Ceriatone AH-50 Build

[PLX]

Polyurethane clear coat dry & cured. Carrying handle, feet, and rear panel screen installed.

Final test fit of all components.

[RockyStar]

Looks sweet!

[PLX]

Spent the past 3 days trying to resolve oscillation.

Initially I could only bias one output tube correctly, while the other was extremely high bias reading.

Found one wiring error in the troubleshooting process, reversed the two NFB mods to cut down variables, shortened PI leads.

I did have concerns about the wiring used to remove the effects loop from the circuit, but after careful study, it turns out I had it correct.

This amp is by far the most complex build I have taken on.

[harddriver]

Once you get to the bottom of the issues and you will...you'll be rockin out............

[harddriver]

You need to route the NFB carefully either around the highvoltage B+ wires and high signal carrying wires. But I remember Novosibir making mention of it when I did the NFB control and Depth mod. Luckily I didn't have any oscillation issues and I don't think I used any shielded wire for either my NFB or Depth on the high gain 4 stage build. I wish I had taken pictures after I finished all the revisions to that amp.

You shouldn't have oscillation or parasitic oscillation in the BE50 design he has a least two plate snubbers dampening the high frequency oscillations out.

Maybe it was a wire routing thing. Not installing the loop shouldn't be an issue.

[lll]

See now this is good stuff here.

We got great "clientele" here.

And we got a dude (PLX) who puts his money where his mouth is (instead of bullshitting about himself online with zero evidence).

Won't see any threads like this over at Soymore Duncan, TGP, Eurofag Talk, etc...

A forum is only as good as the members who post on it, and the poseurs of the world ruin it for all.

[harddriver]

Did you twist the wires that go from the 220K bias splitters to the power tube sockets?

[I.M. Woke]

Wow great work! Wish I could do that but I can't even twist off a beer bottle cap without cutting myself hahahaah



Do you build amps for other people? I want a amp that sounds like a CRATE Blu Voodooo but with a "WOKE" knob on it! hahahahaha

[PLX]

You need to route the NFB carefully either around the highvoltage B+ wires and high signal carrying wires. But I remember Novosibir making mention of it when I did the NFB control and Depth mod. Luckily I didn't have any oscillation issues and I don't think I used any shielded wire for either my NFB or Depth on the high gain 4 stage build. I wish I had taken pictures after I finished all the revisions to that amp.

You shouldn't have oscillation or parasitic oscillation in the BE50 design he has a least two plate snubbers dampening the high frequency oscillations out.

Maybe it was a wire routing thing. Not installing the loop shouldn't be an issue.

I was moving the OT to output tubes pin 3 connections back-and-forth to try to get rid of the oscillation. The first reversal fixed the bias issue, but there was still oscillation.

I also re-routed the output tube grid wires away from the speaker wires, but all these wires run under the turret board. Well, with all this jinking around something shorted the little bridge rectifier chip for the DC heaters. While testing, I flipped the power switch and it popped smoke.

Not gonna lie - scared the shit outta me.

So I disconnected all the leads from the pot-side of the board so I could flip it upside down and see WTF happened.. I had inadvertently left two long leads sticking out of the bottom of the RC206 rectifier chip. They weren't touching anything.. until I was moving those other wires around.

I disconnected all the power transformer leads from the board and measured voltage off all the taps:

14.75 VAC off the DC heaters tap
6.9 VAC off the AC heaters tap
383 VAC off the other tap

I sent Nik at Ceriatone an e-mail asking if these look right (they looked right to me) and he got back to me saying they are correct readings.

I was getting help from the guys at theAmpGarage, but fucking hell.. there's this little eastern European dirt-bag over there who was in my troubleshooting thread making asinine remarks the whole time. When he thought I burned up my amp, he got so giddy about it he starts acting like a seven-year-old wearing Batman pajamas.

Then I realized.. this dude is in Croatia.

He lives in a bombed-out hovel with 4-foot-tall doorways, while his mom is cooking a dead goat's head in a stewpot in the next room.

So, I ordered the 0.68 cent part from Mouser, and it will be here Monday.




Hey, bepone !

[harddriver]

Isn't that amp full DCV on the heaters or only on V1?

Any ideas on the source of oscillation? Maybe the diodes on the DC heater board?

I am trying to remember what the cause was with somebody's build on Metro had a similar issue and it was like they had two wires reversed causing a polarity phase issue. I just can't remember what it was...

Are you just getting noise like high frequency oscillation only or do you get some audio signal?

I'm sure you'll get to the bottom of it.