I have a beautiful 1961 Zenith suitcase record player that worked amazingly until last night when it started humming and then cut-off and started smoking. The transformer seems to be the culprit of the smoke so I am trying to replace it, but I am new to electronics older than 2000.

Here is the radio museum link to my player: https://www.radiomuseum.org/r/zenith_sfd_660sfd66_ch_5d205_d_2.html

Or just search zenith SFD660

I would just post the shematic, but the radio museum site's disclaimer sounds scary.

From what the schematic on the radio museum site says, I need a transformer with 3 secondary windings, two of them center tapped. That makes 8 wires for the secondary and 2 wires for the primary which lines up with the 10 wires coming out of my transformer.

I need a 5 volt winding, a 6.3 v 1.7A winding, and another windings that I can't figure out the specs of (it goes to a 5Y3GT rectifier tube's plates).

Where should I buy a new transformer from? And would anybody be willing to help me figure out the mystery winding?

Thank you for any help!

For some reason I've really been bitten by the super low wattage but still PP amp bug. After some research I stumbled upon these little beauties, the 6EH5. Just under 4 watts for 2 tubes in a PP configuration! 140V plate max, and 120 G2! So obviously, finding a suitable power transformer is an issue right off the bat... was thinking of just using a full wave diode rectifier and an isolation transformer with some voltage dropping resisters to get that B+ down to 140. But then I had the whole, "holy shit do 12AX7s even operate below 150 volts?" panic which I found that yes, of course they do.

And while the 6EH5 data sheet has the specs for a typical setup for class AB operation, I haven't been able to find any actual designs that use them for guitar amps or similar. And so, I figured I ask here if anyone knows of any designs or remembers any actual amps that used these tubes?

Thanks!

I’ve seen mixed reviews on very dated thread outside of Reddit. So now I’m here I guess asking for a more current outlook.

Due to laziness, the chassis design I have in mind to build would require tubes at a distance from the circuit board

I am completely aware of the golden rules of more connections equal more bad and longer signal path equals more bad

I guess I’m asking - exactly how bad

Would a socket saver built into a chassis significantly affect sound? Or is that more of a myth and it would be inaudible?

Has anyone been in this same boat where for chassis reasons you need the tubes higher, is there another way to solve this I haven’t stumbled upon?

Thanks in advance and sorry for potential newbie question. This is my first kit.

EDIT: I spoke to an electrical engineer friend who knows nothing about audio who told me to, and I quote “just solder a tower from the grid to however high you want the socket to be.” That sounds ludicrous to me, but maybe that’s reasonable? I really don’t know.

Does anybody remember a few years back when Western Electric announced they would be expanding their product offerings from just 300B production? I vaguely recall filling out a survey stating what tubes I'd like them to start making. (EL84, of course!)

Anybody know if this is still in the works?

So I bought a used Dynaco st-70 and I was hoping to get some help troubleshooting. I tried to set the bias to 1.56v but both channels max out at 0.81/0.84v (after letting it warm up, etc...). It looks like it's been recapped and the quad cap has been replaced as well. Everything else looks to be original. I tried out a new rectifier tube which had similar voltage readings as the old. Do I just need to replace the output tubes? Any other simple voltages readings I can take/comprehensive testing guides I can look at?

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

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Hi! I hope this is okay to ask here. I recently came into a ton (~200) audio tubes from the 60s through 80s. I don't have a tube tester, and I don't plan to keep more than one or two for myself. A good chunk seem to be pretty desirable (12AX7, 12AU7, and a bunch of others that show up on Tube Depot in the $50-$300 range, as well as maybe 50 in the sub-$20 range). I don't know enough to verify that these prices are accurate, but my tubes seem to match all descriptions. Again, I have no way to verify that most of these actually work, but the majority seem to have never been used and are still in the boxes. I'm worried about selling on Ebay and having essentially zero seller protection. I have an Etsy shop selling unrelated products, and could probably open a section for these tubes if necessary. I really am not sure what other avenues might be open. What do you all think?

