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sjaustin
PostPosted: Sun Jun 16, 2019 7:13 pm 
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This is my first amp build after a couple hundred pedals.

Running through the testing procedure on p. 115 of the instructions, I get the indicator light to come on as expected. The EZ81 rectifier tube glows and gets hot. But my DC voltage at the ON position of the standby switch is about 275V, not the 340V the instructions call for. Should I proceed, or stop and troubleshoot?

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spin
PostPosted: Sun Jun 16, 2019 7:18 pm 
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Are you running through a light bulb limiter?

I would stop to troubleshoot, something is pulling that down.

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sjaustin
PostPosted: Sun Jun 16, 2019 7:25 pm 
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Not sure what a light bulb limiter is. (Edit: I looked it up. Not using one.)

I checked all the wiring to and from the AC input and tube socket; everything looks right to me. Anything else I should check?

Image

Image

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duhvoodooman
PostPosted: Mon Jun 17, 2019 9:23 am 
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What's the stepped up AC voltage level coming out of the PT, Scott?

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sjaustin
PostPosted: Mon Jun 17, 2019 9:45 am 
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duhvoodooman wrote:
What's the stepped up AC voltage level coming out of the PT, Scott?

I’ll check. At what point would I measure that?

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duhvoodooman
PostPosted: Mon Jun 17, 2019 10:26 am 
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sjaustin wrote:
duhvoodooman wrote:
What's the stepped up AC voltage level coming out of the PT, Scott?

I’ll check. At what point would I measure that?

The red wires coming out of the PT that connect at pins 1 & 7 on the rectifier tube socket. Should be around 290VAC, per the TMB18 schematic.

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sjaustin
PostPosted: Mon Jun 17, 2019 10:35 am 
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Getting 309VAC at pins 1 and 7 of the rectifier.

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Morgan
PostPosted: Mon Jun 17, 2019 10:44 am 
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sjaustin wrote:
This is my first amp build after a couple hundred pedals.

Running through the testing procedure on p. 115 of the instructions, I get the indicator light to come on as expected. The EZ81 rectifier tube glows and gets hot. But my DC voltage at the ON position of the standby switch is about 275V, not the 340V the instructions call for.


This is pretty close to the 283 volts Bob was getting when the standby switch was in the off position:
Image

Was your standby switch in the off position?

EDIT: I think that maybe the instructions are a little misleading there. I don't have one of these to test, but according to Bob's chart, you will have lower B+ when the standby switch is in standby.

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Step 8:...Make sure the standby switch is in the “standby” position. Turn the Mains switch on...If you measure the voltage at the solder terminal of the of the ON side of the standby toggle switch, you should read approximately 340VDC. To test the rectified DC voltage, first set your meter to test DC voltage 500V or greater. Then connect the black probe to chassis ground. Then touch the red probe to the various test points.

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sjaustin
PostPosted: Mon Jun 17, 2019 10:55 am 
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Ah! Yes, it was in standby, per (my reading of) the wording in the instructions. So if Bob's results are this close to mine, it's probably OK to proceed with installing the other tubes and testing it out, huh?

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duhvoodooman
PostPosted: Mon Jun 17, 2019 11:18 am 
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I would!

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sjaustin
PostPosted: Mon Jun 17, 2019 11:41 am 
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Holy hell this thing is loud!

:mrgreen:

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duhvoodooman
PostPosted: Mon Jun 17, 2019 1:36 pm 
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sjaustin wrote:
Holy hell this thing is loud!

YES, IT IS!!! :twisted:

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Nwkenning
PostPosted: Mon Jun 17, 2019 1:37 pm 
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Thank god for a master volume control! I love diming the volume and shredding the tube at bedroomish levels.

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duhvoodooman
PostPosted: Mon Jun 17, 2019 1:53 pm 
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Nwkenning wrote:
Thank god for a master volume control! I love diming the volume and shredding the tube at bedroomish levels.

This is exactly why I sacrificed one of the 4 input jacks and installed a MV pot there in a couple of the Brit 45 and Brit 50 amps I've built!

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spin
PostPosted: Mon Jun 17, 2019 6:12 pm 
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Woohoo, glad this was just a whoopsie on the switch position measurement. Sorry for putting an 'all stop' out there, I just didn't want to see a PT burn up if there was a real problem. Looking forward to hearing some clips after you get dialed in.

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sjaustin
PostPosted: Mon Jun 17, 2019 8:39 pm 
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spin wrote:
Woohoo, glad this was just a whoopsie on the switch position measurement. Sorry for putting an 'all stop' out there, I just didn't want to see a PT burn up if there was a real problem. Looking forward to hearing some clips after you get dialed in.

No worries. Better safe than sorry! The clips will have to wait; I leave the country on Sunday until August. I’m gonna look forward to getting back and cranking it up again!

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sjaustin
PostPosted: Tue Jun 18, 2019 6:16 am 
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I had a couple minutes after rehearsal last night to turn this thing up to stage volume. Oh man. I am all in on the Helix, but I could definitely see myself enjoying that amp. Eager to put some pedals in front of it (hello, BYOC classic fuzz!), but again that will have to wait.

Please tell me I'm not going to start collecting DIY amps like I have with pedals. They're much pricier. :mrgreen:

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