Finished ValveStorm 18W Trem. Look Okay?

[58T100]

Greetings from a new guy

Second amp build following a layout with basically little technical knowledge. This was a Valvestorm kit and I used their Tremolo layout with Heyboer 18W transformers. http://valvestorm.com/sites/default/fil ... t_revG.pdf

I think it is ready to plug in but was hoping for some extra eyes & knowledgeable people to look it over and would greatly appreciate any help.

Also any advice on starting it up would be great if it looks okay. I have a light bulb limiter I made for my AB763 build, but haven't found the voltage checklist yet. Is it critical to check any voltages before testing it out fully?

I have a good understanding of safety and don't push it.

[JMPGuitars]

Hi, New Guy, welcome to the site!

I looked at your photos briefly, and it doesn't look too bad at all. I do recommend reviewing the soldering technique and grounding threads in my signature.

You should look over your build carefully for any stray wires or anything touching something it shouldn't. I noticed some of the wire insulation has melted in some spots. Working on the solder technique should help, but it also helps if you can get higher temp PVC wire, or use PTFE instead.

The biggest thing that stands out to me besides that is the heater wiring. That could be a noise source for you as it is currently. You might get lucky, and it might not be too bad, but it could also give you some hum.

This is how I do my heater wiring:

jmpguitars-heater-wiring.png

You can do the outside method like you did, but the wiring needs to be tight to the socket, and twisted all the way to its destination pin.

For first startup, I think this procedure is popular: https://robrobinette.com/Tube_Amp_Startup.htm

Thanks,
Josh

[58T100]

Thanks - I really value the feedback.

I wish I had signed up earlier as I specifically was looking at the heater comments you made in other threads but didn't get to see the picture - would have been very helpful indeed. I'll not hesitate to redo them if I run into an issue.

The start up procedure linked will be very helpful. I looked through it and will see about giving it a go in the AM.

[58T100]

The startup procedure went well and all voltages checked out. The amp was quiet and made sound.

Power tubes did not appear to be redplating but I apparently blew one while trying to check the bias (old Hammond take-outs from Amperex are all I have right now, sad to see one go). After narrowing it to those, replacing the fuse and replacing the power tubes it redplated one again quite quickly.

I pulled the bias resistor and instead of 180 ohms it is reading 130 ohms. I assume that is a big part of the problem?

I was trying to work through the robrobinette bias procedure but was having a very hard time making sense of where to measure things and the numbers were way different than the tweed example he used. I have some notes on that if it might help.

Is there an idiot's guide (that would be me) to checking the bias on these specific amps? This would be a really really big help.

I know I'm imposing a fair bit not having contributed here, but I do pay it forward helping people on another forum I'm knowledgeable in - any help is hugely appreciated.

[58T100]

That Anu guitar is gorgeous BTW.

The numbers before it blew the tube were -

Pin 7 to ground 357V (Plate I believe)
Pin 3 to ground 14.2V (Cathode I believe)

So plate to cathode voltage - 343V

Using that 14.2V drop with a 130ohm resistor sharing 2 tubes = 147.5% Dissipation?

Am I tracking things on figuring this correctly and do the numbers seem reasonable given the low resistor value (although obviously way to high)?

[Bieworm]

The startup procedure went well and all voltages checked out. The amp was quiet and made sound.

Power tubes did not appear to be redplating but I apparently blew one while trying to check the bias (old Hammond take-outs from Amperex are all I have right now, sad to see one go). After narrowing it to those, replacing the fuse and replacing the power tubes it redplated one again quite quickly.

I pulled the bias resistor and instead of 180 ohms it is reading 130 ohms. I assume that is a big part of the problem?

I was trying to work through the robrobinette bias procedure but was having a very hard time making sense of where to measure things and the numbers were way different than the tweed example he used. I have some notes on that if it might help.

Is there an idiot's guide (that would be me) to checking the bias on these specific amps? This would be a really really big help.

I know I'm imposing a fair bit not having contributed here, but I do pay it forward helping people on another forum I'm knowledgeable in - any help is hugely appreciated.

Here's some explanation I gave Dayn some time ago:

Bieworm wrote: ↑Was planning to do that...

