183 build questions
Moderators: pompeiisneaks, Colossal
-
- Posts: 405
- Joined: Thu Jul 16, 2020 6:53 pm
- Location: Southern California
1 others liked this
Re: 183 build questions
I believe that I have completed the assembly of this amplifier, though I have not yet powered it on.
I'm going to go over the layout and schematic again to check and make sure every connection is accounted for.
I am also still waiting for my tubes to arrive, so there's no urge to rush. I've ordered a matched quad of Electro-Harmonix EL34, 2 gain matched Mullard reissue CV4004 12AX7, and a JAN 12AX7WA.
I also went ahead and put the knobs on it and mounted it in it's enclosure (a Carol-Ann head cabinet) because I really wanted to see how it looks.
I'm going to go over the layout and schematic again to check and make sure every connection is accounted for.
I am also still waiting for my tubes to arrive, so there's no urge to rush. I've ordered a matched quad of Electro-Harmonix EL34, 2 gain matched Mullard reissue CV4004 12AX7, and a JAN 12AX7WA.
I also went ahead and put the knobs on it and mounted it in it's enclosure (a Carol-Ann head cabinet) because I really wanted to see how it looks.
You do not have the required permissions to view the files attached to this post.
Last edited by professormudd on Wed Jul 21, 2021 11:02 pm, edited 1 time in total.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
It may very well be that the sole purpose of your life is only to serve as a warning to others.
- ijedouglas
- Posts: 718
- Joined: Fri Sep 22, 2017 9:07 pm
- Location: Southern California
-
- Posts: 405
- Joined: Thu Jul 16, 2020 6:53 pm
- Location: Southern California
Re: 183 build questions
Welp, hit a snag already....
I still do not have tubes, but I wanted to go ahead and power it on to check what I could. B+ from the rectifier is 465 +/- so I believe that is good.
I noticed my power LED was not lighting up. I checked the secondaries coming off of the relay transformer and they are only reading at 1.7VAC and I am only getting a few mV DC out to the footswitch jack. I did verify that there is 120VAC coming into the transformer at the primaries.
I wonder if this transformer is bunk. Any ideas?
I still do not have tubes, but I wanted to go ahead and power it on to check what I could. B+ from the rectifier is 465 +/- so I believe that is good.
I noticed my power LED was not lighting up. I checked the secondaries coming off of the relay transformer and they are only reading at 1.7VAC and I am only getting a few mV DC out to the footswitch jack. I did verify that there is 120VAC coming into the transformer at the primaries.
I wonder if this transformer is bunk. Any ideas?
Last edited by professormudd on Thu Jul 22, 2021 7:46 pm, edited 1 time in total.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
It may very well be that the sole purpose of your life is only to serve as a warning to others.
Re: 183 build questions
Did you connect the center tap of that 12VAC transformer to ground? If so, disconnect it. You'll likely need to replace two of the rectifier diodes too. Hopefully the transformer is still alive.
If you did not connect the CT to ground, then disconnect both of the secondary wires from the board and check for 12VAC across the two wires.
If you did not connect the CT to ground, then disconnect both of the secondary wires from the board and check for 12VAC across the two wires.
Re: 183 build questions
Your secondaries have an output of 3.6 so a 1.8 reading would be correct because each secondary wire caries 1.8 for a total of 3.6. What relays are you using? And did you wire the relay transformer rectifier as just a plain rectifier or rectifier and voltage doubler?
Re: 183 build questions
Re: 183 build questions
Yup disregard what I said Sluckey is right.sluckey wrote: ↑Thu Jul 22, 2021 4:51 pmNo, he's using this 12VAC CT transformer...
https://www.hammfg.com/files/parts/pdf/166F12B.pdf
-
- Posts: 405
- Joined: Thu Jul 16, 2020 6:53 pm
- Location: Southern California
Re: 183 build questions
I did not ground it. I capped it off with heat-shrink and tucked it away.sluckey wrote: ↑Thu Jul 22, 2021 4:41 pm Did you connect the center tap of that 12VAC transformer to ground? If so, disconnect it. You'll likely need to replace two of the rectifier diodes too. Hopefully the transformer is still alive.
If you did not connect the CT to ground, then disconnect both of the secondary wires from the board and check for 12VAC across the two wires.
