John Warren

They are. Is this a crossover application? Thought the OP was looking for an electrolytic for power supply application.

What do you think are the typical tolerances for Al-electrolytics? And, I suppose, if you really want something at or very near 25MF you could buy 100 of them and sort. You should find three or four around 24-26MF.

EGXF351ELL240MK20S United Chemi-Con | Mouser

Excellent! FWIW, I've added a few more boards but intend to keep the format simple. I've used Simple Machines Forum software. It's been around for some time, is powerful, open source and well maintained with regular patches and upgrades. There are two security questions to answer at registration (answers are not case sensitive and are: Binghamton, resistance) and an anti-spam visual verification image to decipher (the bots are pretty good at getting past those however). Might have to incorporate reCAPTCHA if the bots are too much, so we shall see.

I had a CL-90 as it turns out and effect is shown here: Rectifier rolling (cont) (northreadingeng.com)

I've been a regular member on this forum for 22 years! I've posted a lot of stuff here. That said, I've created a forum for experimentalist, builders and engineers. It's not linked to my webpage. It's for those that have interest in designing and building hardware. There's also Marketplace section where gear can be sold and a section where members can list parts and components they're looking to acquire. I have no interest in advertising on it, I have plenty of server capacity elsewhere for advertising. I'm interested in idea generation and exploring concepts. Manufacturers are welcome too but no advertisements. Here's the link: North Reading Engineering Forum - Index Also, a few years back, I tried getting a forum up but had all sorts of issues with bots and attacks and decided to take it down. The forum software (SMF) I'm using now appears to be better configured to resist internet garbage. That remains to be seen. jw PS. I'll leave it up for a few months and contribute to it with projects I'm currently working on! If there's interest in the forum, I'll leave it up. Also, if there's interest in other topics then shoot me an email at forum@northreadingeng.com

Around 1960 give or take.

A few of the McIntosh service shops were doing the same thing with tube amps that came in for work. The rectifier was pulled and replaced with a plug in. The rectifier tube was returned in a white box. I know because I was a technician working on them back then (late 70s).

Ok, here's a forum dedicated to this sort of thing. I've put it on my site. I'll perform various amplifier, network or loudspeaker test if they provide value and are interesting (to me!). I have a well-equipped test bench/lab and can perform measurements in electrical and acoustical domains. Always looking to add capacity to the lab as well and, should a test require a special instrument or setup, will get it. The link is below, no ads and guests can view attachments. If it becomes a bot magnet or just becomes a drag it'll go away. https://www.northreadingeng.com/forum

If you're so inclined, try a "different" output transformer configuration. For example, I have a customer that requested the 299C reproduction amplifier using the Lundahl C-core and based on my listening, sounded excellent. They're a bit pricey. The powder coated enclosure provides a nice aesthetic. A 299C power supply transformer (Heyboer wound) is shown next to the C-core. North Reading Engineering Forum - Index

I had considered this. I've been noodling selling a revised embodiment of this amplifier and, to know how it behaves over a range of operating conditions becomes an issue. The performance with a tube rectifier from 110 to 125VAC on the primary is largely unaffected based on what I've measured. So, what's unaffected mean? Power v. %THD at 20, 500, 1,000, 5000, 10000Hz similar, FFT of components similar, sound same.

Well thanks! I have some experience with this topic and found the topic worth the effort.

I haven't gone thru my inventory but maybe. I'm noodling a good way to record the current v. time thru the power supply primary, tube heaters, etc. I have plenty of meters and can capture max values but would prefer to record the response differences in a plot. The sampling rate has to be high given trying to measure a transient and the resolution of the capture has to be a few mA both AC and DC.

Data Test case, one low-cost Chinese 5AR4 and a 2x1N5408 rectifier plugin. Amp is a 299C scratch clone I made last year. I laid the amp out on PC boards an assembled the entire unit on a CNC machined plate. First test was to measure distortion at equivalent anode voltage, in this case 425 VDC. With a Variac, the PS transformer primary VAC is adjusted to provide anode voltage at 425VDC for both rectifiers. %THD to full output power at 20Hz is then measured and compared. Load is a 50W non-inductive power resistor across the 8 Ohm output tube transformer secondary tap. 5 measurements for each rectifier were taken and compared. If the result was consistent between each, it's reported here. At 117.1 VAC at the PS transformer primary the 5AR4 produces 425VDC with 1243mA at idle. At 111.6 VAC at the PS transformer primary the 2x1N5408 plug-in produces 425VDC with 1245mA at idle. Blue is 5AR4 Green is 2x1N5408 rectifier A measurable difference below about 2W RMS, above that it's a wash. There are other tests that are worth performing but this was the quickest. The next test was to fix the PS transformer primary voltage to 120 VAC for rectifier condition, turn the amp on and measure the PS transformer instantaneous (i.e., "turn on") current thru the AC power entry module. The peak VDC at the anode is also measured. The 5AR4@120VAC peak current 1448mA AC and peak voltage 437.8 VDC The 2x1N5408@120VAC peak current 2586mA AC and peak voltage 488.6VDC The instantaneous current draw is 1.2A or about 2X greater using the solid-state rectifier. Peak anode voltage at turn-on is about 51VDC larger using the solid-state rectifier as well. Note that wall power can approach 125VAC which would create larger differences in magnitude than what's being measured here. Next will be filament current measurements at turn on and the effect of various in-rush current limiters on the solid-state rectifier turn on characteristics.

Before the days of the internet, I measured filament draw at start with tube, ss and ss + various in-rush limiters, AC, DC power on both a few preamp and power tubes. I don't have the data, so I'll have to replicate the measurements. Differences are significant.

I'll get back to you on this.

If you want to hear an improvement swap the tube for a plug-in solid-state rectifier. Rail sag is, for all intents and purposes, eliminated. It's harder on the tubes but that's why we have in-rush current limiters.

No, I don't expect a new tube line manufacturing tubes in 6 months. But I would expect some feedback by now, what are they doing? What's the down-select? What tube or tubes are planned? What's the date of first issue? What's the cost? This isn't hard, J&J has already identified the popular tubes.

I'll leave that to you given you are projecting yourself as an expert. Never thought they sounded "so good".

Going exactly as expected, i.e. nowhere. There's a handful of tubes that can meet the demands of the microscopic tube amp market. What's it take? an $80 pair of EL-34, 6L6, 7591s?

Thank you! Multiple projects including amp, test gear restorations, rebuilds and ground up new makes keep me happy.

At the risk of burdening you with finding another way to disagree with me, I shall agree with you.

Nice job!

Luckily the circuit survived the destruction of the safety cap, it opened. They're designed not to catch fire given the application across mains voltage (CL-X1 and X2). These capacitors have a reputation for failing. They're in all sorts of vintage test gear.

RIFA 0.22uF, 250VAC, CL-X2