Just picked up this 10a variac at the MIT radio flea market and I have some questions. My immediate intended use for this is for turning on some amps I've had in storage since 2019. And in general it seems like it could be useful for someone who is getting more into repairing and building amps.

I have tried looking for a basic rundown on how to use the variac to slowly power up an amp that hasn't been powered in a while. I can't find much info on the specifics of the procedure. How quickly should I ramp up the power to minimize risk of messing up the electrolytics? Reading material on electrolytics and the way they crystallize (if I have that concept correct) would be great if someone can point me at the right words to search and begin learning more. And to test this thing itself do I just plug my multimeter into the output and make sure the ramp corresponds with the dial markings and goes from min to max smoothly? I'm also curious about how out of whack that needs to be for me to consider this thing as needing some work itself. Any links to anything that can give me an in depth understanding of any of these things would be much appreciated. I'd also appreciate even just a basic procedure that works for you as a starting point. Thank you very much!

If anyone knows who might still do FM alignments please let me know. (Though I don’t listen to much radio.) Amp sounds perfect. Full service around 15 years ago.

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Hello

I have recently found a very large box of tubes. Too many that I will ever use, so I thought I'll sell them on so someone else can make use out of them. I wanted to test them before I sold them to check they work and so I don't feel bad selling a duff tube.

Would the tests that the orange VALVE TESTER MKII be sufficient of a test for the tubes it's compatible with?

I have seen other tube testers but they are far more complex and costly and hard to come by.

Any help would be much appreciated.

Hello, I'm about to wire Hammond 291 AEX transformer primary voltage for my 5F1 clone project. My wall voltage is 230V-50hz. Is this the correct configuration to achieve successful 230V wiring or am I doing something wrong? I wanted to ask before trying anything in order to not to burn any component.

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

So I stumbled on this fellow's work using tubes at 3.3v:

https://avdweb.nl/tech-tips/electronics/3-3v-vacuum-tube

I found a 6v6GTA in a pile of junk at a used bookstore for JPY 300, with no signs of damage. I used the above design, but at 5V.

It produced output, but at really high impedance. It did not seem to work as well as with the tube in the design above. I added a buffer made from some junk found lying on the side of the road and called it done. Distortion levels are hilarious, but it does work.

Anyway, only learned about this sub quite some time after. Thought maybe some of you would find it amusing!

https://preview.redd.it/gio9g1jznysc1.jpg?width=4000&format=pjpg&auto=webp&s=3fae61027aaeea8f875324dc38a9ca05b92124a8

Curious what the best option for setting and leaving my SET tube amp volume at while listening. I like having remote volume control through the Volumio player and am curious how you all would set the volume for the amp. My set up is using a Raspberry Pi Volumio player connected to my Project USB Box S DAC to my DIY tube amp output to my Klipsch Heresy IIs. Usually listen to Spotify with their native Ogg 44.1 KHz 16 bit format.

My amp is a Tubelab SSE single end triode I put together about 10 years ago. I get max 6W output with my Telefunken KT-88's installed. With the Heresy's I don't need much power. Heresy's have the Silver Crites cap upgrade and their titanium diaphragm for the tweeter. Currently building a small powered sealed 8" subwoofer I will run inline too.

https://preview.redd.it/us73k1jznysc1.jpg?width=4000&format=pjpg&auto=webp&s=910f85d8b35aa9ee6faed9b135343ba82e2b4201

I usually just set it the volume 3/4 the way up and adjust on my device. Curious if I could set the volume better to maximize my amps best output? It sounds great as is, but wondering if I could adjust the volume any better. Any volume output that may cause the tubes to perform better?

From what I've read it's to protect the transformer in the unlikely even that the tube shorts. The schematic calls for (2x) 1/2 amp but I'm uncertain if it is slow or fast blow?

Any recommendations? I have 2 monoblocks that already had fuses, one had nothing and the other had ceramic resistors