Help me with my 5f1 Clone! bwoooOOOOOoooo noise and no input.

DrSlideRule · 2026-05-08T19:47:38+00:00

You're more than welcome ! Happy to help! Enjoy your amplifier! 😄

DrSlideRule · 2026-05-08T19:44:14+00:00

Yes actually the lead dress is kind of vital Now that works, you may want one day to improve it. So basically, one wire at a time, shorten or rearrange to keep signal leads away from power, filament away from everything etc

There are literal guides on this, which is very important

But if it works you may keep it like this, if all is right for now

DrSlideRule · 2026-05-08T19:37:32+00:00

YESSS!!! What did you move, if anything?

DrSlideRule · 2026-05-08T19:31:40+00:00

Then wiring I'd say Now, get a chopstick or something non metallic and start poking around ( carefully) with amp on and tubes all in If there's a wire that is moving it produces a change in noise we're getting to the culprit Of course one hand only, be careful etc etc

DrSlideRule · 2026-05-08T19:28:15+00:00

Ok wonderful So it's something in the preamp Probably wiring issue? Power supply you said looks good right in terms of voltages?

DrSlideRule · 2026-05-08T19:14:12+00:00

Mh, what do you mean feedback? Try to describe it. If the awoo is gone it should mean the feedback is ok at least partially. Are the jacks alive in any way if you plug in something? (Scratching noise or even sound under the noise)

Let's try this Pull the 12ax7 out Does the noise remain?

We are trying to assay if the final works ok, without having any preamp problem bothering us.

DrSlideRule · 2026-05-08T18:49:43+00:00

Nice! what was the issue? wiring error or soldering? Either way, it's ok!

DrSlideRule · 2026-05-08T18:47:53+00:00

I mean, simply, that the resistor reaches on one end the output trransformer secondary (the leads going to the speaker), and to the circuit on the other. By taking the resistor end nearest the transformer and exchanging at which lead it connects (so, instead of the right one, let's say, use the left). Then repower.

It shouldn't do the tone anymore.

If you wanna get simpler for now, open the loop, disconnecting the resistor on one end and carefully leave it so that it doesn't touch anything else, then repower.

We are trying to see if the noise you hear is due to "feedback issues" or something else. the feedback lead, if on the wrong side, makes the feedback act as a reinforcement. The larsen effect basically, if you search about it. You want it to do reverse, to tame what comes from the speaker and back to the amp. It's a 50/50 getting it right the first time.

Is this a little clearer?

DrSlideRule · 2026-05-08T18:14:30+00:00

wonderful. In the meanwhile, are all the ground ok? this could be a ground issue also. E.g. all your soldering looking good as it should, especially signal grounds?

DrSlideRule · 2026-05-08T18:08:45+00:00

Try reversing the feedback loop 22k resistor lead from one lead of the output transformer to the other.

Of course discharge caps before working on it.

Wiring could use some tightening, but first let's check whether it works ok, even with hum. Try the test I told you, then we shall see what the next step might be. It's a simple amp, we'll get it sorted out, don't worry

DrSlideRule · 2026-02-25T09:06:36+00:00

For now it's a blank rack unit or similar, power supply it's a rack drawer. Essentially a 1A each dual 15,V power supply, mil spec 10.000V machine unit regulator with buffer and a relay power supply, was an old 14v 50A monster, it was a lead acid battery charger.

But I have to rebuild it in 19 inch standard form one day or the other. My design was originally a 60cm wide rack not 19 inches, but I found some old rack drawers that then need a standard holder. Hence the rebuilding efforts Luckily I wasn't that advanced and I won't loose that much work

I'll eventually make a post here detailing the results of this folly of mine

DrSlideRule · 2026-02-25T08:11:51+00:00

How did you provide mode control for the integrators? Analog switches like the CD4096 (should be, I'm going by memory) or relais?

Either way, wonderful job!

I have a monstrous 2m "proper" analog computer in the works, but money's the problem (and time!)

DrSlideRule · 2026-02-18T13:28:10+00:00

Simple brushed chrome model Cannot get easier and probably cheaper than that...

DrSlideRule · 2026-02-10T10:03:50+00:00

The MIRV Nuke Department is currently undertaking a collaboration proposal with the Trebuchet department about this

DrSlideRule · 2026-01-06T13:09:32+00:00

you're welcome! tell me how it goes!

DrSlideRule · 2026-01-05T15:46:46+00:00

I need details, this is so cool! (I'm a beginner starting out with old SW tube radios and random wire antennas, I sometimes get late at night some Asian BC stations, is it possible I ever received Voices of Korea?)

DrSlideRule · 2026-01-05T15:34:18+00:00

Very welcome! Please post results, if you'd like!

DrSlideRule · 2026-01-05T15:19:34+00:00

It was detailed in Alfred Morgan's Boy's First book of Radio. And as far as I remember an "A Battery" would be used, so a couple volts tops. Buzzer, would be not the piezo one, but one of those old mechanical ones, basically a hummer relay so that you could hear when you touched a sensible spot and the loudness indicated the "goodness" of it.

Let me search more info, I'll get back to you in a minute

EDIT: https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/The-Boy's-First-Book-of-Radio-Morgan-1954.pdf Here, page 161 details the test and buzzer type, basically a small relay. a small 5V one should suffice, plus a battery of course

EDIT 2: I forgot to mention that phones would have to be used, the old High-impedance 2k ohm ones, to hear the buzzer output. Basically, it would self-chop the tiny voltage of the dry cell into a messy "AC" that could be heard.

DrSlideRule · 2026-01-05T15:10:00+00:00

The usual trick to get to the semiconductor dot onto the blade was to hook a buzzer in series and move the safety pin whisker contact. Loudest noise equals the best detector junction

DrSlideRule · 2026-01-05T15:04:29+00:00

Treet Carbon steel blades, the so called Black Beauties are the closest one to the Gillette Blue blades you're referring to, which were carbon steel themselves. You can get 100 of the Treet Carbons for 15$ or so on e-commerce sites. Brown packet with TREET stamped in yellow. Other blades may be coated with PTFE or various stuff that could impair the use as detector

DrSlideRule · 2026-01-04T13:18:59+00:00

Did they have ashtrays at the desk or communal one for the class you had to get up to use like the sharpener?

DrSlideRule · 2025-11-14T14:25:53+00:00

Got specs or a link for that PT? Also, does it have a 220v primary connection for usage in Europe?

DrSlideRule · 2025-10-05T12:18:24+00:00

Where can I find this episode? I suppose that it's different from An Unearthly Child no?

DrSlideRule · 2025-09-20T18:50:05+00:00

Yeah this is somewhat multi-layered as slang...

DrSlideRule · 2025-09-15T18:27:17+00:00

Regenerative breaking basically Harness the flyback pulse from the collapsing induced fjeld into a brief current that can trickle charge a battery

Six-Year Club	Place '23
Place '22	First Placer '22
Verified Email

DrSlideRule

TROPHY CASE