Ceriatone AH-50 Build

[PLX]

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

It's DC heaters on the three pre-amp tubes.

The two power tubes and the phase inverter are 6 VAC.

It's a high-gain design, so the idea is to get the AC completely out of the pre-amp tubes to eliminate noise.

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

Man, I have built and modded a lot of amps and this is the first time I've dealt with oscillation. I didn't even know that's what it was because I had just finished low-power testing with a variac and a light bulb current limiter, so I'm running the amp into a dummy load and tryna bias the fucking power tubes.

I'm getting readings off the bias test points that make no sense to me, so I figured I'll reach out for help. I haven't even logged into TheAmpGarage in like 4 years, so I'm thinking, "Maybe it's not the same bunch of angry curmudgeons using KT-88s as butt-plugs."

no such luck.

But they did advise me to hook up the amp to a speaker load and listen for oscillation, and they were right. They were complete assholes about it, but they were right.

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...

Yeah, and now I know. It's the output transformer leads connecting to pins 3 of the output tubes.

I just woke up from my afternoon nap, watching the sun go down in the valley. Playing with my 6 Great Pyrenees dogs in out in the yard.

I'll pull the board outta this in the morning and go thru everything.

If I need tech help I'll either PM you, or I'll reach out to a couple amp guru guys I have e-mail addresses for.


ffs

[harddriver]

Yeah, and now I know. It's the output transformer leads connecting to pins 3 of the output tubes.



ffs

Yep... I think it was the leads from the Output transformer to the power tube sockets. I guess it squeals like a bitch....

Was this it?

Sometimes it's better to walk away and come back with fresh eyes.

[PLX]

Yep... I think it was the leads from the Output transformer to the power tube sockets. I guess it squeals like a bitch....

Was this it?

Reversing those leads solved the bias issue. That's a bitch tho' because the leads are color-coded, and I had them orientated correctly according to the layout and hi-res images of the production amp.

I was still getting oscillation when I hooked up the amp to a speaker cabinet.

I have the turret board out now, and I can see that under the board I had used small ty-wraps to try to keep things tidy. However, this fucked me when I started moving wires around.. It pulled things around under the board and zapped that little rectifier chip.

Since I'm down until I get parts, I'm gonna spend the time goin' over the entire board, above and below, double-checking all my connections.

De-solder the RC206 and the filter cap next to it because it prolly took that with it.

I gotta order a wire kit from Valestorm for both this amp, and my 2203.

[harddriver]

I just looked this Output transformer connections in my Metro assembly instructions hardcopy. Marshall Output transformer connection primary wires are color coded RED and BROWN.

Twist the OPT primary wires. Cut to length and solder in place to power tube socket lugs:

RED to V5 PIN 3

Brown to V6 PIN 3

So the OPT primary wires in the AH-50 kit doesn't have color codes?? How the hell does one keep from reversing them?

[PLX]

I just looked this Output transformer connections in my Metro assembly instructions hardcopy. Marshall Output transformer connection primary wires are color coded RED and BROWN.

Twist the OPT primary wires. Cut to length and solder in place to power tube socket lugs:

RED to V5 PIN 3

Brown to V6 PIN 3

So the OPT primary wires in the AH-50 kit doesn't have color codes?? How the hell does one keep from reversing them?

No, it does. They're brown and blue.

I had them orientated correctly, but sometimes the manufacturer gets that wrong.

Hell, the wiring on the power transformer for this amp was backwards from all the documentation, and I had to contact Nik and get that sorted out right when I started the build.

[lll]

Ya the OT pin 3 wires can easily be reversed and you get the "whu whu whu whu" oscillation; flip em around and problem gone.

Did it myself with my build.

BTW, you post your problem like you did here... over at Soymore Duncan, and they'll laugh at you.

Like any of them have even unscrewed the back panel off of their amps.

This is the kind of dumbshittery we have to deal with:

Online jagoffs with little to no experience trying to one-up those with way more experience.

[PLX]

So, I wake up this morning and log-in to see that I have a "Nasty Gram" from the admin at TheAmpGarage.com forum..

Evidently.. they read this site, and he says, he "..does not appreciate seeing one of their valued members being insulted."

He also informed me that I am not well liked at TheAmpGarage.com and that my membership has been perma-bant.

[harddriver]

So they are over here reading your posts???? Gone are the days when someone who had a problem with an amp build and others pitched in and pooled their brain power to help figure it out.

I had a ton of newbie questions circa 2006/2007/2008 when I undertook my first builds and everyone was extremely helpful on METRO most notably Larry(NOVOSIBIR). No snyde comments about being a dummy or having overlooked something. Every the most experienced can get tunnel vision when working on a project and overlook something it's human nature.

I'm sure you'll find whatever issues is going on with it. Keep us posted and we'll help if we can.

[PLX]

So they are over here reading your posts????

We get a lot of traffic here. A lot of haterz from other gear forums too.

Some jackass reported a GIF I posted here several months ago.

Gone are the days when someone who had a problem with an amp build and others pitched in and pooled their brain power to help figure it out.

Not really. It's just that site. It's a little club of people who know a lot about tube amps, but they expect everyone to 'kiss the ring' if you go there and try to learn something.

I have several folks I can e-mail and get answers for anything about tube amps. I'm a patreon on Mr. Carlson's Lab, and I can ask him anything about electronics and get an answer. I just figured I'd give those turds another try and see how it went.

Those forums have all become toxic little echo chambers. That's why MetroAmp and PlexiPalace are dead now. They run off everyone by being smug and condescending, then wonder why their forum died.

I had a ton of newbie questions circa 2006/2007/2008 when I undertook my first builds and everyone was extremely helpful on METRO most notably Larry(NOVOSIBIR). No snyde comments about being a dummy or having overlooked something. Every the most experienced can get tunnel vision when working on a project and overlook something it's human nature.

Oh, sure.

These guys who run these forums obviously don't know jack about how the Internet works.. but far be it from me to lord it over them by having 8~12 accounts there by using a VPN service.. and having them unwittingly help me anyway by posting without proper spelling & punctuation.

Or having another thread running there right now, about the exact same amp under another user account.

That's not how I roll. I'm not about to stoop the their level by rubbing their noses in how ignorant they are about information technology.

[administrator]

So, I wake up this morning and log-in to see that I have a "Nasty Gram" from the admin at TheAmpGarage.com forum..

Evidently.. they read this site, and he says, he "..does not appreciate seeing one of their valued members being insulted."

He also informed me that I am not well liked at TheAmpGarage.com and that my membership has been perma-bant.

Sounds like a new entry for TheAmpGarage.com needs to be crafted in our Internet Forums section. Also sounds like certain members over there need to be made "famous" here.

Haven't these fuck knuckles learned that being an asshole can go both ways? I mean what, like only they have a corner on the market of assholery?