least 1/2W or 1W if you have them. The issue is that resistors also have a maximum voltage and this can be exceeded on a plate resistors with low wattage values.

I circled the grid leak resistors for the power tubes. Grid leak resistors do not see high voltage or current. If I had to use these 4 resistors, I would put the high wattage ones on the plate of the PI and the low wattage ones on grids of the power tubes.

 

[Jerry garrcia]

Here’s another area that has got me concerned. I can’t quite make the colors out on the PI plate resistors. I think you installed 220K. Regardless, they look like low wattage. I would replace them with at least 1/2W or 1W if you have them. The issue is that resistors also have a maximum voltage and this can be exceeded on a plate resistors with low wattage values.

I circled the grid leak resistors for the power tubes. Grid leak resistors do not see high voltage or current. If I had to use these 4 resistors, I would put the high wattage ones on the plate of the PI and the low wattage ones on grids of the power tubes.

View attachment 944619

Yes. They are 1/4 w. . I’ll order new ones with 1 W and replace them…
The freaking signal wires are in the way the whole time and they are really sensitive.

I have concerns that I do all these modifications and it still doesn’t work.
Can’t I start it up to see if it works? If so, I’ll replace the resistors? Do you get what I mean and does it a sound sane?
In a boring Teams meeting and wife is not home. I’ll switch place with the 220k resistors.

 

[Jerry garrcia]

Here’s another area that has got me concerned. I can’t quite make the colors out on the PI plate resistors. I think you installed 220K. Regardless, they look like low wattage. I would replace them with at least 1/2W or 1W if you have them. The issue is that resistors also have a maximum voltage and this can be exceeded on a plate resistors with low wattage values.

I circled the grid leak resistors for the power tubes. Grid leak resistors do not see high voltage or current. If I had to use these 4 resistors, I would put the high wattage ones on the plate of the PI and the low wattage ones on grids of the power tubes.

View attachment 944619

Redid.

 

[andrewRneumann]

Redid. View attachment 944675

Ok now re-check the 6V6s pin 5 to ground reads ~225K. Also recheck V3 pins 2 and 5 back to B+3 read 220K.

 

[Jerry garrcia]

Ok now re-check the 6V6s pin 5 to ground reads ~225K. Also recheck V3 pins 2 and 5 back to B+3 read 220K.

Pin 5 V6 226K, pin 5 V5 230K
V3 pin 5 218K, pin 2 218K.
Good to go?

 

[Jerry garrcia]

I think I wasn't specific enough about where to measure the plates and screen for the preamp tubes. You need to measure from the correct pin to the B+3 supply capacitor (the last big one in the power supply.)
V1 pins 1 & 6 should be 100K
V2 pin 6 should be 1M, pin 8 should be 100K
V3 pins 2 & 5 should be 220K (or did you leave them 100K?)

V3 pin 1--if you grounded it, it should read 0. I thought you said you were going to ground that pin.

Did you by chance swap the readings on pins 5 & 6 of the V5 & V6? It would make more sense for each pin 6 to read 223K and each pin 5 to read 227K. Or maybe you have them right and you accidentally read pin 5 or pin 6 twice? I would check those again--they are in the ball park, but for some reason the screen grid resistor doesn't seem to show up in your readings.

So... assuming you get the right plate and screen resistances for the pre-amp tubes, all of this makes good sense to me. Nice job.

V1, V2 and V3 are correct to what you are expecting!!! I didn’t use B+3 before.
V3 pin 1 = 0.
So once I get the 2 w resistors I can power this baby up? Could only find 4,7Kohm or 5,6 kOhm and 20 kOhm. 4,7 or 5,6kohm?
Now sleep for me.

 

[andrewRneumann]

V1, V2 and V3 are correct to what you are expecting!!! I didn’t use B+3 before.
V3 pin 1 = 0.
So once I get the 2 w resistors I can power this baby up? Could only find 4,7Kohm or 5,6 kOhm and 20 kOhm. 4,7 or 5,6kohm?
Now sleep for me.

Buy both values. Install the 5,6K.

It’s looking good. Maybe revise your resistance chart with the correct values so we can double check before Friday. If you press the 3 little dots in the menu bar above you can insert a real table. Like this:

	V1 12AY7	V2 …
Pin 1	100k to B+3	…
Pin 2	…	…
Pin …	…	…

 

[Jerry garrcia]

	V1 12ay7	V2 6SJ7	V3 6SC7	V4 6V6	V5 6V6
	Ohm/Current	Ohm/Current	Ohm/Current	Ohm/Current	Ohm/Current
Pin 1	100K to B+3	0K to ground	0K to ground	O.L to ground	O.L to ground
Pin 2	32K to ground	49 to ground	218K to B+3	50 to ground	50 to ground
Pin 3	814 to ground	0K to ground	4,68k to ground	5,3K to B+2	5,3K to B+2
Pin 4	49 to ground	4,7M to ground	417K to ground	464 to B+2	464 to B+2
Pin 5	49 to ground	0K to ground	238K to B+3	230K to ground	226K to ground
Pin 6	100K to B+3	0,99M to B+3	0,98K to ground	N/A	N/A
Pin 7	1M/32K to ground	49,5 to ground	49 to ground	49 to ground	49 to ground
Pin 8	814 to ground	100K to B+3	49,5 to ground	270 to ground	270 to ground
Pin 9	49 to ground	N/A	N/A	N/A	N/A

V1 pin7 values are dependent on the switch position.
V1-V3 have B+3 and V4-V5 have B+2 as reference to screen and plate.
Done?