I removed the secondaries from the relay board and measured 14VAC across the secondaries.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
It may very well be that the sole purpose of your life is only to serve as a warning to others.
- pompeiisneaks
- Site Admin
- Posts: 4228
- Joined: Sat Jan 14, 2017 4:36 pm
- Location: Washington State, USA
- Contact:
Re: 183 build questions
Then this means either there's a short on the relay board, or your secondary is shorted somewhere and loading it makes it go bad, I'd guess the first is more likely. Remember relays and their power supplies should be left floating, not connected to chassis... you might have done something to the relay power supply components by grounding it as Sluckey mentioned.professormudd wrote: ↑Thu Jul 22, 2021 5:12 pmI did not ground it. I capped it off with heat-shrink and tucked it away.sluckey wrote: ↑Thu Jul 22, 2021 4:41 pm Did you connect the center tap of that 12VAC transformer to ground? If so, disconnect it. You'll likely need to replace two of the rectifier diodes too. Hopefully the transformer is still alive.
If you did not connect the CT to ground, then disconnect both of the secondary wires from the board and check for 12VAC across the two wires.
I removed the secondaries from the relay board and measured 14VAC across the secondaries.
~Phil
tUber Nerd!
-
- Posts: 405
- Joined: Thu Jul 16, 2020 6:53 pm
- Location: Southern California
Re: 183 build questions
The layout for 183 shows a ground from the relay board to GND 5, as well as from the footswitch jack to GND 5. I used the same grounding scheme.pompeiisneaks wrote: ↑Thu Jul 22, 2021 5:19 pmThen this means either there's a short on the relay board, or your secondary is shorted somewhere and loading it makes it go bad, I'd guess the first is more likely. Remember relays and their power supplies should be left floating, not connected to chassis... you might have done something to the relay power supply components by grounding it as Sluckey mentioned.professormudd wrote: ↑Thu Jul 22, 2021 5:12 pmI did not ground it. I capped it off with heat-shrink and tucked it away.sluckey wrote: ↑Thu Jul 22, 2021 4:41 pm Did you connect the center tap of that 12VAC transformer to ground? If so, disconnect it. You'll likely need to replace two of the rectifier diodes too. Hopefully the transformer is still alive.
If you did not connect the CT to ground, then disconnect both of the secondary wires from the board and check for 12VAC across the two wires.
I removed the secondaries from the relay board and measured 14VAC across the secondaries.
~Phil
I am going to spend some time nosing around on the relay board.
You do not have the required permissions to view the files attached to this post.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
It may very well be that the sole purpose of your life is only to serve as a warning to others.
-
- Posts: 405
- Joined: Thu Jul 16, 2020 6:53 pm
- Location: Southern California
Re: 183 build questions
Crap. Mis-oriented the diodes.
You do not have the required permissions to view the files attached to this post.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
It may very well be that the sole purpose of your life is only to serve as a warning to others.
- pompeiisneaks
- Site Admin
- Posts: 4228
- Joined: Sat Jan 14, 2017 4:36 pm
- Location: Washington State, USA
- Contact:
1 others liked this
Re: 183 build questions
OH sorry I was thinking about a different relay setup that's used by hoffmans boards, not the ones for dumbles... must not have had enough coffee yet
Glad you found the diodes backwards.
~Phil
Glad you found the diodes backwards.
~Phil
tUber Nerd!
-
- Posts: 3209
- Joined: Sun Jul 22, 2007 7:48 pm
- Location: Mobile, AL
- Contact:
2 others liked this
Re: 183 build questions
Quick and easy find. But don't feel special. You're not the first to do that!
Better check all four of those diodes or just replace them all. I bet there are some dead ones now.
It's perfectly OK to ground the relay supply to chassis since you are using a dedicated PT. "Floating" the relay supply only becomes important if you are stealing 6.3VAC from the filament string. Even then, it's not necessary in all cases. But if you don't know those cases it's just best to float rather than sink.
Better check all four of those diodes or just replace them all. I bet there are some dead ones now.
It's perfectly OK to ground the relay supply to chassis since you are using a dedicated PT. "Floating" the relay supply only becomes important if you are stealing 6.3VAC from the filament string. Even then, it's not necessary in all cases. But if you don't know those cases it's just best to float rather than sink.