If there's a mistake in the mesa schematic, I wouldn't know. What I can tell you, though, is that the peavey does indeed sport 100R 5W resistors on the screens of two out of 4 output tubes. I can trace that out on the circuit board I have on the bench. It might have something to do with the fact that the peavey allows you to pull two tubes to reduce power. I'm not sure, but I will wire all 4 tubes equal.TriodeLuvr wrote: ↑Tue 12/15/20 8:36 pmI just want to mention that the design represented in the schematic regarding the grid stoppers is incorrect. I suspect a misprint in the schematic, but regardless, there's no valid reason for the existence of stoppers on only two tubes. Also, to be effective at eliminating oscillation, stoppers need to be soldered directly to the grid pins with the shortest possible leads.
New 36W build, guidance needed
Moderators: zaphod_phil, Daviedawg, Graydon, CurtissRobin, colossal
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
1 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
You do not have the required permissions to view the files attached to this post.
1 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: New 36W build, guidance needed
Are you referring to R46 and R55? I agree, it looks like R46 should be shifted down and R55 should be rotated 90 degrees counterclockwise, pivoting at its upper end. Is the circuit actually wired that way? maybe the diagram has errors.
0 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
Yup, and it is indeed wired like that. Makes no sense to me, but I guess they must have had their reasons.
Cheers,
Henrik
Cheers,
Henrik
0 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
Cheers!
You do not have the required permissions to view the files attached to this post.
0 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
Progress!
CH1 stage 2, CF and tone stack plus LTP phase inverter.
CH2 5879 first stage also completed.
CH1 stage 2, CF and tone stack plus LTP phase inverter.
CH2 5879 first stage also completed.
You do not have the required permissions to view the files attached to this post.
3 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
It's filling up in here. Hope to hear some noise later this week, if the lady of the house let's me work...
You do not have the required permissions to view the files attached to this post.
1 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
She's alive!
Both channels functional right out of the can. Word of advice: I went in my den to work after nailing a beautiful bottle of red. Had to redo most of that work ..... Glad I caught it before I powered her up. Had the pinout on the 5879 all messed up. I had to make some significant adjustments in the PS to get the screen voltage down below 300, but now we're at 280, with 395 plate volts. Biased to dissipate 15W per side. Sounds sweet now, but I have yet to add a master volume so I'm very limited as to how far I can go on the volume.
To be continued....
Both channels functional right out of the can. Word of advice: I went in my den to work after nailing a beautiful bottle of red. Had to redo most of that work ..... Glad I caught it before I powered her up. Had the pinout on the 5879 all messed up. I had to make some significant adjustments in the PS to get the screen voltage down below 300, but now we're at 280, with 395 plate volts. Biased to dissipate 15W per side. Sounds sweet now, but I have yet to add a master volume so I'm very limited as to how far I can go on the volume.
To be continued....
You do not have the required permissions to view the files attached to this post.
2 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
I've tweaked the PS to where the voltages are sensible throughout and I'm happy to report that it sounds excellent, and LOUD!
However, I have more hiss and static than I'm willing to accept, so now starts the tedious process of trying to iron this out without sacrificing tone. It'll be a tough one.
However, I have more hiss and static than I'm willing to accept, so now starts the tedious process of trying to iron this out without sacrificing tone. It'll be a tough one.
2 x
- TriodeLuvr
- Frequent poster
- Posts: 616
- Joined: Tue 10/16/18 11:19 am
Re: New 36W build, guidance needed
Glad to see it's working! I'm building into a Peavey VK112 combo case, but the original chassis is gone. It's been a challenge to build a chassis this size and to fabricate a front panel almost 500mm (19.5") long. I finished the engraving on front and rear panels a couple days ago, but then my computer crashed. I'm dead in the water until I fix it.
Anyway, I was just wondering where you found the long terminal strips you're using. I have a good stock of terminal strips, but nothing as long as those. That would be handy. Also, did you add the pop rivets holding the parts of the chassis together? If so, are they aluminum or stainless?
Jack
Anyway, I was just wondering where you found the long terminal strips you're using. I have a good stock of terminal strips, but nothing as long as those. That would be handy. Also, did you add the pop rivets holding the parts of the chassis together? If so, are they aluminum or stainless?
Jack
0 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
The pop rivets are aluminium.
The terminal strips are 9-lug items that I found on ebay. Check item no 193375184021.
Cheers!
Henrik
The terminal strips are 9-lug items that I found on ebay. Check item no 193375184021.
Cheers!
Henrik
1 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
Matchless-inspired master volume and treble cut wired up and working well. Sweet-sounding tremolo added to the 5789 channel.
You do not have the required permissions to view the files attached to this post.
3 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
I was going to attach a **** sound demo, but for some reason, the file format was invalid
0 x
- JMPGuitars
- Super Duper Admin
- Posts: 3969
- Joined: Tue 09/18/12 8:00 pm
- Location: South Central, MA
- Contact:
Re: New 36W build, guidance needed
Post it on youtube or another media sharing service, and share the link here.
Thanks,
Josh
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale
Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
Ok. I recorded it on my phone, not using video, so it's not really compatible with YouTube either.
Nevermind, it sounds good though. But there's no way a recording on my phone will portray that anyway, so it's nobody's loss.
I'll upload a schem when I'm all done tweaking.
Cheers!
Henrik
Nevermind, it sounds good though. But there's no way a recording on my phone will portray that anyway, so it's nobody's loss.
I'll upload a schem when I'm all done tweaking.
Cheers!
Henrik
2 x
-
- Newbie
- Posts: 25
- Joined: Tue 11/10/20 2:37 am
Re: New 36W build, guidance needed
Hiss and static turned out to be mostly caused by bad tubes. Some new tung-sol 12ax7s and a different nos 5879 cut the noise by more than half. Replacing the first stage grid stoppers with lower value, higher wattage and better quality resistors did the rest. It's not dead quiet, but better than many new factory built amps I've come across.
Resistor quality is actually of great importance. Be warned that many cheap and pretty metal films don't have real copper leads, but plated steel instead. This is asking for noise issues.
I'm waiting for some new input jacks and I have to do something to spruce-up and correctly label the controls, but other than that, I think I'm done. A very fine amp, if I dare say so myself.
Resistor quality is actually of great importance. Be warned that many cheap and pretty metal films don't have real copper leads, but plated steel instead. This is asking for noise issues.
I'm waiting for some new input jacks and I have to do something to spruce-up and correctly label the controls, but other than that, I think I'm done. A very fine amp, if I dare say so myself.
2 x