Ok, go to robrobinette.com tube bias calculator
Select tube type
Fill in plate to cathode voltage (=value when you subtract the cathode voltage from plate voltage)
Press calculate
Scroll down a little
Fill in number of tubes that share the cathode resistor
Fill in cathode voltage
Fill in cathode resistor value
Press enter
Look at the results

Post your voltages of the whole amp please.

Grtz Bjorn

[58T100]

The startup procedure went well and all voltages checked out. The amp was quiet and made sound.

Power tubes did not appear to be redplating but I apparently blew one while trying to check the bias (old Hammond take-outs from Amperex are all I have right now, sad to see one go). After narrowing it to those, replacing the fuse and replacing the power tubes it redplated one again quite quickly.

I pulled the bias resistor and instead of 180 ohms it is reading 130 ohms. I assume that is a big part of the problem?

I was trying to work through the robrobinette bias procedure but was having a very hard time making sense of where to measure things and the numbers were way different than the tweed example he used. I have some notes on that if it might help.

Is there an idiot's guide (that would be me) to checking the bias on these specific amps? This would be a really really big help.

I know I'm imposing a fair bit not having contributed here, but I do pay it forward helping people on another forum I'm knowledgeable in - any help is hugely appreciated.

Here's some explanation I gave Dayn some time ago:

Bieworm wrote: ↑Was planning to do that...

Ok, go to robrobinette.com tube bias calculator
Select tube type
Fill in plate to cathode voltage (=value when you subtract the cathode voltage from plate voltage)
Press calculate
Scroll down a little
Fill in number of tubes that share the cathode resistor
Fill in cathode voltage
Fill in cathode resistor value
Press enter
Look at the results

Post your voltages of the whole amp please.

Grtz Bjorn

Thanks for the information - most appreciated. I am pretty sure then that I'm at 147% dissipation with the resistor only testing 130 ohm. I have a couple more 180ohm ones coming so hopefully one of them is a bit closer to the specified value.

[Bieworm]

The bias sits indeed at 147.5%, which is wayyyy over the top. You should aim for 80 to 85%. For setting the bias on an 18W you should have several 5W resistor values in stock. 150, 180, 200, 220R
The bias value result is not arbitrary. Somewhere between 75 and 100% is good enough.. but if you want to expand the life span of those 6BQ5 tubes (and preserve sweet a sound), 80 to 85% is best.

[58T100]

The bias sits indeed at 147.5%, which is wayyyy over the top. You should aim for 80 to 85%. For setting the bias on an 18W you should have several 5W resistor values in stock. 150, 180, 200, 220R
The bias value result is not arbitrary. Somewhere between 75 and 100% is good enough.. but if you want to expand the life span of those 6BQ5 tubes (and preserve sweet a sound), 80 to 85% is best.

Thanks, will look for some higher than 180 values to order as well.

Or, given how far off the first one was, maybe just get 10 180s and I'll end up with all of those values and more

[Bieworm]

The bias sits indeed at 147.5%, which is wayyyy over the top. You should aim for 80 to 85%. For setting the bias on an 18W you should have several 5W resistor values in stock. 150, 180, 200, 220R
The bias value result is not arbitrary. Somewhere between 75 and 100% is good enough.. but if you want to expand the life span of those 6BQ5 tubes (and preserve sweet a sound), 80 to 85% is best.

Thanks, will look for some higher than 180 values to order as well.

Or, given how far off the first one was, maybe just get 10 180s and I'll end up with all of those values and more

Lol! That's absurd...
If you have resistors with 5% tolerance they shouldn't be off spec more than 9 ohm

OTOH.. you should use 180R there and tweak the B+ to the 340 to 345V spec

But first apply a decent 180R resistor and see where that's gonna land the B+ value

[58T100]

The bias sits indeed at 147.5%, which is wayyyy over the top. You should aim for 80 to 85%. For setting the bias on an 18W you should have several 5W resistor values in stock. 150, 180, 200, 220R
The bias value result is not arbitrary. Somewhere between 75 and 100% is good enough.. but if you want to expand the life span of those 6BQ5 tubes (and preserve sweet a sound), 80 to 85% is best.

Thanks, will look for some higher than 180 values to order as well.

Or, given how far off the first one was, maybe just get 10 180s and I'll end up with all of those values and more

Lol! That's absurd...
If you have resistors with 5% tolerance they should be off spec more than 9 ohm

OTOH.. you should use 180R there and tweak the B+ to the 340 to 345V spec

But first apply a decent 180R resistor and see where that's gonna land the B+ value

I ordered more 180's and 200's. Is the R different?

