slow AC-30 clone build.

[pompeiisneaks]

You could also just wrap the wires around the terminal and solder in place after a tight crimp with pliers to ensure solid physical contact.

~Phil

[Mark]

Thanks Martin, I've decided I will go that path with the amp. Looking at the tag strip I used, it's only suitable for components and one or two wires. The Keystone tag strip has more real estate.

I had thought of adding fly leads to the ends of the wire, but rightly or wrongly, why add another solder joint if you don't have to. There is the potential there for another dry joint, and I'd probably be wise to use high temp solder as it is harder. The stuff we used at work was Alpha 38, I think it resisted vibration which is the reason we used it.

[Colossal]

Hello Mark,

Any updates on your AC30 build? I received my transformers a little while ago.

Cheers,
Dave

[Mark]

I’m interested in finding out the rail voltage and what I’ll deem acceptable.

I should have bought the low voltage Haddon transformer.

[Mark]

Well, I did say it would be a slow build. Here is a bit of progress. I have had issues with the Mercury Magnetics power transformer putting out 303-0-303vac.

E3CBC9CD-6760-43C7-B0B3-380A58AB59AD.jpeg

[pdf64]

...I have had issues with the Mercury Magnetics power transformer putting out 303-0-303vac...

Is that its unloaded voltage, or with a full compliment of valves drawing current?

[Colossal]

...I have had issues with the Mercury Magnetics power transformer putting out 303-0-303vac...

Is that its unloaded voltage, or with a full compliment of valves drawing current?

Pete, that is the unloaded voltage.

[Mark]

...I have had issues with the Mercury Magnetics power transformer putting out 303-0-303vac...

Is that its unloaded voltage, or with a full compliment of valves drawing current?

Pete, that is the unloaded voltage.

I should have power on the output stage soon, but I think it is loaded with power on it. I will report back.

[Colossal]

Is that its unloaded voltage, or with a full compliment of valves drawing current?

Pete, that is the unloaded voltage.

I should have power on the output stage soon, but I think it is loaded with power on it. I will report back.

Hi Mark,

Mercury specifies all of their voltages as unloaded. I believe you have the Woden AC30 clone PT, MMP-V30W. I have the Haddon, MMP-V30H-M for my AC30/4 build.

See here:

Woden PT

MMP-V30W.pdf

Haddon PT

MMP-V30H-M.pdf

[Mark]

I have the output stage wired up with an 82 ohm cathode resistor. The secondary measured 305-0-305vac unloaded and 297-0-297vac with the load of the four EL84’s. The preamp and P.I. stages haven’t been built yet.

The B+ going to centre tap of the output transformer measures 360VDC. The screen grid node measures 352VDC. The voltage on the 82 ohm cathode resistor is 12.8VDC. The cathode resistor get quite warm even though it is rated at 25 watts. The total current is 156.8mA and the voltage is 12.8VDC, that equates to 2 watts there about.

The output valves are running between 109% and 114% of their total plate dissipation. Though I am measuring screen current too through the 1 ohm resistor on each valves cathode.

I think it is safe to say something has to change with regard to the power transformer's output voltage.

B76D38F5-11AD-4B4D-A202-D693CCE45965.jpeg

6D81F901-4754-4A72-9905-CFCFA475FDB2.jpeg