ODS #183 with 4xEL84s

[PointTwoPoint]

ALL, I am here because my brother and I were in the process of building a ODS but decided to use a quad of EL84s instead of 34s. Well my brother has since passed away from colon cancer in Augest '25. He was going to build his own eyelet boards and engineer this whole project. Then I found the AAelectronics site with the boards and layout and thought I could probably do this now....? We had already purchased the transformers and chasis, Hammond 370FX and 1750G. I really hope if someone could just chime in with some "definite changes" I will need to make to get this thing to function with 4xEL84s. I just purchased a Hammond 194E choke (VoxAC30 30H 100ma). I'm thinking that might have been a wrong move. According to Google A.I. it was.... This is really a big undertaking for me.But thought it would be a huge learning experience and give me something to do since I have retired. (Machinist by trade) My bother did have a jaysg #183 100w layout he put some notes on it...B+,320v,he has multiple resistor value changes,and I was going to obviosly change the EL84 pinouts and screen grid resistors.I'm in no rush to get this done, so if anyone can provide a little positive insight it would be greatly appreciated. Image of where I am at now, Regards -Keith

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[martin manning]

Greetings. This is definitely do-able. A couple of things that you will have to address for EL84's is the B+ voltage should be somewhat lower than the typical ODS, the OT primary impedance should be matched to the 4x EL84 (~4k). and the required bias and drive signal levels for the EL84's is lower than for EL34 or 6L6. The transformers you have elected will work nicely. The choke is overkill, but it will work. A Fender type 4H 90 mA would be adequate, in case you want to save some space and weight. You will have to adjust some component values to get the bias voltage in line and possibly do something about the signal level coming out of the phase inverter. I suggest you share your marked up schematic so the folks here can have a look.

[frusciante89]

ALL, I am here because my brother and I were in the process of building a ODS but decided to use a quad of EL84s instead of 34s. Well my brother has since passed away from colon cancer in Augest '25. He was going to build his own eyelet boards and engineer this whole project. Then I found the AAelectronics site with the boards and layout and thought I could probably do this now....? We had already purchased the transformers and chasis, Hammond 370FX and 1750G. I really hope if someone could just chime in with some "definite changes" I will need to make to get this thing to function with 4xEL84s. I just purchased a Hammond 194E choke (VoxAC30 30H 100ma). I'm thinking that might have been a wrong move. According to Google A.I. it was.... This is really a big undertaking for me.But thought it would be a huge learning experience and give me something to do since I have retired. (Machinist by trade) My bother did have a jaysg #183 100w layout he put some notes on it...B+,320v,he has multiple resistor value changes,and I was going to obviosly change the EL84 pinouts and screen grid resistors.I'm in no rush to get this done, so if anyone can provide a little positive insight it would be greatly appreciated. Image of where I am at now, Regards -Keith
20260813_120832.jpg

Hi Keith, Andrea from AA Electronics here. First of all, so sorry to hear about your brother, my condolences. You can use the schematic/layout available in the website if you need a baseline. And if you share your noted layout we can help you from there

[didit]

Martin's suggestion to post a detailed schematic is a good one. We're better able with that reference. I'll toss in a nudge to review phase inverters in the Trainwreck/Vox style designs specifically built around that power tube configuration.

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[PointTwoPoint]

Thank you all for the kind words and insight on this venture,
The main issue I can't wrap my head around would be power supply adjustments for 4xEL84s.
I can follow the layout and current schematic, but don't have the knowledge to make adjustments that my brother had.
I've uploaded the tranformer spec sheets and notes on #183 schematic and layout.
I purchased a Hammond 194B choke 4H 90Ma.
Let me know if there is more information I can provide,
Thank you again for your time and any assistance you can offer.

[didit]

Quick initial question regarding that marked up schematic -- are those your brother's annotations/changes?

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[PointTwoPoint]

My Brother had really bad copy of the original jayag # 183 drawing...
He was also looking at a Ceritone Overtone Special layout.... which had 100uf 450v caps, and he had 100uf @ 250VDC in with the parts so I thought I might get away with using them even if 250v with the EL84s? (I should buy 300v+ caps...)
I don't know if parts of it were not legible to him in some areas and he wrote what he thought they were....or should be?
I copied them to the new AA Electronics schematic.
I'm attaching my AA layout also for reference.
Thanks again for inquires and help.

AA_183_Layout.jpg

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[martin manning]

Some notes and guesses at revised values. 250V power supply filters should be adequate, giving you 500V capability when they are stacked. No-load voltage should be ~414 VDC. With only 5VAC available for the relays you will have to go with 5V relays. There is not enough voltage headroom for a 12V reg, not even a low dropout one.

[PointTwoPoint]

Thank you for your knowedge regarding my puzzle I'm trying to solve.
My brother bought voltage regulators and relays,but they didn't match the BOM,So I bought new stuff.(7812 + G5V-2 )
It just suprises me that this relay thing was missed my him,he was getting sicker everday and not feeling great...he was also working on a giant toroidal transformer stereo power amp...
I've attached images of the parts he bought,and specs,if it would help? I probably just throw them away (9V volt regulator??) and follow your recommendations.
I have tons of electronic stuff from my brothers estate I'm never going to use.if your looking for something,let me know.
Thanks again,

[PointTwoPoint]

Thank you Martin.
After hours thinking about my options, I think I'm going to order the Hammond 166G6B transformer...
I can just stick to the original 12V layout and components and leave 1M resistors alone.
I'll get the CT 12V transformer and make the other component value changes.
Thank you for your wealth of knowledge on this.

[martin manning]

Could go either way. Adapting the relay system to 5V would not be hard, basically just changing the reg, relays, and resistors for the LED's, and you already have the 5V winding available. Cost is probably close to a wash.

[didit]

Hello —

Voltage tripler is slightly more complicated than that doubler. Another diode and capacitor, and a minor tangle of connections. Estimate it’ll provide raw ~18VDC, readily regulated down to 12V. Relays should tally up to roughly 150mA worst case, and likely less than half that, so minor load for an LM style device.

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[martin manning]

But we’re dealing with a PCB here. Not sure what options are available or if any creative component placement is possible.

[didit]

I concede that. And now looking closely at that as-built today PCB suggest yes, just bolt in the smallest practical mains->6.3V transformer that'll net at least 500mA AC at the input for the board as-is. Desoldering rework for necessary bits is semi-risky and always frustrating.

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