 

[andrewRneumann]

	V1 12ay7	V2 6SJ7	V3 6SC7	V4 6V6	V5 6V6
	Ohm/Current	Ohm/Current	Ohm/Current	Ohm/Current	Ohm/Current
Pin 1	100K to B+3	0K to ground	0K to ground	O.L to ground	O.L to ground
Pin 2	32K to ground	49K to ground	218K to B+3	50K to ground	50K to ground
Pin 3	814 to ground	0K to ground	0 to ground	155 to B+2	149 to B+2
Pin 4	49K to ground	to ground	to ground	464 to B+2	464 to B+2
Pin 5	49K to ground	0K to ground	218K to B+3	230K to ground	226K to ground
Pin 6	100K to B+3	0,99M to B+3	to ground	N/A	N/A
Pin 7	to ground	49,5 to ground	49K to ground	49K to ground	49K to ground
Pin 8	814 to ground	100K to B+3	49,5K to ground	270 to ground	270 to ground
Pin 9	49K to ground	N/A	N/A	N/A	N/A

Will update with the rest of the values when I get home. By some strange reasons I have to work?

This is great. Once we have voltages, we can use the same chart. Don't forget to eat, drink and sleep.

 

[Jerry garrcia]

This is great. Once we have voltages, we can use the same chart. Don't forget to eat, drink and sleep.

I won’t. Just on my way home from work with goodbye flowers. One more day to go in that place. Running a department in a huge hospital organisation wasn’t for me.
So, I will finalise the last measurements in a couple of hours.
Have spent the day with trying to understand bias, grid leak, plate load etc. why didn’t I do that earlier? Also how the shift between the 6SJ7 and the 12ay7 might affect the 6SC7 for the “possible” sound. Becoming a bit nervous

 

[Jerry garrcia]

This is great. Once we have voltages, we can use the same chart. Don't forget to eat, drink and sleep.

Now it is all updated. Hope it is ok?

 

[andrewRneumann]

	V1 12ay7	V2 6SJ7	V3 6SC7	V4 6V6	V5 6V6
	Ohm/Current	Ohm/Current	Ohm/Current	Ohm/Current	Ohm/Current
Pin 1	100K to B+3	0K to ground	0K to ground	O.L to ground	O.L to ground
Pin 2	32K to ground	49K to ground	218K to B+3	50K to ground	50K to ground
Pin 3	814 to ground	0K to ground	0 to ground	5,3K to B+2	5,3K to B+2
Pin 4	49K to ground	4,7M to ground	417K to ground	464 to B+2	464 to B+2
Pin 5	49K to ground	0K to ground	238K to B+3	230K to ground	226K to ground
Pin 6	100K to B+3	0,99M to B+3	0,98K to ground	N/A	N/A
Pin 7	1M/32K to ground	49,5 to ground	49K to ground	49K to ground	49K to ground
Pin 8	814 to ground	100K to B+3	49,5K to ground	270 to ground	270 to ground
Pin 9	49K to ground	N/A	N/A	N/A	N/A

V1 pin7 values are dependent on the switch position.
V1-V3 have B+3 and V4-V5 have B+2 as reference to screen and plate.
Done?

I changed the font color to red above with anything that doesn't look right. I believe you got carried away with "K" on all those heater resistances. Verify that they are all around 50-ohms, not 50K-ohms.

The one big problem is V3 pin 3. It should be 4.7K. You had it before, but you were in there changing the 220K grid leaks. We need to fix that.

V3 pin 4 will be affected by the tone/volume controls. Make sure all your controls are up 100% and that one should be around 500K, reducing to 0 when the controls are down to 0%.

 

[Jerry garrcia]

I changed the font color to red above with anything that doesn't look right. I believe you got carried away with "K" on all those heater resistances. Verify that they are all around 50-ohms, not 50K-ohms.

The one big problem is V3 pin 3. It should be 4.7K. You had it before, but you were in there changing the 220K grid leaks. We need to fix that.

View attachment 945048

V3 pin 4 will be affected by the tone/volume controls. Make sure all your controls are up 100% and that one should be around 500K, reducing to 0 when the controls are down to 0%.

Hi. My bad. I got a bit carried away. The heater pins are not in kOhm. Changed that. The V3 pin 3 is 4,68k to ground. Don’t know why I wrote 0.
So it seams fine there. But another problem. Pin 4 on V3 is 417 kOhm with volume at 100% but actually increases to 458 kOhm when turning the volume down to 0? I have checked the continuity from pin 4 to potentiometer 1-3 and the wire is not broken in any sections. I could maybe resold the connection on the pin.
Could the problem be before the potentiometers?

 

[andrewRneumann]

Let me review the layout again. I’m probably confused myself.