JoaMat

Life is short. Would T2 accept EML 20B-V4 tall base? Yes, she does! For how long?

Here is a Blue Hawaii I built a couple of years ago. Just removed the EL34 (left channel) and put the EML 20B-V4 tall base in place. Held my breath, closed my eyes, pulled the trigger and…. it works

EML 20B-V4, tall base

I’m actually reading the information Emission Labs sent me with the tubes. Regarding filament they say: “The filament voltage must be exactly as specified, under all circumstances. Slow-start filament electronics taking longer than 10 seconds, are not allowed, otherwise this may damage the tubes” “Stand-by mode should not be used with directly heated tubes.

I can’t hear any AC hum – doesn’t mean that there isn’t any though. The filament transformer gives [email protected] out. In order to reduce voltage for tube heating (5.0V +/-5%) I’ve put wire wound resistors in series with heater. Below shows the small board with terminals and resistors mounted to Kevin’s main board on two stand offs. For info I followed this link and bought some SiTubes filament supplies. They work OK for a quarter of an hour or so than the voltage drops to a few tenths of a volt. After some cooling down they are fit for fight again. I should have red data sheet. Maybe this would do if you really want DC heating. Probably overkill??

You are right. Even when completely dark the tubes can be barely seen. Very disappointing, but the sound is OOOK!!! Maybe I should turn up the variac, it’s only at 67% percent...

Continued the rebuilt. Emission Labs DHT Tubes, EML 20B-V4. To the left is variac. Its purpose is to set the two small transformers to appropriate voltage for the filament.

625 mW is more than enough. Max power dissipation of mpsa/w06 is less than 60 mW.

What is printed on the PCB - MPSW06 or 2SC2240?

Thanks, so the servo keep the offset to zero from the start (except from the first seconds when power on) and further on without any fluctuations?

Thanks. Does it mean that you have zero volt offset even from the start?

Anyone that have tested the opto servo. How does it work?

You can’t just replace the mpsw with the 2sa/2sc components that way, can you? I think their pin layout is different.

Great work!

Rebuilt a Blue Hawaii to Grounded Grid - seems very promising.

Replaced 2sj79/2sk216 with ksa1220/ksc2690 on one Blue Hawaii and one DIY T2. No negative surprises so far.

Looks very interesting. Would it be possible to have some pictures of the inner layers? What might the maximum voltage between layers be? Beautiful symmetry of the board.

Blaha!

OK, post deleted.

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Well done. Congrates. The blue electrolytics, are they from the group buy?

As a Carbon amplifier I just use a trimmer to control the offset. Yes, it’s 0603 LEDs – TLMS1100.

A picture of my attempt to build a Circlotron driver.

Absolutely magnificent!