I agree about it being absurd!

[Bieworm]

Thanks, will look for some higher than 180 values to order as well.

Or, given how far off the first one was, maybe just get 10 180s and I'll end up with all of those values and more

Lol! That's absurd...
If you have resistors with 5% tolerance they should be off spec more than 9 ohm

OTOH.. you should use 180R there and tweak the B+ to the 340 to 345V spec

But first apply a decent 180R resistor and see where that's gonna land the B+ value

I ordered more 180's and 200's. Is the R different?

I agree about it being absurd!

No, R is another way of saying Ohm

[58T100]

Lol! That's absurd...
If you have resistors with 5% tolerance they should be off spec more than 9 ohm

OTOH.. you should use 180R there and tweak the B+ to the 340 to 345V spec

But first apply a decent 180R resistor and see where that's gonna land the B+ value

I ordered more 180's and 200's. Is the R different?

I agree about it being absurd!

No, R is another way of saying Ohm

[JMPGuitars]

How many of your 180R resistors are measuring 130? If multiple, I would start questioning the accuracy of your meter. I've never seen a new Xicon 180R with that high of a variance.

[Bieworm]

How many of your 180R resistors are measuring 130? If multiple, I would start questioning the accuracy of your meter. I've never seen a new Xicon 180R with that high of a variance.

Good point!
That would make the other measurements useless too.
I'd check other resistors of any value for accuracy to be sure

[58T100]

How many of your 180R resistors are measuring 130? If multiple, I would start questioning the accuracy of your meter. I've never seen a new Xicon 180R with that high of a variance.

I only received one with the kit. I'll work on trying to confirm the meter.

If I put 180 in the bias calculator with the voltages I read it is only 106% dissipation though.

[Bieworm]

How many of your 180R resistors are measuring 130? If multiple, I would start questioning the accuracy of your meter. I've never seen a new Xicon 180R with that high of a variance.

I only received one with the kit. I'll work on trying to confirm the meter.

If I put 180 in the bias calculator with the voltages I read it is only 106% dissipation though.

The plate voltage will change when you raise the cathode resistor value, so that math won't work like you assume.

[58T100]

How many of your 180R resistors are measuring 130? If multiple, I would start questioning the accuracy of your meter. I've never seen a new Xicon 180R with that high of a variance.

I only received one with the kit. I'll work on trying to confirm the meter.

If I put 180 in the bias calculator with the voltages I read it is only 106% dissipation though.

The plate voltage will change when you raise the cathode resistor value, so that math won't work like you assume.

My point is just that if my meter is wrong and it is actually near 180ohms, and I measured the voltages with it in there, using 180 in the calculator and those voltages puts it at barely over the line. So I don't know if it is possible that just 106% dissipation would have caused what I saw - not sure what the explanation would be unless that resistor is significantly less than 180. I am assuming the meter is at least measuring voltage correctly though.

Trying to find some loose resistors to test.

[Bieworm]

I only received one with the kit. I'll work on trying to confirm the meter.

If I put 180 in the bias calculator with the voltages I read it is only 106% dissipation though.

The plate voltage will change when you raise the cathode resistor value, so that math won't work like you assume.

My point is just that if my meter is wrong and it is actually near 180ohms, and I measured the voltages with it in there, using 180 in the calculator and those voltages puts it at barely over the line. So I don't know if it is possible that just 106% dissipation would have caused what I saw - not sure what the explanation would be unless that resistor is significantly less than 180. I am assuming the meter is at least measuring voltage correctly though.

Trying to find some loose resistors to test.

Don't worry.. 106% won't fry a healthy tube immediately in a cathode biased amp. That's not the problem if that would be the value. But did you take the voltages with the sale DMM? They wouldn't be correct either if the device is faulty.

[Unit_1]

How many of your 180R resistors are measuring 130? If multiple, I would start questioning the accuracy of your meter. I've never seen a new Xicon 180R with that high of a variance.

Every time I start getting crazy results from my dmm I pull the battery and use my *other* meter to check the voltage only to find 7v or something instead of 9v. Replace the battery and back in business. Wondering why they don't have a battery self check, like my MOUSE has one...... lol